Distribution blower filter? Why not?

[jtakeman]

So the control boards are smart enough to see a load decrease and vary the convection blower amperage based on that alone?

The control board is variable to a point. They limit the volts per heat range. Whether the blower takes it all is another variable. See chart on Enviro's controller(its the only one I had handy).

I am assuming(haven't tried it) that as the blower impellet gets full of dust bunnies it will require more amps to get it moving and keep it moving.

I have seen blowers at grainger that have dampers on the inlet to reduce flow. Close the damper and you reduce flow(amp draw drops). As you open the inlet damper the flow increase's and the amp draw increase do to more load on the impeller. Breckwell method uses this to control their stoves combustion air. Blower is supplied full line voltage at all heat ranges. Operator controls the draft by closing the inlet damper.

(broken link removed)

 

[mepellet]

No it is a function of what the blocked input to the blower does to the load on its motor, it decreases it and the motor just goes along for its normal spin around the block. .

If you make the mistake of blocking the discharge the load on the motor increases and the current being drawn through the controller increases leading to problems for both the motor and the controller.

That's what I was taught also. More static (filter dirty or blocked discharge) equals more load on the motor.

 

[SmokeyTheBear]

What happens to the stove temperature however is a different matter, in both case it will increase.

In the case of the blocked input the stove doesn't have any air flow to carry the heat away, in the case of the blocked output it can't get the heated air out of the stove.

So from this we have axiom #1 don't be foolish and block the output of a blower system, and axiom #2 make certain that you can always get air to the blower so it can be sent through the stove to keep its temperature in check and our foolish hind quarters warm.

 

[jtakeman]

If the control boards do have the ability to control RPM to bring the motor up to run amperage that would be great. Then there would be no problems adding filter.

The best way IMHO to see if you have enough filter area is to measure the blowers amperage with no filter applied to the inlet. Then apply the filter. If the amps drop the filter is to restrictive. Increase the area of the filter until the amps are equal to the unfiltered level.

 

[SmokeyTheBear]

That's what I was taught also. More static (filter dirty or blocked discharge) equals more load on the motor.

No there is no increase in load from a dirty filter. A dirty impeller yes but not a dirty filter. Two different things.

 

[jtakeman]

No there is no increase in load from a dirty filter. A dirty impeller yes but not a dirty filter. Two different things.

Exactly, The amperage will drop as if you blocked the inlet. Blower will loose CFM output as if you closed the inlet damper.

 

[Hdhogger]

No it is a function of what the blocked input to the blower does to the load on its motor, it decreases it and the motor just goes along for its normal spin around the block. .

If you make the mistake of blocking the discharge the load on the motor increases and the current being drawn through the controller increases leading to problems for both the motor and the controller.

Ok, here's the skinney. I just had thje guys in the shop grab a small forward curved blower, which is what most stoves have. Ran blower with no obstructions ran at full amp rating. Blocked a portion of the intake, amperage dropped, blocked a portion of the discharge, amperage dropped.

 

[jtakeman]

Ok, here's the skinney. I just had thje guys in the shop grab a small forward curved blower, which is what most stoves have. Ran blower with no obstructions ran at full amp rating. Blocked a portion of the intake, amperage dropped, blocked a portion of the discharge, amperage dropped.

I notice amperage drop when ducting my stove. With 6" duct the blower drew less amps. I increased it to 8" and it drew more amps. Not sure why, But I assume wether you restrick either the inlet or outlet there is less load on the impeller.

 

[SmokeyTheBear]

How much of the flow did you cut off on the output side?

This takes a device to measure the air flow.

 

[Hdhogger]

I notice amperage drop when ducting my stove. With 6" duct the blower drew less amps. I increased it to 8" and it drew more amps. Not sure why, But I assume wether you restrick either the inlet or outlet there is less load on the impeller.

It's because the 8" duct is allowing more air to be moved through the system which makes the motor work harder. And yes, restricting any air to the blower lessens the load on the motor.

 

[Hdhogger]

How much of the flow did you cut off on the output side?

This takes a device to measure the air flow.

About 1/8 of it. If your measuring airflow you need a manometer. It will measure CFM and static pressure.

 

[Hdhogger]

About 1/8 of it. If your measuring airflow you need a manometer. It will measure CFM and static pressure.

Correction, a spirometer measures volume (CFM) the manometer measures static pressure.

 

[SmokeyTheBear]

About 1/8 of it. If your measuring airflow you need a manometer. It will measure CFM and static pressure.

Most blower outputs are larger than is required for their rated outputs.

