Navien 240A suddenly not as hot in internal recirculating mode

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mitch22

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Works fine with recirculation off, reaches the target temperature. But feels about 20 degrees cooler when I put it in internal recirculating mode. Confirmed the dip switches and valve position.

This started a few weeks ago. Cleaned the water filters. Everything else seems to be in working order. Any ideas?
 

HydroAirJoe

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Works fine with recirculation off, reaches the target temperature. But feels about 20 degrees cooler when I put it in internal recirculating mode. Confirmed the dip switches and valve position.

This started a few weeks ago. Cleaned the water filters. Everything else seems to be in working order. Any ideas?

There is a check value in the T connection on the outlet of the pump. When this fails this will introduce cold water into the hot water stream. Depending on your cold water temperature you will get luke warm water to something like you described, 20 degrees cooler. On my NR-240A I had 2 of these fail in 2 years, and the most recent one was yesterday. Luckily I had a spare one since most parts distributions do not keep these in stock. The way to verify if the check valve is the issue, is to check the temperature of pipe coming out of the heat exchanager, if it feels hot, then the check valve is the issue. It easy to replace.
 

HydroAirJoe

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Do you have a NPE or NR? On the NPE that check valve is much longer than the NR. It's weird that it took 8+ years before the first failure then I get another one 1+ year latter. There was was no debris in the old one, it just looked like the spring got weaker over time. Probably due to all the hand washing we are doing these days.

I'm adding this part to the list of extras I keep so that I don't have to wait two-three days for a part to arrive. check valve, flame rod, flow sensor.
 

mitch22

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NPE. I've found the part online. On ours, the valve plunger had pushed through its closed / seated location. Re-assembling it worked, but am replacing it just in case.
 

TxInjun

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Hello Mitch22,

I too have a NPE-240A unit that is having a different / similar problem - in ext recirc mode, the water starts off hot and then the temp drops off in a couple of minutes. If I shut off and restart in a minute, the temp is back to scalding and slowly drops off again. I'm suspecting a leak in the check valve; also not sure if the temp sensor may need replacing and/or the water adjustment valve. I have ordered the replacement check valve - my question is: how easy / difficult is it to replace the check valve - do you unscrew it or does it just pop out with a pull on the black tab? And I assume the insertion of the new valve is just the same steps in reverse?

Thanks for your assistance,

Cheers

TxIn
 

mitch22

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It's relatively easy. I think it was just a turn. It took more time to remove the assembly to reach it.
 

TxInjun

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I want to thank HydroAir Joe and mitch22 - this thread solved my problem. It took me a few days to get the part in-house, but switching out the check valve was a breeze and now (just in time for summer, excellent timing wot) we have plenty'o hot water. The old check valve was indeed unable to fully close due to some mineral deposits on the sealing piston.

Cheers,

TxIn
 

AMC-NYC

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Thank you, HydroAir Joe, mitch22, and glycoski who's thread lead me to this one. I had the same issue as mitch22 so I put the recirc dip switches to the off position and the valve to external recirc since this is not connected to a line. Instantly the issue went away and I had hot water all the time. My question is will leaving it like this cause an issue? I don't think it will and I'm not in a rush to fix a part that seems prone to failure especially since the wait times for hot water is not vastly different without the recirc mode on. I had only gotten the 240A model as it was not a big premium and thought the benefit would be more than what I am actually experiencing now without it.

I don't really understand how the buffer tank works either as water enter and leaves through the same line at the bottom of the tank, with the tank being above the hot supply line. Is there an electric valve on the cold water inlet that shuts when the recirc pump is on? There appears to be an electrical device (parallel to the check valve) on the cold water inlet line before it T's up with the recirc line and then going on to the lower heat exchanger.


To help others who are trying to diagnose this issue because I did not think about the recirc loop at all when the problem arose. The first thing I found online was that the flow valve was a typical failure point. This looked like an easy fix so I bought one as when the flow rate was above 1GPM I would have hot water but with only one faucet open at .4GPM, the burner would not ignite and I would get lukewarm water at best. After replacing the flow valve, I got the same readings and result so flow was not my issue. I continued my search and came across this forum which lead to the check valve. I started monitoring the flow and water temps and noticed the in and out temps varied widely. After cutting off the recirc line, my inlet temp was constant and my outlet temp varied a few degrees which coincided with the burner coming on and going off. I also felt the line just before the flow valve that went into the lower heat exchanger and this would swing between very hot and very cold, which also went away without the recirc line.

IMG_2117_2.JPG
IMG_2142_2.JPG
 
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AMC-NYC

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Found the answer to my question above about the cold water inlet.

https://terrylove.com/forums/index.php?threads/navien-npe-240a-with-navicirc-valves.88186/
All of the Navien condensing heaters have what they call a “Water Adjustment Valve (WAV)” (see pages 25 and 89 in manual). The “A” models have this immediately after the cold inlet and the “S” models have it right before the hot outlet. What this does is limit the flow (GPM) depending on what the temperature of the water leaving your burner is relative to the set temperature. Even though the plumbing in the heater can handle 10+GPM, you will probably never see that even if you turn on every faucet in the house. The heater will restrict the flow to ensure that the temperature you set is the temperature you receive.

