Hello:
I have glycol based in-floor heating system (hydroionic heating). Recently, service man came and changed the Thermal Expansion Tank. Before the replacement, the system was working a 20 to 22 psi. The new expansion tank was pre-charged at 12 psi- he never charged it to system pressure (Which seems to be the best practice, based on my online search)
Now my system pressure is down to 15psi and I can not crank it up.

My question is:

Should I increase the pressure of the Thermal Expansion Tank- while it is hooked to the system?
or
I have to remove he tank from system- increase the pressure- and then reinstall it? (I want to avoid this option as this will result in more loss of Glycol from the system.
Your input will be greatly appreciated.
Thanks
Vishal

if you are only lifting the water to the first floor, 15 psi is plenty.
what you are reading is about well tanks as relates to cut in/ cut out pressure.
if there is glycol in the system, there should be a ball valve at the expansion tank. in fact it is good practice to have a ball valve at the tank for future replacement..
I always install one of these for expansion tanks..

REgardless of what the initial pressure is, assuming it starts out LESS than the system's pressure, as soon as the system is turned on the tank pressure becomes the same as the system pressure, .



Edited 1 times.

The only reason to maintain a pressure on a hydronic heating system is to insure that the system stays filled. Your 20 psi would mean about 40ft from your auto-fill regulator to your highest point of radiation.

Thanks all. so does it mean that loss of pressure in the system is not due to the lack of proper pre-charging but some thing else?
Thanks



Edited 1 times.

since it is a closed system, won't it result in loss of overall system pressure?
Thanks

"but some thing else"
you had better hope not..
that 'something else' would be a leak of some kind..

"since it is a closed system, won't it result in loss of overall system pressure? "
the system pressure goes up and down as the water heats and cools. the expansion tank keeps that pressure change to a minimum.

"Now my system pressure is down to 15psi and I can not crank it up".

What does your system pressure need to be? It's not an arbitrary number. It takes a certain pressure, to raise the water/glycol mix to the highest point of radiation, when filling the system(cold).On a typical water filled hydronic system, there should be a regulator and backflow preventer on the supply line.You adjust the regulator to what you calculated the pressure needs to be, then bleed the air from the system.At that point. if you leave the supply valve open, it will attempt to maintain the pressure at what you have the regulator adjusted to. If you close the valve, and it looses pressure, there is a leak in the system. You have a different animal, in that you have a mix of water and glycol. Your system was probably filled by pumping the solution in. They may have opened the supply valve for a second, once they had the system filled, to apply some pressure, and give you a visual reference. How are you attempting to "crank it up"? Since you are running a glycol system, is it run with the supply valve shut?
Your expansion tank has a bladder in it. If you determined that your system needs to be set to 15 psi. You would fill the bladder in the tank to 15 psi.It must be filled, isolated from system pressure. If you set the system pressure to 15 psi and tank pressure to, say,10 psi, you lose expansion capacity.



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Paul48 (CT),

I will leave further explanation to you

Expansion Tank = open to atmosphere system

Compression Tank = closed pressurized system


albeit, today, open systems are so rare one merely says 'compression tank'

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