Damper on a Direct Vent

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traderfjp
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Post by traderfjp » Tue. Sep. 25, 2007 10:37 pm

I was just wondering if anyone here is running a damper on a direct vent. I have one ready to go but I haven't lit my stove yet to try it out. The fit is great and it attaches to the back of my stove right before the direct vent motor. These is a small hole that needs to be plugged too but that is easy.

 
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Post by JerseyCoal » Wed. Sep. 26, 2007 11:34 pm

Hi Trader:

I am probably the least qualified to comment on what you are thinking of doing but, here goes. If I am correct, a direct vent unit has a fan which mixes some room temperature air with the combustion gas as it expels it out the direct vent pipe to the exterior of your building. If that is the case, I don't know what good a damper would do for you. You are not relying on natural draft to vent the combustion gas so the damper won't help regulate the rate of burn. Furthermore, if you close the damper to any degree, I imagine that it would only serve to impede the flow of combustion gas and make your direct vent fan work longer and harder. It seems that the diameter of the direct vent pipe, and the CFM rate of the fan are both matched to the requirements of the combustion unit as designed and constructed. If it were me, I would leave it alone and not mess with a damper. That is my very non-expert opinion based solely on what little common sense I have. I do hope that some of the more technical fellows chime in on this.
John

 
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Post by traderfjp » Thu. Sep. 27, 2007 12:27 am

Jersey wrote: If I am correct, a direct vent unit has a fan which mixes some room temperature air with the combustion gas as it expels it out the direct vent pipe to the exterior of your building. If that is the case, I don't know what good a damper would do for you.

I'm planning on plugging the hole on the direct vent unit that mixes the room air with the exhaust gases. It's a small hole about the size of a half dollar and when there is a small fire - I believe the direct vent can't get enough air. Evidence of this is that I had a really small fire and the hopper ran low which caused the direct vent unit to suck air from the hopper causing a hopper fire. Luckily I caught it in time but it was a pain in the ass to clean up. With a damper the flap would swing open more when there was a low fire and the direct vent unit could get all the air it needs. On a high fire there is plenty of exhaust for the vent motor to vent out but on a low fire the direct vent has a small amount of exhaust to pull out but is still sucking the same as if it was a high fire. Does this make more sense?

 
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Post by ken » Thu. Sep. 27, 2007 12:18 pm

i have a Keystoker with DV and no damper. the manual never suggested one. I have a 50 lb hopper that has no gasket and 3- 1 inch holes in the top. should I have a problem with the fire getting back to the hopper?


 
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Post by Matthaus » Thu. Sep. 27, 2007 3:27 pm

First let me say that I am no expert, however I have direct experience with almost all types of "girlie man" (stoker) stoves. I have found that hopper fires are almost always a sign of a draft problem and should be corrected ASAP.

Direct vents for coal stoves take three forms (that I know of), one type as is on the Harman DVC500, this type draws in combustion air from outside and uses that to cool the pipe carrying the hot gases from the stove. The stove must be airtight so that the combustion fan pressure helps expel the gases out the vent.

The second type such as on a Keystoker is powered and part of the stove (or mounted very close to the stove) and actually pressurizes the stovepipe or vent (therefore the vent should to be sealed with tape and RTV). The little hole (that draws in and mixes room air) is usually adjustable in size on these units to adjust the draft. This type cannot be used with a damper since the pressure in the pipe will escape through the damper and cause a dangerous condition inside your living space. I REPEAT DO NOT INSTALL A DAMPER ON THIS TYPE, not healthy!

The third type is the SWG which can be used on all coal stoves (Liesure line and Alaska can be purchased with this type). The drawing I posted shows how it works and that a barometric damper is required since it is drawing the gases from the stove much like a chimney would. Proper adjustment of the barometric damper by using a draft gauge or manometer will ensure no drawing of air through the hopper and thus no hopper fires.

Bottom line, each type can cause insufficient draft (symptoms include hopper fires or excessive moisture in the hopper). I suggest you follow the manufacturers instructions for adjusting the draft and definitely use some kind of measurement device..... hope this rambling helps a little :)

Attachments

swgdirectvent.gif

SWG with barometric damper

.GIF | 20.5KB | swgdirectvent.gif

 
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Post by Jerry & Karen » Thu. Sep. 27, 2007 4:34 pm

Matthaus is right. If your using a direct vent , you must place the baro on the negitive side of the draft, inbetween the direct vent and stove. Putting it on the positive side will cause gas to enter the house. Remember, negitive draft is a suction, causing room air to enter the pipe. Positive draft is being forced or pushed out, and will leak out the pipe joints.
Jerry

 
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Post by traderfjp » Thu. Oct. 18, 2007 1:20 pm

I just fired up my stove the other day and installed the baro on my direct vent stove. Everything runs flawlessly. On a lower fire I can see that the baro is sucking more air which is great since I had a hopper fire without the baro. Now when the stove needs more draw it'll be able to get it from the room and not the hopper. Anyway, the real test is when I let the coal run low on the stove. I want to see if the baro will totally elimiate a hopper fire. I also seem to be using less coal. Is this possible?

 
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Post by coaledsweat » Thu. Oct. 18, 2007 1:38 pm

traderfjp wrote:I also seem to be using less coal. Is this possible?
Yes. Not just possible, more than likely.


 
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Post by traderfjp » Thu. Oct. 18, 2007 3:06 pm

Hmmm.... I have my Channing (girlie stove) on low and for the last few days it has hardly used any coal but is taking the chill out of the house. I can't say enough about how much I live burning coal even if I wasn't saving dollars.

 
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Post by WNY » Thu. Oct. 18, 2007 8:08 pm

On our Keystoker Direct vent, there was no adjustment on the hole on the side of the direct vent, same, about the size of a half dollar. It just a little door to adjust the suction thru the fan, There was no damper or baro. It would mix room air and the exhaust gases and vent them outside.

The draft meter hole was on the front ash pan door up in the corner, a small hex allen screw you remove to check the draft.

 
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Post by traderfjp » Thu. Oct. 18, 2007 8:45 pm

On my direct vent I cut a piece of metal to fit over the hole and used caulking used for high heat and then taped over everything with aluminum tape. It seems to be working great.

 
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Post by Donald » Thu. Feb. 28, 2019 11:24 pm

I have run my Channing III for 13 years and have never had a hopper fire. Usually hopper fires happen when coal can't make its way down the grate because of a full ash pan or something preventing the ash from falling into the ash pan. Alaska recommends to never install a barometric damper on a direct vent stove because a true dv stove does cause positive pressure into the exit pipe. Positive pressure would cause the exit gases to leak into your home.

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