Help with Harman Furnace!

[FurnaceFrustrated]

Hi Everyone and anyone. I am new to this forum stuff, but have been using hearth.com for a couple years now. I purchased a new Harman wood / coal furnace model SF-2500A back at the end of 2009 with the intention of heating with wood. After hooking up the unit to the existing propane system and not getting any heat out of it to the upstairs I became so frustrated after a year and a half of trying to get this thing to work in conjunction with our existing system that I took down the duct work to the upstairs and decided to heat the basement. (There currently is a long tapered trunk that has four fingers coming off it). It works just o.K.

The question I have is. Does anyone out there have this unit that has / had problems with it. The problems I have are; 1.) Cannot keep wood in it. burns very quickly. 2.)The blower comes on and off every 5 - 10 min. The temp gets up to the required high to start the blower, then once the blower comes on, I can watch the temp go right out of the firebox within a min. or so. thereby hitting the low on the limit switch which shuts off the blower. I thought these units are supposed to blow warm steady air until the thermostat reaches the desired temp, then the blower shuts off, damper closes, and tampers the fire until thermostat calls again? The blower appears to be blowing all heat right out of firebox! It is on the lowest speed setting. It also takes 4-6 hours to get it warm in the area heated, never hitting desired temp.
3.)I can load up the firebox before bed, and get up first thing in A.M (before sun up), and there isn't a damn hot coal in the thing! I've tried shutting down the combustible air so that it burns a little slower, but it doesn't heat up the fire enough, and smokes. Someone told me to shut the bottom combustible air off completely and open the two door knob vents, b/c bottom is used for burning coal, however manual says different. I do have a barometric damper on it, but someone else told me you don't need it to burn wood....
Could the unit be defective? Called my dealer and Harman directly, and they told me that if wood burns inside the firebox, then their product is working?
I would appreciate any feedback or advice from anyone with wood burning furnace experience. I need help. paid alot of $ and getting nothing out of it.

 

[laynes69]

How tall and what size is the chimney? That will determine whether a baro would be needed or not, a manometer will verify draft. That's a larger furnace, but hearing of short burns isn't too uncommon, especially if draft is too high. It sounds like the ductwork isn't sized correctly or something is missing. We have 40' of heating trunk from the basement to the attic from our woodfurnace and both floors heat fine. Is there any ducting on the furnace now and where are the temps for the blower control set at? Also how large is the home and how's it insulated? Any pics?

 

[JrCRXHF]

I am getting ready to fire up my harman boiler about the same size from what i have read is the top two in the load door should be closed and you adjust the bottom auto intake air for idle and high burn when burning wood.

That is about all the info i can give you until i have mine up and running which should be a couple weeks i hope to get 8 hour burns out of it so i can at least sleep before refilling if it goes out after a long work day well that is just how it is going to have to be.

 

[FurnaceFrustrated]

laynes 69 Thanks for the quick response. The Chimney is approx. 23-26' high. It is a masonry chimney with a 7"/8" x 12" flue, (I believe). I had a few people, (heating guys),out to look at it, and they said duct work looks good. Yes, there is ductwork on it now only to the basement. Approximately 38-40' of main trunk tapered, with 4 fingers running off, ( 2 on each side). We have the cold air return open to basement b/c we are not blowing upstairs. The temps for the blower control are set at 150F =on, and low/shut off @ 100-110F. The house is Approx. 1780 - 1800 Sq. ft. House is new, R-21 in 2X6 walls - pretty tight, holds temps for a while.

JrCRXHF - I've tried everything like that. Did exactly what the manual says, experimented with auto air intake as well as idle air. I hope you have better luck than I with yours. Can't keep wood in her, never coals in the A.M. Very frustrating. An old timer came by and said to take Baro out and just put in old fashioned damper, and use 2 door knob vents for combustible air intake. Basically using it like a wood stove.

Thanks again for any help -

 

[JrCRXHF]

Well that might work the other thing i thought about doing is putting fire brick over the shaker grate and then doing just that and hope to keep more coals up top. Then adjust how much room i leave around the edges to get the burn i want.

