Newbie With New Harman Mark II

Wow, what a nice coal stove! Now to get the most out of it. Typically, I find that if the fan is not running, I do not get much heat out of this stove. Is that common? I have no dampers on the pipe which is only 1 full length, 2 elbows and another pipe about 18" long that goes on into the flue.

I'm considering the recommendations on here for the R/C 6" Draft control (acutally would use the RCBT model in my situation). Would this help me get more heat? I don't want to lose the good draft I have with my 8" 30' high chimney. Stove is in the basement and the top of the chimney is at least 2' above the very peak of the roof of our home.

Also, burn time. I'm using Reading anthracite in nut. Lasts about 12 hours with one full turn open on the draft.

Open to good experienced advice!

Hi MP, welcome to the forum.

Your stove won't put out much heat without the fan running, the sides and front of the stove will radiate heat, but the back and top have the second layer of steel, making the air passageway for the fan, and without the fan washing the heat off of these areas, the stove's output will be a lot less.

Harman recommends a Barometric damper, set at around .05" wc. With your tall chimney, you probably have double or triple that amount of draft. Too much draft will pull a lot of heat out of the stove and up the chimney. The baro damper will control this excess draft and allow the stove to run warmer, use less coal, and give longer burn times.

A steady consistant draft will make the adjustment of your air inlet knob in the ashpan door much easier. this is because without a baro damper, one day with strong winds, cold temps, your draft will be much stronger than the next day with calm winds, and milder temps... So one day 3/4 of a turn open would be about right, the next day maybe 1-1/2 turn is needed to get the same burn time and temp output from the stove... with the draft consistant, the variables will be less, the settings much more consistant.

We have a manometer loaner program so you can borrow one of the traveling manometers, and set your baro accurately.

Hope this helps.. Greg L

I would install a manual damper about a foot above the stove and a Baro set to.05 between the manual Damper and chimney connect .

Replace the top elbo with a Tee plug the end with the baro .
(theres several Pics here in the forum of this type install but you'll have to find them, you'll prolly learn even more while looking)

The baro will prevent over draft and the MPD will slow the flow of hot gasses

Unless you have a manometer set up full time, that is you buy one and install it. And have several CO detectors around the house, stay away from a manual damper, they are just that MANUAL, there can be too many weather changes or a clogged flue that can result in missadjustments and possible health hazzards..

Also, since you have an owners manual that specificly states that a manual damper is NOT to be used, any insurance claim will be denied if there is a manual damper in the system Harman is stating this because it is the safest route.

Untill you have several seasons of experience and a full time manometer to monitor your draft and probe thermometers to monitor the flue temps a manual damper is guess-work and potentially dangerous..

Please, safety first ALWAYS. I've burried too many friends.

Greg L

LsFarm wrote:Unless you have a manometer set up full time, that is you buy one and install it. And have several CO detectors around the house, stay away from a manual damper, they are just that MANUAL, there can be too many weather changes or a clogged flue that can result in missadjustments and possible health hazzards..

Also, since you have an owners manual that specificly states that a manual damper is NOT to be used, any insurance claim will be denied if there is a manual damper in the system Harman is stating this because it is the safest route.

Untill you have several seasons of experience and a full time manometer to monitor your draft and probe thermometers to monitor the flue temps a manual damper is guess-work and potentially dangerous..

Please, safety first ALWAYS. I've burried too many friends.

Greg L

With a barometric damper installed, there is no need for a manual damper on that stove.

A manual damper will in fact slow down the rate of flow of exhaust gasses, but this is not needed with a brand new, airtight Harman Mark xx stove... the fire can be shut right down and starved for air with the spinner air control knobs. Spinner knobs closed = no air to the fire, and no air up the flue.

In a leaky old cast iron stove with joints at each corner and edge, with sliding, sloppy air vent controls, the fire may be uncontrolable with a strong draft and a hot fire. In this situation, I recommend throwing the old stove away or taking it completly apart and resealing it... it is unsafe if it it leaking.. A MPD is only a bandaid for a bad stove in this case.

But with a brand new Harman Mark stove, the ONLY time there could be too much flue gas velocity would be if the ash door was open, and you are trying to wake up the fire prior to shaking and refilling... and at this time, you WANT the added flue gas velocity to pull the air through the fire.

I see no reason to not follow the manufacturer's recommendations and directions. Install the stove as the manufacturer recommends and opperate it by the book for awhile...

Interesting.

I've got a MK II with probably a 35' tall outside masonry chimney. I've never had the air inlet (spinner) open more than 1 full turn. I get a stove top temp of 500 on top of the air chamber, and on the side of the stove it's 600 degrees. That's the highest I steadily run the stove.

Must be the draft that causes the differences.

