Descaling Navien NPE-240A with no shutoff for Recirculation line

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CMaustin

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New user posting. I am look for guidance with regards to annual descaling of our Navien NPE-240A water heater. I have purchased a descaling kit which includes an external pump, hoses, bucket, etc.

The instructions in the User's Manual (Page 11, 4.3 Flushing the Heat Exchanger) show a configuration that does not have a recirculation connection. My setup is a bit different (see attached image) where there are shutoff values for the hot & cold lines going into and out of the WH but no shut-off (ball value) on the recirculation line.

Opening the cover of the WH I see that the 2-way valve inside the unit is set to EXT.

I contacted Navien and explained that my setup does not have a shutoff on the recirculation line. They suggested that I switch the 2-way value to INT and set the DIP switch 1 to ON & switch 2 to OFF, PRIOR to beginning the descaling process and then switch the 2-way value back to EXT and the DIP switch 1 to OFF & switch 2 to ON AFTER completing descaling.

I want to confirm my understanding of how to descale my unit given my setup? I also want to confirm that the WH should be powered off during descaling (i.e. gas valve shut-off and WH shutoff) as noted in the instruction in the User's Manual?

Thanks in advance for your help!
 

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GReynolds929

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That's how I would do it if there's no shut off on the return line. Don't bother with the dip switches if you have your own pump. Power off at the front panel which will open the inlet solenoid and then unplug from the wall.
 

CMaustin

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Thank you GReynolds929 & Breplum for your suggestions! I got a chance to try out your suggestions today but didn't have much luck. Here's what I did.

1) From the front panel, powered off the WH.
2) Switched the valve inside the unit to INT.
3) Unplugged the water heater from the wall outlet.
4) The recirculation occurs under the kitchen sink so shut off the recirculation device and also shut-off the hot & cold water values under the sink.
5) Closed the hot & cold water line shutoff values below the WH.
6) Connected the hoses to the hot & cold water by-pass connectors.
7) Opened the by-pass values to drain water from the WH.
8) Connected the hose going to the cold water bypass to the top of the external pump.
9) Put the hose from the hot water bypass in the bucket with the cleaning solution.
10) Plugged the external pump to start circulating the cleaning solution.
11) Once the external pump was plugged in, the cleaning solution started flowing through the cold water bypass hose and as expected started coming out of the hot water bypass hose.
12) PROBLEM: Initially there was a strong flow of water coming out of the hot water bypass hose into the bucket but about 5-10 seconds later the flow rate started to slow down to the point that it was just a trickle. I unplugged the pump and retried it a couple of times and each time the flow rate would start strong but then drop to a tickle after a few seconds.

Any idea what I am doing wrong and why the output flow rate is dropping?
 

Breplum

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I have done dozens of de-scaling ops with your type set up. No idea what's going on with yours. Sorry. Call the Nav. tech desk.
They won't help homeowners much, but with descale, they ought to be willing to help.
 

Breplum

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I bring two pumps and long extension cords to every descale. Pumps fail, seize temporarily, trip GFI's sometimes.
 

CMaustin

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Thank you GReynolds929 for sharing your perspective & experience!

Posting an update on where things ended up to help others who may have a similar issue in the future.....

I ended up calling the plumber who had originally installed our water heater to show me how to descale my unit. He tried doing the same thing that I was trying to do (i.e. flip the valve inside the WH to INT) and observed the same problem. His conclusion was that the valve inside my WH is not working so even when it's set to INT the descaling pump continues to push majority of the cleaning fluid to the recirculation line thus explaining the low flow out of the hot water line after the tank inside the WH empties.

The plumber ended up shutting off the water supply to the house, temporarily disconnecting and capping the recirculation line at the WH and then proceeded with the descaling process.

He came back and installed a shutoff valve on the recirculation line which, moving forward, will allow me to descale the unit without needing to shutoff the water to the house.

I am not sure how common it is for the valve inside the WH to not work but per Navien support an external shutoff should have been install iin the first place vs. relying on the internal value.

Thank you again to everyone for your insights & guidance!!
 

Nay Lin

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I’m comparing two quotes for installing NPE-240A2. The first quote includes Easy Plumb V2 3 valve set. NAvien web site description is : Navien Plumb Easy Valves (V2) are designed to provide ease of installation and operation as well as for quick maintenance. The 2nd quote does not mention if this option is included or not.

Is it accessory option worth spending extra to add to 240A2 installation? Would it make maintenance easy enough so it will learn to do the annual maintenance of the system my self ( annual service is quote as about $ 250 )?
 
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