Also, if you observe the flow when you turn on a large fixture like a bathtub or a hot water external hoes spigot (something without a flow limiter built in), you will notice the flow starts small and then gradually become stronger. This is also because the “Water Adjustment Valve (WAV)” restricts the flow until the burner fully ramps up.

So, the solenoid valve is there to ensure that during normal operation (when the pump is not running), the water only goes into the cold inlet and not the return line inlet, thus passing though the “Water Adjustment Valve (WAV)” and not around.
 

Monguila

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There is a check value in the T connection on the outlet of the pump. When this fails this will introduce cold water into the hot water stream. Depending on your cold water temperature you will get luke warm water to something like you described, 20 degrees cooler. On my NR-240A I had 2 of these fail in 2 years, and the most recent one was yesterday. Luckily I had a spare one since most parts distributions do not keep these in stock. The way to verify if the check valve is the issue, is to check the temperature of pipe coming out of the heat exchanager, if it feels hot, then the check valve is the issue. It easy to replace.

Joe, is the check valve you are referring to part number 30008359B?
 

HydroAirJoe

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Joe, is the check valve you are referring to part number 30008359B?
For the older NR-A series, the part number is 30002282e
For the NPE-A series, the part number is 30008360A
 
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HydroAirJoe

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One more observation, the 2 times mine have failed were usually after the system was flushed. I figure the flushing dislodged something preventing the check valve from seating. The first time (7 years old valve) really warn. The second failure there was really nothing wrong with the valve other than it just was not seated properly but I replaced it anyway since.
 

Reach4

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One more observation, the 2 times mine have failed were usually after the system was flushed. I figure the flushing dislodged something preventing the check valve from seating. The first time (7 years old valve) really warn. The second failure there was really nothing wrong with the valve other than it just was not seated properly but I replaced it anyway since.
Interesting. It sounds like a circulation pump system should have a filter in line. Plus, maybe the recirculating should be continued longer to dissolve pieces that broke off and might be hung up inside still. Is the pump forcing water in the normal direction, or is it running the solution backwards to backflush?
 

Curt Coffi

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This is a silly question but... I have a NR240 and have the luke warm water problem. I purchased the check valve but I don't see it in the parts diagram? It's listed under #90 but its not on the diagram. Where does it go? Help, Thanks , Curt
 

Monguila

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There is a check value in the T connection on the outlet of the pump. When this fails this will introduce cold water into the hot water stream. Depending on your cold water temperature you will get luke warm water to something like you described, 20 degrees cooler. On my NR-240A I had 2 of these fail in 2 years, and the most recent one was yesterday. Luckily I had a spare one since most parts distributions do not keep these in stock. The way to verify if the check valve is the issue, is to check the temperature of pipe coming out of the heat exchanager, if it feels hot, then the check valve is the issue. It easy to replace.

Hello. I am having a similar problem that just started last Thursday. Is the pipe you are referring to the one on the left side that goes to the bottom of the reserve tank?

Thank You!
 

David.beaton

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There is a check value in the T connection on the outlet of the pump. When this fails this will introduce cold water into the hot water stream. Depending on your cold water temperature you will get luke warm water to something like you described, 20 degrees cooler. On my NR-240A I had 2 of these fail in 2 years, and the most recent one was yesterday. Luckily I had a spare one since most parts distributions do not keep these in stock. The way to verify if the check valve is the issue, is to check the temperature of pipe coming out of the heat exchanager, if it feels hot, then the check valve is the issue. It easy to replace.
Good Morning AirJoe!

I have the same problem, and after changing the flow sensor (which has failed on me several times in the past) I am now thinking it is the Check Valve. I have the NR-240A-NG but I am really unsure where the checkvalve is located. It is not shown on any of the parts diagrams, and the model number 30002282E is quite small and looks like it is fully internally located. You mention a T connection on the outlet of the pump. Could I trouble you or anyone else on this thread to clearly show where the part is located?

NR-240A Parts List.jpg
 

Reflected3718

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Good Morning AirJoe!

I have the same problem, and after changing the flow sensor (which has failed on me several times in the past) I am now thinking it is the Check Valve. I have the NR-240A-NG but I am really unsure where the checkvalve is located. It is not shown on any of the parts diagrams, and the model number 30002282E is quite small and looks like it is fully internally located. You mention a T connection on the outlet of the pump. Could I trouble you or anyone else on this thread to clearly show where the part is located?

View attachment 82501
Hi did you ever get an answer to the location of the 30002282E check valve on NP-240A-NG ? I have the same question and was hoping to get the answer without having to wait until the weekday to call Navien tech support.

UPDATE: found the location, it's actually part diagram number 121 inside the T above the circulation pump. Pretty easy to change out, just unscrew one compression nut and remove two clips to free up the T. The check valve is on the compression nut side.
 
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