Compressor (or?) recommendation to blow out a HEPA filter

[Mark Rainey]

I have an cheap Chinese anemometer I got from Amazon. I can grab the brand for you if you like. I have no idea if it's accurate but as you know, consistency is all that's really necessary. I take off the hose and measure directly at the port, so I have a consistent place to measure, and to eliminate inconsistencies from the variables introduced by the hose.

I don't know if that's actually an advisable way to measure CFM, just the way I've been doing it.

Thanks Ed, yes if you can let me know the brand.

[Mark Rainey]

I have used Oneida cyclones for 20yrs now, I like to take my filter outside and using a nozzle on my garden hose and wash out the filter eliminating clouds of dust, you just have to really make sure it is totally dry before placing it back into use. Here in Florida that is not a problem, plus I have a extra filter so I can easily rotate one while the other is drying.

20 years of experience is hard to ignore Pat. Perhaps I should give that a go - those clouds of dust are obnoxious.

[Pat Rice]

By the way, I have talked to Oneida about washing the filter and they said that was fine except do not use a high pressure washer and stressed that you must make sure it is totally dry.

[John TenEyck]

Has anyone stopped to think about why you need a filter in the first place? Of course it's because the air is being returned to your shop. But if you discharge that air outside, instead, you no longer need a filter. No filter, no loss in performance, actually higher, stable performance, no dust leaks, no ultrafines that get through the filter, and no maintenance, ever. Can't be done? Why yes it can, all year long and in a northern climate. The dehumidifier runs a little more in the summer and the furnace a little more in the winter, but the temp and humidity stay within a few degrees/% of set point no matter how long I run the DC. Probably not a valid option for someone in the deep south but for many it could be.

John

[Ed Mitchell]

Thanks Ed, yes if you can let me know the brand.

Here you go:
https://www.amazon.com/Anemometer-Ha.../dp/B07V2YYR2H

[Jim Becker]

Has anyone stopped to think about why you need a filter in the first place? Of course it's because the air is being returned to your shop. But if you discharge that air outside, instead, you no longer need a filter. No filter, no loss in performance, actually higher, stable performance, no dust leaks, no ultrafines that get through the filter, and no maintenance, ever. Can't be done? Why yes it can, all year long and in a northern climate. The dehumidifier runs a little more in the summer and the furnace a little more in the winter, but the temp and humidity stay within a few degrees/% of set point no matter how long I run the DC. Probably not a valid option for someone in the deep south but for many it could be.

John, I don't consider exhausting outside to be viable for here in the mid-Atlantic. Why? My shop is (err...will be) conditioned space most of the year. But for folks that don't have that concern, it's certainly a good way to eliminate a good chunk of the fines in the shop as well as remove the need to clean filters.

[John TenEyck]

John, I don't consider exhausting outside to be viable for here in the mid-Atlantic. Why? My shop is (err...will be) conditioned space most of the year. But for folks that don't have that concern, it's certainly a good way to eliminate a good chunk of the fines in the shop as well as remove the need to clean filters.

If "condtioned space" means air conditioned because it's above ground then I understand the logic. My shop is in the basement so it has no trouble staying cool even in summer.

I had a guy over this morning to buy some lumber and we needed to go down into my shop to resaw a couple of pieces he wanted. He saw my DC arrangement and said his was set up almost identically with exhaust out the window. For us basement dwellers it's a viable, low cost, no maintenance option.

My point in making the post was to show there often are alternative solutions, not to be confused with alternative facts, of which there are none.

John

[Jim Becker]

AC and heat, John. Minisplit.

[Mark Rainey]

If "condtioned space" means air conditioned because it's above ground then I understand the logic. My shop is in the basement so it has no trouble staying cool even in summer.

I had a guy over this morning to buy some lumber and we needed to go down into my shop to resaw a couple of pieces he wanted. He saw my DC arrangement and said his was set up almost identically with exhaust out the window. For us basement dwellers it's a viable, low cost, no maintenance option.

My point in making the post was to show there often are alternative solutions, not to be confused with alternative facts, of which there are none.

John

John, are there any concerns of too much venting of air causing problems with a gas furnace if it is in the same room?

[John TenEyck]

John, are there any concerns of too much venting of air causing problems with a gas furnace if it is in the same room?

Mark, you have to provide for make-up air if you vent outside. I open a window on the other side of my shop. Otherwise, back drafting from a furnace, etc in the same space would be a definite possibility.

John

[Mark e Kessler]

Has anyone stopped to think about why you need a filter in the first place? Of course it's because the air is being returned to your shop. But if you discharge that air outside, instead, you no longer need a filter. No filter, no loss in performance, actually higher, stable performance, no dust leaks, no ultrafines that get through the filter, and no maintenance, ever. Can't be done? Why yes it can, all year long and in a northern climate. The dehumidifier runs a little more in the summer and the furnace a little more in the winter, but the temp and humidity stay within a few degrees/% of set point no matter how long I run the DC. Probably not a valid option for someone in the deep south but for many it could be.

John

When you say North, how far North? I can’t image exhausting all that air up here in VT winters and the furnace only runs “a little more” , where does the makeup air come from - outside right?

[John TenEyck]

When you say North, how far North? I can’t image exhausting all that air up here in VT winters and the furnace only runs “a little more” , where does the makeup air come from - outside right?

