pre charging expansion tank

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husker

New Member
Oct 18, 2008
19
Nebraska
I havve a 4 gallon expansion tank for my EKO 40 (no storage). What how many PSI should I charge it with? Instructions say 40 PSI but that is on DHW connection?
 
Mine are all pre-charged to 12psi.
 
I would check to be sure it is for a hydronic system not for a well pump, they should not be interchanged.
 
Mine is also 12 PSI precharge Keep in mind that is on a cold system..
 
Hot Rod,and others
Is it possible to gauge the pressure being to high or to low in the expansion tank by feeling the side of the tank and finding where the hot meets the cold, I guess my question is, is there an optimum water to bladder ratio like say halfway up the tank that gives you an idea that it is at the right PSI, or does this fluctuate enough it can not be gauged like that??I ask because I only feel warmth at the very top of my expansion tank,is this an indication of to much pressure on the system??Dave
 
TacoSteelerMan said:
Hot Rod,and others
Is it possible to gauge the pressure being to high or to low in the expansion tank by feeling the side of the tank and finding where the hot meets the cold, I guess my question is, is there an optimum water to bladder ratio like say halfway up the tank that gives you an idea that it is at the right PSI, or does this fluctuate enough it can not be gauged like that??I ask because I only feel warmth at the very top of my expansion tank,is this an indication of to much pressure on the system??Dave

I doubt you could gauge accurately with the "touch and feel" method :) the amount in the tank will vary with the boiler operating temperature. If the tank is already installed, you will need to lower the system pressure to gauge the tank pressure. It's easiest to check and adjust the pre-charge before you install, or pressurize the system.

hr
 
my expansion tank was set at 12 (I checked it- actually originally it was higher, but I lowered it down to 12) and then I tried to fill my system to 12 using the Caleffi calibrated fill valve.

System seems to run at 12-15 cold, 20 hot.

Should I be seeing this variation, or is it a sign of something amiss?

thanks
 
pybyr said:
my expansion tank was set at 12 (I checked it- actually originally it was higher, but I lowered it down to 12) and then I tried to fill my system to 12 using the Caleffi calibrated fill valve.

System seems to run at 12-15 cold, 20 hot.

Should I be seeing this variation, or is it a sign of something amiss?

thanks

More than likely that scenario indicates an undersized expansion tank. You'll get some variation when going from stone cold to 200* but usually not that much.
 
husker said:
I havve a 4 gallon expansion tank for my EKO 40 (no storage). What how many PSI should I charge it with? Instructions say 40 PSI but that is on DHW connection?

Husker, you need to determine if the tank is made for heating system use or for domestic water (well) use. There is a difference in the diaphragm of the tank for each type. A 40PSI precharge sounds like a well tank.
 
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