How to measure dust collector performance. [Archive] - Sawmill Creek Woodworking Community

Vaughn Kaloust

01-25-2013, 12:11 AM

Hi to all. This is my first post, but I sure have been reading a lot, and getting great info here.

After 40 years of abstinence, I am about to start working with wood again. I have set up a decent shop to begin my retirement, which includes dust collection through a separator. However, I am now trying to optimize the system, and was wondering if anyone has suggestions on how to measure the effectiveness of any adjustments I make.

I have seen CFM meters that look like they could do the job, but they range from $35- $500! :eek: Also, I am not sure that this tool would provide me with all the measurements I need to gauge performance of each section of the system.

I have read many posts about dust collection systems, but have yet to find any mention of a method or procedure for accurately measuring performance.

I am hoping someone can point me in the right direction.

Thanks

Ole Anderson

01-25-2013, 10:47 AM

Vaughn, welcome to the Creek! Please edit your information to include your location, always good to know where you are from as folks from all over the world post here.

Depends on what you are trying to measure, cfm or dust particle removal efficiency. If cfm is your goal, best way is to measure the duct velocity just ahead of the separator in a straight section of smooth duct. Several ways to do this, but an anemometer isn't one of them. That is what I have (a Velocitor) and you are limited to measuring the velocity at the end of a duct or hose where you have access. Best to get a proper pitot tube with two connections, one for static pressure the other that is aimed into the airstream. The pitot tube should come with a calibration curve and coupled with the area of the duct, you can plot a differential static pressure vs cfm curve. You can make up a manometer with two dollars worth of 3/16" clear vinyl hose and some water with food coloring added or you can get a Dwyer magnehelic gauge for $30 to $40 on EBay. With this setup you can measure all combinations of gate openings and hood and duct/flex hose changes without relocating the pitot tube.

David Kumm

01-25-2013, 11:17 AM

The velocitor Ole and I use is helpful in telling you the cfm available at the end of the hose going into each machine but will not tell you how the hood restricts that airflow if at all. The magneholic gauge will help you with that. I display amp draw continuously on my vfd so I just compare the draw with the hose not attached and then attached to see if there is internal restriction. It is useful to take readings without machines attached to get an idea of the real airflow the system is capable of delivering at each location. Even with a restriction inside the machine, more air entering means more air flowing through the restriction. Dave

Vaughn Kaloust

01-25-2013, 3:23 PM

OK, now we’re talking. Thanks for the info.

I should have been more specific with my question. I am thinking that the end result is where the collection is done at each machine, so that is what I am trying to measure.

I thought that if I measured the velocity at the drop to each machine, (just before the connection to the machine), that should give me an idea if my suction is sufficient.

I will start looking for the pitot tube, but I have no idea what a velocitor is, and when I Google it, all I get is information on ammunition.

For the manometer, no problem, I have everything I need.

Ahhh, Velocitor is the brand of anemometer, right? Like this?
http://www.centurytool.net/AM50_CPS_Velocitor_Air_Velocity_Meter_p/cpsam50.htm

Now I am a little confused, because it sounds like this is where I started.

Can I simply use an anemometer at the end of each open duct, just before it enters the machine, to get the velocity and CFM? Wouldn’t those two numbers tell me if I have enough draw for that particular machine?

I will check into the pitot , magneholic gauge, and anything else I can find.

If anyone can direct me to a website that describes these tools and procedures, I would appreciate it.

David Kumm

01-25-2013, 3:53 PM

Yes, the fan blade anemometer like the Velocitor or UEI DAFM is what I use. You move it around the opening and will see some variation in readings-10% or so. Take a rough average and convert to cfm. That will give you a pretty good idea of what cfm you have at each machine. If the machine says it needs 500 cfm and you have more life is good. Assuming the hood costs some and most machines can benefit from more than what is stated you want a good margin in excess. If you want to find out if the hood or internal routing is costing or if you need more make up air to satisfy the airflow you need further testing at the inlet. Dave

Eric Kipker

01-25-2013, 4:39 PM

I would recommend you go visit Bill Pentz's web site, before you purchase any meters. It is free and he has done a lot of the leg work. I managed the R&D department for a very large HVAC manufacturer before retiring, and had access to all kinds of meters while I was building my dust collection system, but never saw a need to bring a meter home, especially after reading through Bill's entire web site.

Michael W. Clark

01-25-2013, 4:56 PM

Here is a link for the pitot tubes
http://www.dwyer-inst.com/PDF_files/122d.pdf I would recommend the 167-12 for home use.

A u-tube manometer is probably the most veratile and cheapest. If you get a magnehellic, you will need two for the pressure range if you want to measure static pressure as well. For airflows, you want 0-2"wc (4005 FPM = 1"VP). For SP, you may want to be able to go to -10"wg, maybe higher depending on your system.

http://www.dwyer-inst.com/PDF_files/004.005.d.pdf You would probably best served with the 2002 and 2010 models
http://www.dwyer-inst.com/PDF_files/1211.d.pdf Probably the 1211-12 or 1211-16 would be best (don't forget the gauge fluid and tubing, but it maybe in the kit)

Mike

David Kumm

01-25-2013, 5:05 PM

Eric, Bill's site had the opposite effect on me. Maybe because I don't believe anything I read without some verification I wanted to know what the numbers were for my system. Not knowing the pressure drop of my cyclone or filters but knowing the fan curve of my Cincinnati blower, I needed some way to figure out cfm and how swapping a length of 7" for 8" etc affected the flow or what a drop of 6" necked to 4" delivered vs a full length of 4". There is no way to calculate that given the info we have available. Bill has written his stuff over a period of time so even his views have been refined and even modified. Most of the testing stuff costs less than choosing an incorrect sized pipe and fittings. Dave

Ole Anderson

01-26-2013, 8:58 AM

A u-tube manometer is probably the most veratile and cheapest. If you get a magnehellic, you will need two for the pressure range if you want to measure static pressure as well. For airflows, you want 0-2"wc (4005 FPM = 1"VP). For SP, you may want to be able to go to -10"wg, maybe higher depending on your system.

