Are all hydronic guages the same?

Butch_3

I have a question. I have 2 properties. One is a duplex with an apartment on each floor and a single family home. My question is this. Are the guages on hydronic boilers supposed to all read the same? I have 2 boilers in my duplex and I am not exactly sure what the pressure is supposed to be cold and hot. The same goes for my other boiler that is a gravity fed boiler in my other house. Do they all operate off of the same PSI? The 2 boilers in the duplex are 40k BTU's and the other one is 100000 BTU's. The assumption is that cold it will read 8lbs and hot anywhere between 20&25lbs. Is that correct? Thanks in advance for all your input.

Alan(CaliforniaRadiant)Forbes

Standard Operating Pressure

for hot water hydronic systems are between 12 and 15 psi for a 1-2 story building.

As far as taller buildings, my rule of thumb is to provide enough pressure to lift the water to the highest point in the system and have 6 psi at the top to purge air.

Hot or cold, the gauge should not move. If it does, there may be a problem with the expansion tank, i.e. ruptured bladder, incorrect fill pressure).

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