Boiler PRV popping after installing new Autofill valve and expansion tank

[Captotis99]

Yesterday I replaced the heavily corroded Autofill valve on my otherwise fine running system.

After reopening the supply valve the PRV valve pops. I went to talk to the "pros" at my local plumbing supply house. They pointed me in the direction of replacing the expansion tank and also adding an isolation valve to aid in future sytem service.

After replacing the expansion tank and also the PRV, the system behaves the same way.

Any suggestions.

 

[Plumber69]

Dose it only pop when the system is heating? or will it keep popping with just the fill valve open

 

[Sponsor]

 

[Captotis99]

Initially it was only popping with the fill valve open. Now with the fill valve closed it is dripping after a hot water call finishes. The pressure is lingering between 25-30 PSI. I think my storage tank may be on the way out.

 

[Plumber69]

you lost me. you said you changed them both

 

[Jadnashua]

The autofill valve is adjustable...it may be set too high, or, it might be installed backwards...ensure the arrow is pointing the right way.

The normal range for common boiler systems is in the 14-16psi range. IF you have a taller building, you may need more. The relief valve usually supplied on those is 30psi, so a working pressure in the 15psi range gives it a 2:1 margin that a properly installed ET should handle easily. The precharge on the ET must be set prior to installation, or the system pressure released. That should be precharged to the nominal pressure of your system.

 

[Plumber69]

The autofill valve is adjustable...it may be set too high, or, it might be installed backwards...ensure the arrow is pointing the right way.

The normal range for common boiler systems is in the 14-16psi range. IF you have a taller building, you may need more. The relief valve usually supplied on those is 30psi, so a working pressure in the 15psi range gives it a 2:1 margin that a properly installed ET should handle easily. The precharge on the ET must be set prior to installation, or the system pressure released. That should be precharged to the nominal pressure of your system.

It's the right way.

 

[Captotis99]

The new valve, a Watts 1156F is supposedly preset at 15 PSI. The ET out of the box had 10 PSI in it so I added air up to 13-14 PSI before installing.

The house is a Cape with 2 zones.

 

[Captotis99]

you lost me. you said you changed them both

I replaced the ET and the PRV after initially replacing the autofill valve.

 

[Jadnashua]

WHen the boiler is cold, what does the pressure gauge read? IF the ET is properly installed, when heating, the pressure should not rise much. IF it's too high to start with, that's an issue. Also, some of the autofill valves aren't perfect, and will leak a bit, letting the system pressure rise. IF there's a lot of air in the pipes, trying to get the pressure stable is harder.

 

[Captotis99]

WHen the boiler is cold, what does the pressure gauge read? IF the ET is properly installed, when heating, the pressure should not rise much. IF it's too high to start with, that's an issue. Also, some of the autofill valves aren't perfect, and will leak a bit, letting the system pressure rise. IF there's a lot of air in the pipes, trying to get the pressure stable is harder.

 

[Captotis99]

WHen the boiler is cold, what does the pressure gauge read? IF the ET is properly installed, when heating, the pressure should not rise much. IF it's too high to start with, that's an issue. Also, some of the autofill valves aren't perfect, and will leak a bit, letting the system pressure rise. IF there's a lot of air in the pipes, trying to get the pressure stable is harder.

I went back to the autofill and played with the adjustment. Apparently the factory preset of 15 PSI was a myth. Was able to get the pressure down to 15 PSI after almost 4 full turns. Problem seems to be solved with system running and supply valve to autofill open pressure seems to be maintaing with no PRV activity.