A Thought on forced combustion Fans

[cumminstinkerer]

Rather than hijacking @warno thread on his replumb, I thought I would start a new one. My draft fans hav a habit of getting dirty fairly quickly, mostly my fault, my boiler is in my garage and that is not finished and I don't shut them off when I reload and I get some smoke spillage plus just the normal dust from the wood and other projects. I have to clean the fans once every month or two. I work a a deere dealer and get lots of compact tractor air filters to change that are pristine, I am thinking about making the fans draw through one of those. Any thoughts on that.

 

[warno]

Couldn't hurt to give it a try. Not a bad idea if your fan is filling full of dust.

 

[brenndatomu]

I work a a deere dealer and get lots of compact tractor air filters to change that are pristine, I am thinking about making the fans draw through one of those. Any thoughts on that.

My first thought was why are you changing out pristine filters?

 

[cumminstinkerer]

@brenndatomu as part of the annual service specials program all filter are change regardless of condition, I hang on to ones that are good that will fit anything anyone I know owns

 

[jwise87]

I was actually considering doing the same thing. I had to change a complete air filter assembly on a Terragator the other day at work and thought about using that as a filter for my fan. The only thing I would be worried about is getting enough cfm's through an engine air filter without putting an undue load on the electric motor. I think it would substantially lower performance and maybe fan life. I would think an hvac filter like one would use in a household air handler would create less restriction while still filtering the air.

 

[brenndatomu]

The only thing I would be worried about is getting enough cfm's through an engine air filter without putting an undue load on the electric motor. I think it would substantially lower performance and maybe fan life.

A plugged filter actually lowers the load on a fan...try it, plug a fan in to a kill-a-watt and block part of the fan off (either side) the amps will drop. The only way you will burn it up is if the air is so blocked that the motor cannot even cool itself...which would be pretty hard to do since the amp draw has also dropped...the amount of heat needed to dissipate drops proportionately.

 

[jwise87]

A plugged filter actually lowers the load on a fan...try it, plug a fan in to a kill-a-watt and block part of the fan off (either side) the amps will drop. The only way you will burn it up is if the air is so blocked that the motor cannot even cool itself...which would be pretty hard to do since the amp draw has also dropped...the amount of heat needed to dissipate drops proportionately.

Huh... I had to read up on that. At first glance it seems it should be the other way.

 

[brenndatomu]

Huh... I had to read up on that. At first glance it seems it should be the other way.

Yeah, I agree, seems counter-intuitive.

 

[Fred61]

Huh... I had to read up on that. At first glance it seems it should be the other way.

Yeah, I agree, seems counter-intuitive.

You are reducing the air load on the vanes. Same thing happens when you put the palm of your hand over your shop vac hose. the motor speeds up Could affect cooling or over revving could damage bearings.

 

[leon]

Rather than hijacking @warno thread on his replumb, I thought I would start a new one.

My draft fans have a habit of getting dirty fairly quickly, mostly my fault, my boiler is in my garage and that is not finished and I don't shut them off when I reload and I get some smoke spillage plus just the normal dust from the wood and other projects. I have to clean the fans once every month or two. I work at a deere dealer and get lots of compact tractor air filters to change that are pristine, I am thinking about making the fans draw through one of those. Any thoughts on that.

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The air filters may look pristine but they are not. A paper air filter is only as good as the weakest fold in the cartridge. We used them underground and they were nothing but trouble compared to an Duetz oil bath air cleaner.

The tattle tale HG water gauge restriction indicators are not fool proof either as they stick open.

If you really want to to improve your forced draft system making it simpler you should check with tractor junk yard and find a ford jubilee and rob it of its oil bath air cleaner as it is more than adequate for your combustion fans required HG water gauge capacity BUT you need to pipe the air inlets to the outlet of the oil bath air cleaner and change the oil and scrape out the dirt sludge once a season.

Another option would simply to connect the combustion fans to an exterior air supply using PVC pipe to position the PVC pipe close to the air inlet shutters on the squirrel cage fans to the outside air supply using a simple PVC elbow pointed downward with a screen end on it to keep out vermin and high enough to prevent snow from plugging the elbow.


All depends on what you want to do but using a paper cartridge will only cause you problems as you will need to use 2 filter housings or building a gasketed hinged box with a set up to hold the cartridges in place outside the box and over the air inlet holes in the box and pipe it to each air shutter on the squirrel cage fans.

Building a simple filter box over the fans with 3 filter frames with low,medium and high filtration filter grades and feeding clean air to the air shutters with a common pipe feeding a Tee to feed the clean air to the 2 air shutters will be even less work.