Strange Chimney Draft Issues, Still haven't figured this out.

[baerjo]

This is on a VC Defiant, just installed Dec 2022. It's in the basement, in the corner. Has some stove pipe up, then an elbow out through the block foundation, hits T and goes straight up the side of the house. 6" SS chimney and just clears the roof line, though not the highest point of the roof. I had 3 possible issues, one of which is now fixed.

-High wind causing draft down chimney, new Vacu-Stak topper fixed this.
-Negative Pressure Basement, I did some testing and basement windows open didn't do a thing in solving the problem. Only time flame goes straight up is if stove doors are fully closed, and then it goes out because it hasn't caught the small splits yet.
-Chimney length causing down draft issues? This is something someone mentioned after seeing the height of the chimney. From what I've read it seems tall enough but well...I'm no expert. The installers supposedly were, but yeah. I'll attach a picture, or try to, of the chimney.

Any thoughts on what might be going on here? Temp difference shouldn't be an issue since today it was 32 out and 68 in the house (thank you furnace that works).

 

[baerjo]

Here's some extra info I had sent to the dealer who has been...not exactly the brightest bulb in the box to deal with.

"I was finally able to do a few things I wanted to get done before doing more testing on the stove. I replaced the factory chimney cap with a high-wind one, I’d mentioned this previously. As fortune would have it, that day it was extremely windy so was a perfect chance to test it. I was able to test the draft up the chimney was nice and strong, which is what that cap is supposed to do when it’s windy. Because of the positive draft I had no problem starting it, no smoke at all in the basement, even with a cold chimney. I had a CO tester on all night and everything worked great with no CO leaks or problems.

Enter today’s test with no wind outside. Started from a cold stove/chimney. I tried everything, but in every case I just filled the basement with smoke. Here are some things Roger had mentioned trying regarding negative pressure issues, which I tried:

-With stove door closed tight, flame went straight up but went out quickly before catching properly.

-With stove door slightly cracked, flame went towards the cracked doors and smoke came out into the basement.

-With stove door closed tight, basement windows open, flame went straight up but went out before catching.

-With stove door slightly cracked and basement windows open, flame went towards cracked door and smoke came out into the basement."

 

[begreen]

The chimney pipe does not look like it meets the code required 10-3-2 rule for clearance from the roof. It needs to be 2ft above a 10 ft straight line to the roof. The added chimney pipe will help draft.



You may also need to address the negative pressure. There are multiple causes. What is exhausting air from the house? ventilation system, bath fan, kitchen fan, & dryer are all suspects. So are competing appliances like a fossil fuel furnace/boiler or hw heater.

 

[baerjo]

The chimney pipe does not look like it meets the code required 10-3-2 rule for clearance from the roof. It needs to be 2ft above a 10 ft straight line to the roof. The added chimney pipe will help draft.

View attachment 307842

You may also need to address the negative pressure. There are multiple causes. What is exhausting air from the house? ventilation system, bath fan, kitchen fan, & dryer are all suspects. So are competing appliances like a fossil fuel furnace/boiler or hw heater.

Yeah the chimney height is something I plan to bring up to them. They returned several sections because the installers thought they didn't need it. Likely they did but were too lazy to brace the extra lengths. I do not believe this is causing a wind downdraft issue, see my note on the new cap. Additionally due to thick wind breaks we don't see wind from the side needed to matter. But I have heard a longer chimney can simply help with draft regardless of wind, is that true and what you're saying?

For the possible basement negative pressure, does the fact that open windows right next to the stove didn't help at all disprove negative pressure as an issue? Or is it possibly still an issue?

 

[kennyp2339]

Raise height of chimney (a roof bracket is needed) get rid of the inside elbow and change it to (2) 45s for less turbulence of the smoke, I think the rule of thumb is most stove need at least 15ft of chimney height, every 90deg elbow cancels out potentially 3 ft of the total height, so your existing height look like 15-16ft total, minus the (2) 90's is like running at 10ft, if the chimney is located on the North side of the house, your always going to be fighting with cold startups.
***also make sure your stoves by-pass is open when starting up

 

[xman23]

Yes as said the chimney looks short. Fixing that should help. But is the problem no draft at startup? The chimney won't be fully drafting well until a few reloads and a ripping fire.

