Harman Mark III Chimney/Venting

TCMW · Post by **TCMW** » Tue. Oct. 01, 2013 1:52 pm

Hey everyone

Finally decided on a coal burner and got a nice used Mark III for $600.00.

The manual says 42 to 49 inches min area for venting. Thats based on 8" x 8" sq flue minus its wall thickness(5/8") gives us 6.75 x 6.75 = 45 sq in cross section area.

I will be using class A 316 stainless pipe 33' high. If my math is correct: the area on 6" I.D. pipe = 28 sq in of area. So I need to get 8" I.D. pipe to have 50 sq in of area.

Stove has 6" connector exiting in the rear.

is this correct??
thxs sam

titleist1 · Post by **titleist1** » Tue. Oct. 01, 2013 2:47 pm

Hi Sam...welcome to the forum and congrats on a good decision regarding coal heat.

I heated with a Mark III for about 19 years using a 6" ID SS chimney without any draft issues. Mine is on a rancher so it is only about 20' tall (from the thimble). I do not think you need the 8" ID from my experience.

If you are not familiar with the Mark III, one recommendation I would make is to check the baffle plate on that is on the top of the firebox to make sure it is not warped and it is clean of all fly ash. The fly ash likes to accumulate there and block air flow and lessen the heat transfer to the air tubes. The other place fly ash likes to accumulate (since you have a rear exhaust port) is inside the rear of the stove body.

TCMW · Post by **TCMW** » Tue. Oct. 01, 2013 3:28 pm

Thxs titleist

yea from the little I know I think the round drafts better than square.

and boy are you right about the accumulation in those places. when I got it home I found quite a bit.

no warping on the baffle plate.

planning on using nut size and having some pea on hand for warmer days. what size did you burn?

thxs again

captcaper · Post by **captcaper** » Fri. Oct. 04, 2013 6:46 am

I ran my MarkIII in the basement for about 6 years or so. 6In SS double walled and about 35 or 40 ft high. It went threw the outside wall just above the stove so most was an outside chimney. This was on the gable end. I had to offset were it met the overhang. Superpro had a offset kit. They said not to offset it outside. Not sure why but I wasn't and couldn't cut threw my overhang up that high so I offset around it.
This chimney has such good draft. Never never any down draft or CO back into the room. I used a manual pipe damper shut all the time and never had an issue in any type of seasonal temperatures. And I started in Oct and went until later in April.

I ran Pea in the fall and spring and nut in the coldest part. This Mark III would idle down so nice with Pea during the day when temps rose outside and when night came temps fall fast here so I would only have to bump up for over night. The Pea would just smolder like a slow burning cigarette. Amazing. I now have a Super Mag and I bet I am going to miss that MarkIII in the fall and spring. I can't believe it will idle down so low for me. With the Mark III I could touch the stove top and not get burned.

TCMW · Post by **TCMW** » Fri. Oct. 04, 2013 10:02 am

thxs captcaper

thats what I am doing 35' but no gable to offset.

just curious, was your 6" ss 316 or 304 inside? how did it hold up? seem like the thing to do is to keep it dry, clean and I saw someone in here said they lightly oiled the inside during off season.

great burn info.
thxs again

Post by **franco b** » Fri. Oct. 04, 2013 10:08 am

If they wanted more area for the flue why would they put a 6 inch outlet. Use the 6 inch. It will work much better than the 8.

SMITTY · Post by **SMITTY** » Fri. Oct. 04, 2013 10:54 am

You got a great deal on that stove Sam. Just FYI, I paid 3x that for mine brand new after tax here in MA ....

captcaper · Post by **captcaper** » Fri. Oct. 04, 2013 4:24 pm

TCMW wrote:thxs captcaper

thats what I am doing 35' but no gable to offset.

just curious, was your 6" ss 316 or 304 inside? how did it hold up? seem like the thing to do is to keep it dry, clean and I saw someone in here said they lightly oiled the inside during off season.

great burn info.
thxs again

Mine was 6 in. inside. Double walled which made it 8 in across. So 1 in of insulation around the inner 6in pipe. Inside was different SS then outside. I bought mine at Lowes..Go the Selkirk.com that makes SuperPro SSPipe and download the PDF catalog and write down all the part numbers you might need. At the Lowes plumbing dept a fellow will open the computer there and order the parts. They came fast and I returned extra stuff with no problem even though I ordered it. They had the best pricing. The pipe is twist and lock and has held up against many storms. It sticks up high and away from the roof so I got the roof bracket SuperPro offers. Also I doubled up on the wall brackets. They have quite a selection. The pipe is made by Selkirk and is called SuperPro. Can't remember what grade SS. It has held up for 6 or 7 years now fine. I have a chimney cap on it.
It's at the end of the season and threw the summer that the water or moisture might work havoc and not during the season when burning. As long as it's dry your o.k. against sulfur effects. What I did at the end of the season was to burn oil from the truck oil changes. I got a big cast pot and put some rags in there and lit it up. The smoke and oil soot coats the lining inside the pipe for the summer.

TCMW · Post by **TCMW** » Mon. Oct. 07, 2013 9:10 am

I agree Franco. I', going with the six.

I also read here that some guys burn wood at the end of coal season Captcaper.

Yea Smitty I was the first call on the stove and I told him I was coming that nite. When I got there he told me other people called and wanted to pay more for it. But the guy was a real gentleman and agreed to our deal.