tmy23
New Member
First thanks for all help I receive. Let me describe my situation. This is a residential hydronic. Large, 3 floor victorian, cast iron radiators, 11' ceilings so probably 35-38'' rise from boilers in basement to top of the 3rd floor radiators. Also some long runs (+/- 60') in basement from boilers to vertical turn to upper floors. System is 2 WM HEII's for heat and WM DHW tank controlled by Tekmar controller, outside temperature monitor, etc. All original equipment is about 18 years old.
System was pushing water through boiler relief valve on one of the two boilers. Tried to test the relief valve and it was partially frozen, sticking open and also not re-seating properly. Replaced both boiler relief valves with OEM 30 PSI valves. Still pushing water out of one boiler. Suspected autofill valve. Took autofill valve out, and thought to put in a pressure gauge on the system side of the autofill between the autofill and a pre-existing shut-off valve. Reinstalled the autofill and with the shut off closed, the autofill would not hold pressure and regardless of setting would creep up to about 28PSI. Took the autofill out, disassembled, it was cruddy...cleaned, reinstalled, retested the autofill over a few nights and it held pressure. By completely uninstalling the autofill, I lost the original setting and am trying to readjust system pressure. With the shutoff on the system side of the autofill closed, I have it set to hold 12 PSI, which seems low with my vertical runs, you'll see where I am heading.
With the entire system shut down (circulators, boilers, etc), all the shutoffs open, the expansion tank and the new pressure gauge near the autofill valve both show 12PSI. One boiler gauge shows about 18PSI, the one that still leaks shows about 23PSI. When I start the system and it really heats up i.e. 180+, the boiler with the "resting" 23 PSI vents through the relief valve, and I noticed some seepage around the air vent on the top of the boiler also. The boiler pressure gauge goes up to near 40 psi. The other boiler doesn't vent, and stops around 28 PSI. At this stage the pressure gauge near the autofill is showing about 22 PSI and the expansion tank shows about 22 PSI also.
So for some reason, (Finally my question) , although both boilers are on the primary loop, one boiler over pressures and the other doesn't. I switched the new pressure relief valves, thinking maybe I got a bad valve, but the same result, the same boiler over pressures.
So the only thing I can think of at this point is to (1) turn down the autofill, but I'm concerned I won't get heat to the third floor, (2) check the expansion tank, what pressure should that be set at? or (3) put a 35 PSI or 40 PSI valve on the boiler?
thanks for all advice.
System was pushing water through boiler relief valve on one of the two boilers. Tried to test the relief valve and it was partially frozen, sticking open and also not re-seating properly. Replaced both boiler relief valves with OEM 30 PSI valves. Still pushing water out of one boiler. Suspected autofill valve. Took autofill valve out, and thought to put in a pressure gauge on the system side of the autofill between the autofill and a pre-existing shut-off valve. Reinstalled the autofill and with the shut off closed, the autofill would not hold pressure and regardless of setting would creep up to about 28PSI. Took the autofill out, disassembled, it was cruddy...cleaned, reinstalled, retested the autofill over a few nights and it held pressure. By completely uninstalling the autofill, I lost the original setting and am trying to readjust system pressure. With the shutoff on the system side of the autofill closed, I have it set to hold 12 PSI, which seems low with my vertical runs, you'll see where I am heading.
With the entire system shut down (circulators, boilers, etc), all the shutoffs open, the expansion tank and the new pressure gauge near the autofill valve both show 12PSI. One boiler gauge shows about 18PSI, the one that still leaks shows about 23PSI. When I start the system and it really heats up i.e. 180+, the boiler with the "resting" 23 PSI vents through the relief valve, and I noticed some seepage around the air vent on the top of the boiler also. The boiler pressure gauge goes up to near 40 psi. The other boiler doesn't vent, and stops around 28 PSI. At this stage the pressure gauge near the autofill is showing about 22 PSI and the expansion tank shows about 22 PSI also.
So for some reason, (Finally my question) , although both boilers are on the primary loop, one boiler over pressures and the other doesn't. I switched the new pressure relief valves, thinking maybe I got a bad valve, but the same result, the same boiler over pressures.
So the only thing I can think of at this point is to (1) turn down the autofill, but I'm concerned I won't get heat to the third floor, (2) check the expansion tank, what pressure should that be set at? or (3) put a 35 PSI or 40 PSI valve on the boiler?
thanks for all advice.