The other thing is what kind of wood are you putting in it and how much. The Boiler looks like it will hold a lot of wood i also left some large rounds whole for long over night burns so i would have coals in the morning.

At this point it is just my ideas i have not put any of them to the test yet.


From my understanding these units are really setup to burn coal but you can also burn wood in them. So i figure i can do modification and adjust the unit to make it burn wood better. For the price i got the unit at and the fact i have no room for hot water storage made this the best option for me.

 

[maple1]

I have read only one manual for a coal/wood burning appliance, and it read that if you were burning wood, you should remove the grates and lay in some firebrick on the bottom of the firebox.

Not sure if that is applicable here.

 

[Singed Eyebrows]

Hi Everyone and anyone. I am new to this forum stuff, but have been using hearth.com for a couple years now. I purchased a new Harman wood / coal furnace model SF-2500A back at the end of 2009 with the intention of heating with wood. After hooking up the unit to the existing propane system and not getting any heat out of it to the upstairs I became so frustrated after a year and a half of trying to get this thing to work in conjunction with our existing system that I took down the duct work to the upstairs and decided to heat the basement. (There currently is a long tapered trunk that has four fingers coming off it). It works just o.K.

The question I have is. Does anyone out there have this unit that has / had problems with it. The problems I have are; 1.) Cannot keep wood in it. burns very quickly. 2.)The blower comes on and off every 5 - 10 min. The temp gets up to the required high to start the blower, then once the blower comes on, I can watch the temp go right out of the firebox within a min. or so. thereby hitting the low on the limit switch which shuts off the blower. I thought these units are supposed to blow warm steady air until the thermostat reaches the desired temp, then the blower shuts off, damper closes, and tampers the fire until thermostat calls again? The blower appears to be blowing all heat right out of firebox! It is on the lowest speed setting. It also takes 4-6 hours to get it warm in the area heated, never hitting desired temp.
3.)I can load up the firebox before bed, and get up first thing in A.M (before sun up), and there isn't a damn hot coal in the thing! I've tried shutting down the combustible air so that it burns a little slower, but it doesn't heat up the fire enough, and smokes. Someone told me to shut the bottom combustible air off completely and open the two door knob vents, b/c bottom is used for burning coal, however manual says different. I do have a barometric damper on it, but someone else told me you don't need it to burn wood....
Could the unit be defective? Called my dealer and Harman directly, and they told me that if wood burns inside the firebox, then their product is working?
I would appreciate any feedback or advice from anyone with wood burning furnace experience. I need help. paid alot of $ and getting nothing out of it.

Can you get some larger chunks of anthracite coal? Use these with the wood & you should have coals that last overnight. You don't need a lot of coal so this won't be much of an expense. You are out east so hopefully this is available, Randy PS, don't use soft(bituminus) coal.

 

[laynes69]

Your chimney is fairly tall. When the fire starts, draft would be low, once it warms up the draft would be too high. A furnace that size shouldn't have a problem reaching a set temp with that amount of footage. We heat with a different furnace, but we have a large old large Victorian home. Our furnace has a firebox about half the size of a harmon, but in the mid teens we had a 9 hour burn over night with a 70* house in the morning and a nice coal bed. It's all in the design of the unit. Does the unit have forced draft or natural? If it's natural draft you could try a manual damper to lower draft some. As far as the blower kicking on an off quickly, the manual should have requirements with static pressures in the ductwork. If there's little restriction, the blower may cool the furnace too quick and cause short cycling. Other than the burn times, does it heat well? I would think there's little heat needed in a new home.

