Expansion tank question

eugd

I have a Weil McLain ultra 155 boiler with expansion tank coming off the taco air scoop valve just underneath the branch of the taco Waterfill valve that expansion tank 8 psi. As per the manual I checked the PSI default is 12 psi. also I have another smaller expansion tank coming off the hot water heater that is indirect And the psi is set at 77 the water pressure to the house is 79 psi my question is what should the tank on my boiler be set at to because it seams low for my with the system. Also. I noticed that caution the pressure gauge on my boiler is set at 30 psi. Thanks for all of your anticipated help.

Intplm.

@eugd.
Ahh, Gauges ! The bain of my existence.

But seriously. I have found that one gauge to another can vary in readings as much as 3psi. ( digital or analog. ) That being said, If your heating system is working properly without unusual noise or leaks I would say to not worry about it.
The expansion tank on your boiler is used with the heating system of your house and the tank on the water heater is strictly used for the hot water coming out of your faucets. So, they are separate.
You can adjust the water pressure on your heating system at your pressure reducing valve ( PRV ) to supply the 12 psi required.
Start with a cooled boiler.
The PRV under your air scoop appears to have a slide lever that will manually feed the system. ( Can't really tell from the pic )
As you slide the lever you should hear and see the water pressure go up.
After setting the pressure at 12 psi monitor your systems pressure for a while. Give it a look every other day or so.
If the system is losing pressure, you could have a leak on the system and or a problem with your auto feed / pressure reducing valve.
It's always good to have the PRV and expansion tank pressure at the pressures specified in the owner's manual. Usually 12 or 15 psi.
Note the pressure will rise once the boiler heats up.

eugd

Thanks. I have no leaks but boiler pressure was closer to 30 psi than usual at the since I started it up. The hum it produced It sounded a bit more louder at last night so I Bleed the lines and the pressure reduced back to it normal. I check the tanks once a year or two. Just rather stay on top of it than let it go and then there a issue. I put some air back into the tank to make it 12 psi. Just wanted to make sure I didn’t need more. Thanks again for your quick response

Zman

Unless the expansion tank is isolated from the system, checking or adjusting the pressure of the tank will do nothing productive.
I would question the accuracy or the boiler gauge at 30#. The PRV should be releasing water if that was the case.

A gauge like this is an easy way to get a second opinion for any system. You just thread it onto the boiler drain.https://www.supplyhouse.com/Watts-0069770-IWTG-2-1-2-Hose-Connection-Gauge-0-200-psi?gclid=Cj0KCQjw6KrtBRDLARIsAKzvQIG0d9MV-QGPE9TeJAASjrlIjA0L8AGAffM96I0BndWO20wMJLhKvtQaAhrZEALw_wcB

eugd

The boiler gauge is just a red visual marker that can be moved around. The real pressure in the system is the white marker.


I already checked the pressure to the house with that spiked gauge at its 79psi.

Zman

The expansion tank should be removed and the pressure should be set at that time. 12# is OK for a single story home. 15# would be better for 2 stories. The pressure is then maintained by the boiler fill valve.

eugd

Zaman
I have a two story two zone house. To make sure i understand. Remove and make sure I pump in a few ponds of pressure to make it 15 psi. That’s what you mean by the #15?

Zman

That is correct. The important part is that the tank is isolated, other wise the reading is meaningless. Your expansion tank support leaves a bit to be desired so be careful removing. This little valve allows you to check and replace the tank without a system draindown. https://www.supplyhouse.com/Webstone-41672-1-2-Pro-Pal-Full-Port-Brass-Ball-Valve-w-Hi-Flow-Hose-Drain-600-WOG?gclid=Cj0KCQjw6KrtBRDLARIsAKzvQIGZlEELyEvkFapMsKmk9TICoJVmEcqjo8rAYUUqCR1SFKx1FP70DPUaAuVFEALw_wcB

eugd

Ok great. Thanks for all the info.
I’m going to order the valve and make sure the pump some air in to make to make 15 psi

Zman

So 2 steps, isolate and charge the tank, then fill the system with water to 15 psi....

eugd

Thanks again