Harman Mark I Window Gasket

I picked up a used Harman Mark I stove with brass trim. Prior to installing it I am refurbishing it.

I noticed that the window only had gasket material on the left and right sides and none on the top or bottom. At first I assumed this was due to burn out and figured I'd replace the gasket and wrap the entire window, sides, top and bottom, with gasket material.

But, I was leafing through an owner's manual that I downloaded from Harman's website and found information that seems to support the conclusion that maybe the window gasket I found; i.e. only the sides of the window gasketed, is what is called for.

On page 7 of the Harman Mark series coal stoves Installation and operator's manual is figure #7 showing a side profile of a Mark series stove. The drawing shows a cut away side profile and indicates the primary air control (the large air dial on the ash pan door) which allows air to enter underneath the grates. What is interesting and somewhat vague is on that same drawing it shows what is called a secondary air supply and points to the glass window of the top loading box. The drawing indicates air entering the fire chamber. There is no air control mechanism on the Harman Mark series stove in this location and the text did not address this issue. Thusly I'm left wondering if the side gaskets I found on my used Harman Mark I is a design feature.

I know that the SF-250 has air control dials on its fire box door.

If any one can address this issue I'd be greatly appreciative.

Actually, now that I look at it, the old gasket is not burnt at all, but clearly cut. I guess this is how Harman intended it.

Thanks,

Town

Well, after all that typing!

I called a Harman dealer and learned that the open sections of the window gasket were for a reason,... air flow.

I guess its pretty simple once you think about it.

Stove is coming along great. Heres a photo after painting. I'll have some more once its fired up.

Town

Tomorrow I was planning on going to the store where I bought my stove. They are a Harman & Quadra dealer. Mostly Harman though. They had a Mark I on the floor the last time I was there. I will check the new one on the floor for you, and inquire about it just to be on the safe side.

(Edit) Opps, I guess I don't type fast enough. But I'll check anyway. It won't hurt.

Regards, Ray

Thanks Ray,

I'd appreciate that.

What kind of stove do you have?

Also, where in Connecticut are you?

Town

Townsend wrote:Thanks Ray,

I'd appreciate that.

What kind of stove do you have?

Also, where in Connecticut are you?

Town

I live in Plainville and I bought a new Harman TLC 2000 10/25/06 after 30+ years with my other coal stove.

I was going over to the store anyway so its not out of my way.

Hey... Thats a nice looking used stove. It's looks almost new.

Here is a picture of my new one. I think this stove is going to work out just fine.

Regards, Ray

I doubt it is airflow as you don't really want air coming in above a coal fire. Maybe it helps keep the glass clean.
I may be mistaken, but I think the reason for only doing the two opposing sides is to prevent the glass from cracking.
I know with boiler sightglass tubes (High pressure) you do not want the tube to contact the metal hub that it terminates in at each end.
The reason is that the metal and glass expand at different rates as the temperature rises. If the glass was affixed to the door very well all the way around it may fracture from the stress. That is one big piece of glass.

A footnote here; seeing the three of us are CT, we should PM local price/supply info maybe?

Townsend,
I stopped at the dealer today and all they had on the floor was the Mark I and a Magnum Stoker. Looks like your ok.
Even the stoker had the same gasket design as the Mark I.

He wasn't sure 100% but thought it might be combination of air and expansion for the glass.

Looks like it only wraps around the corner about 1 1/2 on the top and bottom.

Regards, Ray

coaledsweat.
My stove is a wood and coal combination and it does have an air wash system. Even though I have the vents on the door closed completely, the manual says there will be a little air to keep the glass clean. I don't burn wood in this stove just coal. Maybe the secondary air for the Mark I is a built in constant amount? I really don't know.

The coal stove I replaced had both primary and secondary adjustments.
(edit) I just checked Harmons site and all the Mark I II and III stoves have a built in air wash system.

Regards, Ray

The Harman SF-250 I have also had a loose gasket. It would allow some air to sneak by. It would also allow some FLAME to escape! Nearly wet my pants the day I had her fired up and closed off the draft rather quickly. I heard a *woooof* and a flame shot out of the window seal and nearly burnt my eye brows. Guess I was watching the blue flames from just a little too close.

I since replaced the gasket with a newer/tighter fit. My unit also has the dials which should be cracked open to allow air across the top of the bed to burn off excesssive flammable gases.

my Harman mag is the same way with the split gasket. the theory behind the openings on the top and bottom is to allow air to enter slightly from the established draft. this clean room air is swept accross the glass to keep it clean. the only way I have found it to work its best is to constantly keep an -05" continous draft or higher on the stove. even then I have found it to accumulate fly ash. it gathers much more quickly when the draft is less than -.05" because of my configuration and operating conditions.

I have a Mark III, and last month the window was broken by an
errant lacrosse ball. (oops)the stove wasn't burning at the time. (thank god)
anyway, I found out about this secondary air supply, or
air wash for the glass, by the dealer, and again reading
the manual I found online.
I did as instructed, and a week or so later we got cold enough
and I started the fire.
I have to admit, that since the new glass was put in, with it's
new gaskets, the stove didn't seem like itself. I wonder if over the
previous winters that ash may have plugged up this secondary air
supply and it wasn't working as designed.
My daily coal usage was high, ash etc seemed excessive, and I had
a very hard controlling temps and keeping a day long burn constant.
Over this past weekend, I used the old gaskets and stuffed them in the
top front and bottom front of the glass to reduce this extra air into the box, and wow, it seems like it's old self again. long, even burns,, and
much less ash and less coal usage.
Now, Is it me? (still new at this) or is it possible that with this secondary air supply my stove wasn't very efficient?
there is a weighted damper on the stove pipe before it goes into the
masonry chimney, the stove is in the basement of a ranch house, with
a tall chimney going up thru main floor of the house and then up to the peak of the roof... in the center of the house. (not on an outside wall)

Once I noticed this, I am also considering using some foil over the damper to see what kind of affect that may have,,, but from what I read that is really necessary, and may be counterproductive to cover up.

The last thing you want with Anthracite is secondary air.

[quote]The last thing you want with Anthracite is secondary air.[quote]

I agree for most room heating stoves. But for some central heating stoker boilers secondary air becomes part of the heat output conrol system. When the boiler water comes up to the high limit and the combustion blower is turned off a contolled amount of secondary air above the firebed is allowed. My AHS S-130 does this by a passive flaper valve that is sucked close when the combustion blower is running stoping the secondary air.

Yanche

for the amount that the secondary air that is admitted (air wash) I don't think its that detrimental to the proper firing of any Harman unit unless you have a very low draft. if anyone thinks this secondary air system is affecting your stove then you have problems elsewhere with the operation of the unit.

with coal my air wash works only 50% of the time because the bottom portion of the glass where there is no gasket in a short time fills up with flyash and only air from the top side is admitted to keep it clean.

with the proper set up per the manual for setting forced draft air, the draft is set below the door via supplied test port with a good fire burning prior to making any adjustment. this part of the set up already has secondary air included into the formula. basically it's like an air scavenger and steals it from the room.

i agree no secondary air ( after burner, co-firing, or any manual adjustment) should be on a coal fired unit for it to function properly.

the only reason for the window is for the elegance and appearance for viewing pleasure. in order to maintain that appearence there has to be a means for keeping the window clean as a result a fair amount of radient heat is driven off of a clean window. [/quote]

so is the consensus that I should not follow the manufacturers recommendation and use gasket material all the way around
the glass? it makes sense to me that it would draft better,
but i'm not an expert by any means.

thanks for any input