I have a Weil-McLean CGa gold boiler. Up untill this year I haven’t been been having a problem! When the unit calls for heat the pressure gauge drops 2-3psi. It was at 12 psi cold but when heat called I’d be in the 8-9psi. Once the water heated up the pressure did rise like it should. I upped the cold psi to around 15psi so when the pump kicks on it doesn’t go lower then 12psi. The unit is piped this so, boiler unit pipe goes up gauge then pump. Does anyone know why this is happening all of the sudden?
Boiler pressure drops when call for heat
- Thread starter Alexhoc10
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John Gayewski
In the Trades
Is that gauge on the auction side of the pump? Your picture does not have enough definition to see clearly. It's piped wrong. Are you sure this has been a normal thing for this boiler/piping?
The gauge is right before the pump on the suction side. That’s how it’s been since I’ve moved there. But it had never done this pressure drop since this year. I haven’t changed or done anything. Just bled the air out of the system. I even checked the user manual I have for this and that’s how it says to have everything. So according to the manual it’s right?
John Gayewski
In the Trades
Yes you should pump away from the boiler, but your expansion tank/ fill valve / air seperater should also be in there before the suction side of the pump. This keeps the pressure from dropping on that side of the pump. To me this is acting normally for what you have.
Oh ok. Well I can replumb all that in the summer for sure! But for now should I drop the cold pressure back down to 12 instead of 15. I only upped it to 15 so when the pump would turn on the 2-3 pressure loss would still be above 12?
GrumpyPlumber
Licensed Grump
I'd wager the flow is improved since bleeding the air, causing a more pronounced decrease on the suction side.
So leave the cold pressure at 15 and when the pump kicks on the gauge reads 12 or reduce the cold pressure back to 12 and when the pump kicks on the gauge reads 8-9ish?
John Gayewski
In the Trades
Static pressure at 15.
Ok thank you! Then just replumb everything in the summer and drop it back to 12 and then the pressure shouldn’t drop anymore?
GrumpyPlumber
Licensed Grump
If the autofeed's piped near the gauge it could become a problem where it refills when reading less than 12 psi, then exceeds 30 psi on heating, keep an eye on the relief valve for dripping, if it hasn't dripped, leave it be.
The auto fill is plumbed on the top but I have it closed for the time being so it’s not filling. Just didn’t know if 15 pounds was to high for a cold start even though it is dropping to around 12 when running.
Fitter30
Well-Known Member
Take some more pics. Need the ex tank and piping. Ex tank probably on the discharge of pump.
Yes it is the tank is on the discharge side. But it’s been that why way for year and I never had this problem? I will get more pics when I get home in the morning for you.
Fitter30
Well-Known Member
Ex tank can't tell what it's piped into.
It’s piped from the cold water fill then goes to the hot side from the boiler. Expansion tank and cold water fill are both after the circulator pump
GrumpyPlumber
Licensed Grump
Beyond the observation of a 3psi pressure drop, it seems to be working.
If it ain't broke, why fix it.
Just doesn’t seem right and don’t want any long term issues if I can fix it now.
John Gayewski
In the Trades
It's fine. This won't cause long term issues.
