Navien Tankless Water Heater Issue/Question

Old 12-29-09, 05:46 PM
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Location: New Endgland, USA
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Question Navien Tankless Water Heater Issue/Question

We have a new Navien condensing tankless water heater which was recently installed (CC-180A LP). For the first half of today the unit was quiet, running normally and only turning on mainly when we called for hot water (or every now and then to keep its internal buffer tank temp up). This evening I noticed the direct vent blower turning on and off every 30 seconds. Exactly every thirty seconds. On for 30, off for 30, and repeat.

There is another issue that might be related to this.... every once in a while, when the unit would turn on to maintain its internal buffer tank temp, I would hear it click on and off a bunch of times before it started up normally. When I took the cover off to check the unit it was displaying an error stating "Flame Loss". So I watched the unit carefully and could see it start up, the blower would turn on low, I could see the blue propane flame light up through the little glass window, the flame would maintain itself on low and then the blower would kick into high gear and an instant later the flame would go out. After this the unit would shut down and try this all over again. After half a dozen tries eventually when the blower kicks into high gear the flame would not go out and would also burn at a higher rate until the unit got up to temp and then it would shut down normally.

I did have the propane company out and they measured the pressure at the unit and all was good, so its not a lack of pressure which was the primary troubleshooting in the manual "make sure the gas is turned on".

I don't know enough about the inner workings of these high efficiency tankless units to really troubleshoot it... but from what I am reading usually its some sensor that turn components on and off. For example, on other tankless models the gas valve might control when the blower turns on/off. So I guess I need to try and figure out what is turning on the blower and why. If it is something connected with the gas mechanism then that could also explain my other issues with the flame going out.

A plumber friend helped me do the install and the unit is setup with default settings. I assured him when we started this project that he was only helping me with the install and not liable to fix or maintain it so I am on my own or I need to call someone.

Any ideas?
Old 12-30-09, 02:19 PM
Join Date: Dec 2008
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"pressure is good"

Untill you know the actual inlet pressure with it off and under full fire we may never know. Sure sounds like low inlet pressure or reduced capacity.

Also you may need to adjust the air/gas mixture which requires a digital dual port manometer which is tough as a diy installer without proper tools

I would be looking at inadequate gas supply, regulator, piping and pressures.

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