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Marc
Marc, Plumber
Category: Plumbing
Satisfied Customers: 1126
Experience:  Plumbing heating & home maintenance contractor
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I have Navien ch240 also.. When everything is at rest,

Customer Question

I have Navien ch240 also..
When everything is at rest, pressure used to read 11.6-12.3.
When calling for heat or DHW was 18.1-18.9...
Was consistently at those readings for 2+ yrs.
Now at rest reads10.9, when running
no more than 17.4(calling for heat and DHW at same time)
I realize this not a problem if it doesn't continue to go lower, but is this normal- just curious..
Submitted: 11 months ago.
Category: Plumbing
Expert:  qwasert replied 11 months ago.

Hello, my name is ***** ***** I will do my best to assist you with your problem.

Expert:  qwasert replied 11 months ago.

Can you tell me how old the unit is?

Expert:  qwasert replied 11 months ago.

However, just off the top of my head you may want to check the auto fill or makeup water valve and the expansion tank. I had one of these last week the expansion tank was ruptured and the system would not maintain working pressure. I believe that model is good to run between 10 and 30 psi. The pressure relief valve should lose water above 30 psi.