08:26PM | 01/07/14
Hi, I'm trying to find out if my boiler pressure is to high! We're caught in this "polar vortex", it's 7 degrees F outside and my heater is cranking. It normally hovers in the 100 to 150 psi range and now it's showing over 200 (see attached). Recently a plumber installed a new pressure relief valve as the old one was getting calcified.

I'm heating a 3 story house, about 2300 square feet, sealed radiators. Should I be worried?

Please advise ASAP so I can have peace of mind! (or not)

Thanks in advance.


Duane, Moderator

10:44PM | 01/09/14
Member Since: 11/14/13
91 lifetime posts
The picture is a little blurry; however, it appears that the pressure id the top row of number on the gauge, and the needle is pointing to 25 psi.
This would be well within the normal range.

Please check it and let me know.
Duane, expert moderator


12:56PM | 01/15/14
Member Since: 01/24/06
1626 lifetime posts
Me office1
HECK YEAH you need to be scared stiff with 150 + PSI

Setting the water temperature above 200 deg is not only wasting energy it is down right dangerous.

Also having very high water temperature puts a lot of stress on the piping do to the coefficient of expansion per degree change per inch.

You also stated you have 12 PSI is that cold fill or the actual working pressure?

12 PSI is on the lower side of the automatic feeder / pressure reducer and as water is heated it expands.
You did not mention how high the highest radiator /base board is from the boiler?

When installing a boiler one would not only take a heat loss BUT also the following

1- Fill the system and bleed all air out and then read the static pressure Height x ..433 in this case your said your reading 12 PSI which means the height of the highest heater is around 27.7 feet

2- To prove this we would take the 12 PSI and X 2.31 = 27.72 ft PRESSURE required to raise the water this high

3- Take the 27.72 X .433 = 12 PSI correct?

As a boiler installer and inspector I would first get a cold fill reading THEN add 4 PSI for a fudge factor to make sure I have positive pressure bleeding out all air.

Now when the boiler is firing you take the reading which is higher as the temperature rises.

Double check your 12 PSI reading and get an accurate COLD water reading before you end up causing a major catastrophist explosion when your excessively high water temperature flashes into steam when a pipe bursts.

It is a shame that boilers do not come in one size fits all huh?

You should contact a LICENSED heating professional as the life you save maybe your own

Replacing a relief valve one should ask why it failed, is the expansion tank water logged? is the pressure reducer working properly or allowing excessive pressure into the system?
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