Pressure Release Value on Furnace is being tripped frequently -- how can I get the pressure to remain steady?

The pressure release valve on my 20+ year old Hydrotherm Multi-Temp MR-420 gas furnace has been opening up a lot recently, spewing about a gallon a day of water (more or less). This is the first time I’ve seen this. I am wondering if it is a flag for some other issues? The release valve was changed a couple years ago and appears to be in working order. The release valve reads “50 psi, No 13570, 1,048,000 BTU”. The system is 5 zones with thermostats on each floor going down to a controller. On the furnace gauges the altitude reads 75 and never seems to change. The water pressure sits around 25 when the furnace is not heating. I have not seen it go up to 50 psi, but I imagine it does, which is presumably when the release value triggers. The heat in the building is fine. 

How do I get the system to maintain an even pressure? Will turning down the temp on the furnace (its set at 160F) do anything? I bleed air out of the top of the system once or twice a year. Will doing that more frequently make a difference? Thanks for your help.

housepoor

in Furnace Repair 12 years and 5 months ago

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housepoor | 12 years and 5 months ago

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The expansion tank had failed. Its been replaced along with the pressure relief valve (to be on the safe side since, as it was explained to me, when they trigger so often it stresses the seals) and any air bled out of the system. Working like a charm. Thanks for your help.

Master Plvmber | 12 years and 5 months ago

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Or you’ve got a passing pressure reducing valve, or both.

eman134 | 12 years and 5 months ago

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replace the expansion tank on the system, sounds like it has failed