Help with Harman Furnace!

[FurnaceFrustrated]

Laynes 69,
Correct. If I set temp @ 72 on wood Furnace it either never reaches the temp or it takes the whole day to get there due to the very short cycle times on the blower. Yes, limit control is located correctly according to Harmans manual. 3 different Heating guys have been to my house to look at proper ductwork and correct sizing, and all of them said everything was good. I've already tried the whole fiddling with the H/L switches. Did that all last year. I still think that there is something wrong with the unit. Harman claims it is a firebox,- if it burns wood then there product is working. Something just isn't right internally, when the blower starts on low and all the heat goes right out of the fire box within a couple minutes.
I don't understand either. How do you think I feel with all the $ we've spent on the unit, the ductwork, and troubleshooting?

 

[willworkforwood]

Well I had an old friend who is in the heating / A/C business stop and take a look. He said everything looks fine, however, it appears that I have a severe draft problem. Apparently all the heat is going straight up the flue. He told me to get rid of the Barometric damper and just put in a regular wood stove type damper. He said it looks as though the Baro was actually accelerating my draft going up and out the chimney. I am not burning coal, only wood. He claims the baros are needed mostly for oil and coal burners. Any thoughts?

I think your friend has it nailed that most of the heat is going up the flue - you describe 300-400 with a mag flue therm, and that would translate to 600-800 actual - way too high. But, I don't know anything about your unit, and can't speculate on his advice to replace the baro with a regular damper - as said previously it may not be possible to do so with a furnace like yours. However, one thing you could do is run some hands-on experiments, by temporarily placing some metal objects (tin cutouts, etc) into the flue-connector portion of the baro. The goal would be to see if reducing the draft results in the furnace producing effective output. This, of course, is just for testing, and would need to be closely monitored to make sure that nothing goes South (smoke coming out the baro, etc.). If you can prove that the furnace produces good (usable) heat with less draft, then you can go back to Harman and get more specific help on somehow slowing down the air flow going through the unit (which may be a flue damper if that's possible for this furnace). The statement "if wood burns inside the firebox, then their product is working" is basically useless - they need to do better than that. If this unit is designed primarily for coal, and mods need to be done for wood burning, then they should be able to completely walk you through that process. Or, if firebrick (or something else) is the answer, then they should be able to give you that information. And, if you're not getting any results, try contacting their head banana and tell him that the folks on Hearth.com are interested in knowing how the problem with their furnace gets resolved ;-)

 

[laynes69]

I couldn't imagine going through that, especially a second year. Can you post pics of the install? Has the draft speeds been tested without a baro or damper on the flue? I know a flue size that large can affect draft. For us when we lined our chimney, performance increased a bit.

 

[spirilis]

Is there any kind of baffle inside the unit that's missing? Could account for high fluepipe temps and poor heat... but I don't know how those furnaces are laid out...

 

[maple1]

There is only so much that can be done over the internet, without actually being there & seeing some things in person.

This is a re-hash, but,

the BD should be able to be adjusted to reduce your draft to near zero (not sure what kind of damper you have, mine is I think a standard one - turn the nut/weighted disk so that the damper flapper is steadily quite open). Just playing with that should confirm or rule out draft issues. The other thing I think I remember mentioned is grates. I know nothing about this particular unit, but coal/wood ones I have read about recommended to remove the grates & replace with fire brick. Did you do anything on that? I would think just covering your grates (if hard to remove) with fire bricks and trying that would see if that had anything to do with it.

Your flue temps do seem high - could they be verified with a better therm?

Maybe you could expand on your comment above on a draft coming out of the unit when the blower is running? Exactly where does it come out?

Think that is the extent of all I can offer.

 

[laynes69]

I was reading a FAQ of another furnace manufacturer and remembered this problem. One of the questions was why is my blower short cycling? The answer was if the cold air return is not connected to the ductwork of the home this will happen. When your pulling air from the basement, it's much cooler than air from the living space above. This low return temp will kick off the controls faster causing short cycling. It's something to check into.

 

[FurnaceFrustrated]

laynes 69,
Checked that last year. We currently are running only to the basement. Nothing ducted to upstairs. Last year it was hooked up to the cold air return when we were ducted to the upstairs living space. It still did the same thing. I have a chimney guy coming out, gonna pick his brain about draft. I think this is the last possible thing it could be. Thanks for keeping me in mind. Will let you know how things go.

 

[FurnaceFrustrated]

Laynes69 -
Getting back to one of your previous posts, There is not a forced combustion air or fan for the combustible air on this unit. It has an automatic damper which lets the air in at the bottom of the unit when the thermometer calls for it. That being said, couldn't I put a manual damper on it? I will try anything at this point. may even get some fire brick to line the center of the bottom grates so heart of fire doesn't burn out so quick.

 

[laynes69]

Yes, that's what I would do. I was under the impression you had a forced draft. A manual damper will also keep more heat in the flue and chimney over a baro. Just experiment and keep an eye on the chimney. Just remember to open it when you load the furnace. I wouldn't mess with the firebrick, just tame the draft.

 

[maple1]

Might be some mixup on last couple of posts between draft damper, and air intake draft door (aka damper door to some).

