Condensation in boiler flue

Chris S

I agree - not normal
6" Flue was sized by chimney pro- for my 160M btu boiler
Boiler is piped primary/secondary, I don't see low water on the return side-
Stumped

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Chris S

Condensation in boiler flue

I have an older house with an exterior masonry chimney. My chimney sweep inspected , and reccommended a SS liner for the boiler, fireplace flue was good. They installed an insuletd liner, we then installed a new natural gas low mass boiler.
We have had condensate issues ever since. I have to keep a bucket under the T to catch the water. It's gotten worse as it's been getting warmer.
Anybody have any thoughts on this? I've been told that some people install drains & condensate pumps on their chimneys.

Chris

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Jim Bergmann_5

Boiler

The return water temperature is likely to low, If the RWT drops below 140 the boiler will likely condensate. I would consult the installation instructions and review the piping. Normally there is a bypass arrangement in the piping to keep the RWT up if you need to reset the boiler to a lower temperature. The liner could also be over-sized. What you are seeing is not normal and a professional should be consulted.

Boilerpro_5

Another common problem....

is short cyling of the boiler. If the burner short cycles it will not allow the flue to warm up properly. Typically this is caused by an incorrect themostat anticipator setting or cycles per hour setting or a low mass boiler (copper tube or Weil Mclain residential boilers)used with multiple zones. Also a boiler with too much capacity could cause this problem. A 160,000 btu/hr input boiler is typically needed only for commercial applications or very large homes (5,000 sq ft and up). Also primary/ secondary piping in and of itself will not necessary protect a boiler from low temperature operation.

Boilerpro

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JackR

Outside Chimney?

Is this an outside chimney?

Chris S

Yes- it's an outside chimney- masonry shared with fireplace, but seperate flues.
It does short cycle, I am running 6 zones of baseboard, and yes the house = 160m btu unfortunately. It's a post & beam barn converted to a residence in 1950 3600 sf drafty as hell. We replaced windows doors & insulated what we could without doing a total gut out. The heat loss equals the amount of BB installed however I could see some of the small zones being an issue. I did order a 2 stage gas valve to replac the single stage currently on the unit- which was orderd by mistake. Will this help?

Thanks, Chris

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Boilerpro_5

Very likely....

especially if is a copper tube boiler. Raypak used to use a simple modulating gas valve that allowed about an 8 to 1 or so modulation of the input to help prevent this. Honeywell, for some reason, has stopped making this valve....so much for progress. Also, you may want to set up some of the zones so they will not call on the boiler by themselves. Pick the zones that tend to stay warm easily and only allow the zones that have to work hard call on the boiler.

Boilerpro

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