Mike

Make that three if you want to keep track of filter losses. After a while, that becomes the go-to gauge, everything else is a one-time measurement. Sometimes with my saw running I glance up at my gauges to make sure I turned on the DC. A low filter gauge reading means I remembered to close my last open gate before opening another.

michael osadchuk

01-28-2013, 12:28 PM

Vaughan

A different way to go is to buy an dust particle counter such as

www.dylosproducts.com

which is very useful in detecting problems in new dust collection points as well as more directly advising you of the air quality in the workshop.

More than a few woodworkers have the Dylos so if you do a search for 'dylos' in this forum you should get some further information on this option.

good luck

michael

Bernie May

01-29-2013, 9:11 AM

I second getting a Dylos meter. Best investment ever. First thing I turn on in the shop before I start. I was totally surprised at what I learned about the dust collection at different machines. who knew drill presses made so much dust or sweeping for that matter.

Vaughn Kaloust

03-12-2013, 4:21 PM

Thanks for all the advice and suggestions.

To start, I made a manometer from some plastic tubing and a yard stick. I used a plate with the clear tube mounted to it to measure at different tools in various points in my shop.

Although this tells me almost nothing about CFM or how truly effective dust collection will be at any particular tool, I thought it would give me some idea of how tight my system is.

I was a little surprised at the results??

1) I think my system is indeed pretty tight, as I could not find any difference in the vacuum at any of my outlets. All measured the same, or the difference was so small I could not detect it on my simple manometer.

2) Now, keeping in mind that I live at 5,000 feet in Denver, so I could never achieve the same type of vacuum that could be done at sea level. I could only pull about 3” on my manometer? This is much less than I expected, but I have no benchmark to measure this by, and maybe this is normal for a dust collector of this size.

I have a HF collector with the stock bag that came with it. But I had the outlet disconnected and made my first measurement directly at the inlet (the grate/grill is still in place as I have yet to remove it).
Just for fun I connected my shop vac up and did the same test, and of course it pulled enough of a vacuum to start sucking the water out of my manometer.

Does 3 inches of vacuum seem normal (at 5,000 foot altitude)?

Thanks

Paul Stoops

03-12-2013, 5:40 PM

Hi Vaughn,

Welcome to Sawmill Creek Forum!

Am I understanding you correctly that you blocked off your fan inlet with a plate and attached a manometer and got a reading of 3" WC? What is the HP of your DC motor? Do you know what the diameter of the fan impeller is?
That reading seems quite low, unless you have some serious leaks somewhere. I am not familiar with the HF dust collectors, but I would expect a static pressure of at least 6"-8" WC (or more) at the inlet with no back pressure from the outlet.
Has anyone on the forum measured the static pressure of an HF dust collector? Would the altitude in Denver affect the SP that much?

To measure CFM airflow in the ducts you will need additional test gear, as the folks above have explained. But it seems to me that it would be prudent to first understand why your static pressure is so low. There is a lot of experience in this area here on the SC forum, so we should be able to help you. Be patient, this DC stuff can be knarly.....................:-)

Michael W. Clark

03-12-2013, 6:33 PM

3" at the hood is good, kind of low at the fan inlet.
Mike

David Kumm

03-12-2013, 7:43 PM

The altitude correction factor is about 1.2 at 70 degrees and 5000 ft. Some harbor freight collectors run with a forward inclined blade. Provides high cfm at low pressure but really craps out a high. If you are running that configuration I would expect low but not that low. Dave

Mark Burnette

03-12-2013, 8:09 PM

For measuring velocity directly the ideal tool is a hot wire anemometer. This is a thin probe you insert in the flow. Inside the probe and exposed to the air is a length of wire heated by the instrument. Airflow cools the wire and the change in resistance is measured and converted to display velocity. Because its a thin probe it has little effect on what you are trying to measure--unlike the fan type which has a big effect on the airflow. Those cheap pocket-size fan anemometers are really only good for relative measurements in your own system. Not as a reproduceable measurement to compare with others, or with fan specs.

Vaughn Kaloust

03-12-2013, 8:28 PM

Hi Paul,

Yes, you pretty much have it right. I have a flat plate with my gauge hose connected to it. I placed this against the inlet side of my fan, with the outlet of the fan open to atmosphere, and no filter in use. After testing at the inlet, I hook up my manifold, which is a run of about 12 feet of 6” duct, and then test at each of 5 gates.

All tested at 3” on my simple manometer. It could be changing, but I can’t see any movement.

I did find a site which shows how altitude affects vacuum systems, and from what I can see, at 5,000 feet, I will have about 16.8% less vacuum that at sea level. So, guess that means that my 3” here at altitude would equate to about 3.4” at sea level.

http://www.anver.com/document/vacuum%20lifters/atmospheric%20pressure.htm

To answer a few of your questions, the HF is 2hp (really 1.5) and I think the impeller is 10”. I can’t imagine any leaks because all I have in the system is the impeller housing and a motor??

Hope that sheds some light on things.

Paul Stoops

03-12-2013, 9:54 PM

I certainly don't mean to insult your intelligence, but is it possible that the motor could be wired so that it is turning backwards? Is this a new unit, or did you purchase it from a previous owner? With the inlet and outlet open does it put out a lot of air? Do not run the motor this way for more than a few seconds so that you don't damage the motor.

Are you comfortable working around electric wiring? If so, I would disconnect the motor plug from the wall and open the motor junction box and inspect the wiring. Is it connected in accordance with the wiring diagram usually found inside the J-box cover? Are you running the DC on 110VAC or 220VAC? Are you using an extension cord?

Do you have a clamp on AC ammeter? Harbor Freight has them on sale right now and they are quite inexpensive but adequate for this job: http://www.harborfreight.com/clamp-on-digital-multimeter-95683.html

The motor current can be measured by clamping the meter around either one of the wires coming into the motor. Set the meter on the highest AC Current range and start the motor. How does the reading compare with the current rating on the motor label?

It has been my experience that in trying to troubleshoot a problem, it is best to eliminate each possibility one at a time. I hope this helps. The more information we have, the easier it will be for us to help.

Paul

Vaughn Kaloust

03-13-2013, 8:58 AM

This is a new 110v unit that was pre-wired. I have it on a 20 amp circuit, and it seems to be running fine. Seems to pull lots of air.

