New wood stove setup - double walled elbow

[Charliedog]

I recently had a woodstove installed.The flue exits through the wall to an outside prefab. It is a corner install, but the flue exits off to the side and not straight out the back. This means that I will have 2 elbows in my flue which will affect the draw. I had it looked at by a WETT professional and he suggested an adjustable elbow right off the stove top and another one at the wall. My contractor did it this way but he used single walled adjustable elbows with a double walled flue pipe in between. The joins were not pretty given it was a single to double connection. There were gaps on the outside, not sure how the inside looked.

From what I have read so far, the small gaps at the joins are not serious as long as the chimney is functioning correctly. During the first night that we had the wood stove going i woke up to the smell of smoke. When opening the door to re-stoke I would do it slowly but always seemed to get some smoke in the room and opening a window did not make a noticeable difference. I have not burned the fire since and have realized that I have a negative pressure problem. This will interfere with my draw as well. So I have 2 problems affecting draw, negative pressure and the 2 elbows.

My questions are:
1) should I have angled straight off the top of the stove with an elbow as the tech. suggested or should I rise the 36" then angle toward the chimney and end with another elbow?
2) the technician suggested that I could replace the singel walled adjustable elbows with double walled adjustable elbows. I did not think it would be possible for such a thing to exist, but he insisted there is. I have not been able to find one online, so maybe the joke is on me.
3) What do I do with the negative pressure issue? I appear to have adequate clearance above the roof line, my neighbours house is higher but a good 20' away.

Its pretty frustrating to say the least. Any suggestions would be greatly appreciated.

 

[begreen]

Welcome Charlie. The installation should not have mixed the single and double-wall pipe. It is hard to say for sure but it looks like the install could have been solved with a pair of double-wall 45's and a telescoping, double-wall connector.

Regarding the negative pressure, how was this determined? Where is the stove installed, in a basement? What is competing for the airflow there? Dryer, furnace, hot water heater, bathroom fan? If you open a nearby window or door a little bit (1/2" is fine), does the problem go away?

 

[Charliedog]

I don't think 2 45's will do it since I can't go straight from the stove to the chimney, I have to go right and up at the same time beacause of the offset chimney location. I cannot move my stove out any further to get the straight shot due to clearance with the hearth. Thats why i was wondering about the adjustable double walled elbows, but maybe i am wrong.
With regards to the negative pressure, maybe i have the lingo wrong but when the stove isn't burning there is a lot of backdraft that is occurring. that heavy cold air is just flowing int o the house through the stove. Opening the window next to stove did not seem to eliminate the backdraft of smoke, but maybe I did not have it open long enough. The stove ii in the basement and is competing with a nat. gas furnace and water heater. there are 2 bathroom fans in the house but they were not operating when I opened the stove door. I ended up with back draft the first night becasue I had adjusted air supply as to have the fire smoulder all night. It must have burned too cool and the chimney could not function correctly.

 

[SteveKG]

I have not heard of any double-walled adjustable elbows. I looked for them a few months ago and never could find any. When I gave up and bought, instead, a couple of 45 deg. dbl wall elbows and had to move the stove a foot or so to accomodate them, everything worked out ok. Adjustable dbl walled elbows would definitely have made my life easier, installing a new stove here, but it was not to be.

Looking at the elbows carefully, which I did, I couldn't see a way to make an adjustable version. If there are any, I couldn't find them.

I cannot tell from your small photo whether a couple of insulated 45's would work, but I trust your assessment that they cannot. The premium set up would be, as someone else mentioned, the insulated 45s and a section of adjustable straight pipe. But if it won't work, you may be relegated to using your current set-up. If the single-wall elbows and the dble wall pipe you have fit together reasonably tightly, you should be ok. I say that without being able to stand there and look at it for myself. There are all sorts of mixes and matches done to get stovepipe and chimney pipe all set up on some installations. Yours may well be another of those.

Use it for a while. If you still have concerns later on, or you can tell something isn't working well, you can get another opinion.

 

[Charliedog]

Thank you. I will stop looking for the double walled adjustable elbows and go back to drawing board. Any suggestions re my draft problem. Whn I get it back together will try opening the window longer and maybe not turn down the air supply to stove during the night as to starve the fire and cause draft problems.

 

[Highbeam]

Your draft problem:

You have other devices sucking air out of the basement so hard that they are sucking air down the chimney. This issue will go away if you can duct outside air to your stove. Not sure on your stove model but my Hearthstone allows a 100% air supply through the air duct. This would prevent the basement from sucking on your stove's air supply and keep your draft going up.

Alternatively, you can supply combustion air to each appliance.

The other potential problem is that your house is a better chimney than your chimney. This is due to leaks in your upper floors to the atmosphere. Those leaks allow hot air to escape to your attic or out of the upper windows which puts a suction on the lower levels of your home. This suction is enough to suck cold outside air down your chimney. Outside air ducting to your stove will fix this too.

Also consider that if your chimney is having reverse flow that your other fossil fuel chimneys may also be reversing and sending Carbon monoxide into your home. Hope you have a detector.

 

[Charliedog]

The house has been recently upgraded, new doors, windows, etc. I will check my attic hatch door as this may be an area of concern. I installed two whirly birds to increase circulation of flow in the attic, I wonder if they would be sucking air into the attic? I thought about wedging them to stop them from spinning during the winter season. My stove is a basic Contempro 1600 front loader. Not sure if i can add the external air supply to it but will check it out. I have installed a CO detector. I just wish I could get the flues installed so that i can try and figure out some of the drafting issues. Thank you.