LOWERING PRESSURE IN BOILER

[Adrian Saunders]

I have hot water baseboard heat. Closed system with the diaphram expansion tank . Pretty standard system. My boiler pressure gage reads 25 psi. It should be 12 to 15 . Every time I try to lower it by opening the blow off valve for a couple seconds I loose a lot of water and the pipes gurgel. How do I lower the pressure and keep the system full of water? Thanks RDB

[fourth yearParticipant]

Check the expansion tank to see if it has the proper air charge and the diaphragm is not ruptured.

[SylvanLMPParticipant]

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In reply to message posted by RDB:
I have hot water baseboard heat. Closed system with the diaphram expansion tank . Pretty standard system. My boiler pressure gage reads 25 psi. It should be 12 to 15 . Every time I try to lower it by opening the blow off valve for a couple seconds I loose a lot of water and the pipes gurgel. How do I lower the pressure and keep the system full of water? Thanks RDB

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Who told you the boiler should be 12-15 PSI?

An automatic boiler feeder factory set for Hydronic systems is SET at 12-15 PSI

This number is not taken out of the clear blue sky by some engineer looking up.
the pressure is derived on a COLD FILL boiler and knowing that 12 PSI will elevate water 27.72 feet HIGH and also knowing that you REALLY want a positive pressure on the system to keep air out Most heating guys will add few pounds to make sure we don’t get air in AIR BAD, PRESSURE GOOD So by adding a few more pounds COLD fill we know that we still have a fudge factor for the HOT water to EXPAND.

What we professional heating folks do is fill the system and look at the attitude part of your TRI gauge.

Now when we get a dribble out of the upper most radiator, convector, etc.,
we “set the arrow so the next stumblebum will now what the cold feed was.

Now we know dribbling water pressure is not how to make friends in the heating world so we add 4-6 PSI for good measure.

now when water is heated in a closed vessel like a piping system this causes EXPANSION and thus MORE PRESSURE HUH?

Now what to do with this UNCONTROLLED increase?

How about adding and “expansion tank”?

Amazing how the parts all seem to fit in a system Now what happens if someone adds a booster pump to say reach the folks of the 18 floor of a building? Wow we are going to be popping the 30 pound relief valve so WHAT are we going to do?

Oh well I guess the 12-15 PSI is not such a bad thing when you consider the OTHER applications where we REALLY need pressure huh.

Amazing what is out there dabbling in “Heatin” stuff

Like has anyone checked the autmatic filler to make SURE is is not seeping? Do you have a tankless coil that may have sprung a pin hole?

Is there Air in the system as WE know Air can compress and THUS build up pressure?

Did you take the diaphram tank out of the system to check the charge?

Is your tank properly sized for the gallon in this system?

Where is this tank located in relation to the circulator?
Yup just guessing is the right way we heatin guys find problems.

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SylvanLMP

» This message has been edited by SylvanLMP on 09 October 2001

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