I am fairly familiar with both AC and DC circuits, and I have measured the amps and all seems good.

I may be giving the wrong impression about my system. I do not know if my system is performing well or not. It may be working great, but I have nothing to compare it to. What I am trying to find out is what would a good benchmark be for my system at my altitude?

I wanted to start with static pressure, and when I have that as good as I can get it, I will move on to CFM.

Thanks for the help.

Michael W. Clark

03-13-2013, 9:23 AM

Vaughn,
If you are measuring this SP at the fan inlet with the manifold connected as you describe (6" duct all the way to the machine), you should be pulling around 875-950 ACFM, assuming 5,000 ft AMSL. Your SP at the hood (near the opening) will be around 2"wg. You really don't have that much loss in the 6" duct. Your amp draw will be low due to less power required to move the lighter air.

Remember that SP and CFM are related for a given system. If you change one, you change the other. You can't really optimize one, then move on to the other to optimize it.

If you have the manometer, the next logical step to get CFM is to use a pitot tube. The 12" mini from Dwyer would be perfect for your needs. You can also use the pitot tube to measure SP, although sticking the hose to a hole on the side of the duct will work too.

Mike

Edit: I am not affiliated with Dwyer, just familiar with their products and use them.

Vaughn Kaloust

03-13-2013, 10:34 AM

Thanks Michael, but I am not measuring SP at the fan with the manifold connected. I am measuring it at the fan only, with the inlet connected to the manometer only. Here is a simple drawing of my setup.

256816

I have also done the same test with the manifold connected, but I am not measuring at the fan. I am simply moving my plate to the gates that are connected to the manifold. I also get the same 3" readings at each of those outlets, and you are correct that this seems right, as there is very little loss in the 6" duct.

No air is flowing in any of my test as the ducts are completely plugged and connected to my manometer only.

I am looking at the Dwyer gauge, and as soon as I am sure I have good SP I will move on to the CFM question.

Paul Stoops

03-13-2013, 10:57 AM

Hi Vaughn,
I am still puzzled by the low SP. With the inlet and outlet open, what motor amperage did you measure? What is the motor nameplate rating? Under those conditions, you should see motor amperages at least as high as the nameplate rating and probably higher. If the amperage is low, I would suspect a problem with the motor, or possibly something related to the incoming line, such as a faulty breaker, bad connection, other devices on the same circuit, etc.

The SP and CFM are interrelated, and having a low SP will make it difficult to obtain a high CFM without the SP to overcome system losses. I notice in the new testing that WOOD magazine reported in the current issue that they list 800CFM @ 5.5"WC Static Pressure as being the minimum they recommend for a typical shop layout, tho they do indicate that shorter runs can be accommodated with lower numbers.

Vaughn Kaloust

03-13-2013, 11:46 AM

Rod Sheridan

03-13-2013, 11:57 AM

Hi Vaughn, can you verify that your impeller is rotating in the correct direction?

If I understand your test setup, you completely blocked the airflow with your test plate at the fan inlet and only measured 3"WC?

That seems far too low, I would expect somewhere around 8"WC with no airflow........Regards, Rod.

Vaughn Kaloust

03-13-2013, 12:09 PM

Hi Rod, I agree that 3" WC seems too low. I can check the impeller, but if it were running backwards, wouldn't I get pressure and not vacuum at the inlet side of it? I would think that would be the case anyway?

Paul Stoops

03-13-2013, 12:10 PM

I agree with Rod, the SP is way too low, even for your altitude. I checked the HF website and the 2Hp Model 97869 is listed at 20A peak. That tells me that it should be pulling a lot more than 8-9 Amps with the inlet and outlet open, in spite of you altitude. Are you sure you are at ~5000 ft. and not 65000 ft? :-)

I would check the motor wiring against the diagram that should be under the j-box cover. It sure sounds like the motor is running backwards to me. Please let us know what you find.

Paul

Michael W. Clark

03-13-2013, 12:46 PM

Vaughn,
There are threads on here about the wheel running backwards on the HF units.

I am not sure by your diagram how you are measuring SP? SP acts in all directions and is usually measured perpendicular to airflow. Simply drill a hole in the side of the duct and cover it with the open end of the tube. Make sure the other end of the manometer is vented to ambient. The reading is the total displacement between the two columns of water (+ on one side, - on the other), not just how much the fluid moves on one side. If you are putting the tube in the inlet or inside the branch duct, you will get wacky readings. Just cover the drilled holes with duct tape when you are done. A 3/16" hole works well with the Dwyer mini, you need a 3/8" hole with the full size pitot tube. Just saying this so you only have to drill the holes once if you get a pitot tube in the future.

Shut all your gates and measure the SP, it should be maxed out and well above 3"wg. Your amp draw will also be minimal (not moving any air). Next open all the gates and read it again, you should have a much lower SP and much higher amp draw. I don't know that you will be able to trip the breaker or get FLA at your elevation. The HP requirement is less due to the thinner air.

Mike

Vaughn Kaloust

03-13-2013, 1:10 PM

Sorry Paul, there seems to be no wiring diagram anywhere on the motor.

I am not sure if the impeller is turning the right way or not. I just checked it, and the best I can do is to show it in a picture. Hopefully someone can tell if this is the correct direction.

256833

Vaughn Kaloust

03-13-2013, 1:19 PM

Michael, You may have found my mistake. As I show in my simple drawing, I am not adding the amount the manometer rises on one side, to the amount it falls on the other side. If that is how it is supposed to be done, I have screwed this up, and I am actually getting 6” WC. Is this correct? I mean are you supposed to add how much the water drops on one side to the amount it rises on the other side?

Paul Stoops

03-13-2013, 1:24 PM

David Kumm

03-13-2013, 1:38 PM

This may sound a little wacky, but could you post a pic of your wiring in the J-box? Maybe we could figure out how to reverse the direction of the motor for a test. I am not familiar with curved bladed impellers, so I don't know which way it should rotate.

