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Harman PF100 Fan Controller Question

Post in 'The Pellet Mill - Pellet and Multifuel Stoves' started by Ejectr, Dec 30, 2012.

  1. Ejectr

    Ejectr Minister of Fire

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    I currently have my fan controller set to 150 degrees fan on and 120 degrees fan off. I checked the temp of the air coming out of my floor registers and they were all basically the same...arounf 100 degrees.

    I was just thinking that if I increase the fan "on" setting to a higher temp and the fan "off" setting differential to the same 30 to 40 degrees, then the air out of the registers should be hotter...correct? And I shouldn't see any increase in pellet use because the furnace is kept form getting to a hotter temp by the fan coming on at a lower temp and keeping it from getting up to...say..165 degrees, which it would. The ESP keeps the exhaust temp from going above 165 when the thermostat is satisfied and it's maintaining, but I believe the heat exchanger is warmer than that. Not really sure of that one.

    I know I'm losing some heat in the transfer due to some of the duct not being insulated, which I'll get around to next year, but is my train of thinking correct with the fan controller set temps and the pellet use?

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  2. Labrat

    Labrat Member

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    It is an interesting thought. I would say that it would increase your register temps, but I do wonder that you may burn more pellets as the increase in temp before the distribution fan kicks on means the furnace has to absorb the heat, making mewonder how much of that extra heat would go out the flue.
  3. Ejectr

    Ejectr Minister of Fire

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    I thought along the same lines, but then I figured it would only take more pellets to get up to that higher fan on temp. Once it was stabilized at the higher temp, it would cycle on and off just like it did at the lower temp. The only thing that would cause more pellet usage is if the thermostat called for a heat increase, and it wouldn't be doing that.
  4. Labrat

    Labrat Member

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    I'd give it a shot. If you burn a few more pellets then you learned something. If you burn the same amount of pellets you still learned something. I am guessing that you have metal ducts so melting them shouldn't be an issue.

    How big is your place? Mine is 1400 sq ft. I can run my furnace in manual on a night like tonight and have a stable 74 degrees:cool: , once the sun comes up here the temp in the house rockets up into the high 70's low 80's way too much for me:eek: . That is just with the maintaince fire going! I wind up putting it back in auto during the day.
  5. Ejectr

    Ejectr Minister of Fire

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    I have about 1200 I'm heating. Have an unheated upstairs that I'm trying to figure out how to get heat up there in a post and beam design. The heat stops at ceiling level in the kitchen where the open stair well is and right at the ceiling level on the stairs there is a wall of cold air that starts there. This house was built by whoever with no pre planning what so ever.

    I keep it at 70. Can't take the higher temps. I think I will give it a shot just for curiosity sake.
  6. Labrat

    Labrat Member

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    The post and beam house pretty to live in but hard to heat in your situation. I presume that the Windsor is for the 2nd floor then?

    I wish I could get away with 70, my wife likes it on the warm side. We have got two kids at 3yrs and 1.5 years. Let me know how your expirement works out.
  7. Ejectr

    Ejectr Minister of Fire

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    The house is a colonial reproduction of a house that is in Sturbridge Village. The prior owners tried to keep it as period as possible with the sacrifice of some sensibility in areas. It has two working fireplaces I don't use unless the power goes out. One in the kitchen and one in the living room.

    The Windsor heats a 16 x 28 cathedral ceiling room that is attached to the back of the kitchen. Sits on a 2' foundation crawl space. The heat they installed was 2 electrical wall heaters with fans in them. and a very small wood stove that wouldn't burn all night. I yanked the wood stove and put in the pellet stove. The room is actually closed off via a door from the rest of the house and I keep it cold. I only crank the Windsor when we want to use the room..
  8. DexterDay

    DexterDay Guest

    My Fahrenhiet is set to 160* on and 120* off.

    I like a higher air temp. It takes longer to kick on when in pilot/maintenance burn, but ensures a good air temp when it kicks on.

    Although different system than the PF-100, it's still a furnace and I can adjust the On/Off temps.

    I would try it. And like Labrat, my place overheats very quickly in the daytime. I am on level 1 (manual) right now and my place is 74*!!! Upstairs is 2'180 and basement area is 800 sq (where pellet furnace resides)
  9. Ejectr

    Ejectr Minister of Fire

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    That's good information, Dex. I'm going to give that a shot and see what happens.
  10. Lousyweather

    Lousyweather Guest

    hey, you can always change it back!
  11. Ejectr

    Ejectr Minister of Fire

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    Indeed...
  12. kinsmanstoves

    kinsmanstoves Minister of Fire

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    It takes more fuel to make more heat. The PF100 computer does nothing to the circulation blower.

