Anybody installed a Filter Efficiency Gauge from Oneida?

[Ben Martin]

So I have to laugh about this one...

I had been scouring eBay lately for the parts to build the filter efficiency gauge myself, I had put in lowball offers on a couple of gauges but didn't win anything. I had book marked a auction earlier that appeared to include everything that I needed including the gauges, tubing and pitot tube but was a bit more. I decided to quit wasting time and just buy what I thought was the complete kit.

Needless to say I started laughing when I received the package and discovered that what I had bought (not advertised as such) was the Oneida Filter Efficiency kit, complete in original box. Just missing the instructions. So a quick call to Oneida and I have the instructions in hand. Now just need a break from the nursery build to get it installed!

Some times you get lucky! I paid $42 when Oneida is selling this for $120.





Ben

[Ole Anderson]

I have a 1-5" magnahelic on my 2 hp Oneida. The suction loss you see is a function of two things, filter clogging and air flow. Best to read your gage with a standard number of gates open, I usually read mine with both my TS top (3") and bottom (5") gates open, pulling about 1000 cfm. New I was reading 1.3" if I remember correctly, now even with my best cleaning it rarely gets below 1.6" and I clean it when it gets near 3" or when I dump the container. My best filter cleaning finishes up with a trip outside and a visit to my Stihl leaf blower.

And maybe Mr. Clark can help out here, but I don't see the necessity of the "L" shaped inlet for just measuring static pressure in a duct. I just drilled and tapped the duct for the barbed x 1/4" brass fitting that came with my gage. And doing it again, I might just opt for using a clear plastic "U" tube with colored water in it.

[Ben Martin]

And maybe Mr. Clark can help out here, but I don't see the necessity of the "L" shaped inlet for just measuring static pressure in a duct. I just drilled and tapped the duct for the barbed x 1/4" brass fitting that came with my gage. And doing it again, I might just opt for using a clear plastic "U" tube with colored water in it.

A Pitot tube is it's engineering name, . If you just drill a hole you are only measuring the static pressue. The Pitot tube measures the static and dynamic pressure passing by, called total pressure. The Magnehelic gauge is than measuring the difference between the atmospheric and total pressure. It also prevent dust from getting into the tube/gauge.

http://en.wikipedia.org/wiki/Pitot_tube

Ben

[Ole Anderson]

A Pitot tube is it's engineering name, . If you just drill a hole you are only measuring the static pressue. The Pitot tube measures the static and dynamic pressure passing by, called total pressure. The Magnehelic gauge is than measuring the difference between the atmospheric and total pressure. It also prevent dust from getting into the tube/gauge.

http://en.wikipedia.org/wiki/Pitot_tube

Ben

I guess my brain must be on vacation too, pitot tube, I knew that. But when measuring filter losses, do you really want anything more than static pressure? That was my real question. You need dynamic pressure when measuring velocity, but we aren't measuring velocity, just static pressure, which begs my question, why did Oneida include a pitot tube in the kit? And if it is for keeping dust out of the gage, which way is the tube pointed in the airstream? By the way, I think I would be very difficult for dust to make it way all the way up the tube to the gage because as soon as the pressure differential returns to zero, and dust would just be pushed back into the duct from the pressure built up in the tube.

[Michael W. Clark]

Ben, see if the L-shaped probe has a hole in the end and/or holes in the side. I've seen SP probes that look similar although not quite as long.

SP is measured perpendicular to the airflow, it acts in all directions and is the pressure that tries to collapse the duct. The filter gauge should measure the differential pressure across the filter, which is the duct SP minus the ambient pressure.

Another pressure in the duct is the velocity pressure (VP) and it only acts in the direction of airflow. It cannot be measured directly. A pitot (or some people call it a prantl) tube has a hole in the end that faces into the airstream and holes on the side of the tube that are perpendicular to the hole in the end. The hole in the end measures the SP+VP which equals total pressure (TP). The holes in the side measure SP. When you measure the differential between these two ports, you get VP.

The velocity pressure allows you to calculate velocity if you know the gas density. Then, knowing the duct area, you can calculate CFM.

Some SP probes extend into the duct, not really necessary, unless you are in a turbulent area and then you need multiple readings from different points in the duct cross-section. I've used a hole drilled in the side of a duct and held the hose over it with my hand. Measuring the SP away from the side of the duct may get you a truer SP, but you are more interested in the change as the filter gets dirty, not the true number. Repeatability under the same circumstances is the key for noticing the trend like Ole does.

Mike

[bruce erdman]

Bruce,

Can you post some links of where you got the parts? I would like to add one too!

Ben

Gauge: http://cgi.ebay.com/ws/eBayISAPI.dll...E:L:OC:US:3160

The A-302 tip from http://www.dwyer-inst.com/Product/Pr...ories/Ordering

The A-497 bracket from at patriot-supply.com.

[Michael W. Clark]

The A-302 tip is a static pressure tip. The SP tips I have seen (A-303) do not have a hole on the tip, but have radial holes around the circumference of the tube. You want the tip to point either upstream or downstream. this puts the holes perpendicular to the airflow. If the tip faces perpendicular to the airflow direction (holes facing into oncoming air), you will read total pressure, not static pressure.

A properly sized hole drilled into the duct with a hose barb threaded into it also works. Then, you don't have the tiny holes to plug with material.

Mike