Harman 256 Dual Fuel Insert Having Trouble Keeping It Going?

 
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CoalCracker3
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Coal Size/Type: Nut, nutty, nuttier
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Post by CoalCracker3 » Mon. Nov. 09, 2015 8:14 am

Good morning members:

Need a little help. Here's the set up... Harman 256 dual fuel insert installed in fireplace with 25 feet masonry/tile lined chimney 8x8. No BPD or MPD due to no pipe. Stove is set in fireplace opening and all border areas packed with fiberglass batt insulation. Stove trim peices cover border areas. I have the fire box reduced 50% with firebrick and rockwool. The stove has good draft and burns great until it warms up outside then I loose the fire even if I'm actively trying to keep it going. Was able to recover but it took adding charcoal to do it. I think what's happening is draft is really strong during cold periods but rapidly drops off when am warm up occurs. Not sure how to deal with primary air adjustment to compensate. Also stove temps never seem to get above 200deg. The blower system works great pours the heat into the house seems to keep the firebox too cool?!? Any ideas would be appreciated. I live near Pottstown in SE PA.

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Lightning
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Post by Lightning » Mon. Nov. 09, 2015 2:15 pm

What exactly are we looking at in the second picture? The square opening, is that the exhaust port? Never seen anything like that. I'm kinda shocked that there isn't a pipe leading up into the chimney where it would be sealed, instead of around the unit. :? :shock:

A manometer would help you but where would you install it? Normally the stove pipe gets probed.

Is it possible that the chimney draft is being satisfied by other means? Like air is getting in somewhere else? If so, This would severely inhibit your draft.

 
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CoalCracker3
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Location: South East, PA
Hand Fed Coal Boiler: Outdoor coal/wood stove sequoia 200000btu
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Hand Fed Coal Furnace: Harman sf256 coal/wood, Harman magnafire insert
Baseburners & Antiques: Buckwalter Villa potbelly, Keeley Columbia Oak
Coal Size/Type: Nut, nutty, nuttier
Other Heating: Very cold oil burner (never had a delivery)

Post by CoalCracker3 » Mon. Nov. 09, 2015 3:54 pm

Hello Lightning

Thanks for the reply. You are correct the second picture is the back of the stove. I have had a couple air tight wood stove inserts over the years that had similar exhaust set ups so I really didn't think anything of it when I installed it. It sure does limit the use of dampers and a manometer. I used a inscents stick to due a smoke test and it doesn't seem to be pulling or leaking draft around the stove perimeter. I'm sure it's not a perfect seal but I was very carefull packing the perimeter knowing the CO concerns with coal. It seems to draft fine when it cold. Trouble is maintaining a low fire as the day warms up. May be its just gonna be a bugger in the shoulder mos. I had to contact Harman to identify the stove model no. They had trouble identifying it but after consulting with Mr. Harman he stated it was a SF256 basically an SF250 adapted to a insert.

 
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coalvet
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Post by coalvet » Mon. Nov. 09, 2015 4:06 pm

Just as an experiment I would not use the blower, if it is cooling the firebox to much it will affect the burn adversely.

 
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CoalCracker3
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Location: South East, PA
Hand Fed Coal Boiler: Outdoor coal/wood stove sequoia 200000btu
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Hand Fed Coal Furnace: Harman sf256 coal/wood, Harman magnafire insert
Baseburners & Antiques: Buckwalter Villa potbelly, Keeley Columbia Oak
Coal Size/Type: Nut, nutty, nuttier
Other Heating: Very cold oil burner (never had a delivery)

Post by CoalCracker3 » Mon. Nov. 09, 2015 4:27 pm

Thx Coalvet. It does have an aftermarket blower. May be moving to much air!

 
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Lightning
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Post by Lightning » Mon. Nov. 09, 2015 4:30 pm

CoalCracker3 wrote:It seems to draft fine when it cold. Trouble is maintaining a low fire as the day warms up. May be its just gonna be a bugger in the shoulder mos.
Are you using an exterior chimney?
If there is a clean out for it, is it sealed well?
Last edited by Lightning on Mon. Nov. 09, 2015 4:51 pm, edited 1 time in total.

 
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CoalCracker3
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Location: South East, PA
Hand Fed Coal Boiler: Outdoor coal/wood stove sequoia 200000btu
Hand Fed Coal Stove: Dual comfort coal/wood
Hand Fed Coal Furnace: Harman sf256 coal/wood, Harman magnafire insert
Baseburners & Antiques: Buckwalter Villa potbelly, Keeley Columbia Oak
Coal Size/Type: Nut, nutty, nuttier
Other Heating: Very cold oil burner (never had a delivery)

Post by CoalCracker3 » Mon. Nov. 09, 2015 4:51 pm

Ok chimney is block exterior has 3 flues one flue to boiler in basement, one to second floor fireplace and one to first floor Harman insert. Looks like terra cotta tile lined. It seems to be tight sealed with no clean out. There is about 20 feet of flue pipe leading to a stone exterior chimney cap. Only place it cold be leaking is at fireplace firebox to chimney seam or possibly a bad terra cotta seam that I can't see


 
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Lightning
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Post by Lightning » Mon. Nov. 09, 2015 5:05 pm

I had the same trouble with my exterior chimney. It would not draft well during warm weather burns. I had many draft failures. What happens is, the chimney gets cold overnight and then when it's warm during the day, it takes time for the chimney to adjust to the new outside temperature. Essentially, the top half of the chimney is cooler than the ambient air around it. This creates a problem with drafting. If the flue gases cool down lower than the ambient temp outside, the chimney draft will fail. This problem don't show up when its cold out because the stove is running hotter.

