expansion tank sizing

nytech28

hay techs, i found expansion tank with water in the bladder on hot water boiler for 1st flr , its size EX15 made by amtrol & looks smaller physically, was curouse if it was sized probably, the 2nd flr boiler ex-tank model seems like model 30 with the same 70K btu input, 2nd flr boiler ex tank larger im size & on the return side of system before the circulator, 1st flr ex-tank is on the supply with air vent above by ceiling , thinking to install new ex.tank before the circulator for the 1st flr , any ideas would be great besides that problem i need to replace the PRV valve not filling up boiler after testing , you guys in this community gave me great suggestion on my last job, is there any charts on the forum to properly size up ex-tanks on boilers or domestic hot water tanks ??? .i.ll attach pictures to understand job easily.tnx

hot_rod

https://www.amtrol.com/resources-rewards/selection-tools/extrol-com-sizing/

Wessel and Zilmet have sizersonline also.

No harm in over sizing an expansion tank.

The precharge pressure should always be checked an adjusted when you pull it from the box.

If you go with a #30 I would add a better support, nipple up is the preferred mounting position.

nytech28

yes i.ll go with the #30 tank ,as for the support i.ll have to strap it , also the EXTROL chart you sent me doesnt work , how do I find water valume for the boiler on the tag of the boiler ?

hot_rod

You would need to look up the boiler spec sheet to get exact. Guestimate 10 gallons it will not make a huge difference. Try plugging in various "system volumes" to see the result.

https://www.westank.com/wp-content/docs/WebTankSizingGuide.pdf

Extrol installating sheet note:

nytech28

I was able to access amtrol & Westtank websites ,seems like its asking for size #15 for the boiler 4.72 water valume, & 70k btu ,but waiting on tech spprt response, also I draw new location for ex.tank & thats on the return line before the circulator pump , & crossed off the existing location which is the supply line pumping into ex-tank .with this new location circulator will be pumping away from the ex.tank .

hot_rod

Best to not have the tank right over the boiler. Swing it off to the left.

They leak from time to time.

nytech28

yes am gona have it swinged away from boiler the picture was just to show new ex-tank beining installed on return side a 12-15" far from the pump ,so it can pump away !!