The rotation is correct if the drawing is correct. Most blades on DC impellers bend the other direction. HF to my knowledge is the only one using a forward curved blade. They deliver more cfm at lower pressure but generally are not as desireable at working pressures. I don't why they do what they do. Dave

Paul Stoops

03-13-2013, 1:39 PM

Yes, I think you measure the difference between the height of the liquid on each side.
From Bill Pentz's site:
"This test measures the vacuum
that "pulls" the air through the tube so the water on the side of the gauge
gets pulled up causing the water on the other side to go down. Do not
measure the water height from the center, measure from both ends of the
water column. This Max. SP should be the highest pressure you will ever
see from the blower.

If you are actually seeing 6" WC, that is probably okay, considering your altitude -- as they say,"Bigger is better" in this case.

Vaughn Kaloust

03-13-2013, 3:20 PM

OK. So this is where I am at now.

Thanks to David, I now know the DC is turning in the right direction.

I also know that I am actually measuring 6” WC thanks to Michael and Paul, and the 3” WC was pilot error (I was the pilot).

The only question left to answer is why I am pulling only 8.5 amps at full load, and I will check into that. I guess that will be either pilot error again, or the altitude really affects the load on the impeller.

Thanks to everyone for helping me understand this better.

Michael W. Clark

03-13-2013, 7:26 PM

Any idea what the FLA rating is for your motor?

Vaughn Kaloust

03-13-2013, 10:07 PM

Well, the specs say it is a 20 amp motor, but most of the threads I have read say that it starts at about 20 amps and then immediately drops to about 14-15 amps. This is under a load, meaning that at least one blast gate is open. I assume that with no gates open it would run at about 7-10 amps.

I am now considering that my problems, including the low amp draw, could be because the impeller is just too small for my altitude. This seems to be pretty well known to some of the experts, as they recommend a larger impeller for higher altitudes.

Wish I could just add a slightly bigger impeller to mine as it looks like it could hold a 12" (has a 10" now).

David Kumm

03-13-2013, 11:12 PM

10" is too small to pull much cfm at pressure. Since the altitude also allows for a lower hp motor- correction is 1.2 also- you could use a 12". I would get the blades bent in the other direction or a straight blade impeller. Almost any impeller with the correct sized arbor should work. most housings are reversable so you can correct for the blade configuration. Dave

Vaughn Kaloust

03-13-2013, 11:38 PM

Wow, thanks Dave. I have been searching the net to see what I could find, but all I have found were blades that are straight and I thought that wouldn't work.

So just to see if I have this right, you are saying that I should be able to use a straight blade, 12" impeller? And it obviously needs to fit in the housing and on the shaft. I think Jet has one that will work. I think if I can get to 12" it will draw a more appropriate amount of amps. and improve CFM dramatically!

Any other recommendations?

Michael W. Clark

03-13-2013, 11:42 PM

Vaughn
Take a look at this link.
http://www.cincinnatifan.com/catalogs/SPB-401-internet.pdf

On page 5, there is a good explanation on how to use the tables at different densities. If you go through the example, this will give you a good insight on the effects of density and fan selection. You and David are correct that a larger fan and/or higher RPM is needed at lower densities to move the same volume. However, the HP requirement goes down as apposed to operating at standard conditions.

There is also a picture of a typical BC fan wheel which is opposite your HF wheel. You may be able to order a wheel from Cincinnati Fan if you are interested in a replacement. I think there was a thread on here several months ago where someone reversed the rotational direction of their HF wheel and saw a significant increase in motor amps (increased volume)?

Mike

David Kumm

03-13-2013, 11:47 PM

Vaughn, three things to expect with a straight blade impeller.

1. It will be loud. Like an airplane
2. It will pull more cfm when hooked to pipe and flex but less with no restriction
3. It will pull more amps. Should be no problem but to be safe you want to check the amp draw closed and then open one gate and check. Finally all open to make sure you are not exceeding FLA. If by chance you are you just can't run it with all gates open. I don't believe you will have a problem at that altitude and the straight blades may be a help at that altitude.

Any Grizzly, Asian fan should work. Dave

Vaughn Kaloust

03-14-2013, 12:17 AM

Mike and Dave, thanks for all the effort.

Mike, really good info. I may give them a call tomorrow, but looks like they may be high dollar,but you never know.

Dave,
1) NP as I am nearly deaf already. :rolleyes: I do wear ear protection in the shop.
2) Good! I only need the CFM when I am connected to the ducting, so that works perfectly. :D
3) I will follow these directions to the letter. And Paul already sent me a PM where he showed me his setup for monitoring amperage, and I will get that hooked up before I start testing.

This forum has been so helpful to me today. Thanks to all.

David Kumm

03-14-2013, 12:26 AM

I find the Cincinnati fan tables so useful I printed them out for several models. Ebay and CL are good sources for stand alone blowers. I bought a 7.5 hp CF RBE9 for $600 that included a Baldor motor. Smaller ones can go pretty cheap. If you have the CF brochures you can watch for the right one. Dave

Mark Burnette

03-14-2013, 12:22 PM

...Paul already sent me a PM where he showed me his setup for monitoring amperage, and I will get that hooked up before I start testing.
I'm interested in some ideas on monitoring fan current. All the handy "Killawatt"-like devices I've seen are 120V only. 240V ones on eBay that I saw all had european round pins on the back. Also on the 'Bay I found this cheap ($15) idea:

http://thumbs2.ebaystatic.com/d/l225/m/mbOS-YY8jsolty0uiJ3gKFw.jpg

search "240V amp meter"

I'm considering building this into my contactor box if there's room.
Any other ideas?

John Lanciani

03-14-2013, 12:52 PM

I'm interested in some ideas on monitoring fan current. All the handy "Killawatt"-like devices I've seen are 120V only. 240V ones on eBay that I saw all had european round pins on the back. Also on the 'Bay I found this cheap ($15) idea:

http://thumbs2.ebaystatic.com/d/l225/m/mbOS-YY8jsolty0uiJ3gKFw.jpg

search "240V amp meter"

I'm considering building this into my contactor box if there's room.
Any other ideas?

I'm going to give one of these a try, too. You might want to search for item #310604994957 on the bay, exact same meter for $8.99 shipped. For 9 bucks it's worth giving it a shot.

