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timmymo
carbon monoxide help
timmymo

Last summer several times when we had the air conditioner on and tool a shower about 30min to an hour after the carbon monoxide detector would go off. If we opened up the house it would not or during the winter it never goes off. We had someone come look at it and they had no clue what to do. they just ended up saying they house didn't have good air flow. We talked to the people who lived in the house before us and they said the same thing would happen. I really don't know what to do and we will be having a baby soon and want to fix this problem. Any help out there would be appreciated.

keith3267
Re: carbon monoxide help
keith3267

Let me guess, a natural gas water heater. Have it inspected by a professional, attention to the vents.

ed21
Re: carbon monoxide help
ed21

Flues can get partially clogged and there needs to be makeup air to make sure the flue draws properly.

Fencepost
Re: carbon monoxide help
Fencepost

Possible scenario:

  1. Your home is tightly sealed, maybe about 20 or 30 years old.
  2. You have a gas water heater.
  3. The air conditioner has a leaky duct that's leaking into unconditioned space such as the crawl space.
  4. You turn on the exhaust fan in the bathroom when you shower.

Here's what I theorize is happening. Because you are using a lot of hot water during your shower, the water heater runs for an extended period of time. The leaky duct blowing into the crawl space, plus the fan being on, results in a negative pressure that attempts to draw air back into the house. Because the house is so tightly sealed, the only place to get sufficient air is through the water heater flue, which backdrafts the carbon monoxide into the house.

It doesn't happen in the winter because the air conditioning isn't on, and the house is just barely drafty enough to be able to supply sufficient makeup air for both the water heater and the bath fan. But once you add the leaky ductwork when the air conditioner runs, there isn't enough draftiness to compensate for that too, so air backflows through the water heater flue.

Experiment: when the A/C blower is not running, turn on the bath fan. Above the water heater, you'll see a gap between the top of the water heater and the flue. Do you feel air coming in? Now, with the fan still running, turn on the A/C blower (there's usually a switch either on the air handler or the thermostat that allows you to manually turn on the blower). Do you feel air coming in through the water heater flue?

If so, check your A/C ducts for leakiness and repair it. Also, you are right on the cusp of insufficient makeup air anyway, so you probably should increase the draftiness of your house somewhat. One way you can do this is to run a 3" or 4" duct from the outside to near your water heater. Another way is to run the duct from the outside to the return duct of your air handler.

Does your A/C air handler already have a duct from the outside that goes into the return duct? If so, does it have a damper that's closed off, or an outside grille that's blocked? You might want to make sure that's open.

dj1
Re: carbon monoxide help
dj1

Check ALL appliances - gas water heater, gas furnace, fireplace, gas oven and cook top range, gas dryer - check vents too, including all connections. Make sure nothing leaks.

Then check the detector itself: how old it? how are the batteries? It is very likely that your detector is faulty and needs to be replaced.

ed21
Re: carbon monoxide help
ed21

CO detectors only last about 10 years. It should say on the back.

keith3267
Re: carbon monoxide help
keith3267

All the above is good advice and again, I do encourage you to have the flue inspected by a professional. A gas water heater should be in its own closet, or a closet shared by the HVAC system. This closet should be open to the attic, or to a garage if it is located next to the garage. This is so that fresh air for combustion comes from the outside and not from the conditioned air in the house.

If yours is set up that way, I will add that you should check the door(s) to this closet and see if they have weatherstripping around them. They should be sealed from the rest of the house.

If your HVAC and water heater share the same closet, and your house air filter is located at the base of the HVAC unit, make sure the door that covers the filter is closed. If it is missing or open and the vent for the water heater is not working properly, then vent gasses could back flow into the cabinet and be sucked in around the air filter.

If you have a high efficiency gas water heater, the flue may need a fan on it to force the cooler exhaust gases out, or it may have a fan that is not working, that is one reason for having a pro look at it.

ordjen
Re: carbon monoxide help
ordjen

I am not sure how CO sensors operate, but I can tell you from personal experience that very high humidity will set off fire detectors. If your shower is in close proximity to the sensor, it may simply be high humidity. Winter time air can be bone dry in a house, this might explain why it is not happening in winter. Obviously, anything that lessens the moisture, or distributes in throughout the house, rather than let it concentrate around the sensor, will lessen the chances of it going off. Perhaps just moving the sensor further away from the source of the moisture would help.
My CO sensor is kept in the hallway right outside the bedrooms, far from the showers.

Re: carbon monoxide help

Please check the following items before proceeding:
1. How old is your detector?
2. Try to test it and clean up it from dust. The sensor may have a problem.
3. If the problem still exists, call a technician for help.

I hope this could help you out of the problem.

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