 

[bholler]

Yes as said the chimney looks short. Fixing that should help. But is the problem no draft at startup? The chimney won't be fully drafting well until a few reloads and a ripping fire.

What do you mean it won't be drafting fully until a few reloads? It should be after 10 mins or so

 

[kennyp2339]

Yes as said the chimney looks short. Fixing that should help. But is the problem no draft at startup? The chimney won't be fully drafting well until a few reloads and a ripping fire.

Idk, mine even on a cold stove has a little flow going, nothing major but it a put a plastic food store bag over the bottom of the pipe you could see it suck in a little bit

 

[bholler]

Idk, mine even on a cold stove has a little flow going, nothing major but it a put a plastic food store bag over the bottom of the pipe you could see it suck in a little bit

Oh on a cold start i usually need to warm the chimney to get air moving up and out. But that only takes a min or so of a torch in the stove

 

[baerjo]

Oh on a cold start i usually need to warm the chimney to get air moving up and out. But that only takes a min or so of a torch in the stove

Yeah I've heard the hair dryer method as well. Since this is supposed to be for a backup/supplemental heating solution, I'd rather not have to count on random chimney warm up solutions. I did contact dealer and they're coming back out to add more height. I get either zero draft up and out, or slight draft down chimney into the house. Not a great setup that way. I'll report back once they add those and see if that fixes things.

 

[bholler]

Yeah I've heard the hair dryer method as well. Since this is supposed to be for a backup/supplemental heating solution, I'd rather not have to count on random chimney warm up solutions. I did contact dealer and they're coming back out to add more height. I get either zero draft up and out, or slight draft down chimney into the house. Not a great setup that way. I'll report back once they add those and see if that fixes things.

It's an exterior chimney no matter what you do it's probably going to need to be prewarmed on a cold start. But it absolutely needs more height. That will probably address the wind issues.

 

[kborndale]

I've burned my whole life in a lot of different fireplaces and stoves and have always used a piece or two of newspaper lit and held up to the flue to get the draft going. Always thought warming the flue was standard operating procedure when starting a fire from cold.

 

[xman23]

What do you mean it won't be drafting fully until a few reloads? It should be after 10 mins or so

Just saying if your not getting a good quick cold start, you won't ever get a strong draft, going. The start up can go south real quick with bad wood, week draft, and badly stacked wood in the stove. But after a few reloads, bed of coals red hot stove, my draft is like a jet engine. My cast iron beast takes a lot of time to get there.

 

[begreen]

IIRC, there was a lady a while back that had a very tall exterior, masonry chimney that was extremely balky. She had weak draft symptoms made worse by the basement location. Her stove, an Absolute Steel I think, was hard to start and ran poorly until all that masonry got warm, and then she had the opposite problem, the stove took off like an uncontrollable rocket and had a tendency to self-destruct.

 

[bcrtops]

When the heighth of the chimney is less than the height of the house, the house is very often a better chimney creating draft issues & reverse drafts. Woodheat.org has good explanations of this negative affect. https://www.woodheat.org/how-chimneys-work.html

Several things working here oppossed to a good draft:
--Outside chimney
--Too short in comparison to house heighth
--90 degree elbows
--basement install (stoves often lower than the lowest available air supply of entry -- outside air preferably should come from the stove height or lower -- basement intalls frequently cannot accomodate unless walkout type / daylight type. Outside air pipe inlet (if installed) should NEVER be higher than the stove's air inlet, or said pipe will act as a chimney ).

 

[baerjo]

So next week the dealer is coming to add height. Hope that fixes things a bit.