I don't have any equipment around here to measure or play with anything in the HVAC world.

But blocking the coolant flow is a big no no and that is what happens on the output side if you place a "normal" filter there.

I'm sure that there are data sheets specifying the air flow characteristics of various filter materials on a per square foot or square inch basis.

Otherwise there would be no way to construct a filter for a normal hot air furnace.

 

[Hdhogger]

Most blower outputs are larger than is required for their rated outputs.

I don't have any equipment around here to measure or play with anything in the HVAC world.

But blocking the coolant flow is a big no no and that is what happens on the output side if you place a "normal" filter there.

I'm sure that there are data sheets specifying the air flow characteristics of various filter materials on a per square foot or square inch basis.

Otherwise there would be no way to construct a filter for a normal hot air furnace.

That' right, any restrictions that are added to a designed system will have negative affects. That's why I don't agree with adding filters, unless air flow can be increased to the original CFM output.
Most of the filters I deal with are rated in static pressure. So we design and apply a blower to overcome the SP to deliver the required CFM.

 

[jtakeman]

Correction, a spirometer measures volume (CFM) the manometer measures static pressure.

Most of us simple peeps won't have this stuff to play with. Heck most won't have a way to measure the amp draw(luckily I have a clamp on amp probe). Taking an amp reading before filter installation and after filter installation should be close enough for the common folk.

 

[mepellet]

motor amperage drops because of a reduced air load on the blower wheel and motor.

Right. To come back up to original cfm discharge, the bhp would increase.

 

[heat seeker]

On pipe organ blowers (centrifugal, not squirrel caged) blocking inlet or outlet will reduce amperage. It is a major no-no to run one of those blowers with no restriction. They are designed to have back pressure limiting their load. Output pressures vary, some a low as 1 or 2 inches WC, and on theater organs, as high as 50" WC. Lots of air volume, at times. The organs actually use pneumatic regulators to control the pressure.

Nothing to do with stoves, just thought I'd throw this into the mix.

 

[Hdhogger]

Most of us simple peeps won't have this stuff to play with. Heck most won't have a way to measure the amp draw(luckily I have a clamp on amp probe). Taking an amp reading before filter installation and after filter installation should be close enough for the common folk.

Your amp draw should decrease after filter install. I'm probably as common as you can get. And I'm sure everyone has their expertise in some field. Been doing ventilation for to long

 

[Hdhogger]

Right. To come back up to original cfm discharge, the bhp would increase.

Correct, the BHP and RPM would have to be increased to deliver the same CFM with an added filter.

 

[mepellet]

Correct, the BHP and RPM would have to be increased to deliver the same CFM with an added filter.

That is what I was getting at earlier. Also why i asked if the control boards could see the reduction in load on the fan therefore, increasing the bhp to deliver the required cfm to avoid overheating. Sorry for the confusion. We are on the same page. While I do not have the 39 years experience you do, I work in the same field.

 

[Hdhogger]

OK, I'm not touching the pipe organ!

 

[Hdhogger]

That is what I was getting at earlier. Also why i asked if the control boards could see the reduction in load on the fan therefore, increasing the bhp to deliver the required cfm to avoid overheating. Sorry for the confusion. We are on the same page. While I do not have the 39 years experience you do, I work in the same field.

I understood your point, no confusion. It would be a great feature if the boards could auto adjust blower speed and output. I'm wondering if any do this.

 

[mepellet]

I understood your point, no confusion. It would be a great feature if the boards could auto adjust blower speed and output. I'm wondering if any do this.

It certainly would. I wonder if any of the models that you can add ductwork to have this?

 

[SmokeyTheBear]

Ok, now that we have determined a filter added to the input side of the room air system will not destroy the controller by increasing the current flow through it or the blower by overworking the motor on it, we are left with the question of will there still be enough airflow through the system to safely cool the stove and thereby heat our hind ends.

Or in the alternative how can we construct a filter that presents very low resistance to the air being sucked through it and still act as a filter?

Please remember there is a 20% variation in the amount of heat that we need to remove just due to pellet caused differences.

 

[Hdhogger]

Ok, now that we have determined a filter added to the input side of the room air system will not destroy the controller by increasing the current flow through it or the blower by overworking the motor on it, we are left with the question of will there still be enough airflow through the system to safely cool the stove and thereby heat our hind ends.

Or in the alternative how can we construct a filter that presents very low resistance to the air being sucked through it and still act as a filter?

Please remember there is a 20% variation in the amount of heat that we need to remove just due to pellet caused differences.

This is the 6 million dollar question. Right now I'm starving, going to get lunch.