CO alarms set off during first burn of season...why?

Basement 30NC. Freshly and Fully cleaned insulated SS flu. 4 year old stove. (burning every winter since installed).

Woken at 3AM to the sound of all FOUR CO detectors and ONE smoke alarm. (though no smoke in house).
One CO monitor is near basement Englander. One in stairwell. TWO others on main floor.

The fire was made and burning normal (as always) around 4pm. Got it going good and hot...then shut back the air halfway and called it a night.

After the startling awakening, I got all windows and doors open. Went down to check the fire and there was almost NOTHING left in the box. There was about a shoe box full of glowing ashes. This is normal and has been fine for years this way.

I emptied the fire box down to absolutely nothing and dumped the embers outside in the fire pit. Reset all the alarms and sat awake all that night scratching my head....

I am looking for ideas on what is going on. Not building any more fires till I get this sorted out.

Thanks.

begreen said:

Possible draft reversal? Were any windows slightly open upstairs? Attic door ajar, attic vent in hallway still not sealed up for winter?

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As much as I searched, I don't see any thing open. Windows all closed. Attic door closed (sealed). Outside temps were clear , crisp, cold (38). Fire drafted fine while I was awake.

?

Hogwildz said:

Are the alarms all tied into each other? Meaning, when one goes off, they all go off?
Co alarms are typically good for 7 yrs. Then they get funny. I had one start going off periodically right at 7 yrs. Changed it for new, problem solved in my case. Don't discount the fear, just trying to rule out obvious issues.

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The detectors are ALL separate, individual units. Some are 3 years old, the others only 2 years old.
They REALLY did their job.

Just bought 2 more with a PPM display to add. Gonna try another fire today.

The one monitor I have with PPM display read at 86 PPM PEAK, from that night.

begreen said:

Were there any changes made to the house this year? Like a new furnace, gas or oil hw heater, ERV system, etc.?

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As I sit here thinking more and more , I had to go down to look at the stove over and over....

We have a heat pump with Central AC / hot air registers (outside pump, inside air-handler). We've had it for 6 years. Been burning wood for 4.

Then BOOM it hits me... Last summer we had troubles with the AC not running up to par. The service people came out and had to replace the condenser and found a leak in the coils which led to a loss of "freon" (or whatever it is now). They got to system runningbut the tech said he would like to see MORE cold air on the RETURN side of the ducts.

He CUT A 16 x 16 inch HOLE IN THE SIDE OF THE AIR HANDLER RETURN LINE/DUCT. Well, the airhandler sits 6 feet away from the wood stove. BINGO!

So, I deduce that the furnace air-handler was strong enough to suck the fumes right out of the stove box VIA the air intake ports??.. And then distribute the poison air throughout the house via the duct work.
Anybody agree that's possible???

begreen said:

Well, for one, that is against mechanical code. The return air needs to be at least 10ft away from the stove. It would be better to duct it upstairs. Your hypothesis is sound. You could try turning the system off for a couple nights and see if the problem repeats.

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The basement has never had ANY return air until they cut that hole this passed summer. And we have never had an issue with CO before.

I actually remember telling the guy I would prefer any additional return air to come from the living quarters instead of the basement because I wanted the humidity reduction to work best when the AC was running. (removing moisture from upstairs). He told me it doesn't matter where the air-handler gets its return air from, it will work the same no matter what.

begreen said:

If this is the issue then in the least I would cover the new register in the winter. It's fine for the summer.

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I can cover it for winter. But, would that make the air-handler's computer reading of available return air change, and therefore decrease the efficiency of the system?

Hey, would adding the OAK to the stove help? That would eliminate the source for the furnace to draw CO from out of the firebox.

PaulOinMA said:

Is the opening he cut in the return right on the furnace allowed by code where you are? I was present at our home inspection for our NJ house in 1994, and the homeowner had one of the returns on the side of the furnace open to the basement. Homeowner was also present. Inspector turned to the homeowner and asked, "do you get a lot of headaches?"

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I don't know about the code. I just assumed if a "professional" Carrier Certified installer added the new air return then it must be OK. I should know by now at this stage of life.

PaulOinMA said:

You may need to get another HVAC person in to look at your system. If he agrees that more return air is needed, may have to get it from somewhere else.

The homeowner solution to the open basement furnace return I mentioned above was to cover it. The unit then burned out because it wasn't breathing. I had an HVAC guy come in, and he said the unit was HUGE for our house. 190,000 BTU! Builder was going bankrupt while he was putting up the few homes in the development before he went under. Maybe it was a furnace he had somewhere and just threw it in the house.

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This is what concerns me. If I cover it, will the system get enough air or have more issues later on?

moresnow said:

Another Ahaaaaa moment! Your forced air system was working fine for years before the repairman updated it? Now its goofing up the stove. Cover it up. Betting it will cure your problem. Scary

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Little leery to cover it just yet as the tech said the heat pump computer stated the system needed more return air. I gotta get air from somewhere else I guess.

begreen said:

Mechanical code regarding return air. It sounds like there may be more than one violation here.
View attachment 231449

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WOW! I see them.