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Benjamin

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Hello everybody,


I thought I’d share with you all how my hot water recirculation project is going. For the water heater I have a Navien-240A. For accessories I got the Hotbutton kit and two Navicirc thermal bypass valves.


I set DIP switch #2 “ON” for external recirculation.


I set Perameter #17 “ON” to enable thermal bypass. I believe this will disable the internal temperature sensor for the 100deg shutoff feature that the Hotbutton has as one of the “Operation Conditions”. The internal temperature will never reach 100deg because of the Navicirc. However, the external temperature sensor that attaches to the Hotbutton control board will continue to work just fine. This is important and ill explain later.


I set Perameter #12 to 5min (maximum allowed). This is how long the pump will stay on if triggered. It takes a little over 4 min to get the hot water everywhere from a cold morning.


I installed the each Navicirc into the two most used bathrooms. My hot water only splits into two branches that cover the whole house. One bathroom is at the end of a branch while the other sits about half way down. When the pump runs it will deliver hot water to about 75% of the house.


Now, the Hotbutton kit comes with wired wall mountable buttons. Installation may be possible if you can get though the walls, but then there’s the "first world problem” of being bothered to press the button each time like a second light switch…. ridiculous. My goal was to make everything wireless using motion sensors. The closets thing I could find was an EXPENSIVE kit from Rinnai. A wifi unit with wireless buttons or motion sensors $190 each! Nope, not doing that. So I decided to do it myself using Arduino.


I bought and arduino “starter kit” off amazon along with some cheap motion sensors, radio transmitters/receivers, and some extra arduino mini’s. Everything cost me $80. Several forums and many youtube videos later I got that basic setup working. The transmitter (powered by a 12vdc plug) would see motion and send a radio signal. The receiver (powered by the 12vdc from the Hotbutton contacts) gets the transmission and sends 5vdc to the signal contact on the Hotbutton board. VOILA, the pump turns on and it work! However range is s#!t. So I went to Digikey and for $30 got some good radio chips and now range is amazing. Walk into the bathroom and by the time you’re done with your business the water is hot and ready.


However there were some problems. The pump would keep turning on with every back to back motion sensor trip. The solution was an easily programable delay into the receiver to ignore all inputs for “30min” after a trip. This was only about 80% of the solution. If someone had just used the water on the 29th min, and then proceeded to trip the motion sensor, the pump would again turn on and continue to work despite the Navicirc being closed. The burner shuts itself off because the flow has seised, but the pump continues to work until the time has expired. I was worried this may lead to the pump wearing out prematurely.


Without reducing P#12, The only other way to shorten the run cycle of the pump is by using an external temperature sensor. The resistance of the supplied temperature sensor at 100deg F was about 5k ohm. When I bridged the “Sensor 1” connectors with a 5k resistor while the pump was running, it immediately shut off. Now using a simple transistor as a switch and 5k resistor, I can program the arduino to turn the pump off on demand! Clearly the pump needs to be told to turn off once the Navicircs have closed. So I began looking into how the water heater measures flow. Turns out it’s a simple HALL Effect sensor. I tapped the arduino into the HALL sensors data wire and programed it to turn off the pump if the flow measures 0.


To break it down the logic goes:

if signal received — turn on pump — begin to measure flow — if no flow — turn off pump — don’t accept any new signals for 30 min


Now it works great! Sure it’s a bread board bundled mess but I am in the process of creating a custom PCB in a tiny box for cheap (easyeada). Anyway, if you’ve gotten this far, thank you! It’s been a fun and interesting project with unexpected twists. Hopefully this has been an enjoyable read for you. Any question, ideas, or criticisms please feel free to post.
 

Bannerman

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Thanks for the update and out-of-the-box thinking.

One thing you did not mention is adjusting setting for On-Demand Pipe Target Length P.16. The default setting is only 30' so if the run to your most distant NaviCirc is greater, hot water might possibly arrive faster than 4-minutes with a higher P.16 setting. Since a remote temp sensor will normally override the Target Length setting, because you placed a resistor across the temp sensor contacts, I anticipate the Target Length setting will be probably overridden currently.

There was a recent poster who also obtained the HotButton kit but also did not want to push buttons but instead activate the pump using verbal commands through Alexa interfaced through Z-Wave. He found obtaining the necessary Z-Wave components too expensive as he wasn't certain it would work.

I suggested the inexpensive WIFI Smart Switch below as it will link to both Alexa & Google Home and incorporates a momentary contact relay so it should function similar to a HotButton button.

https://www.amazon.com/dp/B0752P57Z...fcd98392bd94c34a45a30dfb2&tag=twhomeshow07-20
 

Benjamin

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Hmm interest little device. I wonder if it worked with IFTTT. Just bought it. Ill mess around with it see what its capable of.

Oh and I just checked my P.16 and its disabled. Turning on P.17 or removing the supplied jumper on for the external temp sensor seems to nullify P.16. All I see is "- - - -".
 
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