I live near Niagara Falls, NY. It's cold and snowy in the winter. 20 - 30F is typical and occasionally we get down to 0. Everyone thinks that exhausting your DC outside and bringing in outside make-up air will cause the temperature in their shop to plummet, but they fail to realize that basement shops are giant heat sinks. All that concrete sunk below grade is a giant reservoir of heat. The make-up air has almost no mass compared to the concrete, etc., so the temperature goes down a few degrees while the DC is running but easily comes back to ambient once it's shut off. I heat my shop to 65F, whether or not the DC is running. I regularly run my DC for an hour in the winter. Never has the temperature dropped to 60F. Within 15 minutes after turning off the DC the temperature is back to 65F. I can't tell you exactly how much additional fuel it takes, but I would guess it's less than $30/month. I'm perfectly fine with that.

John

One might wonder why I don't use a filter system and return air to my shop. I did at one time, but then I bought a new bandsaw and the DC couldn't handle all the sawdust it makes when doing wide resaws. In looking to understand why I started measuring the static pressure drop at various locations in the DC system. The cyclone I had added resulted in a huge loss in SP, over 4" I think. The one or two micron filter bags I was using were at least that bad, too. Some poor piping choices added a few more inches lost. So it was either time to get a higher capacity DC or make some changes. I'm an engineer and I'm generally frugal so I started looking at ways to improve what I had. Just getting rid of the filter bags and ducting the exhaust out the window got me close, but actually not quite there. I ended up tearing apart the DC and mounting the fan inlet directly on top of the cyclone, with an expanded inlet diameter. I think that move alone gave me back 3" of SP. I also increased the outlet diameter of the exhaust from the fan, another gain of an inch or two. I also reconfigured some of the piping to smooth out the flow from the bandsaw. Combined, I now had enough SP at the bandsaw to handle all the sawdust it can make, and it never falls off because there is no filter to get blinded over time. Motor amps are still comfortably under the limit. These changes cost nothing but my time and a few DC fittings. The benefit of zero maintenance has been an added bonus.

John

[Mark e Kessler]

I live near Niagara Falls, NY. It's cold and snowy in the winter. 20 - 30F is typical and occasionally we get down to 0. Everyone thinks that exhausting your DC outside and bringing in outside make-up air will cause the temperature in their shop to plummet, but they fail to realize that basement shops are giant heat sinks. All that concrete sunk below grade is a giant reservoir of heat. The make-up air has almost no mass compared to the concrete, etc., so the temperature goes down a few degrees while the DC is running but easily comes back to ambient once it's shut off. I heat my shop to 65F, whether or not the DC is running. I regularly run my DC for an hour in the winter. Never has the temperature dropped to 60F. Within 15 minutes after turning off the DC the temperature is back to 65F. I can't tell you exactly how much additional fuel it takes, but I would guess it's less than $30/month. I'm perfectly fine with that.

John

One might wonder why I don't use a filter system and return air to my shop. I did at one time, but then I bought a new bandsaw and the DC couldn't handle all the sawdust it makes when doing wide resaws. In looking to understand why I started measuring the static pressure drop at various locations in the DC system. The cyclone I had added resulted in a huge loss in SP, over 4" I think. The one or two micron filter bags I was using were at least that bad, too. Some poor piping choices added a few more inches lost. So it was either time to get a higher capacity DC or make some changes. I'm an engineer and I'm generally frugal so I started looking at ways to improve what I had. Just getting rid of the filter bags and ducting the exhaust out the window got me close, but actually not quite there. I ended up tearing apart the DC and mounting the fan inlet directly on top of the cyclone, with an expanded inlet diameter. I think that move alone gave me back 3" of SP. I also increased the outlet diameter of the exhaust from the fan, another gain of an inch or two. I also reconfigured some of the piping to smooth out the flow from the bandsaw. Combined, I now had enough SP at the bandsaw to handle all the sawdust it can make, and it never falls off because there is no filter to get blinded over time. Motor amps are still comfortably under the limit. These changes cost nothing but my time and a few DC fittings. The benefit of zero maintenance has been an added bonus.

John

Ok, suppose in a basement could work but i am on a slab at grade and that slab is always cold, great for the 2 months of summer but there are multiple months of 0f and weeks of below zero…. Also no issues with combusting making devices or wood stove?

[John TenEyck]

Ok, suppose in a basement could work but i am on a slab at grade and that slab is always cold, great for the 2 months of summer but there are multiple months of 0f and weeks of below zero…. Also no issues with combusting making devices or wood stove?

Not "could work", does work, in any shop that has a lot of mass. Not just basement shops but any shop that has a lot of mass from the structure AND the contents that are maintained at a temperature comfortable enough to work at. It would not work for light weight structures with little mass inside, nor ones where the heat is turned off/down at night. In that case, the furnace/stove is needed just to heat the air back up to some workable temperature during work hours, but the structure and mass in the building never get to that temperature before the heat is turned off or idled back again.

John

[Mark e Kessler]

Not "could work", does work, in any shop that has a lot of mass. Not just basement shops but any shop that has a lot of mass from the structure AND the contents that are maintained at a temperature comfortable enough to work at. It would not work for light weight structures with little mass inside, nor ones where the heat is turned off/down at night. In that case, the furnace/stove is needed just to heat the air back up to some workable temperature during work hours, but the structure and mass in the building never get to that temperature before the heat is turned off or idled back again.

John

Yup, definitely sounds like it could work in some situations…