Boiler pressure

Old 02-15-08, 12:36 PM
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Boiler pressure

New boiler installed, used a watts autofill, seems as though the boiler guage says it somewhere about 20#'s. Does the watts 1156f have a default setting on it for psi?

What happens if the system is running at 20# or even 25#?
Old 02-15-08, 03:30 PM
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Keep in mind that the auto-fill setting will set the pressure when the boiler is COLD. When the system is heated, the water expands and the pressure RISES. This is normal.

HOW MUCH it rises is controlled mainly by the capacity and condition of the EXPANSION TANK.

If the pressure rises more than say 5 PSI from cold to hot, you might want to investigate whether your expansion tank is either too small, or in the case of a bladder diaphraghm type tank (looks like a gas grill propane tank) the air pressure pre-charge could be improperly set. Even an 8 PSI rise is not cause for concern. So, if you are at say 12 PSI cold, and 20 PSI hot, don't worry about it.

If the pressure rises to 25# start concerning yourself with the possibility of the PRESSURE RELIEF VALVE starting to open up and weep water ... Pressure Relief is set to open at 30 PSI, but in general, you want to keep the operating pressure 10% below that, or 27 PSI .

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