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Damp basement when the boiler runs

ar7499b's picture

Damp basement when the boiler runs (post #205678)

ar7499b on Thu, 01/26/2012 - 11:03
in

I have an 1940's brick colonial in northern IL. The basement is 1/2 finished and heated. On the unfinished side I have a large boiler that heats water filled radiators. It has an automatic 'safety' damper on a sealed flue that leads to a service chimney. 

The burner is open on the bottom, so you can see the glow of the flames when it is running.

When the boiler is running, the humidity level goes WAY (70%) up. I have a dehumidifier that is in this part of the basement, and it can't keep up. It can keep up with extreme summer humidity.  The humidity only really climbs when it is mild and damp out, like it has been this winter.

This side of the basement is cooler, maybe low 60's, but not cold. The numerous heat and hot water pipes gives off enough heat to keep the area comfortable (all the heat pipes are wrapped and sealed with foam).

I am not that concerned about the moisture causing mold or anything like that. I am mostly concerned with whether this indicates a safety issue with the exhausting of combustion fumes. There is a CO detector on this level and it has never been triggered, but it doesn't seem right, and my wife is concerened.

 

Any insights about the safety, and any posible solutions would be truly appreciated.

 

Thanks,


ar

 

-A +A

It sounds like your safety (post #205678, reply #1 of 8)

by xxPaulCPxx in reply to ar7499b [original] on Thu, 01/26/2012 - 11:14

It sounds like your safety dampner isn't opening.  Your CO detector may not be going off because the combustion is still very efficient.

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  Is this a gas or oil (post #205678, reply #2 of 8)

by rdesigns in reply to ar7499b [original] on Thu, 01/26/2012 - 11:19

 

Is this a gas or oil boiler?

If the flue or chimney is blocked, or, if for some other reason, the flue gases are exhausting into the basement, the water vapor produced from burning gas will add humidity, as you suspect. (You get about 1 gallon of water for every 100,000 BTU's of gas burned.)

With your hand, you should be able to feel warm, moist exhaust escaping from some point at the boiler or the flue connector.

The fact that the CO detector has not alarmed does not prove that the boiler is not backdrafting. This can be because clean-burning gas appliances do not produce significant amounts of CO--they give off CO2 and water vapor. Or, you may have a faulty CO detector.

If it's an oi-fired boiler, you should be getting a strong odor from the flue gases, but possibly not with a gas-fired one.

Thanks for the quick (post #205678, reply #3 of 8)

by ar7499b in reply to ar7499b [original] on Thu, 01/26/2012 - 11:31

Thanks for the quick resonses, It is a gas boiler. 

My understanding is that the damper has to open, or the boiler won't fire. When the heat is first called by the thermostat, you can hear the sound of what I believe to be the damper turning inside its' housing, and then about half a minute later you hear the ignitiors clicking, and then the woosh of ignition. I think there is a mchanical switch in the damper which prevents the boiler from firing if the damper isn't open.


The flue definately gets warm above the damper when it is running.  Right below where the flue enters the chimney, there is a small pipe coming out of the chimney for draining excess moisture within the chimney. I have not noticed drainage from this pipe.

The CO detector is almost brand new, first alert wireless talking fancy stuff.

The windows are new (6 years). So, maybe the room is sealed much tighter than when the boiler was originally installed.

Thanks for the continued dialog,

ar

 

I'm baffled. Warming the (post #205678, reply #4 of 8)

by rdesigns in reply to ar7499b [original] on Thu, 01/26/2012 - 11:52

I'm baffled.

Warming the air in the basement will lower the relative humidity, and I can't imagine that the combustion air needed for the boiler's burner would raise the RH because the cooler outside air, even if humid outdoors, will lose RH once it's inside the heated space.

Your description certainly makes it appear that the humidity is coming from the combustion gases, but it seems to me there ought to be a very obvious source, either at the boiler itself or in the flue connector, or the chimney itself.

The condensate drain you mention may not drip water if the vapor in the flue gas is hot enough not to condense.

Can you look inside the masonry part of the chimney to see if it gets wet during a firing cycle? I have seen cases where vapor condenses inside the cooler masonry chimney and runs down to puddle at the bottom. Even if that's the case in your chimney, it's still hard to imagine that as the source of elevated humidity only during times when the boiler fires.

duplicate (post #205678, reply #6 of 8)

by ar7499b in reply to rdesigns [original] on Thu, 01/26/2012 - 15:06

somehow double posted

There is no access to see (post #205678, reply #5 of 8)

by ar7499b in reply to rdesigns [original] on Thu, 01/26/2012 - 15:05

There is no access to see inside the chimney, except maybe from above, but no chance of going up there in the summertime, let alone now that is might be icy.....

 

It is warm today, so the boiler is not running much. This weekennd should give me a chance to think about it some more. I guess is it possible I am blaming the wrong appliance. It turns out that my wife did a heavy round of laundry, so I guess it could be related to the gas dryer, or even the water heater. I am pretty sure it happens even when the dryer is idle., and I know that the dryer vent is clear to the outside.

I suspect you have either a (post #205678, reply #8 of 8)

by xxPaulCPxx in reply to ar7499b [original] on Fri, 01/27/2012 - 10:31

I suspect you have either a plugged stack or some serious negative air flow issues.  A plugged stack might be able tobe rodded out, negaive air flow can be handled by opening a window or cutting a hole.

CO2 an CO in the house can have really serious consequenses.  The CO detector is a backup to a well funtioning HVAC system... and your primary isn't functioning.

Seriously, you are in Life and Death territory here.

Something is seriously wrong that can endanger everyone in your home.  Call out a specialist TODAY.

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Yeah, you're right to be (post #205678, reply #7 of 8)

by DanH in reply to ar7499b [original] on Thu, 01/26/2012 - 18:30

Yeah, you're right to be concerned.  The others have covered the most obvious stuff, but one important check is to simply feel around everywhere that the flue gets close to, checking for warm air/exhaust blowing out.  Start inside the unit itself.

The other possibility, of course, is that there's a leak somewhere in the hot water piping.  Of course this would cause the water level to drop in the unit, but some units have an automatic makeup water setup.


We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy -- sun, wind and tide. ... I'd put my money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that. --Thomas Edison