Coal Neophyite Draft/Fire Control

Michacite · Post by **Michacite** » Sun. Nov. 30, 2008 9:11 pm

I just installed a Harman SF 3500 furnace and am suspicious that it has too much draft. I have 7" Selkirk stainless steel HT insulated Supervent Chimney. It is 36 feet tall and I have the furnace hooked directly into the insualted chimney with a T. The cap on the T has blown off a couple of times, and did it last night and the fire died with most of the coal unburned after the night. The fire is hot and the furnace will kick on. When the automated draft control closes a noise and a pulsating comes from the chimney. Can anyone help direct me. My dealer told me that I do not need to install a barometric damper, but I am not sure. Any help would be appreciated.

rberq · Post by **rberq** » Sun. Nov. 30, 2008 9:43 pm

What does your Harman manual say about whether to use a barometric damper?

When you have a good draft going, and the input air control closes, the chimney will pull air from wherever it can, including from the chimney top if that's the only way to satisfy the partial vacuum in the chimney. So either the chimney or the air column will vibrate like a musical wind instrument but at a much lower frequency. It might still do that a bit, even with a baro installed, but the baro will open and should greatly reduce the effect. My oil burner chimney used to do the same pulsation thing, even with the burner combustion air going full blast, and the pulsating draft would shake the smoke pipe violently and blow out the burner flame. Installing a baro fixed it.

P.S. I used to hook a wood stove into a tee at the bottom of a SS chimney. The plug on the bottom didn't fit tight enough and would sometimes fall out. My solution was to stretch an elastic tie-down strap across the bottom. The plug was recessed a couple inches, so I put a block of wood between the strap and the plug and that solved it.

Michacite · Post by **Michacite** » Sun. Nov. 30, 2008 10:26 pm

Thanks for your help. The Harman installation manual said that a baro may be needed if there was too much draft. I have four wood stoves that have not made the sound, but I installed a draft control on two of them since they went up more than 20 feet and that was the only way I could keep the wood stoves from over heating or burning too much wood even though they were new stoves. I guess my question really was that I am since I have not burned coal before, and the noise freaked me out. I installed a band to secure the cap, so that should take care of the cap falling out. Hopefully this should make the coal burn better. How do I know if I need a barometric damper? Should I purchase a manometer? If so, how do you hook it up?

gambler · Post by **gambler** » Sun. Nov. 30, 2008 10:50 pm

Michacite wrote:How do I know if I need a barometric damper? Should I purchase a manometer?

You need to measure your draft and that will tell you if you need a baro. But if it were me I would put one on reguardless.
You can borrow a manometer from the loaner program on this forum but for all the more they cost I would just buy one and hook it up permanently. If you are like a bunch of other coal freaks on this sight (me included) you will want to check your draft all of the time and be able to tweak your appliance. It is good to know as many readings as possible to help with any trouble shooting that may need to be done.

Michacite · Post by **Michacite** » Sun. Nov. 30, 2008 11:23 pm

Great, and thanks as well to you. Is there a brand of manometer that is better? Should I put in a flue thermometer, and if yes, what is the temp that it should be at?

gambler · Post by **gambler** » Sun. Nov. 30, 2008 11:33 pm

Michacite wrote:Is there a brand of manometer that is better? Should I put in a flue thermometer, and if yes, what is the temp that it should be at?

Get a dwyer model 25 with the 0 to 3 scale. I think they are around 35 or 40 bucks. Some use a magnetic thermometer that goes on the flue pipe (buy it anywhere that sells wood stove products) and some use a probe type thermometer that goes in the pipe. I have a magnetic one and see temps from 100 to 260 degrees but the actual flue gas temps taken with a probe thermometer are probably double that.

LsFarm · Post by **LsFarm** » Mon. Dec. 01, 2008 5:03 pm

With 36 feet of 7" ss chimney, you have enough draft to tee off and use the chimney as a central vacuum system for your house..

I'd bet that your chimney with a hot coal fire going, the draft is in excess of .12 to .15" wc.. that's inches of water column.. your fire wants .04"wc.. you are losing a lot of heat up the chimney.. your dealer needs some education too !!

I'd install a 7" or 8" Fields type M or type RC barometric damper asap.. you can PM member Matthaus to get one of the loaner manometers mailed to you.

I'm still shaking my head that a dealer selling coal appliances, and a customer with 30+ feet of chimney said that you didn't need a baro damper..

Anyway, once you get it set up correctly you will be very happy with coal and the heat it supplies as well as the long burn times..

Greg L

.

WNY · Post by **WNY** » Mon. Dec. 01, 2008 6:38 pm

Here for $31

https://www.coleparmer.com/i/mn/6806258

Ebay has a couple for $15-20+

Michacite · Post by **Michacite** » Mon. Dec. 01, 2008 9:15 pm

Wow this is so great! I can not believe all the help. I was shaking my head as well at the dealer. I have manual dampers on my wood stoves and this has 10 feet more! I will get a Baro ASAP. I am burning quite a bit of coal and the only way I can get the furnace cool enough to kick off is to shut it down.