Carl Beckett

03-14-2013, 7:07 PM

I'm going to give one of these a try, too. You might want to search for item #310604994957 on the bay, exact same meter for $8.99 shipped. For 9 bucks it's worth giving it a shot.

I have seen generator hookup panels with this basic setup. I had a grizzly drum sander that had an ammeter... I wonder if you could purchase these components as if they were a replacement part? (should already be calibrated that way)

Edit: just took a look and this one has the pickup included

http://www.ebay.com/itm/Digital-AC-300V-50A-Blue-LCD-Amp-Volt-Ammeter-voltage-Panel-Meter-110v-220v-/180920422127?_trksid=p2047675.m2109&_trkparms=aid%3D555003%26algo%3DPW.CAT%26ao%3D1%26 asc%3D142%26meid%3D6247225418680475330%26pid%3D100 010%26prg%3D1076%26rk%3D5%26sd%3D181004140330%26

John Lanciani

03-14-2013, 8:02 PM

I have seen generator hookup panels with this basic setup. I had a grizzly drum sander that had an ammeter... I wonder if you could purchase these components as if they were a replacement part? (should already be calibrated that way)

Edit: just took a look and this one has the pickup included

http://www.ebay.com/itm/Digital-AC-300V-50A-Blue-LCD-Amp-Volt-Ammeter-voltage-Panel-Meter-110v-220v-/180920422127?_trksid=p2047675.m2109&_trkparms=aid%3D555003%26algo%3DPW.CAT%26ao%3D1%26 asc%3D142%26meid%3D6247225418680475330%26pid%3D100 010%26prg%3D1076%26rk%3D5%26sd%3D181004140330%26

The one I referenced includes the current transformer too. I'm going to incorperate it into my drum sander, I'll keep you posted.

Chris Parks

03-14-2013, 8:34 PM

We have been using these Ebay ammeters on installations and they work well.

Paul Stoops

03-14-2013, 9:37 PM

Wow! That looks like just the ticket! I am going to look into incorporating one into my Performax sander since it doesn't have the SmartSand feature. Like other folks I have had problems with unintentional overloading and tripping the breaker. For those of you who have used this meter, what is the input drive voltage across the two leads on the back of the meter, or does it just hook up to the incoming line?

The information Mark was mentioning was in reference to using a clamp-on ammeter and a shop made current loop for monitoring my DC motor current. If I like this meter , I may change my DC monitoring system to incorporate this device since it is so compact and will work with 220VAC.

Thanks guys for sharing this information.

Paul

Mark Burnette

03-15-2013, 10:26 AM

The eBay meter gets its power off the line. They are available with 2 different pickup configurations: onboard current loop, and remote current loop. With either version you just pass one of the wires through the loop. The onboard version is simpler but the remote version might be a better choice in a tight spot or if the display isn't close to the motor wires.

I ordered mine last night. I couldn't find a single seller that ships from the US so we have to wait a couple weeks for it to arrive from China :rolleyes:

How is it packages can be shipped from China cheaper than I can ship local?

Paul Stoops

03-15-2013, 11:02 AM

Thanks, Mark, for the information. Looking forward to getting some of them for my shop.

Joe Hillmann

03-15-2013, 1:15 PM

Michael W. Clark

03-15-2013, 1:54 PM

A pitot tube is the cheapest way to figure out air speed, cfm and suction pretty accurately. The problem is finding charts online otherwise you have to do quite a bit of math. If you do a google search for "Kevin Horton pitot tube air speed" you should be able to find a chart that goes from 15 mph up to 200 which is where I started when trying to figure out which blower to use for my laser ventilation.

Joe, you can use the following formula. This is what the tables are based on. It has a conversion factor in it for the units commonly used in DC.

V=VP x sqrt(4005/df)
where
V = duct velocity, ft/min
VP = velocity pressure measured from pitot tube (differential), "wc
df = density factor, 1.0 for standard air, <1.0 for less dense air (high altitude, high temp, low pressure, moisture), it is the ratio of the actual density to the standard density. For most applications here it will be 1.0 unless you are affected by altitude. The temp, pressure, and moisture corrections for most home ww shops are negligible.

You could easily make a table in the units used for DC instead of working in MPH. (ACGIH already has this table at standard density for both VP to V and V to VP conversions)

When using the pitot tube, read the VP at multiple locations across the duct area, calculate velocity for each reading, then average the velocities (don't average the VP readings). Multiply the average velocity by the duct area in ft2, you have the ACFM. As you can imagine, this lends itself very well to a spreadsheet when doing multiple readings.

Make sure to keep the pitot tube pointed directly into the airflow and that the ports do not get plugged with particulate.

To get SP, swap the hoses, but only read the SP port. This the one perpendicular to the main stem of the pitot tube. Place the tube in the duct just as you were taking an airflow (VP) reading. This gives you the SP and the correct sign (+/-). You should be able to take this in one or two places within the duct and get a good reading.

Because of the mathematical relationship between SP and CFM, SP is very useful and quick to measure for future checks. It is often used to verify flow and contol system flow without the significant investment in flow meters and their assiciated maintenance cost. However, the SP and flow relationship has to be defined initially for it to work.

Mike

Mark Burnette

03-16-2013, 11:46 AM

A pitot tube is the cheapest way to figure out air speed, cfm and suction pretty accurately. ...
Does a pitot tube interfere with airflow in a 6" or 4" pipe? I'm only familiar with it's use in free space.
Cheapest isn't best or accurate if the instrument interferes with the measurand. This is the #1 bugaboo in measurement & instrumentation.

Michael W. Clark

03-16-2013, 1:02 PM

Mark, it shouldn't affect the flow reading. As long as you don't change the velocity of the air or the static pressure, you will get good readings. Accuracy is usually guaranteed +/-10% for NEBB and EPA. The manufacturer's claim +/- 5%. Repeatability is usually within 1%. I like the mini for small ducts. I've never used a Pitot in free space, not sure how that is done? I've used an airfoil (by Shortridge Inst.) and was back checked by an anemometer for hood face velocities. They came out the same.

