Negative pressure issue-i think

[DENIKA232]

Hello,
We are in deep need of help. We are pretty sure we have a negative pressure issue. We have been able to light up fires( this goes well when we open a window beside the woodstove). It burns well. BUT as soon as the chimney gets cold again we get that backdraft. Cold air coming in and nasty smell in the basement. The stove is new. Got the chimney cleaned before the winter. We have NEVER had this much trouble with a woodstove. And, the problem isn't always just when theres a lot of wind..feels like it's really sucking air from outside to bring it inside. Anu suggestions? It's an exterior brick chimney, thank you

 

[MR. GLO]

Burn 24/7 to keep warm flue
Burn then in am sometime in am remove the coals and ash so no co.
Add a draft collar but plan on increase in electric bill.
Get ultra low co detector.
Or keep room warm after fire goes down with alternate heat....like electric..might not work...
Even with the cold air drop like you I don't get a smell. But try empty coal ashes to see if it goes away and look inside at back of stove. For creosote buildup.

Start up issues try preheating flue.
Check to see what other appliances are running and attic openings etc.

Describe backdraft some more....is it during the burn or coaling?

 

[MR. GLO]

Also is chimney lined and insulated?

 

[Gearhead660]

Do you have gas water heater? What is your main source of heat? Any exhaust fans that run on a regular basis? How old is the house?

 

[DENIKA232]

Hi, thanks for your response. Chimney is not lined or insulated. The smell only comes when the chimney( inside of the house) is cold. No smell or smoke comes from it when it's burning or when it's out but the chimney is still hot(for a couple of hours inside). However, as soon as the fire is out and chimney gets cold(after a few hours of cooling down), the odor starts to come in..it is not our primary heating as we jave elecrric heating but we do lile to have fires once in a while, espicially when it's -30 outside so not looking to run it 24/7..we are very close to taking everything out and just not using it anymore..we have never had that mich trouble with a wood stove before..bought this house 6 months ago and previous owners never really make fires..thanks!

 

[DENIKA232]

Do you have gas water heater? What is your main source of heat? Any exhaust fans that run on a regular basis? How old is the house?

Our house is a 1997 built but was fully renovated and isulation in the addict is really insulated. Our main heat source is electric and we do have an air exchanger.

 

[MR. GLO]

Try removing the coals and ash the next morning after you let a fire go out. Since its a new stove, if it still smells most likely the unlined chimney.

Don't get frustrated many wood stove owners have the cold chimney issues and some don't realize it. Cold air drops. Still keep it for emergencies.

A new insulated.liner might help but I'd start with the suggestions of empty coal and ash first and let us know the results.

What brand air exchanger?

 

[begreen]

The first step is to line and insulate the chimney. That will help keep the flue gases warmer.

Examine the house for any actual or potential leaks upstairs. This could be an attic door seal, an upstairs window cracked open. Multiple bathrooms with exhaust fans, a high-velocity kitchen exhaust fan, dryer running, etc. In the basement, look for competing appliances like a clothes dryer, fossil fuel furnace or boiler, gas hw heater, or radon exhaust fan. If they exist, do they have their own combustion air supply?

If there is no easy resolution then the options get smaller. An HRV with the ability to pressurize the basement may be the best solution.

 

[wagne223]

Since you say it is only bad when windy, I would locate the stove air inlet hole(s) (usually on the bottom) and get a magnet to cover them.
If the stove has the collar for an outside air kit, you may be able to find a plug or cap for that collar. The goal is to keep air from coming out of the stove.

It might also help to change burning habits a bit.
Burn hotter to keep the flue and firebox clean. On the last load (ie: your going to let the stove go cold), open air control during coaling stage to fully burn coals, add some kindling to fully burn coals.

As mentioned, you can also shovel out any ash or coals.

 

[MR. GLO]

Just note some erv and hrv turn into exhaust only mode during the winter or cold temperatures....

I'm curious to hear from somone who has erv hrv and it helped....and what model.

It's possible they could be creating negative pressure.

 

[begreen]

Just note some erv and hrv turn into exhaust only mode during the winter or cold temperatures....

I'm curious to hear from somone who has erv hrv and it helped....and what model.

Some have user controls for when it runs and customizable flow rates.

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[Commodorefirst]

I have an Ideal Steel and a ERV, that we set up with a slight positive pressure. I also have plumbing for an outside air kit that I have not attached to the stove. I purchased the stove with an outside air attachment, but because of the ERV, I do not need it because I have excellent draft, sometimes in deep cold and high winds almost to much. The fan speed on the ERV was set by our HVAC installer. It is a basic dumb unit, that you set the switches for the exchange rate. I keep it on all the time except when we are cutting hay in the summer because of the extreme dust in the fields around our house When cutting bailing. Our house is tight spray foam, walls, r25 blown attic r50,

We tested our stove with three bathroom vents on and and running the IS had no stove issues, however, even with the + ERV pressure, since it is only slightly positive, I have to be careful when cooking. In my kitchen the cooktop is 15-20’ from the wood stove stove, and the cooktop has a large commercial 48” high speed hood, I can only turn on the hood to the first two settings when running the wood stove, I never turn on the hood to level 3/4 (750 cfm and 1200 cfm) because the draft reduces on the IS, and I get a very rare occasional back puff when the hood is on high. (build up of gases inside the stove box) nothing loud or bad, never smoke puffed into the room, but just a quick extra gas ignition poof.

Just some information for your situation.

