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Posted by jim on January 09, 2004 at 11:48:53:
In Reply to: System Pressure posted by JH on January 09, 2004 at 10:17:54:
: I recently had a new autofill valve, expansion tank, autobleed valve, and pressure reliefvalve installed on my boiler. The sytem was purged, temp. set for 190, and the fill valve set for 12psi. When the system is running the psi reads 17-18 psi at 190 degrees. I am not having a problem heating my two story home. However, I noticed the other day that my pressure read 6 psi after the boiler was off for a while and the temp on the boiler was below 70. When The boiler fired and came to temprature the prssure went back up to 12 immediately and eventually to 17-18psi when at 1900 degrees. My question is; Why did the pressure read 6 psi if the fill valve is set for 12psi? Thanks for your help and suggestions.
When the water cooled it contracted reducing the pressure in the system. when it re heated it expanded again increasing pressure