Hi Islander, I think that lots of new stove owner/operators try to make too much heat too fast... These are not meant to put out peak heat all the time... the beauty of a good coal stove is long burning even heat.. Not a blast furnace followed by a reload every few hours like a lot of wood stoves.. [been there].

Every stove, house, chimney and instalation is different.. the leak rate into the house [infiltration] has a lot of effect on the draw through a stove, and it is very hard to put a value on it without instruments... But there are quite a few forum members who have benefited by installing a dedicated outside air source to the combustion air inlet in their stoves.

The location of the house and it's chimney has a huge effect, on a hill or in a valley, in a wind shadow, or blocked by other buildings..

Greg L.

LsFarm wrote:Hi MP, welcome to the forum.

Your stove won't put out much heat without the fan running, the sides and front of the stove will radiate heat, but the back and top have the second layer of steel, making the air passageway for the fan, and without the fan washing the heat off of these areas, the stove's output will be a lot less.

Harman recommends a Barometric damper, set at around .05" wc. With your tall chimney, you probably have double or triple that amount of draft. Too much draft will pull a lot of heat out of the stove and up the chimney. The baro damper will control this excess draft and allow the stove to run warmer, use less coal, and give longer burn times.

A steady consistant draft will make the adjustment of your air inlet knob in the ashpan door much easier. this is because without a baro damper, one day with strong winds, cold temps, your draft will be much stronger than the next day with calm winds, and milder temps... So one day 3/4 of a turn open would be about right, the next day maybe 1-1/2 turn is needed to get the same burn time and temp output from the stove... with the draft consistant, the variables will be less, the settings much more consistant.

We have a manometer loaner program so you can borrow one of the traveling manometers, and set your baro accurately.

Hope this helps.. Greg L

Excellent information - thank you Greg. I've contacted my Harman dealer and will be picking up the draft regulator today. We are on top of a hill and have a 30+ mile view to the south. So when we get an east or south wind it can be very interesting up here! No problem with downdrafts, just mostly the wind making too much - so the regulator will surely stabilize the stove. THANK YOU!

I am also interested in the manometer loaner program so I can set this draft control to peak performance - that would be very much appreciated! Thank you for your helpfulness.

I've used coal before, in my first church with two potbelly stoves! That was an amazing experience with stoves that are not airtight! Big difference with the Harmon!

Islander wrote:Interesting.

I've got a MK II with probably a 35' tall outside masonry chimney. I've never had the air inlet (spinner) open more than 1 full turn. I get a stove top temp of 500 on top of the air chamber, and on the side of the stove it's 600 degrees. That's the highest I steadily run the stove.

Must be the draft that causes the differences.

That's exactly what I am finding with this stove - 1 full turn works excellent. When I give it only a 1/4 turn at nighttime (no wind blowing outside), it does not do well and just leaves a bed of grey coals by morning.

I usually run with the spinner open 1/2 a turn. Gives me 250-300 degrees stove temps. Only when it gets cold do I have to crank it up more. 3rd year with the stove, so there aren't too many surprises left, but there are some.

MountainPreacher wrote:

Islander wrote:Interesting.

I've got a MK II with probably a 35' tall outside masonry chimney. I've never had the air inlet (spinner) open more than 1 full turn. I get a stove top temp of 500 on top of the air chamber, and on the side of the stove it's 600 degrees. That's the highest I steadily run the stove.

Must be the draft that causes the differences.

That's exactly what I am finding with this stove - 1 full turn works excellent. When I give it only a 1/4 turn at nighttime (no wind blowing outside), it does not do well and just leaves a bed of grey coals by morning.

I'll bet with that chimney and location that the draft to the stove without the barometric damper will be quite high.

Well, I have the draft control and we'll get that draft down and keep some of that heat inside where it belongs!

OK, though I haven't set the draft control with the manometer, these are the readings I just took from the stove open one turn and a steady fire loaded 4 1/2 hours ago:

Top of stove: 400

Pipe (up 2' from elbow): 160

After draft control: 100

That is sounding about right,, I assume you used the 'rough scale' on the baro damper to set it at about .05" wc? You should be able to see the damper's flap/door moving with the wind, and maybe close when the wind is calm and the fire is low... but with a hot fire, or a strong wind, the baro should be 'working' and keeping your draft at roughly the setting on the slide-weight.

Your spinner knob settings will have to be relearned... I have to suggest that you write down what you try... it may seem silly, but there are enough variables that having it written down helps sort them out... and next year you will love haveing records to refer back to.

So: write down the outside temperature, the wind if you can guess it, or just say light/ med. / very windy. and then write down the number of turns open on the spinner knob, and take a look at the stove temp, and stack temps after the stove settles down for about 30 minutes...

Hope this helps... Greg L

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