Sizing expansion tank for commercial systems

Wayco Wayne_2

I'm looking to size an expansion tank for a new boiler change out we are doing. It will have 4 boilers @400K input each. I'm a little out of my comfort zone here. I had a good feel for residential, but this commercial sized stuff I feel limited. How should I proceed?

hot_rod

It is mainly about system volume, both Amtrol and Wessels have commercial tank sizers online.

http://westank.com/calculator/

The boiler output has some effect on the sizing of the pipe connection to the tanks. The Amtrol Engineering Handbook has a formula for that calculation.

JUGHNE

Being a change out, there would have been a tank there for comparison purposes? New boilers might hold less water than old. That is if that is the only thing changed.

Paul Pollets

Commercial boiler installations require an ASME certified expansion tank. Size according to load and system volume using the sizing charts on Amtrol's website. If the tank is undersized, there's risk of blowing off the relief valves.

Wayco Wayne_2

I just measured all the pipes in the system and converted into gallons. 278 gallons, not including boilers. The boilers are 4 Laars copper fin boilers @ 400K each. The height of the system is less than 10 feet. I looked at a vertical bladder tank on the Amtrol site but it said it was a non ASME tank. Not what I want. I feel like I'm getting close.

SWEI

The threshold where an ASME expansion tank requirement kicks in varies a bit by jurisdiction, so read the fine print.

The calculator link Bob posted above (or this one) will get you a solid answer on sizing if you input your minimum and maximum temps. Don't forget the water volume in the emitters and boilers.

hot_rod

Wayco Wayne said:

I just measured all the pipes in the system and converted into gallons. 278 gallons, not including boilers. The boilers are 4 Laars copper fin boilers @ 400K each. The height of the system is less than 10 feet. I looked at a vertical bladder tank on the Amtrol site but it said it was a non ASME tank. Not what I want. I feel like I'm getting close.

Look at multiple tanks also, sometimes the smaller tanks connected together end up being less $$, if it is a common off the shelf size.