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High pressure in boiler

I have a Federal Boiler that when the temp. goes above 160 degrees the pressure goes to 45 psi. I have changed the pressure tank and drained the boiler and refilled. Any ideas what the next step might be.

Re: High pressure in boiler

You should NOT operate the boiler if indeed the water pressure is exceeding 30 psi when you run it---there is a pressure relief valve that should open to spill some water on the cellar floor at 30 psi---this is a safety device to protect the heating equipment from excessive pressures---you would have to replace this pressure relief valve as a first step.

It's possible that the boiler gauge is inaccurate & giving a wrong reading, so you can test this with a srew-on pressure gauge (HD/Lowe's) that you can attach to the boiler drain valve at the bottom of the unit, to insure that the water pressure readings on the boiler gauge are accurate.

For a next step, could you post back to indicate what your current setup is for the domestic (tap) hot water???

Do you have a separate hot water heater, an indirect HWH, or a "tankless coil" inside the boiler???

If it's not the expansion tank, then the problem indicates that the high house pressure (40 to 60 psi) is somehow getting into the boiler water, which operates at 12 psi.

Also check the new expansion tank you bought to make sure it's the right type--it should say "12 psi" as the pre-filled air pressure.

The boiler water system is isolated from the house water pressure by a PRESSURE REDUCING VALVE at the point where the water enters the boiler--- (Google "Watts pressure reducing valve") to get a photo of what this valve looks like---they all have a long, 3" adjusting screw coming out of the top of them to adjust the WP to around 12 psi----assuming the boiler gauge is OK, the pressure reducing valve could be the culprit---but check the other components first: namely, temporarily isolate the domestic hot water system (hot water heater, tankless coil, indirect, etc.) by closing off the valves that hook up these components to the boiler system.

In other words, temporarily shut off any house pressure (50 psi) water pipes coming into the boiler system (12 psi) to see if the pressure on the boiler gauge comes back to 12 psi---if it does, it means you have an internal leak in one of the components that supplies hot tap water to the house.

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