Reduce Boiler PSI?


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Old 10-12-06, 01:52 PM
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Reduce Boiler PSI?

Have an Oil Fired Weil-McLain WTGO Boiler....system works perfectly except that the boiler has 29 PSI, so 30 PSI relief valve drips constantly....how do I reduce the PSI?....what PSI do I reduce it to?....

Thanks,
Paul
 
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Old 10-12-06, 03:45 PM
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reducing PSI

You can drain some water from the boiler drain until the pressure comes down--you'll need around 12 PSI for a single story ranch so water can circulate. How many floors?

Increased pressure can be caused by a bad PRV, pin leak in the domestic how water coil if the boiler has one, a bad expansion tank (shows when system is hot).. Some detective work might be needed. Is the fill valve on or off? Has the pressure always been that high, and is it something new??
 
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Old 10-12-06, 03:56 PM
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Thanks for your response!

Drained water from the drain valve but PSI didn't go down at all; stayed at 29?

Is a single story ranch with an unheated basement.

Yes, domestic hot water; works perfectly.

Expansion tank is brand new; not waterlogged.

Automatic Fill Valve is ON.

Has always been 25-30 psi from the day I installed it?

Paul
 
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Old 10-12-06, 04:33 PM
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Psi

I'd wait for Grady to chime in, he's one of the pro's on the forum. Sounds like the gauge may be stuck--they do that! But, that doesn't explain why the pressure was ever that high, or the dripping safety valve.

cheap guess: bad pressure relief and a bad gauge to boot. A pin hole in the domestic coil won't stop it from making hot water, but it will over pressurize the boiler. But, opening the boiler valve and draining a little water should have reduced the pressure...
 
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Old 10-12-06, 05:05 PM
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Try closing the valve before the pressure reducing (auto fill) valve and then draining off a small amount of water. If this lowers the pressure then your PRV is not adjusted properly.

I would strongly suggest that you replace the safety valve if it has been dripping. It may seal again when the pressure comes down to normal operating level but most likely if it has been dripping for a while the seat/disc is eroded.

When the system is cold the PRV should be adjusted to shut off at about 12 psi. The air-side pressure in the expansion tank should also be the same. When the system is at operating temperature the pressure will rise; the amount of pressure rise is dependent upon the total water contained, the size of the expansion tank and the temperature change from cold to operating temperature. Generally the operating pressure is 15 to 18 psi.

When operating properly the PRV (auto fill) will NOT add water to the system, it will only add water when the PRESSURE drops below the setting of thePRV.
 
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Old 10-12-06, 06:27 PM
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High Pressure

Furd is exatly correct. As a check on the pressure gauge, you can use a tire gauge on the air valve of the expansion tank. The tire gauge will read the higher of the tank pressure or the boiler pressure. It the boiler gauge reads 29 & the tire gauge shows 15, your boiler gauge is bad as is the relief valve.
 
 

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