Navien NPE-240A circulation pump not working

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rlj51

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Hi,

I had a new Navien NPE-240A tankless system installed about a week ago. This replaced a standard tank, which also had an external circulation pump that run continuously. I purposely chose the 'A' model as I was told it had a built-in circulation pump that offered a similar experience.

Anyway the new system works great except that it can take a 1+ minutes to get hot water out of the taps. Its clear that the circulation pump is not running. When it was first installed the plumbers had dipswitch 1 on and 2 off for "internal" circulation. They were confused as to what that meant. After looking at the manual it was obvious that I wanted the "external" mode. So I convinced them to change it to 1 off and 2 on, with the internal valve set to "EXT". After they left (they have come put 3 times total) it had never really worked.

I have included a few pics of the system. That copper pipe that is 2nd from the left is the recirc line. Its never hot! I check regularly and its always the cold. The pipe next to is the hot water and it hot whenever I check it.

Does anyone know how to get the recirc pump to run on a regular basis? Or what would stop it from running? Thanks!

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Andrew Herman

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In my case, in order for the circulation system to work like I wanted, with almost instant hot water, I had to change one of the installer settings. If I remember, the factory default is for the system to check the recirc temp only every 30 minutes, so the while the water moved, it didn't stay hot. I changed that setting to every 5 minutes and it has been much better.

That worked for me. Your setup might be different.
 

rlj51

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Ok so I have my dip switches set to:

1:OFF
2:ON
3:OFF

I have also set P.14 Preheat Interval Time to 5 minutes (default was 30). In my master bathroom it still take 1+ minute to get hot water out. Also when I randomly go check the circulation line next to the heater the pipe is always cold. Its never hot or even warm.

What else could be wrong?
 

breplum

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FYI, your gas flex is not sized properly for 199K BTU, and your water supply piping is not supported properly.
Hot water pipes should all be insulated completely, but you knew that already. Is condensate safely neutralized?
Navien tech support will walk a plumber and sometimes a homeowner through all the tests to check it out. Your installer should be helping you.
 

rlj51

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Hi Breplum, thanks for the info. As for the condensate, there is a pump and a line that goes outside. Is that what you mean by "neutralized"? As for the other things, I had a professional plumbing company do the install. They have been back twice since then to address the circulation pump but have not been able to solve it. They keep saying things like "these tankless hot water systems are very finicky" and "each one is different". They clearly don't know how to program or troubleshoot them. I am the one that pointed out to them that "internal recirculation" means inside the water heater itself. We want "external circulation" since I have a dedicated return line. They were quite confused about this.

I'm not sure what to do at this point. If I have those same installers back they are just going to stare at the system and scratch their heads some more. Any advice? How do I troubleshoot the circ pump? It appears that its either not running often, or if it is its pushing cold water around.
 

rlj51

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Just to follow-up here, the problem was that the original plumber installed a check valve backwards in the circulation return line! So water was not able to return to the hot water system. Very frustrating.
 
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