Tried the hair dryer for 5 minutes up the chimney and then tested draft, vast improvement. Had been doing newspaper rolled up but it never warmed it enough unless I had some wind outside to help.

Due to having a small house, basement was the only option. Good to know on the fresh air info, they had recommended it but that'd be impossible from the basement.

Negative pressure wise, flame doesn't change at all if I open basement windows right next to it, so doubt that's a problem.

 

[JohnDaileyNH]

This is also a big downdraft stove that is going to require proper draft to run well. These stoves tend to be a little finicky so if the draft isn't perfect to spec they don't run right. Any slight deviation people have begun to get varying results. You should post this question on the VC specific forum and see if there are any further suggestions. That group has been most helpful

 

[begreen]

So next week the dealer is coming to add height. Hope that fixes things a bit.

Hope they add enough to properly meet the required 10-3-2 rule. They will need to have the chimney braced at 5' above the roof.

 

[Poindexter]

I agree with begreen and bholler your first problem is the 3-2-10 rule most likely.

I have flown in to Minneapolis a couple times, the claw marks on the ag sized dirt show a pretty strong wind pattern from I think NW to SE. It doesn't sound like that prevailing wind is currently working for you.

If meeting 3-2-10 doesn't solve your issues, my next suggestion is to bring your chimney inside your insulation envelope. It will cost you some sqft inside the home, and would be better placed with chimney piercing the roof nearer the ridge pole; but it is what it is.

I do advise against an exterior (insulated) chimney chase if you are planning to keep the house for several years. They work, short term, but they do not (as a rule) last.

Good luck and best wishes.

 

[baerjo]

They came by today and added a few sections. The downdraft problem had been fixed by the Vacu-Stak topper but this definitely was the way to go to meet what they should have done initial install. When I restarted the stove the initial smoke was a normal plume whatever direction the wind was going. Before it would buffet all over and sometimes downwards at the roof itself. So I think we have all the chimney issues solved. I posted on another thread that I got my first 8hr burn the other day after tightening the ash tray latch so the gasket sealed tighter. I think we can actually enjoy it now. Has been a 6mo experience with this dealer. Had it not been for insurance demanding a "pro", I could have done it myself much faster, oh well.

 

[baerjo]

I agree with begreen and bholler your first problem is the 3-2-10 rule most likely.

I have flown in to Minneapolis a couple times, the claw marks on the ag sized dirt show a pretty strong wind pattern from I think NW to SE. It doesn't sound like that prevailing wind is currently working for you.

If meeting 3-2-10 doesn't solve your issues, my next suggestion is to bring your chimney inside your insulation envelope. It will cost you some sqft inside the home, and would be better placed with chimney piercing the roof nearer the ridge pole; but it is what it is.

I do advise against an exterior (insulated) chimney chase if you are planning to keep the house for several years. They work, short term, but they do not (as a rule) last.

Good luck and best wishes.

Everything I've heard and read is that these stainless steel ones are long lasting, the galvanized ones are a different story. Inside the house was not an option with the floor plan and loads of "stuff" the women in the house have accumulated. I guess we'll see.

 

[begreen]

They came by today and added a few sections. The downdraft problem had been fixed by the Vacu-Stak topper but this definitely was the way to go to meet what they should have done initial install. When I restarted the stove the initial smoke was a normal plume whatever direction the wind was going. Before it would buffet all over and sometimes downwards at the roof itself. So I think we have all the chimney issues solved. I posted on another thread that I got my first 8hr burn the other day after tightening the ash tray latch so the gasket sealed tighter. I think we can actually enjoy it now. Has been a 6mo experience with this dealer. Had it not been for insurance demanding a "pro", I could have done it myself much faster, oh well.

I'm glad the draft issues have been solved. Hopefully, you are seeing good heating now.

The chimney is not properly braced. That is a long run unsupported. I'd add a support bracket to the house, just below the eave. Then the roof brace should be at 5 ft above the roof line, and another at 10 ft over the roofline if it goes that high.