Navien CH240 pressures off

technologypa

Good Evening,
I have a 3 yr old Navien CH240 propane combo boiler. This morning I noticed there was a fair amount of water (maybe half a gallon or so) that was on my basement floor from the pressure relief valve on the heating side. I believe the valve is a 30psi pressure relief valve. The pressure on the unit at the time was around 22 psi. I immediately thought the expansion tank failed. There is an air valve on the bottom of the expansion tank, where I used a tire pressure gauge. No water came out, and the tank read 29 psi. I am still getting heat in the house and hot water and no error codes have popped up. When I ran a sink for hot water to clean dishes the unit was at 55 psi. I'm not sure what the normal pressures or pressure range are supposed to be, but my understanding is if the pressures go too high the unit would shut down. Any suggestions or ideas on where I should go next?
Thank you

Jamie Hall

Say again, please? What pressure was at 55 psi? The heating side? Because if so the PRV should have been wide open.

The heating side pressure should be being controlled by the expansion tank, and should have nothing to do with the domestic hot water side pressures -- except that there is an automatic feeder valve in there.

If the expansion tank air pressure really is 29 psi, then it can't absorb any expansion until the system pressure is also 29 psi -- which is close enough to the relief valve setting to cause problems.

njtommy

Sounds like the heat exchanger maybe leaking through from the DHW side to the heating side. I would give the installing company a call to have them confirm this. The unit should still be under warranty for the heat exchanger.

It's could be the pressure transducer, but generally when they go the pressure relief doesn't blow it just reads high.

Do you have an pressure gauge on the system to confirm the pressure is reading correctly?

njtommy

@Jamie Hall The Naviens have there own water make valve built into them up based on system pressure.

You could close the valves down for the DHW side and bleed pressure of me the heating side with the valve for the water make up off. Let the boiler sit for a few mins. Then open the valves to the DHW side and see if the pressure goes up again.