We tried anemometers, but they get out of calibration quickly in dirty airstreams. HVAC people have good success with them but DC systems are very dirty and mess them up. We also had trouble with factory calibration on the anemometers, I was told they didn't agree with the pitot tubes directly back from calibration. It could have been the brand, not sure. It was before my tenure.

Mike

Bill Space

03-19-2013, 8:24 PM

Hi,

I started reading this thread and must admit I did not get past the first page...

Anyway, after all the measurements are made and all the analyses are completed, at the end of the day the real measure of dust collector performance in my mind is how well the system works.

Are chips and dust being collected satisfactorily? Does the system filter out the fines well enough that dust is not being dispersed from the dust collector bags? IF the answer to these and possible other questions is yes, the system is performing satisfactorily. If chips/fines clog up the piping at the machines, or if the shop becomes a dust laden atmosphere when the dust collector is used, the system needs improvement.

That is the way I see it anyway. Measure all you want, but your machines and eyes (and lungs) should give you an answer pretty clearly...

Bill

Jim German

03-20-2013, 9:01 AM

Measure all you want, but your machines and eyes (and lungs) should give you an answer pretty clearly... You can't see dust particles smaller than ~20 microns and the health effects of particularly small particles (0.3-0.5 range) may not be immediately evident. Particles in that size range are hard for your lungs to filter out (just like they are hard for filters to capture) and they can get deep into the alveoli of your lungs.

Chris Parks

03-20-2013, 9:19 AM

Mark Burnette

03-20-2013, 12:34 PM

You can't see dust particles smaller than ~20 microns and the health effects of particularly small particles (0.3-0.5 range) may not be immediately evident. Particles in that size range are hard for your lungs to filter out (just like they are hard for filters to capture) and they can get deep into the alveoli of your lungs.
This line of reasoning reminds me that Dylos readings of tiny particles outdoors are usually higher than readings in workshops with decent (but not cutting-edge micron-efficient) collectors. Our lungs deal with this size particle quite well. It's the sub-micron smoke, toxic particles and allergens that cause trouble. With DC's all improvements are good (but not necessarily cost effective) but we shouldn't use scare tactics a la Pentz to drive people to spend ridiculous money on "nano technology" filters & such.

David Kumm

03-20-2013, 1:22 PM

Actually Nanofilters are pretty reasonable if appropriate and Beane bags can be had for > $50. If you do a little homework you can get a pretty decent system for the price of a few artery clogging meals. Dave

Bill Space

03-20-2013, 3:02 PM

You can't see dust particles smaller than ~20 microns and the health effects of particularly small particles (0.3-0.5 range) may not be immediately evident. Particles in that size range are hard for your lungs to filter out (just like they are hard for filters to capture) and they can get deep into the alveoli of your lungs.

Jim,

I am sure this is true. But all measurements of dust collector performance like power usage, flow measurements and so on give no useful information on particle size either.

My comments were directed towards the aspect most of the measurements mentioned above, related to moving dust/chips from the tools to the collector.

But you do bring up A good question! How can we evaluate the particle size being emitted from our dust collectors?

Manufacturers claims may not satisfy everyone and may be inflated for marketing reasons, or not easily repeated in the real world...

I do not know the answer...

Bill Space

03-20-2013, 6:45 PM

Well as threatened, I will try to attach a few pictures of my "chip separator".

This is the setup. Note the window in the door. Best improvement I ever made. Before that I had to guess when the garbage can that catches the chips was full. If I were late...well, I had to make some dust transferring the extra into something else...

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You can see the baffle inside that directs the stream down towards the bottom of the enclosure. All the bigger chips and some dust drops into the plastic can. The 6" pipe from the dust collector connects at the top of the baffle, on the left side.

257701

I will have to go to a second post as somehow I cannot get the third image to upload...

Edit: For some reason I can't upload images to the second post either, but I don't think it matters as these two are enough to tell the story. The piping from the machines come into the top, and there are two inlets, as that was the most convenient way for me to run my piping. Since each tool has blast gates, the number of pipes coming into the top is a matter of convenience, dependent upon how you need to run your pipe.

As far as filtering capability, a dust collector is what it is, and certainly clears the air better than not having a dust collector. I am happy with the performance of this simple system, and there is no doubt that it keeps a lot of stuff out of the air in the shop. But it is not an air purifier by any means. But it does enhance the overall performance of the Grizzly unit, as it is much simpler to just open the door and drag the plastic can out, without having to deal with the cloth bags. Also, I believe the bags filter a little better as they get coated on the inside with fine particles. At some point they need to be taken off and cleaned of that buildup, when the air restriction becomes too great.

Hope this is of some interest!

Bill

Michael W. Clark

03-20-2013, 9:28 PM

Hi Bill,
That is the classic drop-out box. They actually work quite well if you have the space. The trade-off on those versus a centrifugal type of separator is that a centrifugal separator can get better efficiency in a smaller space. The consequence is more energy required (pressure drop) for the centrifugal separator, in otherwords, there is no free lunch. The drop-out box has less pressure drop (theoretically speaking), so you get to maximize the CFM and make sure the dust gets in the duct.

The OP asked specifically about CFM in his post and eventually effects of elevation. True, a particle counter is the ultimate measure, but it won't tell you anything about CFM, density, etc if that is the concern. The particle counter will point out that there is a problem and how bad it is, but it will not direct you in how to fix it. Am I loosing the dust at the filter, leaks, at the hood, do I need more flow, more pressure, clean/replace the filters, etc.

Thank you for your post of the drop-out box!

Mike

Chris Parks

03-21-2013, 1:45 AM

At the least the dust counter tells you that a problem exists. A lot of people would be or are under the illusion that because they installed a DE that the problem is gone. So if you don't take any steps to check the dust levels you are under an illusion that the advice you have received and what you did with that information has resolved the dust problem to a level that is inconsequential. I would bet money that most installations do not function to the level that is ideal for our health.

Rod Sheridan

03-21-2013, 8:58 AM

Chris, I was amazed when I received my particle counter and found that the cyclone reduced the particle count of the shop air to 25% of the outside air count after running for 10 minutes.

It also demonstarted how poor the collection on my band saw was, something I've improved with a small box and a bungee cord.

Regards, Rod.

