hot water system pressure too high

Ron Schroeder

Hi Charlie,

It is normal for the pressure to increase as the water in the boiler AND piping heats up. But it sounds like your pressure is increasing too much. The inflation pressure in the tank when it is empty should be the same as the fill pressure of the system. I suspect that either the extrol tank is not pressurized to the proper pressure or more likely, it is too small for the systems total water volume.

Ron

Charlie DiCarlo

Hot water system pressure too high

I recently serviced a Pennco hot water boiler. The boiler is 4 years in service.This is a single zone system.This was a typical service including cleaning the burners, changing the thermocoupling, changing the air vent(no air scoop, only a tee) and inspecting the castings. The system was originally either radient hot water or steam. The rooms have radiatiors with key vents. After completing the service, I purged and bled the key vents. I fired up the boiler(Gas burner) and brought the system up to 180 degrees.From a cold start it took 35 minutes to get to temperature. I let water out of the boiler to reduce the pressure to 20psi. All seemed to be well until two days later. The home owner noticed that in the morning only when the boiler was starting up after the night time set back, the relief valve opened.Inspecting the relief valve I noticed rust had grown up into it as the installer had left only a short black nipple on the discharge side. I replaced the relief valve. Again, I purged and bled the key vents. The next day the same thing happened. With the system cold I put an air guage to the extrol tank(#30) and there was no pressure. There was no water either. I replaced the tank. Next day the same thing happens again. On this call back, I watched the automatic fill (wolverine brass)and saw that it was feeding at 15psi. I changed the feeder. After purging, the feeder stopped smack on 12 psi. I brought the system to 180 degrees and the guage pressure went to 19psi. Two days later the homeowner called to say the guage pressure went to 25psi at 155 degrees. The relief valve had not opened. I'm scratching my head now. Any thoughts on what is going on here?

Charlie DiCarlo

system pressure too high

Thanks Ron. What you suggested seems to be the consencis of three other techs I have spoken with. I'm going to add a second #30 extrol to the system. When I posted my situation with this boiler I mistakenly said "radiant" instead of gravity hot water. Thanks so much for your input. Charlie