EXPANSION

Paul S_3

Can anyone tell me how to size a expansion tank to a typical hot water system?....when should i use a #15,30,60,90 etc.....i am having a problem with a mono-flo system, with a #30 extrol...and at least once a month i will be called to the home and the relief valve has blown.....boiler is piped properly(pumping away)....reducing valve is set to 12 psi....extrol tank pressure is at 12psi. I am going to try to put a #60 extrol, to see if that solves it.......

kcopp

It all ...

depends on the BTU output of the boiler and the type of radiation/ system volume. If its cast iron radiation almost always use a #60. Amtrol gives a  sizing guide. Always check your  tank pressure.

http://www.pexsupply.com/pex/control/ExpansionTankSizeCalculator?intcmp=calc;extrol-cat

Paul S_3

thanks

thank you...it calls for a #90

Steve Whitbeck

tank pressure

Expansion tank pressure can only be checked when the system water pressure is at 0 pressure. Otherwise the tank pressure will read the higher of the system pressure or the air pressure in the tank. Tank pressure 5, water pressure at 12 PSI.

pressure showing on tire guage will be 12 PSI.

Paul S_3

yes...

yes, i checked tank pressure with system pressure @ 0psi....i usually just take it off when i check it. When i raise system pressure i increase tank pressure.....for example reducing valve filling to 18 psi, i increase tank pressure to 18psi....

Paul S_3

therm-x-trol

what about a THERM-X-TROL....if potable water pressure is at 80psi...do i increase tank pressure to 80psi??

icesailor

Potable water pressure:

Potable water pressure shouldn't be 80#. Not more than 75#. And last time I noticed, the Extrols are rated at 75# Maximum. You need a pressure reducing valve to get it below 75#. 60# at the regulator will give you all the pressure you need in a normal house.

When used in well pump applications, you install 75# relief valves on the tank cross.

The precharge pressure in the tank should be the same as the working pressure in the system. After a PRV, not before. The PRV is a check valve.