OAK, Ash Dump and Venting

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notch

Member
May 2, 2012
57
7 miles north of Boston
Greetings Hearth.com members!
After many years of procrastination, I recently took the plunge and purchased an experienced Accentra insert - circa 2004 but (supposedly) only having seen around 10 tons. I am now trying to figure out how best to install the venting and I had a couple questions that I can't seem to find answers to from other threads. Any insight you folks can provide would be greatly appreciated.

First, outside air. I'd like to use outside air but not sure I can. I have a two story chimney, approximately 23 feet from the combustion fan to the top of the chimney, with a standard sized clay liner. I also have a ash dump with an external clean-out door. The stove will sit on top of the ash dump, so there is no way to install a pipe through it to feed the air intake. I was thinking that I might be able to install a PVC snorkel-type attachment through a sheet metal plate on the external clean-out door to allow the stove to draw air in through the ash dump hole in the bottom of the fireplace floor. My concerns about this method are: 1) the circulation fan, being on the bottom of the stove, would pull cold air from the ash dump opening and reduce the heat output of the stove; 2) the stove would pull inside air around the surround since it doesn't seal tightly; and 3) when not in use the open ash dump would allow cold air to be blown into the room even if I use a snorkel with an upside down "U" shaped trap on top.

The other OAK option would be to install a full exhaust liner through a block-off plate to the top of the chimney and another 3-inch OAK pipe through the block-off plate halfway up the existing chimney, and connect a PVC pipe down the side of the chimney a foot or two and connect it to a hole in the top plate to allow outside air into the chimney. This is venting option #1 in the operating manual.I've read posts here from folks who did that but had bad results in terms of the flame quality after installation. Any thoughts on doing this method with a 23 foot chimney?

Lastly, if I do not do the OAK at all, or leave the ash dump open, my preference (because I am frugal - not cheap - frugal :) would be to run a 5 foot flex pipe through a block-off plate into the existing chimney. My chimney (three flues - one for the oil-fired boiler, one for a fireplace in the basement and the center flue for the first floor fireplace where the Accentra will go) is currently capped. This is venting option #3 in the operating manual. Anyone have any thoughts on potential problems or draft issues with this method?

Thanks in advance for your insights.
 
Try it without the OAK, Harman makes an adjustable vented term cap plate that if you can seal off the top of the exhaust it will allow fresh air to flow under to the stove. Great insert, you should have no problems with it.
 
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