Boiler inlet pressure regulator question

Old 11-17-10, 07:42 PM
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Boiler inlet pressure regulator question

Hello, we live in a split level house with hot water baseboard heat. Boiler is located in the basement level, 2 rooms in basement have radiators, 2 rooms in mid level and smallish rooms in upper level. Question is this...a couple of days ago I noticed water coming from the pressure relief valve on the boiler, a quick call to our heating company gave me a few things to check. After running the heat for about 5 mins, the boiler pressure was at 30psi and the valve was spitting. So I tried to drain the joist mounted expansion tank with no luck. This morning, the heating company sent over a guy to get us back on track. He finally got the tank drained and upon opening the supply to the boiler back up, he pointed out to me that he didn't think the pressure flo valve was plumbed in correctly. The fill line to the boiler is tee'd off of the line that goes to the expansion tank. His logic said that he was afraid that the valve would read the empty pressure in the expansion tank and overfill the boiler. Now, he ran some water into the boiler, and then shut off the supply valve and told me that he always leaves the boiler supply shut off and that you can't trust the 12psi regulators. Problem comes when I get home today, first there is no hot water...I realize that he turned the low side of the temp controller to off. Fix that, and then I see that the pressure in the boiler is at zero. I run the heat for about 10 mins and the pressure stays at zero. Now, is his thinking in leaving the fill valve off correct. I opened it up until I saw about 12 psi on the boiler gauge and then shut if off again. I wasn't real impressed with his knowledge and now wonder if our boiler is running correctly. Thanks for any help.
Old 11-17-10, 09:35 PM
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Some professionals like to leave the "make-up water" off and others like to leave it on. If there are no leaks in the system then leaving it off makes sense. However, when your technician stated, "...he was afraid that the valve would read the empty pressure in the expansion tank and overfill the boiler." he was showing his ignorance as the pressure difference between the boiler and the expansion tank in that configuration is almost zero.

Posting some pictures would help us to help you. To post pictures you need to first upload the pictures to a photo hosting site such as or and then post the public URLs for the pictures (or album) here. More pictures are always better than fewer. Please have CLEAR pictures and have both close up pictures and ones from a far enough distance that we can see how the various parts are interconnected.
Old 11-17-10, 09:54 PM
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Was there pressure in the boiler when he left? If so, where did that pressure go?

You brought it up to 12 PSI... was that with the boiler COLD? or HOT?

Be careful about filling a HOT boiler with COLD water! C-R-A-C-K-! ...

If COLD, then keep your eye on the gauge... if the pressure drops consistently and you have to keep adding water, you've got a leak somewhere.

If HOT, then you may not have enough pressure in the system.

Let the boiler get COLD, fill it to 12 PSI, shut off the manual valve and keep a strict eye on the gauge for a couple weeks.

Whenever you look at the pressure gauge, also note the temperature! The two go hand in hand. You should always see the same pressure at the same temp. Temp goes up, pressure goes up.

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