Vaughn Kaloust

04-07-2013, 1:01 PM

Has anyone received one of these amp meters yet? I bought one about 3 weeks ago, but it hasn't arrived yet. Just wondering if it got lost in transit from Hong Kong?

Paul Stoops

04-07-2013, 2:24 PM

Chris Parks

04-07-2013, 8:05 PM

Mine took so long to arrive I wrote it off to experience then lo & behold it arrived some weeks later.

Chris Parks

04-07-2013, 8:08 PM

Hi Vaughn,
Yes, I ordered mine on 3/15 and received them 4/5, so it does take a while. That said, these look like a terrific value -- especially for $3.29 ea. + $5.99 S&H. I do not understand how they can sell these things at this price -- wonder if they pay their worker bees in grains of rice.......................???

Paul

I don't understand the Chinese logic but I do approve of it in my case. I buy direct from a factory about 25 VFD's a year and I get treated as though I buy thousands. Nothing is too much trouble for them even to the point they will ring me if necessary. It is the ultimate customer experience.

Vaughn Kaloust

04-07-2013, 8:48 PM

OK, good to hear. Thanks!

Pretty amazing the price on these. Have any of you used them yet? How do they work? I was half expecting to receive an empty case because of the price, so I am anxious to hear your experience with these meters. I can think of more uses if they work well.

Chris Parks

04-07-2013, 10:17 PM

They work.

Mark Burnette

04-08-2013, 10:51 AM

Also bought mine 3/15 and it arrived 4/5. Not installed yet.

FWIW a co-worker asked me if I had any suggestions for him to rig up a wireless remote so a thermostat in one room can operate a fan in another. I told him of my experience with cheap Chinese eBay stuff. He bought a 4 channel remote receiver & keyfob transmitter for under $10 and it works great with enough range to operate it anywhere in his house. Amazing how little these things really cost to make & ship. As a consumer I'm happy but we're doomed as a producer.

Dan Schrecongost

04-13-2013, 11:36 AM

OK, I measured the amperage in both conditions. With no load (all inlets closed) I am pulling 7.9 amps. This seems ok to me based on what I have read. With a completely open system, I am only pulling 8.5 amps. This seems wrong because the DC should be working at maximum load. I would expect at least 14 to 18 amps. I have read others with the same HF dust collector often tripping 15 amp circuit breakers, so I know that similar systems often pull about 15 amps.

I have this on a brand new dedicated 20 amp circuit, and have never tripped it. I guess I never will if it only pulls 8-9 amps. Lol

Maybe the air is so thin at 5,000 feet that this is normal?? Or maybe something really is wrong.

Is there anyone at a similar altitude that can that can compare readings with me?

Paul, there is no plate on the motor, but I have read a lot on forums about this DC and know it is called a 2hp, but is actually about 1.5 hp. It also seems to pull just about 15 amps in normal operation for most people that have the same unit.

Again, remember this seems to be moving a lot of air, so I don't even know if I have a problem?

I recently tested the HF 2 HP DC using a pitot tube and digital manometer ( Shortridge Instr.). This is a new DC; the motor does not have a nameplate so full load amps is unknown. The impeller is 10" diameter, forward curved. There are 7 blades on the impeller, so if you measure tip to tip you get 9.75", but center of shaft to tip is 5", so the diameter is really 10".

The motor drew up to 60 amps at start-up but quickly settled down at 13.1 amps. True power was 1.12 kw. I tested using a new oversized felt filter, 10 feet of 5" galvanized duct connected directly to the blower with the open end of the duct bare ( i.e., no flat plate or bell mouth). Measurements were made 5 feet from the fan inlet.

Velocity was 5115 feet/min, static pressure was 3.08 inches water column. Airflow was calculated as 628 cfm using the center of duct velocity x 0.9. My altitude is 1250 feet.
259836

Michael W. Clark

04-13-2013, 11:57 AM

Dan,
Cool to see someone else familiar with the Shortridge. That is the one we used when doing system balancing and troubleshooting. Great instrument.

One question though, why did you use the center of duct velocity instead of averaging multiple points? Not that I am saying there will be a noticable variation with your setup, but taking multiple readings quickly and averaging them is the strength of the Shortridge (what you pay for).

Edit: If your density is less, then the ACFM is higher at the same pressure drop at standard conditions. It looks like you reduced your airflow based on a lighter density (elevation) so your airflow would be closer to 700 ACFM.

David L Morse

04-13-2013, 3:18 PM

I recently tested the HF 2 HP DC using a pitot tube and digital manometer ( Shortridge Instr.). This is a new DC; the motor does not have a nameplate so full load amps is unknown. The impeller is 10" diameter, forward curved. There are 7 blades on the impeller, so if you measure tip to tip you get 9.75", but center of shaft to tip is 5", so the diameter is really 10".

The motor drew up to 60 amps at start-up but quickly settled down at 13.1 amps. True power was 1.12 kw. I tested using a new oversized felt filter, 10 feet of 5" galvanized duct connected directly to the blower with the open end of the duct bare ( i.e., no flat plate or bell mouth). Measurements were made 5 feet from the fan inlet.

Velocity was 5115 feet/min, static pressure was 3.08 inches water column. Airflow was calculated as 628 cfm using the center of duct velocity x 0.9. My altitude is 1250 feet.
Thanks Dan. I recently did some testing on my HF DC using a homemade manometer and pitot tube and am glad to see measurements made with professional equipment that are in reasonable agreement with mine.
I was actually evaluating the effects on performance of a Thien baffle added to the collector ring. The following was obtained with the homemade instruments at an altitude of 670ft and and averaging factor of .83 instead of .9:
259852
I sometimes get a bit enthusiastic about taking data (my family calls it something else) so I also took motor current readings along with the pressure and flow data:
259853
The excellent fit of the regression line means that I can reliably use motor current as an in situ measurement of total CFM!

Dan Schrecongost

04-13-2013, 3:22 PM

Vaughn Kaloust

04-13-2013, 4:59 PM

Hi David,

This is some great data, and looks to confirm my original thought that the performance of my HF collector is less than optimal primarily because of my altitude. The main difference is that you are able to obtain higher amps than I am, and I also think this is because of air density.