 

[laynes69]

Your chimney is fairly tall. When the fire starts, draft would be low, once it warms up the draft would be too high. A furnace that size shouldn't have a problem reaching a set temp with that amount of footage. We heat with a different furnace, but we have a large old large Victorian home. Our furnace has a firebox about half the size of a harmon, but in the mid teens we had a 9 hour burn over night with a 70* house in the morning and a nice coal bed. It's all in the design of the unit. Does the unit have forced draft or natural? If it's natural draft you could try a manual damper to lower draft some. As far as the blower kicking on an off quickly, the manual should have requirements with static pressures in the ductwork. If there's little restriction, the blower may cool the furnace too quick and cause short cycling. Other than the burn times, does it heat well? I would think there's little heat needed in a new home. A newer furnace like ours burns the smoke at the same time lowers the rate of burn. This ends up with little smoke, and longer burns. If you don't want smoke, you will have to burn a little hotter which will result in lower burn times. Have you tested the draft with a manometer?

 

[FurnaceFrustrated]

Well that might work the other thing i thought about doing is putting fire brick over the shaker grate and then doing just that and hope to keep more coals up top. Then adjust how much room i leave around the edges to get the burn i want.

The other thing is what kind of wood are you putting in it and how much. The Boiler looks like it will hold a lot of wood i also left some large rounds whole for long over night burns so i would have coals in the morning.

At this point it is just my ideas i have not put any of them to the test yet.


From my understanding these units are really setup to burn coal but you can also burn wood in them. So i figure i can do modification and adjust the unit to make it burn wood better. For the price i got the unit at and the fact i have no room for hot water storage made this the best option for me.

That sounds like a pretty decent idea. That would slow the air to the core / heart of the fire and yet still supply air for combustion. But couldn't you just shut down idle air as well as automatic draft flapper and open the 2 knobs on the front of the door? That would eliminate the need for firebrick - No?
I'm burning mostly ashe, cherry and maple with some oak. I've loaded that damn thing to the top on a couple occasions right before bed, and ran downstairs when I got up 6-7 hrs later and there was nothing but cold ashe. The unit wasn't even warm.
I was told by another dealer in NH that those units were made for coal, and they shouldn't be marketed for wood. (Would have been nice to know before I purchased it.)
I think the biggest problem for me is that as soon as the blower starts, I can literally see the temp go down, (I drilled small hole in plenum next to high / low limit and stuck a thermometer in it to verify H/L unit was working properly.), within a minut or so. I thought the idea was to have a steady stream of warm air until the thermometer is satisfied? This thing goes on and off so frequent, I'm afraid I'll burn out the motor over time.

 

[laynes69]

Is your wood seasoned? Wood that's not dry will produce less heat and lower burn times. If there is a heat exchanger make sure it's clean. Do you have any pics of the setup? I would think the blowers should run more than a couple minutes. Do you have a thermometer to measure flue temps? How's the return ducted on the furnace from the basement or living area above? I wouldnt do anything with the grates. Verify flue speeds, moisture content of the wood and pressures in the ductwork first. With our old furnace it was hit and miss. If I slept in an hour or two we would wake to a cold furnace. I understand your frustration, it's no fun. Mixing coal isn't a bad idea.

 

[FurnaceFrustrated]

Is your wood seasoned? Wood that's not dry will produce less heat and lower burn times. If there is a heat exchanger make sure it's clean. Do you have any pics of the setup? I would think the blowers should run more than a couple minutes. Do you have a thermometer to measure flue temps? How's the return ducted on the furnace from the basement or living area above? I wouldnt do anything with the grates. Verify flue speeds, moisture content of the wood and pressures in the ductwork first. With our old furnace it was hit and miss. If I slept in an hour or two we would wake to a cold furnace. I understand your frustration, it's no fun. Mixing coal isn't a bad idea.

Yes, the wood is seasoned, nice and dry. Yes there is a therm. to measure flue temps, gets to about 300-400F when getting decent heat from unit. Currently the return is open to the basement,(no ductwork coming off filter box - using lower basement air ), b/c we are only supply ducted to the basement, not upstairs. It just seems to be blowing the heat right out of the unit too quickly. I almost want to get an even slower blower speed than it has currently. It is a 1000cfm three speed blower and it is on the lowest setting.

