# boiling boiler?



## spudwrench (Sep 15, 2009)

Long story short (I hope). Oversized CI boiler. 4 zones and an amtrol hot water maker. Limit set to 175 actual on gauge 185. Spirovent and decent near boiler piping. Expansion tank failure changed out by others. Charged to 20 psi. I lowered the tank charge to 12, and PRV to 12. No prior problems, but since the tank change, the owners hear a boiling sound from the boiler proper. I heard it too. I thought that the cause was over pressure, not so.When the thermostats are satisfied and the pump shuts off, the boiler temp. rises to 200-210. That is when the pot of boiling water sound occurs. The boiler is in a basement with 2 stories above it, the master BR is directly over it so the sound transmission is very evident to the homeowners. Any one know what kind of animal that I am dealing with here? All copper fin tube above us. My next move is to change out the expansion tank, to go back to where this started. Thanks for any input!


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## MarkToo (Dec 17, 2011)

Thermostat failure?

Is boiler still running when the call for heat is satisfied and the pump shuts off?


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## eddiecalder (Jul 15, 2008)

Air in the system?


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## Plumbworker (Oct 23, 2008)

sounds like a control issue.. From what you described it seems like the burner is still running.


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## intohotwater (Feb 10, 2012)

Sounds like latent heat. The pump should remain on for a min of 30 sec. After the call for heat is satisfied. I set my boilers to 120 sec.


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## CTs2p2 (Dec 6, 2011)

Where is the aquastat located, is there a domestic coil?

Sound like the aquastat isn't reacting fast enough, by the time it(the aquastat) thinks the boiler is 180 and should shut off, the temp is really maybe 200 or more..
I've seen the aquastats not pushed in the well deep enough, the well could be gummed up acting as if it's insulated. If there is a coil the outside of it could be all gummed up and the aquastat is in the middle of it..


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## OldSchool (Jan 30, 2010)

Main pump should be on an aquastat 

Once the boiler reaches minimum temp pump should be on until the boiler temp returns to minimum temp

Also everything depends on system lay out

If it's a cast iron boiler like you say there should be a bypass loop or a primary loop

Sent from my portable office....yes I am at work


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