[Lobstah]

The relief valve on my furnace is discharging. At first I thought it was a faulty valve, so I replaced it. New valve does the same thing. I took a closer look and discovered that the pressure on the gauge reads 30psi, well above the 12-17psi operating pressure.

I checked the accumulator tank, it is cool on the bottom, warm on the top, so I don't believe the bladder is ruptured.

Any ideas on what to check next? I don't know what regulates the internal pressure of the boiler.

Lob

[acetc]

There should be a pressure regulating valve on the water make up line near the expansion tank, probably bad, Good luck, Mike

[Lobstah]

I checked the cold water feed to the furnace, there's a shutoff, a backflow preventer, and a regulator, then the copper feed goes into the inlet side of the heating system.

Is that it? Is that "feed" the water make up line?

Thanks for your help,

Lob

[acetc]

That sounds like the critter to me. It is probably stuck.Should replace the regulator.

[Lobstah]

Thanks... it's about the only thing left that I haven't swapped.

I see it has a release on it... not sure what that does? There is no hose fitting or outlet, it's just an inline valve.

Lob

[acetc]

It should have a tag on it saying the pressure limits,

[Lobstah]

Yes, it does. Says 12-17psi.
Not sure that's it though. I flipped the spring lever a few times.

There is a pipe that comes out of the boiler that has a gray relay box on the end of it.
I know there are relays inside, but not sure what the relays do?
Is there anything in there that could be causing this symptom?

Lob

[acetc]

If that gray box is attached to the water piping it may be a low water cutout switch, if it is attached to the gas piping it will be the gas control valve neither will cause the increased pressure.

[tsa7man]

Another question to you... do you have an indirect water heater piped off the boiler, that heats your dom. Hot water for your faucets??