Noritz boiler pressure valve leaking

ryan1983

I just replaced an old boiler for in floor heat with a noritz ncrb 199. The system has 3 zones with an external pump and a 4.4 gallon expansion tank. The system works great when the heating loops are on or the DHW. The problem I have is when the dhw and the heating loops are both on the 30 psi pressure release valve continuously has water running out of it. This does not happen if one or the other is one only if the radiant is calling for heat and then you turn on DHW. The system pressure is set at 12 psi.

STEVEusaPA

Is the pressure at 30 psi when it’s releasing water?
When one or the other is calling, what pressures are you seeing?
And of course is the gauge accurate/working properly?
If you’re pumping away, and all air is purged, the next thing to do is isolate and check the charge in the expansion tank.

JUGHNE

What size of exp tank was on the old boiler?

ryan1983

Same size I just replaced it with the same size. I have done some more diagnosing and found out that when you call for hot water when the heating loops is running the external pump will not shut off and builds pressure on the return side. If I disable the external pump on the control board this doesn’t happen. Do I need to install closely spaced t on the heating loop to avoid building pressure on the heating loop.

EzzyT

Sounds like there is an issue with the near boiler piping but could only confirm that if you where able to post some pictures of the boiler installation and all near boiler piping.

EBEBRATT-Ed

@ryan1983

What @EzzyT said