Navien NPE-240s-NG Suddenly 93 degrees versus 120

[Canadianeh]

Found this site searching google. My water heater is suddenly only kicking out 93 degrees versus 120 that its set at.

Haven't ever had a problem until today.

I noticed a lot of threads said the check valve could be the issue for Navien heaters.

1) Do you think this is the case? Not sure this model even has a check valve according to the manual?
3) Anything else I can try?

Thanks in advance! It's the NPE-240s-NG model.

 

[Breplum]

the S series has no check valve.
Error code?
Has to be run through a series of checks to see if it is reading flow accurately.
Ever descaled? that is a question we always ask, but only sometimes relevant.

 

[Sponsor]

 

[allencanning]

I realize that this message is a little old, but I just saw this. My Navien NPE-240s-NG has done the same thing.

Here is the story. Started leaking water out the condenser pipe like crazy. Had a plumber confirm that the heat exchanger was bad. Bought a new heat exchanger and replaced it. Worked fine for about 2 weeks, then the water was only lukewarm. After reading some forums online, it was suggested that it might be the flower sensor. When replacing the flow sensor, I noticed that the drain connector on the heat exchanger had slipped off. There was a tiny amount of water in the bottom of the unit. So, I put the pipe back on and secured with the locking clamp. I then replaced the flow sensor. Still lukewarm. Replace the two mixer valves as well. Still lukewarm. I descaled the unit for 30 minutes. Still lukewarm.

After checking the front panel (B information setting), I can see that the water output never goes above 94 degrees.

Any idea what other sensor might need replacing? I don't get any error codes.

 

[Breplum]

defective hot water (cold water) sensors maybe. there are two. one is secondary heat exchanger input sensor and the other temperature sensor is direct water, removed and measured for resistance should not be higher than 30 ohms.
Your unit must be older than 15 years if you didn't get a warranty heat exchanger from Navien.

 

[Fitter30]

Look at exhaust temp Page44. Page 61 thermister resistance

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View and Download Navien NPE-180A service manual online. NPE series Condensing Water Heaters. NPE-180A water heater pdf manual download. Also for: Npe-210a, Npe-180s, Npe-210s, Npe-240s, Npe-240a, Npe-150s.

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[allencanning]

defective hot water (cold water) sensors maybe. there are two. one is secondary heat exchanger input sensor and the other temperature sensor is direct water, removed and measured for resistance should not be higher than 30 ohms.
Your unit must be older than 15 years if you didn't get a warranty heat exchanger from Navien.

It is not. it is only 9 years old. Navien has been completely unhelpful. Turns out it was a bad PCB. just replaced it and I have hot water again. Well, for now...

 

[allencanning]

Look at exhaust temp Page44. Page 61 thermister resistance

NAVIEN NPE-180A SERVICE MANUAL Pdf Download

View and Download Navien NPE-180A service manual online. NPE series Condensing Water Heaters. NPE-180A water heater pdf manual download. Also for: Npe-210a, Npe-180s, Npe-210s, Npe-240s, Npe-240a, Npe-150s.

www.manualslib.com

Thank you for this information, it is exactly what I needed. Turns out it was the PCB. replaced it and now I have hot water again.