Expansion tank, how do you know if it is size right & if it is b

Joe.G

How do you know if your expanison tanks is bad? what happens if it goes bad? is htere any thing I should do to it once in awhile? how long do they last? and how do you know if your's is to big or small for the house? i have a extrol #30 tank that is pre charged from the factory at 12 lbs, when I re did the copper lines in the house I checked the pressure and it was 4 lbs (my friend did let air out before I checked it0 i recharged it to 12 or 14 lbs I forgot. What would happen if it went bad and I did not know? Thanks

Al Letellier

expansion tank

You did the right thing in re-charging the tank. The first sign of a bad tank would be an increase in system pressure as the unit heated the water. Build past safety valve rating and it blows off. Watch the pressure during a normal boiler cycle after the boiler is up to temp. If the pressure remains steady or only increases a pound or two, your tank is OK and doing its job. If the pressure builds close to the blow off point, the tank is going bad. But be careful. A bad expansion tank is not the only thing that will build system pressure. Could be the feeder or a leak in the coil, if you have one.

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Joe.G

I have a boiler that stores the hot water in the unit it self. The pressure does rise up and down quite a bit, I set it at 12 lbs and the boiler goes up to about 25 lbs by it self, the blow off vavle has never gone off thought.

Al Letellier

expansion

That's a lot of pressure swing in my book. How big is the system (BTU Input)? Either the tank is going bad or the tank is too small for the system. If your set points in the aquastat are about 20 degrees apart ( HI @190 LO @ 170)that is too much pressure increase for normal operation.
What kind of system is it? Baseboard or radiators? What size is the tank?

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Joe.G

The tank is a #30 extrol tank it looks like a gray propane tank, How do i check the stat auqastat? where would I find it? and when i find what should it be set at? and I have the old cast iron radiator. My boiler does run for a while, i have it kick on at a 2 degree drop in temp and in runs for a while.

Joe.G

If it is not blowing the blow vavle should I worry about it? I have never seen it go past 30 lbs, Be fore next heating season should i pull the tank and check the pressure? The tank only feels warm about 1/4 of the tank(top 1/4) How do i know what size system I have? thanks

Joe.G

BTT