I don't think there would be much of an advantage in replacing the automatic draft door opener, with a manual one - if that is what you mean. Could be trouble if it accidentally gets left manually open. Also, a barometric damper should provide more even draft, all else being equal - a manual damper can't respond to wind gusts over the top of your chimney in its own.

I'm still maintaining that filling in the grates with firebricks might be a worthwhile experiment - but improvements in a poor draft situation might make improvements from the grate situation not as significant.

Keep posted.

 

[laynes69]

Yeah I could see that re-reading the post. I was talking of installing a manual damper (key) in the flue pipe. While a baro will regulate draft better, if it's not burned correctly creosote can accumulate quickly. Also with the size of the chimney, a baro could cause excessive condensation to form in the chimney. Been there, it's not fun.

 

[maple1]

I've got both a key & baro damper in mine. Not sure why, just the way it was put in. I'm always opening/closing the key damper, on fill ups. I know what you mean about creosote - I mostly use my baro as a cleanout access point, to stick my arm in & scrape the stuff downstream until it falls into my cleanout. The influx of cooler air there can definitely create a creosote condensation area. Can't wait to get rid of this creosote generator of mine...

 

[FurnaceFrustrated]

laynes 69 & maple 1,
I spoke with my rep from the place I purchased the unit and he said that he has had to put in a manual damper on some units with draft problems in addition to the baro. (below the baro). Over the weekend I opened the baro almost full, and got much better results as far as cycle times on the blower. It stayed on much longer, however, the temps in the room never really got above 68. This with a full load of wood and reloading when necessary. The thermostat was set for 75. Once again never reached the temp to close auto air intake door. This was with unit running almost all day! I would think the unit should be heating up to a much warmer temp than that, much quicker. Once again I'm burning seasoned wood. Also, I spoke with a guy from a different stove shop and he said that he wouldn't sell me a liner I didn't need, however, he said the 8X12 flue may be too big. Reducing the size may help. At this point, I really am starting to think it is a draft problem, and would like to know the easiest way to correct it. Harmans manual says vent to nothing smaller than an 8X8 flue and I'm at 8x12. What if I dropped a liner in there that was smaller diameter? Do you think a smaller liner in addition to a manual damper would help? Not that I want to spend any more money on this friggin' thing, but it would really be a godsend to figure this thing out. The heat just has to be going up the chimney, where else could it be going?
Thanks for keeping me informed, All your posts and ideas are greatly appreciated.

 

[laynes69]

Based on the square footage your heating, the insulation values and age of the home I would get rid of the furnace. A liner will improve draft and create a solid burn. You would still need a baro or manual damper for draft would too high for the furnace, but you would have better draft during a lower burn. With that said I find it odd a furnace that size cannot heat a new home. I would remove the baffle of the furnace and thoroughly clean the firebox. Scrape all exposed steel to metal. Maybe there's ash that's insulating the furnace? Do you know what temps are at the register while the furnace is burning good and hot? If it was me, I would sell the furnace, put in a 6" stainless liner and put in a better more efficient furnace that will heat. I know it sucks, but you've been through alot.

 

[FurnaceFrustrated]

Hi everyone,
Well, I finally got my draft measured with a manometer. It was at .05 when first fired up and went to .07 when furnace was really rolling. These #'s don't seem to out of whack seeing as how the harman manual calls for draft readings of .02 - .06. The draft did read a notch or two higher than .07 at a couple times during the process, but for the most part settled around .07. Any thoughts on this draft reading?
Laynes, I appreciate your thoughts on getting a new unit, however, financially it is not in the cards. My question for you is, would a smaller diameter liner increase flue draft speeds or slow them down? The rep from the place I purchased the unit claims it would speed it up. I don't want any more heat going up the chimney than is necessary.
I realized this past weekend, that due to the vast amount of cold concrete, in the basement, the walls and floors were acting like a heat sink, essentially sucking up all the heat. Once I stayed with the furnace for a couple days and things warmed up, the furnace ran much better and a little more efficient. Temps reached thermostat calling temp. I think I can get this headachesmoothed out with a little more guidance.
Thanks -

 

[FurnaceFrustrated]

I have spoke to several different "specialists", techs, chimney cleaners reps, etc......regarding chimney liners and size of them etc. Could someone please give me a straight answer? I called Harman directly and the tech said that if I were to line the chimney it would definitely help the efficiency of the unit. The question I have is in regards to size. The chimney height is ~ 30' give or take a few feet. The stove pipe is 7". The harman tech said b/c it is that height, that I would need a little bigger liner. He suggested a 9". The current masonry flue is 8x12. If having a bigger flue allows more heat to escape up the chimney, wouldn't you want to have a liner about the size of the stove pipe?
Any thoughts?

 

[laynes69]

There's only so much you can do with efficiency. You need a percentage of the heat for draft in the chimney. A larger flue causes sluggish draft due to the chimney cooling the gasses. A proper sized liner allows the gasses to stay hotter in the chimney, therefore reducing the chance for creosote buildup and promoting a strong draft. Weak draft causes poor fires and heat output. A good steady draft allows for a better fire through the whole burn. If the furnace has a 7" output then a 7" should be used. Our furnace requires a 6" flue. When we had the furnace on a 7x11 chimney, performance suffered. After a 5.5" liner was installed in our 32' chimney, there was a large gain in performance.