Expansion tank location

hot_rod

This question comes up a lot when I do trainings. In either case shown we are pumping away from the PONPC. If the boiler is a "wide open" style, little pressure drop, then the tank on the return is fine. It puts it in cooler fluid and less heat loss through the shell.

High pressure drop boilers prefer you pump into them as shown in installation manual suggested piping methods.

Critical on both is the air separator at the hottest point in the system.

The expansion tank need not be at the air separation device.

EBEBRATT-Ed

I agree as long as on the "high resistance boiler" the pump doesn't have enough head to open the relief valve. If hooked up pri/sec it wouldn't be an issue

leonz

Hello Bob,

Would you mind also uploading a diagram of a steel compression tank system with the Airtrol valve as well for everyone? This way they can compare them and understand how the steel compression tank was used first in "pressurized" hydronic heating systems.

flat_twin

Have you ever seen an expansion tank tied to the system at two points? This is a direct return layout with 2.5" supply and returns.
The system return for the main part of the house has a PONPC and the system return for the rear part of the house has a PONPC. These points are within 2 feet of each other directly above the boiler. The returns combine immediately after the PONPC just ahead of the circulator and then to the boiler so it is pumping away. Not seen in the pic is the system feed and pressure regulator where the expansion tank threads in.

hot_rod

Yeah, you really don't want two different expansion tank tie- in, in different locations.

Basically you create two PONPC, as such the pressure in various places around the circuit could cause issues like sub-atmospheric conditions allowing air vents to suck instead of blow

If in fact they tie into the same pipe within a few feet of one another it probably will not cause issues. Are they pre-caherged to the same pressure?

hot_rod

leonz said:

Hello Bob,

Would you mind also uploading a diagram of a steel compression tank system with the Airtrol valve as well for everyone? This way they can compare them and understand how the steel compression tank was used first in "pressurized" hydronic heating systems.

Here you go. And a a copy of the Amtrol Handbook to learn a lot about expansion tanks types and applications.

flat_twin

hot rod said:

Yeah, you really don't want two different expansion tank tie- in, in different locations.

Basically you create two PONPC, as such the pressure in various places around the circuit could cause issues like sub-atmospheric conditions allowing air vents to suck instead of blow

If in fact they tie into the same pipe within a few feet of one another it probably will not cause issues. Are they pre-caherged to the same pressure?

Only one expansion tank. Years ago it was a steel tank with no bladder and the system fill was 20' away. The fill and pressure regulator were moved to the neck of the new bladder type expansion tank when the modcon was installed. https://i.imgur.com/ad5hyFh.jpg

leonz

You need to get that fixed.

SuperJ

With two points of tie you will create an unwanted bridge for flow if there is any pressure difference at the pickup points.

hot_rod

flat_twin said:

hot rod said:

Yeah, you really don't want two different expansion tank tie- in, in different locations.

Basically you create two PONPC, as such the pressure in various places around the circuit could cause issues like sub-atmospheric conditions allowing air vents to suck instead of blow

If in fact they tie into the same pipe within a few feet of one another it probably will not cause issues. Are they pre-caherged to the same pressure?

Only one expansion tank. Years ago it was a steel tank with no bladder and the system fill was 20' away. The fill and pressure regulator were moved to the neck of the new bladder type expansion tank when the modcon was installed. https://i.imgur.com/ad5hyFh.jpg

I get it now, single tank tied into two places.