Be ware of over heating on Navien Combi units.

Be ware of over heating on Navien Combi units.

by Les
(Fort Morgan, Co. USA)

I am a licensed master plumber and have just finished the install of a Navien 240 NCB. This unit serves a residential home with hot water baseboard heat.

When the system was turned on and run tested I found that when the unit is in the heating mode set at 180 degrees for the baseboard heat and there is a call for domestic hot water (which is set to 120 degrees) I measured 138 degree water coming out of the domestic faucets for about 15 seconds. 138 degree water can scald very fast. I called Navien tech support and was told that Navien was aware of this issue and that I needed to put in a thermostatic mixing valve on the domestic hot water piping system to the house.

I reread the install manual and could not find any place where Navien had put a beware notice. I am very upset about this as I had to eat close to $500.00 labor & material for the install of the mixing valve. ( this job is a 30 minute drive from my shop 1 way) I would like to here from anybody else who has had this issue.

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water heaters