I am going to try to get the Rikon 12” impeller, and hopefully that will give me a bump in performance, but I do have a question.

How did you make a homemade pitot tube?

Dan,

Also great data, and seems that you have the proper tools to do these measurements.

You said that you got 3.08 inches of WC in your SP test, and I am wondering if I am confused as to how to do this test. The reason I ask is that I originally did this test with a homemade manometer, and I got about 3” also. But then I found out that I had to add both sides of the water column together to get the correct reading. So, in my case the water went up 3” on one side and down 3” inches on the other, for a total of 6” SP. This seemed to match what others were getting after correcting for my altitude. They were getting about 7-8” and that seems to match the graph that David just gave us.

Can you advise me on the correct way to measure SP?

Thanks

Michael W. Clark

04-13-2013, 5:30 PM

Michael-
Laziness? I was testing the impact of blower-to-filter ring combinations for three different blowers, so I was interested in relative airflows, rather than very accurate measurements of a single installation. By using the 0.90 factor, I was compensating for the center of duct air velocity being faster than other locations in the duct, a shortcut recommended in the Shortridge manual and Bill Pentz's website.

Hi Dan,
I understand, I thought you had done the readings to check performance and couldn't understand why you would do it that way considering the accuracy and speed of the shortridge.

Mike

Michael W. Clark

04-13-2013, 5:37 PM

altitude of 670ft and and averaging factor of .83

What is the 0.83 factor for?

Mike

David L Morse

04-13-2013, 6:02 PM

What is the 0.83 factor for?

Mike
It's the ratio of average flow in a pipe to flow at the center.
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Reynolds number is around 2x10^5 for typical dust collector flows. From the graph you can see that the value is pretty flat in that range.

David L Morse

04-13-2013, 9:16 PM

How did you make a homemade pitot tube?

First of all I want it to be clear that I made a pitot tube NOT a pitot-static tube. The latter is a moderately difficult to build arrangement of two coaxial tubes with the inner one generally used for measuring the stagnation pressure with a port at the front and the outer tube with ports along the sides to measure static pressure. This works well for measuring local velocity in complex geometries but requires accurate alignment with the flow and sometimes some calibration to get accurate static values. When flow is constrained to the interior of a round pipe it's much easier and actually more accurate to measure static pressure at the wall, thus a simple pitot tube suffices for measuring total pressure at the center.

I dug out a wad of 1/4" Copper tubing from the scrap barrel and managed to form some of it into an "L" shape. I hammered one end into a rough hemisphere and tapped the other 10-32 to match my pressure fittings (http://www.mcmaster.com/#catalog/119/163/=mb5whc) (I've put these in various places on my DC for pressure measurements).
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The scrap pile also yielded a 30" length of 4" S&D pipe. I would have preferred somewhat longer but that's what I had. A hole and some hot glue for the pitot and a tapped hole for the static port and it's time to measure some CFM.
259865259866

Michael W. Clark

04-13-2013, 9:22 PM

David L Morse

04-13-2013, 9:26 PM

As long as you have enough straight duct up and downstream of your reading for the profile to develop.

Most of the readings I have had to do are in less than ideal spots and velocity can vary significantly from one side of the duct to the other.
Agreed. A longer test section would have been better but I wasn't willing to make a trip to the borg for a 10' piece.

Michael W. Clark

04-14-2013, 12:15 AM

Agreed. A longer test section would have been better but I wasn't willing to make a trip to the borg for a 10' piece.

Hi David,
I did not intend to suggest that you need a longer duct. My point is that, in most cases, you rarely have enough straight duct to have a fully developed velocity profile at your measurement location. The widely accepted method for pitot tube readings is to take readings at multiple points over the cross section of the duct and record the pressures, convert them to velocities, then average them to get the average duct velocity. Using this method, there is no factor unless you are correcting for non-standard air or are using a pitot tube with a calibration factor (s-types). Most air is non-standard, but you have quite a bit of leeway on the conditions before seeing a significant impact on the flow reading.

Mike

Dan Schrecongost

04-14-2013, 10:23 AM

Hi David,

You said that you got 3.08 inches of WC in your SP test, and I am wondering if I am confused as to how to do this test. The reason I ask is that I originally did this test with a homemade manometer, and I got about 3” also. But then I found out that I had to add both sides of the water column together to get the correct reading. So, in my case the water went up 3” on one side and down 3” inches on the other, for a total of 6” SP. This seemed to match what others were getting after correcting for my altitude. They were getting about 7-8” and that seems to match the graph that David just gave us.

Can you advise me on the correct way to measure SP?

Thanks

Both of our readings are correct; we were measuring different points along the fan curve, however. You measured a higher static pressure because there was no airflow whereas I had 10 feet of 5" duct with an open end, therefore substantial airflow and lower static pressure.

If you look at Davids 1st curve above, look for the point on the curve that matches your static pressure reading, then drop down to the horizontal axis to read the CFM. Then do the same with my 3" SP reading. Basically, the fan curve tells you all of the combinations of CFM and static pressure that it is capable of providing. Where the fan actually performs depends on the system of ductwork, filters, etc. that you ask it to work with. So in one installation, it may perform at a higher CFM and lower SP because the duct system imposes lower friction losses than it would in a different installation.

Dan Schrecongost

04-14-2013, 10:38 AM

The excellent fit of the regression line means that I can reliably use motor current as an in situ measurement of total CFM!

David-

Great test data! Your family is right! :-) My family feels the same way about me, BTW.

The motor amperage vs. airflow shows a great correlation, but it is important to note that the amperage axis ranges from 8 to 13, not 0 to 13. So a 10% drop in amperage does not equal a 10% drop in airflow. This is because some current is required to energize the stator in the motor in order to set up the magnetic field that the rotor reacts to. This current is required regardless of the motor loading. For motors, volts x amps x power factor x square root(# phases) = watts. The power factor may be as high as 0.90 when a motor is fully loaded but drops as the motor unloads. Below 50% loading, power factor falls off quickly.

Thanks for sharing your data. The fan curves with the various filters and baffle for the HF 2HP will be very helpful to many of us.

-Dan