Navien NPE-240A Hot Button woes

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pestojest

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UPDATE 2: Okay, I think the fixture distance setting might have solved my initial issue. But here's what I'm now dealing with... Should the internal buffer tank still be working when externally circulating with the internal pump? Because immediately after triggering a recirc cycle, if I go to the farthest fixture and open the hot, i do have hot water, but then I get a cold water sandwich. Which suggests that when the heater kicks back on (because I've opened the hot tap), it's sending some cold water out before the burner ignites. But isn't this exactly what the buffer tank is designed to prevent? Are these two systems designed to work in tandem so you get the best of both worlds?

UPDATE: My post hasn't even been approved yet, but have got some more info to share. I kept digging and found some more posts here that speak to this issue. There's another param that sets the distance of the furthest fixture, and it's defaulted to 30ft. Odd that this param isn't mentioned in the button manual. I increased it to 100ft just as a test (I remember my plumber saying it's actually about 60ft), and yeah it's definitely running longer. But on a couple of tests, it ran only for a few seconds again. That would make sense if it were detecting the copper return line was already hot, but in this particular test, it wasn't. It was still room temp at best. I guess I'll keep trying different settings. Might also be a good idea to just install the temp sensor at the farthest fixture, since that's the most accurate way to run the pump.

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This topic has been discussed before and in my case, this post in particular. But there weren't any replies and OP seemed to solve it on his own...

Moved into this house last year, it already had a ~2yr old Navien NPE-240A installed, but with no external recirc line. I had my plumber run the line a few months ago and we set it to the normal external recirc mode, Intelligent mode disabled. That was fine...a noticeable difference, but still not optimal, so I flipped the dip switch to try out Intelligent mode. It was way worse. We have odd schedules so it never really seemed to learn.

Decided to order the PZZZ-00046 hot button kit and hook it up to a dry contact relay controlled by Home Assistant, inspired by this post. It was easy to install, no issues. Checked the params in the settings, as described in the install manual...they were as expected. Recirc cycle time (P. 12) set to 5m. I didn't install the included temp sensor, as it says it's optional and I just wanted to get it working generally before deciding whether I want that or not.

But it just doesn't seem to be working right. Closing the relay doesn't always cause the Navien to react (which I suppose is expected, because apparently there's internal logic to prevent a cycle within X minutes of a previous cycle or hot water being used at all)...but on the occasions where it does react, here's what happens...

1. I hear the Navien spring into action
2. The recirc and burner symbols light up
3. I feel water just barely starting to move thru the return line
4. 2-3 second later, everything stops and the Navien returns to inactive

That's it. Nothing else happens. And the return line is still cold.

I read multiple posts talking about the Energy Saver mode controlled by the #2 dip on the hot button board. Mine has the solder points, but no switches. So I soldered #2, re-installed it. No change in behavior at all. And I'm not even convinced that was the issue, anyway. Because Energy Saver mode is supposed to restrict the cycle to 30 seconds, not 3.

This can't be correct, right? What is causing it to seemingly start a recirc cycle and then immediately shut down?

The Navien is working perfectly normal otherwise. Calling for hot water from any faucet continues to work fine.
 
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Breplum

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As an experiment I'd pull the hot button and revert back to non-hot button setup with External recirculation.
You should get robust pumping until the return line is very hot, when it ought to turn off the pump.
When ext. recirc is set, the flow inside the unit still includes the buffer tank.
Do follow the 1 and 2 dip switch settings from the manual. The lever should be always set to EXT.
 

GReynolds929

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Like @Breplum states, my first step would be to make sure the two way valve is set to external. Can we get pics of the piping?
 

pestojest

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Thanks for the replies @Breplum and @GReynolds929. Pics below. Everything looks installed correctly. My plumber says he installs these all the time and was very familiar with how the recirc works. I just didn't ask him about the hot button kit because I didn't even know it existed at time.

It sounds like you're both suggesting that I shouldn't get a sandwich in that scenario with this configuration. Maybe I should install the temp sensor to see if that helps. Here's how I hope it would work in a test...

1. Trigger a recirc cycle
2. It cycles until it senses threshold temp at the farthest fixture
3. Open the hot tap
4. Buffered hot water leaves the Navien, right behind the hot water that had just left the unit during the recirc
5. New hot water flows right behind the buffered water, leaving no sandwich at all

Obviously, this isn't a true real world example. In most cases, Home Assistant would've triggered a recirc at a set time and the hot tap is opened maybe 5-10 minutes after that. So the recirc'd hot water would've cooled a bit in the pipe. So it'd first be less-hot water followed by fully hot water, with no sandwich.

Am I misunderstanding how it should work?
 

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GReynolds929

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The two way is currently set to internal, rotate counter clockwise till the tail points at 6 o'clock. Lift the flap above the display and post a Pic of the dip switches also please. Everything else I see looks fine so far.
IMG_4603.jpeg
 

pestojest

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@GReynolds929 first, sorry for what seemed like a late reply...my replies were hung up in moderation for a couple days.

I'm super confused at this point. I thought the way that valve was oriented, that it already was on EXT (the tip of the knob pointed to the right, where EXT is). I just looked at the manual and I see that you're correct...it actually needs to be turned counter-clockwise to put it in EXT mode.

But I don't understand. If that's the case, then how has my recirc been working at all up to now? I'm definitely getting recirc out to my farthest fixture where my plumber tied in the pex return line, which transitions to that copper running alongside the Navien. Does that make sense?

Furthermore, just a few minutes ago, I decided to try the temp sensor on that copper return just as a test. When I went to connect it, I noticed a jumper pre-installed in the temp sensor terminals. I removed that and hooked up the sensor. Then I triggered the recirc and sure enough...it ran for the full default 5 minutes (because while the return line immediately warmed up, it only got up to around 88F).

So now I'm thinking that simply removing the jumper is what allowed the cycle to run for the full default 5 minutes and now I seem to have exactly what I need.

But again, how is this possible if my plumber never actually flipped the valve to EXT? Isn't this now working exactly as expected?

Thanks.
 

pestojest

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Pic of the dips (set to external recirc, non-intelligent mode, per the manual) below.

Now I'm wondering...is the recirc working despite the valve being set to internal, just because...it can? There's a place for the water to flow, so it's also taking that route, but if the valve were closed, it'd work better?

So strange that we've gotten any benefits of this at all to date, with it open this whole time.

Based on how everything is plumbed/set, am I safe to flip that valve with no other changes?

dips.png
 

GReynolds929

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Dip switches look good for recirc settings. Flip valve to internal and good to go.

With it set to internal there is still a path through your return line but a majority of the water will take the easy route internally, the return line would get a little bit of recirculation. It should work much more quickly and efficiently and shouldn't short cycle the return cause your not prematurely getting internal hot water causing the unit to think it has satisfied the recirculation demand when it hasn't actually.
 

pestojest

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I just closed the valve and triggered a cycle and sure enough, the hot water got back to the unit much faster and much hotter.

And I think you're right... That was the reason why it was cycling so quickly before, it was sensing the hot water immediately upon starting because it wasn't actually going anywhere

I guess my plumber wasn't as familiar with this unit as he claimed. I can't believe that valve was open this whole time...facepalm. My wife just quipped, "You know, I didn't want to say anything, but I never thought it was a huge improvement after he left..."

Many thanks!
 

GReynolds929

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Just to clarify proper dip settings. Natural gas, 0-2000ft, not on a well.
 
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