There are a couple of work arounds. You can run the stove hot when its warm out and overheat the house and burn unnecessary amounts of coal doing so, which is no fun.. OR what I have found that works really well is using excessive amounts of secondary air. If your unit has independent adjustable secondary air controls, open them up and turn the primary air down.

Another thing I have had success with is cracking my load door an 1/8 inch. It works just the same as opening the secondary air.

 
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Lightning
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Post by Lightning » Mon. Nov. 09, 2015 5:08 pm

The spinners on the load door, do they allow air in over the fuel bed??

 
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Post by Lightning » Mon. Nov. 09, 2015 5:11 pm

I also wanted to add that you could probe a manometer thru that shroud that seals against the fireplace. It would only take a 3/16 inch hole to do it.

 
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CoalCracker3
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Location: South East, PA
Hand Fed Coal Boiler: Outdoor coal/wood stove sequoia 200000btu
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Hand Fed Coal Furnace: Harman sf256 coal/wood, Harman magnafire insert
Baseburners & Antiques: Buckwalter Villa potbelly, Keeley Columbia Oak
Coal Size/Type: Nut, nutty, nuttier
Other Heating: Very cold oil burner (never had a delivery)

Post by CoalCracker3 » Mon. Nov. 09, 2015 5:18 pm

Yes load door spinner is secondary air over the fuel. Thanks for the ideas. I believe what your saying could be true. The thermal mass of the chimney is not helping it's a large block structure and my stove and flue runs cold to begin with, due to the efficient blower system. Maybe to efficient!

 
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Post by Lightning » Mon. Nov. 09, 2015 5:22 pm

CoalCracker3 wrote:Yes load door spinner is secondary air over the fuel.
Excellent. Run those suckers wide open next time you want to achieve a low slow burn during warm weather. I think it could solve your problem.. :)

Edit - The extra heated air mass that the secondary air provides will promote maintaining a healthy draft.
Last edited by Lightning on Mon. Nov. 09, 2015 5:31 pm, edited 1 time in total.

 
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CoalCracker3
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Location: South East, PA
Hand Fed Coal Boiler: Outdoor coal/wood stove sequoia 200000btu
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Hand Fed Coal Furnace: Harman sf256 coal/wood, Harman magnafire insert
Baseburners & Antiques: Buckwalter Villa potbelly, Keeley Columbia Oak
Coal Size/Type: Nut, nutty, nuttier
Other Heating: Very cold oil burner (never had a delivery)

Post by CoalCracker3 » Mon. Nov. 09, 2015 5:28 pm

Will do thanks

 
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Post by Razzler » Tue. Nov. 10, 2015 8:43 am

are you filling the stove up to the top of the fire bricks when reloading? The fire box will hold about 120 lb of coal. You can see 500 to 600* on the front of the stove when you have it cranked up. Try not running the fan on the warmer days that should keep the stove temp up higher and keep your draft going. If you open the draft knobs all the way on the load door I think you will loose the fire. That's a lot of air. I had a SF250 for 5 years they are great stoves one of the best hand fired stove you can buy.

 
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CoalCracker3
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Posts: 49
Joined: Sat. Aug. 22, 2015 8:20 am
Location: South East, PA
Hand Fed Coal Boiler: Outdoor coal/wood stove sequoia 200000btu
Hand Fed Coal Stove: Dual comfort coal/wood
Hand Fed Coal Furnace: Harman sf256 coal/wood, Harman magnafire insert
Baseburners & Antiques: Buckwalter Villa potbelly, Keeley Columbia Oak
Coal Size/Type: Nut, nutty, nuttier
Other Heating: Very cold oil burner (never had a delivery)

Post by CoalCracker3 » Tue. Nov. 10, 2015 11:26 am

Hello Razzler

Thanks for the reply. To answer you question I am filling to the top of the bricks in the back half of the stove. I am running a restictor plate in the front half. So the initial fuel load is about 60# of nut coal. I know my coal is good because I'm burning it in other stoves with no issues. My stove is set up with the blower/heat exchanger on the opposite end of your old stove. I will attach a picture side view so you can see what I'm saying. I was hoping a former SF owner would post. Were you running a BPD or a MPD on your sf250? Did you ever run a restrictor plate? I've had good luck with my other stoves finding how they like to burn. I can tell you this even with the restrictor this stove will run you out of the house. I can't imagine how much heat it makes with a full fuel load. When it runs its impressive. Today I gave the stove a little more secondary air (1/2 turn open each wheel was at 1/4 each) and turned the blower rheostat way back and it's burning well. At night I've been running primary air at one turn open and 3/4 turn during the day.

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