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PSG caddy low heat output

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by bluecloud, Jan 23, 2013.

  1. bluecloud

    bluecloud New Member

    Joined:
    Jan 7, 2013
    Messages:
    3
    I recently installed a PSG Caddy wood-only furnace. I also have a 80,000 btu propane furnace that is 95% efficient. Both furnaces run through the same duct work, but I set them up so that they can't be run at the same time (I block off the ducts to the one I'm not using to prevent hot air from going into the return air ducts).

    I installed the Caddy per the installation manual. The chimney connection is a double-wall tee on the back, then a barometric damper, then 35 feet of 6" Class A Supervent (insulated) chimney pipe. The hot air plenum is 24" high (per manual) and the return air plenum is about 32" high. The main duct line is 8" x 16".

    My house is an older 2 story house 2,000 sq ft plus full basement. But the basement is not really heated. I know the house needs more insulation and some air leaks sealed up. I am only heating the main level right now.

    My issue is that I estimate the heat output of the Caddy to only be about 20,000 btu's. The brochure says max output of 140,000 btu's and average output of around 76,000 btu's. When it was 30 degrees outside, I ran the Caddy all day with a full fire, and it only brought the house up to 58 degrees. The last couple of days, it has been close to zero outside, and the Caddy could only keep the house in the low 40's with a full fire going.

    If I run my propane furnace, it would only cycle on about 25% of the time to get the same amount of heat that the Caddy produces. That is why I estimate the heat output at 20,000 btu (25% of 80,000).

    The ductwork in my house is not very extensive, and I run the fan on the lowest setting, which is about the same fan speed that the propane furnace runs on.

    The Caddy hogs though a lot of firewood. More than a wheel barrow a day, if I keep loading it up. Burn times are not very impressive (load it up and it's gone in 4 hours). My firewood is high quality and dry. It is all hardwood, cut 2.5 years ago, split over 1.5 years ago, and covered from the rain. It is not rotten at all. I have tried firewood from another source and same results. The fire will burn really hot, I just don't know where the heat is going. Obviously the thermostat that controls the inlet damper is worthless right now, since it would always be wide open due to being so cold inside. So I have been controlling the inlet damper manually by propping it open with something when I want the fire to burn hotter. I am getting the secondary burns (I think), meaning that I see flames shooting out of the little air pipes in the top. And everything is burning down to a nice fine white ash.

    I have played with the fan limit control switch, all different settings. The best seems to be on around 160 deg and off at 110 deg. I had a problem with the switch sticking, it would run for hours blowing out cold air, then I go over and tap the limit switch and it would shut off. I think I have fixed that problem. I have my own probe thermometer in the plenum. It will go up to 160 deg, then when the fan comes on it cools down very quickly (less than a minute) to 100 deg, but the fan will keep running for a few more minutes. At night if I have a lower burning fire (mostly coals), it will never get hot enough to kick on the fan (it only gets to around 120 deg), so I have no heat in the registers all night.

    I think my chimney pulls a good draft, because even when there is no fire going, I can feel a draft going through the chimney, just because of how tall it is. I have also played with the settings on the barometric damper, moving the weight back and forth. I have even tried taking the barometric damper out so that it is just a wide open hole into the chimney. I can stick my hand through there into the flue, and the flue gasses do not feel that hot. The chimney is hardly ever hot to the touch, on the Class A portion of it. I have not tested the draft on the chimney, but even if I did, I don't know what options I would have if there is too much draft. I can't make the chimney any shorter or narrower.

    The manual says one cause of low heat might be that the return air is too cold. I understand it makes the furnace run inefficiently, but how am I supposed to get hotter return air when the thing won't put out of enough hot air from the registers???

    So I don't know where the heat is going and I'm out of ideas. Tonight it is very cold out and I did not even bother making a fire, I am just using the propane furnace tonight so that the pipes don't freeze.

    I have over $5k invested in this thing (including the chimney, ductwork, wiring, etc), and I'm very disappointed in it so far. Any advice on how to improve the performance of this thing would be greatly appreciated!

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  2. sloeffle

    sloeffle Member

    Joined:
    Mar 1, 2012
    Messages:
    100
    Loc:
    Morrow County, Ohio
    I have the same furnace that you have, but mine has the panels to take out for electric or oil. I heat around 2200sq ft in Central Ohio without any issues at all.

    Do your wood burning furnace have the 4 speed fan ? I have mine set to medium low per the manual and I have no issues pushing heat around.

    Have you checked your static pressure in your duct work ?

    On a normal day I burn through about half wheel barrow load. If it is really cold out like it has been we burn through a little more. Have you checked the static pressure in your chimney ?

    Scott
  3. laynes69

    laynes69 Minister of Fire

    Joined:
    Oct 2, 2006
    Messages:
    1,809
    Loc:
    Ashland OH
    There's no way your burning a load in 4 hours, and only putting out 20,000 btus. You need to set your draft with a manometer and check your static pressure. Our home is so drafty, I can smell the fresh air from outdoors. Not proud of it, but it is what it is. Even then we have no problems keeping warm. The temperature of the air from the woodfurnace will not be that of the gas. If it was, the home would be a 100 degrees. Either your home isn't as tight as it could be, or there's something wrong with the installation, or operation of the furnace. Going from 160 degrees in the plenum to 100 within a minute tells me something is wrong. I watch our limit control and when there's a good fire, the temps read between 130-140. At 1 degree the other night, we had a solid 6.5 hour burn overnight with a very heavy call for heat, holding the home at 72* and our home isn't small. In the mid 20's to 30's we can see 8-10 hours overnight. Above that it's half loads overnight. At 30 degrees we easily could have it 80.
  4. bluecloud

    bluecloud New Member

    Joined:
    Jan 7, 2013
    Messages:
    3
    Thank you for the replies. I hope to do some more testing on it this evening. sloeffle, I probably have the same furnace that you do. Mine has a panel that can be removed to add electric heating element (and maybe oil...not sure). Which I think would be really dumb to heat with electric on one of these, even if it was working right, I think a lot of the electric heat produced would go out the chimney, even if there was no fire. Just my thinking.

    I will try to get the static pressure in the ductwork checked. But I don't really think it would make too much difference. I have the fan on the lowest setting, and it is cooling off the plenum pretty quickly. Going to a higher speed setting would just cool it off even faster. And the propane furnace is basically on the same ductwork, and it works fine, and the air coming out of the registers is much hotter.
  5. laynes69

    laynes69 Minister of Fire

    Joined:
    Oct 2, 2006
    Messages:
    1,809
    Loc:
    Ashland OH
    You need pressure in the ductwork, the slower the air, the less pressure. Bump up your fan speed to med-low to med-hi, your not putting enough heat from the furnace into the home. My ductwork size is 8x18 off my plenum. If I set my fan to low, I would never heat the home. You will not see the output temps from the Caddy that you see from your central furnace, it's not designed that way. Also make sure the exchanger is clean for maximum heat transfer. The electric add-on has nothing to do with the chimney, neither are tied to each other. 100% of the electric heat would be put into the home. Your propane furnace is an off-on system, that's not how a wood furnace operates.
  6. laynes69

    laynes69 Minister of Fire

    Joined:
    Oct 2, 2006
    Messages:
    1,809
    Loc:
    Ashland OH
    I'll also add, running with the damper open isn't going to put more heat into the home, but push it out the chimney. Get ahold of a manometer and set the barometric damper to the manual (.04"-.06").

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