Pressure release valve spec for Navien boiler

tomtomsf

Hi,
A contractor has just installed a Navien NHB-55 boiler in our house and due to seemingly defective inbox pressure (30psi rating), he swapped it with a 150psi rated pressure release valve. Is this ok? It seems to me that a lot of pressure can build up before this valve releases it.
The boiler is connected to a radiant heating circuit with Pex tubing.

Thanks

Jamie Hall

tomtomsf said:

Hi,
A contractor has just installed a Navien NHB-55 boiler in our house and due to seemingly defective inbox pressure (30psi rating), he swapped it with a 150psi rated pressure release valve. Is this ok? It seems to me that a lot of pressure can build up before this valve releases it.
The boiler is connected to a radiant heating circuit with Pex tubing.

Thanks

Absolutely not. The specified and required valve is set for 30 psi.

That said, 30 psi is too high for a hot water heating application unless you are heating a young skyscraper. 15 psi should be ample for your application -- 12 psi if this is basically one story.

I'm not quite sure what you mean by "inbox pressure". I suspect that your contractor hasn't a clue.

If we assume for the moment that 12 psi is ample, there should be a pressure regulating valve on the feed from the domestic water, set for 12 psi (there should be a backflow preventer, too). There should be an expansion tank, also precharged correctly to 12 psi. There should be a pressure gauge and, when the system is cold, it should read 12 psi. It might get up as high as 15 psi when the system is not.

Your contractor has left you with a dangerous -- not to mention illegal -- situation, and either he or she needs to fix it, or you need to find a contractor who knows what he or she is doing to fix it.

tomtomsf

Thanks for the feedback.
Sorry my initial post had a few typos: I meant that the Navien NHB-55 boiler had an inbox pressure relief valve that was rated to 30psi, but due to the defect the contractor replaced it with a 150psi rated pressure relief valve they had available at the time.
I'll work with the contractor to get that fixed

pecmsg

tomtomsf said:

Thanks for the feedback.
Sorry my initial post had a few typos: I meant that the Navien NHB-55 boiler had an inbox pressure relief valve that was rated to 30psi, but due to the defect the contractor replaced it with a 150psi rated pressure relief valve they had available at the time.
I'll work with the contractor to get that fixed

Shut it off until its changed.

Id also find a different contractor!