Hand Fired Stove Lights OK, but Doesn't Get That Hot

Have to say, this is a great forum. I bought a Harman furnace (2500 SF) two seasons ago. Have it connected to the forced air system in my house. It uses the air handler blower from the much larger electric (Goodman) furnace, runs 220Volts.

I ran it two winters with wood, last year at least 6 cords. Didn't have to buy the wood, but wow, getting your own firewood is a lot of work. The folks who saw my furnace said "Jeez, get some coal". So I got 3 ton of chestnut coal (I guess that's anthracite) from the nice fella in Stroudsburg, PA.

This is probably a good stove/furnace, but have to say that the Harman folks are pretty strict. Not allowed to call them. I bought this from Stoves-n-Stuff on 611 (Stroudsburg too?). They are real nice, but don't necessarily know that much about every stove, flue, etc. Kind of convoluted asking them questions.



Anyway, I have read many of the threads here about starting coal fires. I can get the coal burning, the "blue flames". Yes, looks like the burner of a natural gas kitchen stove. But my Harman never gets very hot. It seems to run somewhat hot only with the clean-out door slightly open. You can see that here with the electric damper as well.



The electric damper is run by a sensor in the vertical hot air (plenum?) duct. The damper closes when the sensor hit 140 degrees. Burning just coal, it has reached 140 yet.



I haven't put a very large amount of coal in the combustion chamber yet, (isn't really that cold outside), but it really seems the fire is not getting enough air
Probably what's in there now is a little more than half of a 5 gallon bucket.



I just cleaned the chimney flue (I think 8" square) and exhaust pipe (8" round?). The furnace burns plenty hot with wood. I would never run a wood fire with the cleanout door open.

Thanks for any comments or suggestions!!

Welcome to the FORUM my friend.I don't know about all them thar electric thingy's, but, you're going to have to get a lot more coal in her to find out what she can/will do. Be patient, you'll get plenty of suggestions. Hell, if she worked good on wood, I bet you'll be thrilled with coal--you just gotta get the combination figured out.

not sure how your controls work,fill to the top of your firebrick(at least 8" thick) of coal,after 12 hours shake then you will need about half 5 gal. bucket of coal to replentish. you will have plenty of heat

It almost looks like a Hotblast. I want to.say you could bolt a blower onto the cleanout door. From the looks of it you don't have any way to control air on the ash cleanout. It looks like a blower attachment on the botton ash door. You need some way to control the air intake.

Why aren't allowed to call Harmin?

You need at least 4" or more of RED hot coals to get a good burn and heat. Also you need to have the box filled right up like an ice cream cone to get a long burn thru the night. But in the morning make sure you still have 4" of red hot coals going. Then you'll have good heat.

i used the combustion blower and natural draft(damper on ash door) the both worked. the combustion blower seemed to heat the coal a little .just make sure your close the loading door air off,they are only needed with wood.

Forget everything you know about burning wood, it does not apply to coal.

Coal likes to be thick and left alone. Loading twice a day is the MAX you will need to do. With the amount of coal that unit can hold, getting 24-36 hour lower temp burns are not out of the question. The amount of coal you are showing is about right for when the fire is dying and going out. Let me repeat coal likes to be loaded up and LEFT ALONE TO BURN. Coal does not like going up and down in temp like oil furnaces which is what your automatic controls are trying to mimic. Personally I would disconnect the auto control on the ash door and put a screw damper on there. Once you learn how to use this, your 2 load door screws will be just barely cracked, 1/8 to a 1/4 turn each. Coal needs its air from under neath, with just a little above the fire air, very different from wood. You will need very little air coming in through the ash door. Open like you show is only for when you are banking the fire, loading up with coal.

As to getting the most out of this unit, coal needs to run at a relatively steady temp. My unit, for example once lit and loaded properly can run at 300 degrees for around 36 hours and still have enough fire to reload. The coal will be about 9 inches deep when I am done loading. I would suggest forgetting the thermostats in the house, you should try running the blower on the air handler constantly and learn to run a nice steady fire. You will learn to control the temp of the unit with the air flow. First you will need to LOAD IT UP TO THE TOP of the fire brick. This will take several lifts as you will need to get each lift to start burning before putting the next one on. Go look at the various how to like a hand fired stove topics, there are some good videos in there. You will use a lot more than a half a bucket at each loading. More like one to two buckets depending on how hot it is running.

Do you have a Barometric damper on the flue pipe, and if so where is it set? This may or may not be right for your application. My units are WAY more efficient with manual flue dampers, but you need to know how to burn coal and what is involved with using it properly before you go here.

