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Navien CH240

Good Afternoon,
I have a Navien CH240 that I have had very good luck with, however have it has been tricky to maintain.

I did an annual flush today and when I was inspecting the inside of the unit I noticed on the air vent on top of the circulation pump about a quarter sized dot of water, and a lot of scale from water dripping down the sides of it. It looks like it has been weeping for some time. Is this something that needs to be replaced, cleaned... has anyone experienced something similar?

Another question I had was after the descale procedure, I always have issues with the heating side and air. Before I even start I shut off the isolation valves. When I am done flushing I keep the isolation valves on the heating side closed, however I keep the hot water domestic open and turn on the cold domestic water (basically push water from my plumbing system through the heat exchanger and out the hot water flush port on the domestic side to push any remaining descaler out. I shut the flush port on the hot water side, and thought the unit should be full of water? I open up all valves on the heating side and plug it in.

As soon as I plug in the unit the 30psi pressure relief blows off on the heating side and I get a 002 code saying low pressure on the heating side. After starting and restarting the unit it finally worked the air free. Is this the way it is or should I be doing something different.

Any info would be great. Thank you


  • njtommy
    njtommy Member Posts: 1,105
    Not sure what you have going on after the flushing, but the air bleeder on top the pump should be closed after your done purging and getting the air of the system.