Thanks to all of you for your help and expertise. I have been doing wood for about 5 years, and the coal is great, but I needed help. It drives me crazy

that my dealer did not know, thanks so much again to all of you for your help!

LsFarm · Post by **LsFarm** » Tue. Dec. 02, 2008 5:33 am

How about a photo of your instalation?? We don't have many of your coal unit on the forum.

Greg L
..

Michacite · Post by **Michacite** » Thu. Dec. 04, 2008 9:24 pm

Sure,

I am also a neophyte to this type of forum. I see you live in MI, I only know of one dealer in my area, the coal is anthracite and fairly large. I am curious to try different coal types as well. How does anthracite compare with other types of coal?

LsFarm · Post by **LsFarm** » Fri. Dec. 05, 2008 8:35 pm

PM me with where in Michigan you are,, I know of coal available in N Ohio, and N Indiana.

Greg L

Michacite · Post by **Michacite** » Mon. Dec. 08, 2008 5:23 pm

Thanks to all of you for your help. I installed a baro this last weekend, and my coal burn times went up dramatically like you all said. I find that when I run the wood, I have to back off the draft a little more than with coal. I actually have had coal burning nicely in the mornings, and the unit has not gone out since I installed the Baro. Thanks to you all, I am grateful for all your help!

Michacite · Post by **Michacite** » Mon. Jan. 19, 2009 8:29 pm

I finally got the Manometer I ordered hooked up. I purchased a new Dwyer. I am only getting .02" of WC. This does not make any sense to me. It does not increase if I cover the Baro, and I am really confused. It is 3 degrees outside and I have a full bed of hot coal that is to the top of the fire bricks in the furnace. I shake it (I had to reweld the arm on the shaker) in short quick strokes to get the ash out, and in the morning I have a couple of spots where the coal is still red, but mostly just ash and unburned coal pieces on the top. I have only an elbow (7") coming out of the furnace and it goes directly into a 7"-8" increaser and into the Baro. After the Baro it goes back down to the 7" SS insulated chimney up 36 feet to the roof. The Manometer fitting is right above the elbow but before the Baro. I ran a brass compression fitting into the 7"-8" increaser feeding a copper line and into the vinyl hose for the Manometer.

I continue to have the problem with the fire out in the morning with unburned coal. The Harman dealer is no help

, he says he has never run one of these furnaces. He did suggest that I should modify the automatic damper door so that it can get more air. I have had the stove up and running since right after Thanksgiving, and have burned 3.5 tons of nut coal. I have switched brands of coal (I am burning Reading now) and it still goes out each am. As soon as the thermostat calls for less heat at night, the fire dies and the house drops to 56 degrees. The furnace then has to be cleaned out and relit and the drama starts over. The first person that actually has one of these furnaces at Harman said that the coal I am burning is too wet. He said bagged coal is wet and I am wasting energy trying to dry it.

I have played with the Baro, played with the damper, adjusted the air valves on the front of the door, and am confused. While it is easier to feed only one stove (versus 4 wood burners) when it got cold, the fire went out, my pipes froze, and I feel like I will never get this. I have tried to follow all of the excellent advice, and either I am deluded (possible) or there is something I am missing. Sorry that this post is so long, but you folks are my only hope.

rberq · Post by **rberq** » Mon. Jan. 19, 2009 9:12 pm

My first thought was, too little shaking and therefore too much ash buildup, which reduces the space for new coal and chokes off the draft. But you said you are cleaning it out each time before restarting the fire. Are you cleaning it out completely, i.e. getting rid of all the ash buildup?

I'm looking at a picture of the unit: Do you close off both of the air inlets on the loading door? I think they should be completely closed once you have a good fire going. I see the ash door says "dual fuel" so those two air inlets would be open only for wood burning. Air for a coal fire should come ONLY (or 98 percent) from under the grates.

There appears to be a manual shutter on the ash door air inlet, to provide minimum air. In other words, when the automatic control has closed the air inlet, you still need some air to keep the fire idling along. Do you have that manual shutter adjusted to maintain a minimum fire?

When you load it up and start the fire, how many pounds of coal does it take? Are you filling it right up to the top of the firebricks before leaving it for the night?

When the fire goes out, is there a lot of unburnt coal still in the firebox, or has it all burned out to ash?

What draft setting does your Harman manual recommend? (I am guessing it is in the range of .05 to .10).

You mentioned multiple wood stoves. Are any on the same flue as the coal stove? That could constitute a severe air leak and reduce chimney draft.

Lots of questions, I know -- but that's how we will figure this out. It looks like a super stove/furnace, so I'm sure there's not too much that is wrong. Can you post pictures?