In the end, lots more coal in the fire box, get a STEADY fire going, leave the fire alone till it is time to reload. You will be able to control the temp of the unit by regulating the amount of air going through the coal. You may need to open a windowstat now and then. Your unit should be more than capable of running you out of the house with heat on some of the coldest winter days. Most stoves can be easily run between 150 and 600 degrees by learning to control the air flow for that unit. Hang in there through the learning curve and the black rock will reward you. It will probably take a full season or two to learn how to properly burn coal, but it will be well worth it in the long run.

i don't know if you still have the manual but if you go to harmons web site and click on the instlation manual it has some info on burning coal in this unit.. hope this helps

Your unit does not need a blower to go in the ash door. You can easily over fire the unit just by leaving the ash door open. 7 or 8 inch flue will be more than sufficient to vent your unit. You just need to learn how to burn coal. It is a learning process. Burning coal is not just throw some in and see what happens. Learn the techniques and methods that coal needs and you will be rewarded with smooth even heat.

Take a look at some of these previous posts:

How to Light a Hand Fired Coal Stove
How to light a hand fired coal stove




This is a series that William put on YouTube about his particular stove, but the basics of building and maintaining a coal fire apply to all hand fired units. There are several parts to this series, but they should all come up. Well worth the time to watch and learn

Harmon Hand Fired Coal Furnace.
This one is about the same brand of coal furnace. Around the 9th posting, DLJ says the following

That description sounds like the original designers were thinking fuel oil furnaces... It sounds maybe OK for wood, but not coal. I think you are loosing a lot of heat up the chimney. You've called this a furnace so I'm assuming this runs hot air for heat circulation. I think you need to think of how to take the fundamental design to go from an "on-demand" to a "continuous" heat source. So your suggestion is definitely going in the right direction.

Second is to look at how to keep more heat in the house and not going out the stack...

As the others have said...
First you need to learn how to burn coal...
Forget everything you know about wood fires...
You got the coal started, now you need to fill the stove to the top of the bricks...
Then the auto/electric damper will do its job...
Make sure enough air gets in to maintain a idle fire when the damper is closed...
Looks like there are idle holes in the damper door which should do the trick...
The other issue is the heat going up the stove pipe...
A baro should be installed if you are burning strictly coal...
Baro and wood is a no-no...
Question on the electric damper...
does it slowly open/close the air feed damper in small increments...
or is it full open to full close more like an on/off switch..

coal bob wrote:i don't know if you still have the manual but if you go to harmons web site and click on the instlation manual it has some info on burning coal in this unit.. hope this helps

Thanks, I didn't see that. Answers some of my questions.

Bear038 wrote:Personally I would disconnect the auto control on the ash door and put a screw damper on there.

What's a screw damper?

Bear038 wrote: I would suggest forgetting the thermostats in the house, you should try running the blower on the air handler constantly

OK, I explained poorly. The Goodman air handler has 8 speeds. When the Harman furnace is burning I set the blower to the lowest speed, and leave it until the fire in the Harman is out. It is a very quiet blower speed, can't hear it, barely feel it. Nice. As opposed to the Goodman auxilary heater, or my Goodman heat pump. When those suckers go on, the blower sounds like take-off at Newark International Airport.

Bear038 wrote:Do you have a Barometric damper on the flue pipe,

no dampers on the flue pipe. The stove was installed by the fellas that Stoves and Stuff sent here. They installed the exhaust pipe. A few weeks later, my HVAC man connected the whole system to the existing Goodman electric furnace, added a dedicated cold air return, and other fire protection cladding. He said I was good to go.

OK, I can see that most of my problem is not enough coal to pull the draft. Looking forward, next 5 days, weather says hits 60 degrees each day. I am wanting to try filling up the firebox, see what this bad boy can do. But probably not in the next five days.

One of the things I want to add, don't see much specific mention in other threads, is the comfort of wood combustion, coal probably the same. We live in a damp area (Blairstown, NJ) natural springs everywhere, have a creek in the back, pond next door. And never seems to stop raining. If I run the Goodman electric heat, it just never seems to feel warm, no matter what the thermostat says. Having this Harman here (the past two years) just so much more comfortable.

CapeCoaler wrote: Question on the electric damper...
does it slowly open/close the air feed damper in small increments...
or is it full open to full close more like an on/off switch..

The electric damper is either full open or full closed. Nothing in between. But it does have an adjustment for how large "full open" is

You have two screw dampers on the fire box door. The round things that screw in and out to regulate the amount of air.

The "experts" who installed your unit with out either a baro or a manual flue damper obviously did not know what they were doing. No wonder they have not been of any help to you trying to learn how to burn coal in your unit. You need to control the draft through the fire.