 

[JrCRXHF]

My idea with the fire brick is to keep some of the ash up on top to make sure that it gets burned all the way plus i think this would help to keep a coal bed. My idea is to more or less set it up like a normal wood burning stove on where and how much air it gets. I still like the idea of air coming in low on the fire so i figured i would fire brick off everything but maybe the from 12" x 1" on the sides and see what happens. Fire brick is cheap so i figure it is worth a try.

The inside of my boiler had lots of creosote build up in the higher parts of the fire box so i know it does idle down. That and or the last owner burned some really green wood in it.

 

[bpirger]

I think it might be rather fair to say that the majority of these types of problems is the wood. When you say seasoned, what does that mean? Was it split/stacked for a year? What specie of wood? Have you checked a fresh split with a moisture meter? How big are the pieces?

Sounds like the house is tight...so if you are burning good, dry wood, at 6000 BTUs/pound, hard to understand how it isn't getting warm someplace...unless the wood is wet, a window is open, or there's a big draft somewhere that is not expected (like into an attic vent or something).

 

[FurnaceFrustrated]

I think it might be rather fair to say that the majority of these types of problems is the wood. When you say seasoned, what does that mean? Was it split/stacked for a year? What specie of wood? Have you checked a fresh split with a moisture meter? How big are the pieces?

Sounds like the house is tight...so if you are burning good, dry wood, at 6000 BTUs/pound, hard to understand how it isn't getting warm someplace...unless the wood is wet, a window is open, or there's a big draft somewhere that is not expected (like into an attic vent or something).

bpirger,
That's what everyone says, however, This stuff has been cut and split for over a year. Good and dry. Yes, it does get warm currently in the basement, however, it takes half the day to do it, b/c the blower keeps going on and off.

 

[maple1]

Reading back I see a lot of different suggestions. Have you followed through on any?

Generally speaking, when trying to trouble shoot, I like to try to put myself at the beginning of things, and work forward to methodically eliminate possible problems. So the first thing I would do here, is get my draft measured with a manometer (since the first item of business with any wood burning unit is a sound & properly spec'd chimney), to see if it is within specs of the furnace. Given that some are saying this unit was designed more for coal than wood, maybe a spec isn't spec'd for that unit for burning wood -if that is the case, if you measure your draft & post it, you would likely get some good feedback on your draft with respect to similar units.

It is sounding to me that you might have an overdraft, that together with using grates that were made for coal might lead to all your heat being sucked up the chimney - but without quantifying things, everything is playing darts in the dark.

How accurate is your flue temp thermometer? I just have an ordinary magnet one, seems it reads almost 100 too low when compared to the IR thingy I have.

 

[FurnaceFrustrated]

Reading back I see a lot of different suggestions. Have you followed through on any?

Generally speaking, when trying to trouble shoot, I like to try to put myself at the beginning of things, and work forward to methodically eliminate possible problems. So the first thing I would do here, is get my draft measured with a manometer (since the first item of business with any wood burning unit is a sound & properly spec'd chimney), to see if it is within specs of the furnace. Given that some are saying this unit was designed more for coal than wood, maybe a spec isn't spec'd for that unit for burning wood -if that is the case, if you measure your draft & post it, you would likely get some good feedback on your draft with respect to similar units.

It is sounding to me that you might have an overdraft, that together with using grates that were made for coal might lead to all your heat being sucked up the chimney - but without quantifying things, everything is playing darts in the dark.

How accurate is your flue temp thermometer? I just have an ordinary magnet one, seems it reads almost 100 too low when compared to the IR thingy I have.

Maple 1,

I don't have a manometer, but would like to know where to get one. Is there a good online website you could suggest where I could get one? The spec from the mfr. says the chimney must be capable of producing a minimal of .06 water column on a draft meter. That's it for info given on setting Baro and draft. It also says to install a Barometric Damper for proper operation, (I'm assuming for burning coal). One thing I did notice just last night, is that when the blower is running, I can feel a draft coming out of the front of the unit. Almost like there is a leak of some sort. AS far as the flue temp therm. , it is only a magnet one as well. Do not have an IR therm.
Thanks -

 

[maple1]

Here's mine, and where I got it:

http://www.dwyer-direct.com/shop/it...em=25&manufacturer;=&manufacturerItemNumber;=

It got here in less than a week. Been sitting in a box on my floor since, haven't had a chance to use it yet. I'm in Canada though, and I think it came from here too, but there are lots of places to get these from.

