cracked boiler?? steam from chimney?? constantly refilling...


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Old 02-10-06, 08:21 PM
R
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cracked boiler?? steam from chimney?? constantly refilling...

Steam System, oil fired boiler is probably 10-15 yrs old. Water Heater is a separate gas burner.

I am constantly have to refill the boiler, but I thought one of the radiator fittings was leaking the steam, tho they all check out ok...

was home today at noontime (approx 32F) and noticed the shadow of the top of the chimney on the lawn, and there was enough white smoke/steam/vapor to cast a shadow. Persisted for about 3-4 minutes after the burner shutoff... system seems fine otherwise...

is it possible that a steam/water could be escaping into the exhaust stack / chimney??

thanks

jr
 
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Old 02-11-06, 06:45 AM
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It is possible but water vapor during cold weather is not that unusual. It is the humidity from inside your home condensing as the exhaust cools. It could be boiler leakage too so maybe you could pick a warm day and turn the boiler off for 12 hours and see if you get any noticable leakage on the floor.

Ken
 
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Old 02-16-06, 08:22 AM
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Vapor in the exhaust just from household air??

Vapor from the cooling exhaust?? But the 'cooling exhaust' consists of
residual/unburned fuel vapors and the air that surrounded the furnace/burner , ie
normal household air at 65 degF and probably 65% humidity. There
just isn't enough vapor in air to present like that.

There are no leaks on the floor ever. Boiler could be cracked high up, above
the fill line.
 
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Old 02-16-06, 09:32 AM
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You might be surprised how much moisture there is in that air. It all has to do with the dewpoint. The dew point of air in the example you gave is 53 degrees. However your estimate of 65% relative humidity was much higher than a house ever gets to. Using 40% rh as a maximum, the dewpoint of air that started at 65 degrees will be about 40 degrees. That means that from any temperature at or below 40, you could see water vapor in the exhaust. If the house humidity was 30% the dewpoint would be about 33 degrees. The idea of having exhaust temps above 350 on most older equipment is to prevent the exhaust from getting down to the dewpoint until after it leaves the chimney top. Then as it cools, it condenses and the moisture falls harmlessly on the birds sitting around the edge of the chimney. The ability of air to hold moisture is less as the temp falls and around 10 degrees, I think everybodies chimney shows signs of water vapor. Even the PVc outlets on 90% gas furnaces.

Play with this dewpoint calculator and you'll see what I mean.

http://www.decatur.de/javascript/dew/

Ken
 
 

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