    Eric
  13. Ejectr

    Ejectr Minister of Fire

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    Not in this case. The furnace is being kept from making more heat with the supply it is getting based on the ESP and the temp setting by the fan coming on and cooling down the area where the heat exchanger heats the box area where the fan controller sticks into and the heat exchanger. With a constant feed of pellets at the same rate, without the fan coming on, the heat would build and build until the over temp setting on the fan controller was reached to cool it down. Then the fan shuts off and it heats again until it gets warm enough to come back on. If the fan didn't come on, it would initially use more pellets until it stablizes on the higher temp and then the cycle would start of fan on...fan off... The potential for a higher temp is already there in the current pellet feedrate if the fan didn't come on to cool it down. I'm just shifting the operating temp...not asking the furnace for more heat by kicking up the thermostat. Not using more pellets to get more heat. Just getting the heat out of what is already there with the supply it's getting.

    As I said, the potential for a higher furnace temp is already there with the amont of pellets it is currently feeding it. I'm just not allowing that potential to be used because of the lower fan temp settings. I'll let you know the results. Obviously, if it starts using more pellets, I'll set it back to where it was.
  14. kinsmanstoves

    kinsmanstoves Minister of Fire

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    Without coming to your house I would be blaming a few other things than the PF100 such as a blower not sized correctly by the installer. Duct work not sized to the unit, cold air returns not working or installed correctly. The furnace will only do so much.

    Eric
  15. Ejectr

    Ejectr Minister of Fire

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    Eric, my man....I'm not looking for something to blame. The furnace was installed by a reputable dealer that posts on this site. The ducting was installed by a heating contractor in business for over 40 years and the blower is the largest they have. All I'm saying is, I believe I can be running this with hotter air that won't require increased pellet use. Right now the furnace is heating the house nicely. I'm just going to see if I can get it nicely +.

    We'll see. I'll post the results here. Thanks for your input.
  16. kinsmanstoves

    kinsmanstoves Minister of Fire

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    What I am saying is the unit is making the heat. The blower is attempting to move the heat (largest blower is the 1638 four speed blower) and the duct work should transfer that heat. We do get much higher temps than 100 degrees but I also use an HVAC certified installer for this portion. Proper blower and duct work sizing is above my knowledge on the central heating installation. I can work on the unit all day but if the blower and duct are not the correct size you will not get good heat transfer which is what you indicated in the opening post.
  17. imacman

    imacman Guest

    Hmmmmmm.
    kinsmanstoves likes this.
  18. kinsmanstoves

    kinsmanstoves Minister of Fire

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    The fan limit control operates on it's own and is not connected to the computer in the unit. For proper setting you need to run output temperatures at the ducts and adjust as need be. Yes not using insulated ducts will hurt heat output temps at the grills but should not be that much of a difference. If your cold air returns are not sized and hooked up this will cause a problem. If the ducts are not sized for the blower this will be an issue. If the high limit on the fan limit control switch is activating YOU HAVE A PROBLEM. Just saying.

    Eric
  19. Ejectr

    Ejectr Minister of Fire

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    I understand. I'm not anywhere near the high limit on the fan controller and I understand the fan controller works seperately from the computer. I believe I said all that in my prior posts. I'm just going to make some higher adjustments and see what I get and see what I burn. Thanks all for the educated input. I'm not a heat tech. I'm just a tinkering slob with a pellet furnace.
  20. Ejectr

    Ejectr Minister of Fire

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    These are my results. I kicked the fan controller up to 180 degrees on... from 160 and left the off temp at 120. I measured the register temp and it was 112 degrees vs the 100 I was getting. The furnace went into maintenance mode with the ESP telling the auger to feed at 5 second intervals. This went on for about 20 minutes and the fan had not come back on. Then the auger time went to 30 seconds. I could tell that the temp in the house had dropped due to the long fan off time and the thermostat was calling for heat. I decided that the 60 degree span was too large and I kicked up the off temp to 140 degrees, so 180 on...140 off. This ended up being the sweet spot for me.

    Now with the higher register temp, the thermostat is satisfied with the hotter air coming out of the registers in the maintenance burn. The fan comes on for 2 minutes and is off for 5 minutes and the furnace remains in maintenance burn with a 5 second auger feed. I sat there for hours and timed the fan on/off times, the auger feed times and had my wife watch the digital thermometer we have in the same room as the thermostat. So end result was similar fan on/off times as before.....warmer air out of the register and less pellet usage.

    As I had surmised, the potential for higher temperature from the amount of pellets being fed with each 5 second auger time was not being allowed to be experienced because the fan came on at a lower temperature and cooled the heat exchanger down, so the pellet load was just being used to rewarm the exchanger. With the fan being set to come on at a higher temperature and off at a higher temperature, I was able to get more heat from the pellet load from that 5 second auger feed.

    So yes... I got higher register temps....less pellet usage...similar fan on/off times by just shifting the operation point of the furnace, not cranking up the thermosat to burn more pellets for more heat so it is possible to burn the same amount of fuel to get more heat by just letting what you're burning give up its heat before cooling what it is heating down.

    A hell of a way to spend New Year's day but I'm retired anyway, so they're all New Year's day to me.
    kinsmanstoves and DexterDay like this.
  21. kinsmanstoves

    kinsmanstoves Minister of Fire

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    Glad it is working

    Eric
  22. Labrat

    Labrat Member

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    Thats great to hear!:cool: Just shows that what comes from the factory may not always work the best for everyone but there is adjustability built in to customize for your needs!

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