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Distribution blower filter? Why not?

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by P38X2, Dec 1, 2012.

  1. jtakeman

    jtakeman Minister of Fire

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    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). Voltage specs[1].jpg

    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.

    http://www.grainger.com/Grainger/DAYTON-PSC-Blower-1TDN7?Pid=search

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  2. mepellet

    mepellet Minister of Fire

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

    SmokeyTheBear Minister of Fire

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    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.
  4. jtakeman

    jtakeman Minister of Fire

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    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.
  5. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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

    jtakeman Minister of Fire

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

    Hdhogger Member

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    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.
  8. jtakeman

    jtakeman Minister of Fire

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    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.
  9. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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

    This takes a device to measure the air flow.
  10. Hdhogger

    Hdhogger Member

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    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.
  11. Hdhogger

    Hdhogger Member

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

    Hdhogger Member

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    Correction, ==c a spirometer measures volume (CFM) the manometer measures static pressure.
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  13. SmokeyTheBear

    SmokeyTheBear Minister of Fire

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    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.
  14. Hdhogger

    Hdhogger Member

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    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.
  15. jtakeman

    jtakeman Minister of Fire

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    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.
  16. mepellet

    mepellet Minister of Fire

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

    heat seeker Minister of Fire

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    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.
  18. Hdhogger

    Hdhogger Member

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

    Hdhogger Member

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

    mepellet Minister of Fire

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    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.
  21. Hdhogger

    Hdhogger Member

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    OK, I'm not touching the pipe organ!
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  22. Hdhogger

    Hdhogger Member

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    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.
  23. mepellet

    mepellet Minister of Fire

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

    SmokeyTheBear Minister of Fire

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    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.
  25. Hdhogger

    Hdhogger Member

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

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