My prospective new furnace requires 0.1 in. draft, and the literature on it suggests a 26 foot chimney (but to verify draft with measurement) - to give a rough idea about chimney heights & drafts. Does it spec a max draft? Do you know if the 0.06 is for coal and wood? It doesn't sound too out to lunch for wood. If installing a baro, you should have a manometer to tune that with too. I might have missed it - but do you have a barometric damper in yet? If so, you could just play with it and set it to lower your draft considerably, to see what difference that makes to your situation - seat of the pants like.

You just may well find that draft has nothing to do with your problem, but at least then you'd rule it out.

 

[FurnaceFrustrated]

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?

 

[laynes69]

If the furnace has a forced draft or combustion fan, you cannot use a manual damper. I would think it could pressurize the firebox. A baro may accelerate draft after a baro, but will reduce draft on the woodfurnace itself. What speed did the draft test at?

 

[bigburner]

A good baro will be calibrated for inches water column, should be able to get draft close with that. some clear tubing and a tape measure will tell you draft. It does sound like an over draft issue, I am not opposed to trying a manual damper, is the flue connector the same as the stove?? You will never heat the up stairs the way you have it set up. If you can get duct to the second floor [sounds like there was some] pull some return air from second floor and make sure there aren't any stairway doors closed. Sounds back wards but you aren't getting natural convection threw the house, this will help.

 

[maple1]

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?

That doesn't sound right to me - I think it is physically impossible for a barometirc damper to increase or accelerate draft at the appliance. It is actually designed to decrease it at the appliance - can't for the life of me figure out how it would accelerate it. Did he or you try simply adjusting it to see what effect that has?

 

[FurnaceFrustrated]

maple 1,
I did try adjusting it over the weekend. Nothing worked. Still get quick cycle times and the heat goes right out of the plenum in a couple minutes.
I'm ready to give up.

 

[FurnaceFrustrated]

A good baro will be calibrated for inches water column, should be able to get draft close with that. some clear tubing and a tape measure will tell you draft. It does sound like an over draft issue, I am not opposed to trying a manual damper, is the flue connector the same as the stove?? You will never heat the up stairs the way you have it set up. If you can get duct to the second floor [sounds like there was some] pull some return air from second floor and make sure there aren't any stairway doors closed. Sounds back wards but you aren't getting natural convection threw the house, this will help.

bigburner,
Haven't officially measured draft. How do you do it with clear tubing and tape measure? The thimble is a 7" and the stove/ furnace pipe is a 7" as well, (according to the manual). the chimney flue is an 8x12. I wonder if the flue is too big? Manual calls for nothing less than 8x8 in size. Maybe this is for the oil and coal models? I realize about the duct work. We took it down to the upstairs b/c my Harman rep said it was the ductwork and not the unit. We got it down to a very simple system in the basement to test that theory, and it still is doing the same thing. Quick cycle times, I can watch the heat going right out of the plenum within a couple minutes. That eliminates that theory. Since the day I have first fired this unit, I have never seen it reach the required temp on the thermostat. The automatic draft damper on the front of the unit has never been called on to close on its own. And we have tested that as well.

 

[laynes69]

So let's say if the home is set for 72*, the wood furnace won't reach that temp? Also if the thermostat upstairs is calling for heat, the combustion blower on the furnace runs correct? I find it odd that the furnace won't heat the home or reach a set temp. The limit control is located correctly and have you measured the static pressure in the ductwork with the furnace running? You could lower the off temp a little which will allow for the blower to run longer. It still may not solve your problem. Our home is 150 years old and our firebox is half the size and we have no issues. You need a manometer, trying to make one can be difficult and if not built correctly it will be inaccurate. This way there's no guessing. What temperature is the house being heated to and what was the outdoor temps? I just don't see why you are having these problems.