 

[MR. GLO]

I have an Ideal Steel and a ERV, that we set up with a slight positive pressure. I also have plumbing for an outside air kit that I have not attached to the stove. I purchased the stove with an outside air attachment, but because of the ERV, I do not need it because I have excellent draft, sometimes in deep cold and high winds almost to much. The fan speed on the ERV was set by our HVAC installer. It is a basic dumb unit, that you set the switches for the exchange rate. I keep it on all the time except when we are cutting hay in the summer because of the extreme dust in the fields around our house When cutting bailing. Our house is tight spray foam, walls, r25 blown attic r50,

We tested our stove with three bathroom vents on and and running the IS had no stove issues, however, even with the + ERV pressure, since it is only slightly positive, I have to be careful when cooking. In my kitchen the cooktop is 15-20’ from the wood stove stove, and the cooktop has a large commercial 48” high speed hood, I can only turn on the hood to the first two settings when running the wood stove, I never turn on the hood to level 3/4 (750 cfm and 1200 cfm) because the draft reduces on the IS, and I get a very rare occasional back puff when the hood is on high. (build up of gases inside the stove box) nothing loud or bad, never smoke puffed into the room, but just a quick extra gas ignition poof.

Just some information for your situation.

Great info...Can you explain before and after install of erv any reload smoke, if you need to pre warm the flue or have an co issues at coaling? As for co issues...Im guessing the only way to know would be a ultra low co meter. thanks...

 

[Commodorefirst]

Great info...Can you explain before and after install of erv any reload smoke, if you need to pre warm the flue or have an co issues at coaling? As for co issues...Im guessing the only way to know would be a ultra low co meter. thanks...

sure, Our new home was built and we moved in March 2018, stove arrived a few months later. We ordered a custom artwork Ideal steel unit, and I had the builder install the chimney, and placed cement board behind the stove location, and two layers of board and tile underneath the stove while the home ws being built. I did my homework, researched erv units, , and fortunately, the local builder listened to me and these custom features were part of our build. We bought our farm 10 years earlier, and when we retired, moved to the farm full time after retirement. There was an old “farm house” , but the quotes mean glorified camping, small 900sf 70 year old building, nothing for perm use, so we tore down the house and built on the same spot.

anyway…. our house was set up with a + pressure on the erv unit, because we knew a wood stove was going to be installed. When the stove arrived that summer, I waited for first burn until the first Winter. During our first burn in fires, I did not test the range hood, or bathroom vents when doing the first few days of firing and burning in the paint.

We had our first single digit temps when I did our first experiment. I burn 20-40 days a year. Since my house is so efficient, the newer heat pumps work great and are great down into even the single digits, but to save on electricity, and for wood warmth I run the stove when day time temps are upper 20s or lower, and night time then drops lower. Usually 20-40 days here in the Missouri Ozarks.

During that first full load cold weather burn, ERV on, zero smoke, zero smoke spillage on lighting, reloads, etc etc, and the IS is a front door loader. I also tested reloads with ERV off, and still no smoke spillage, however it was noted that smoke was rolling around in the box a lot more, but because of the tall chimney, I still had a good draft, but there was a difference, but no smoke spillage.

Next day, testing further, the erv was on, full load burn, on reload, door cracked, going good on relight, I had my spouse turn on the hood, on setting 1-2, nothing came out cracked door, on 3 a few wisps of smoke, and on 4, well, you can guess how a 1200com exhaust fan 20’ away will pull smoke out of your fire box, lol. After turning off the hood we turned on all three bathroom vents, and the stove behaved like the erv was off, drafting ok, no spillage. We were happy, Even with a tight house during a power outage and erv not running, we can run our wood stove with inside air, and there is always crack a window option if needed. No need to drill through our tile hearth to hook up to the outside air pipe in the basement that runs to the covered patio.

Also, we have a good co unit nearby the unit, plus another few in our bedrooms, never had a blip, and never registered.

We never pre warm the flue, bottom or top down starts makes zero difference. Our straight chimney drafts very well, May still put a damper in. The IS burns about half the time with a black box, but cat on, when turned way down for overnight burns, black of course after the secondaries go out.

pick of our stack and how close the hood is to stove.

 

[stoveliker]

Draft reversal happens when there is no warm air going up the flue. So, when the stove is cold AND the room is cold, it can happen. That's not a stove issue, it's a flue-physics issue.

As physics is hard to circumvent (though, keeping the room warm enough that you'll always be drafting out of the stove up the chimney is an option - but it might require a warmer room than you want, AND you'll be wasting heated air up the flue), I suggest figuring out where the air supply holes are, and in the morning when the stove has gone cold (after an evening fire), to plug those holes. Magnet on the hole or tight cloth in there. This way, if there's cold air in the chimmey, it won't enter your room.

You will have to be diligent in never forgetting to take off these air-blocking things when you light the stove, for obvious reasons.

However, I'm surprised - with the ERV pressurizing the home, you should be blowing out air through the stove rather than letting in cold air from the chimney through the stove. Is the ERV on when you're not using the stove? If not, I'd see if you could keep that on. (And if it IS on, then your home is not as tight as you thought it was, because with it on it evidently still allows air infiltration through other places - in this case the stove... - meaning the overpressure in the home due to the ERV is less than the pressure of a column of cold air in the chimney. And this pressure of the column of air is not all that much...)

 

[MR. GLO]

If the stove is in basement and chimney is cold and room is cold how would blocking inlet stop co from coming out from coals? I'm assuming it would escape at joints and secondaries...

And some stoves the secondaries can't be blocked and hidden.

Really need to see if erv helps in cold rooms....I'm guessing with a cold room and cold chimney it won't help either...but I'll keep testing too.

 

[stoveliker]

Because modern stoves are (supposed to be) tight. Otherwise the secondary tubes wouldn't be firing.

Of course it needs access to secondary air entrance.

I think the complaint is about smell, and about a duration longer than the duration of CO danger. I.e. smells can be there long after coals are done producing CO. And that I still something that the OP wants to resolve.

Regardless, having working CO detectors, as you mentioned, is of utmost importance.