Navien 240a recirculation

[harrydoyle]

Have 2 navien 240a. On one the recirc system not working. (It does eventually heat up and run normally) All thermistors ohm out at specified temperatures. I know flow valve works cause when in regular mode and open successive faucets gpm increases and responds appropriately to opening/closing faucets. When pump is put in test mode and I back probe pump connectors I get 117 volts (in spec) display reads on then off BUT gpm reads 0. Other good unit when it's pump put in test mode registers a gpm (2.4). My question to the group is anyone had similar experience and your thoughts if it's the pump or anything else you've discovered

 

[Fitter30]

Pump might be bad. Just because it.has power could have something stuck in it.or motor has failed.

 

[Sponsor]

 

[harrydoyle]

Thank you. I do feel pump vibration when in test mode as it goes on and off, don't know if that means it's OK. You mentioned motor. Is the pump 2 separate parts, i.e. motor and impeller?

 

[Breplum]

If pump is running, the display shows the image of a faucet with spray, dip switches set correctly and shows zero gpm in diagnostics, then pump isn't pumping.
You can remove that slotted screw cap right on the front of the impeller to see if the pump is spinning. Often you will get some water bleeding out when you remove that cap.

 

[jake48]

If pump is running, the display shows the image of a faucet with spray, dip switches set correctly and shows zero gpm in diagnostics, then pump isn't pumping.
You can remove that slotted screw cap right on the front of the impeller to see if the pump is spinning. Often you will get some water bleeding out when you remove that cap.

I think my pump is not pumping as well. I have a Navien NPE 240a. The dip switches are set for external recirculation and the internal 2 way valve is set to EXT. I noticed the hot water was taking much longer than usual to reach the source so I tried to turn off and back on the power to the unit. When I did it threw a 438 error code. Reset wouldnt get rid of the code, but if I turned the power off and opened a hot water faucet and then turned the power to the unit back on the code went away. If I turned the power to the unit off and back on with the faucet closed, the error code would show 438 again. As long as I had a faucet opened when I turned the power on the error code would not pop up.

I then went into test mode and when I tested the pump it flashed off / on / gpm over and over. I never heard the pump come on nor did I hear the sound of a relay clicking and on each cycle the display read 0.0 gpm. I should also note that I have not heard the pump turning on and off to recirculate hot water for quite some time.

I hate to spend the $175.00 if it is not the pump. Does the above information warrant replacing the pump? Is there anything else that would cause the pump not to work other than a defective pump?

 

[harrydoyle]

Since I've got 2 240a's in the house and there's only 2 people (kids grown up) in the house, we have the other one to use so eventually I will work on the 1 we've been talking about. It'll be interesting to see if the check valve is involved in this diagnosis since its between pump and flow sensor.. (On the one unit that works, it's check valve replaced 2 years ago since the plunger o ring was missing). For 6 bucks and draining unit anyway, its easy to pull out and check especially since this forum says this can be a weak link in the Naviens.
I'll let you all know and thank you all for your input. Any further inputs please continue to comment.

 

[jake48]

Since I've got 2 240a's in the house and there's only 2 people (kids grown up) in the house, we have the other one to use so eventually I will work on the 1 we've been talking about. It'll be interesting to see if the check valve is involved in this diagnosis since its between pump and flow sensor.. (On the one unit that works, it's check valve replaced 2 years ago since the plunger o ring was missing). For 6 bucks and draining unit anyway, its easy to pull out and check especially since this forum says this can be a weak link in the Naviens.
I'll let you all know and thank you all for your input. Any further inputs please continue to comment.

Prior to my suspensions that my pump may be bad, my check valve like many others here, went bad. Because the issue with the check valve is that it sticks in the open position and it occurs randomly, you will get many different symptoms. Generally, however, you should notice that water doesn't heat up consistently as cold water gets pulled into the hot water and very rarely does your water heat to the high temp set.

 

[Fitter30]

438 abnormal operation of the recirculation pump. When's the last time units been serviced along with pumping vinegar through them?
1
Check the circulation pump.

2
Check water filter for blockage.

3
Check the cold water main line

4
Check the flow sensor.

5
Set to Internal Recirculation mode and verify flow rate.

 

[jake48]

438 abnormal operation of the recirculation pump. When's the last time units been serviced along with pumping vinegar through them?
1
Check the circulation pump.

2
Check water filter for blockage.

3
Check the cold water main line

4
Check the flow sensor.

5
Set to Internal Recirculation mode and verify flow rate.

Fitter - thanks for the advice. The last time I back flushed with vinegar was a little over a year ago. There does not appear to be any blockages as the heater works fine once the water reaches the destination and when I check the flow rate with the faucet wide open it is the same as it has always been. It just takes a long time to heat the water, which leads me to believe the water is not being recirculated through my external loop for pre heating (I have tried all three DIp settings - Internal only, Internal pump with external loop, Intelligent learning). When I get the 438 code it is on the start up self check when I turn the power off and back on. When I turn the power off and start the heater with a faucet open I do not get the 438 code nad it does not come back unless I turn the power off. This tells me the flow meter is working as the flow is being measured with the open faucet on the start up.

Can you instruct me as to how I check the circulation pump on internal mode? I know how to set the dip switches 1 on 2 & 3 off with the two way valve set to INT, but I have not been able to find any instructions on how to run the test. I called Navien and they were completely useless and would not help me. They essentially said they would only help me if I was a licensed plumber...

 

[Breplum]

Did you remove the slotted screw cap mentioned in my previous post ?
That will reveal to you if the pump is running, which is probably not. The pump on the NPE A series is very easy to remove after you drain water.
It’s also easy to bench test once its out if you use alligator jumpers plus, I think I might’ve just used paperclip pins. Of course, be very careful.

 

[jake48]

Did you remove the slotted screw cap mentioned in my previous post ?
That will reveal to you if the pump is running, which is probably not. The pump on the NPE A series is very easy to remove after you drain water.
It’s also easy to bench test once its out if you use alligator jumpers plus, I think I might’ve just used paperclip pins. Of course, be very careful.

Breplum,
I did see your post and removed the inspection plug without removing the pump. I don't know how to active the pump to see if anything spun. Without removing the pump and jumping the pump motor on a bench, is there another way to make the pump turn over while looking at the pump with the inspection plug removed?

Other than a bad pump, is there anything else that would cause the pump not to spin?

Thanks

 

[harrydoyle]

438 abnormal operation of the recirculation pump. When's the last time units been serviced along with pumping vinegar through them?
1
Check the circulation pump.

2
Check water filter for blockage.

3
Check the cold water main line

4
Check the flow sensor.

5
Set to Internal Recirculation mode and verify flow rate.

 

[jake48]

I think you missed my response to fitter above. If you know how to explain the steps required to do # 5 it would be appreciated

Thanks

 

[Breplum]

https://irp.cdn-website.com/5486d14b/files/uploaded/Navien%20NPE%20Service%20Manual.2015.09.01%20%281%29.pdf

 

[Fitter30]

1 on
2off
3 off
Dip switches 1 to 10

 

[jake48]

****UPDATE***

I tested the recirculating pump / circuit board by putting the heater into test mode (hold down wrench in upper left corner until menu comes up). I unplugged the two wire lead to the pump and using a volt meter connected it to the plug and ran the pump test (cycle the menu until it reads pump, then depress info button to start test)

The test mode cycles for a few minutes going from off / on / gpm. When on flashed on the screen I verified power was going to the motor from the circuit board. When the screen showed gpm it read 0 and when the screen said off volts returned to 0

I concluded the board was doing its job sending voltage to the pump , but the pump was not working and ordered a pump. I installed the new pump and no more 438 error code on start up along with the pump test showing pump worked flawlessly

I set the dip switches to intelligent learning - 1 up, 2 up, 3 down with internal bypass set to EXT

Now we wait and see how "intelligent" this thing is...

 

[harrydoyle]

Referring to the Harry Doyle string started on November 2nd I have completed the repair of the Navien 240A. The check valve came out in pieces and the plunger oring had swelled and the plunger was on the other side of its seat. So when the circ pump went on it forced the plunger to close off flow hence 0.0 gpm reading when pump in component test mode. Now everything works great.
.Thanks Breplum for posting manual. Also you had mentioned this circ pump bleeds itself when all the fixtures are turned on. Is the red cap on top of pump ever used for air bleeding? Thanks to Fitter also