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remote thermostat/recirc. pump switch for tankless water heater


sparky7

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Since I'm thinking about wish-list items...

I have a Navien tankless water heater that has a built-in recirculation pump. It has a wired remote that allows setting the temp and putting the pump on a schedule. The scheduler for the recirc. pump allows on/off times on any 30 minute interval, but it has the same schedule for all days of the week. It works great for the times the schedule has the pump running, but if it's in the middle of the day, say, on a Saturday, when the pump is scheduled to be off, it's not so convenient.

I would really like to be able to trigger the pump from a motion detector in the master bath, and from a button in the kitchen. Right now, if the pump has been off for a while, it takes a good five minutes of running the faucet to get hot water to the kitchen sink. The remote is in the basement next to the heater, so it's not convenient to reach from the kitchen or bathroom. :/ And it would also be nice if I could set the temp from a touch panel -- then I would know the bath water would be just the right temperature every time.

Since the remote controls both temp and the pump using a 2-line wire, it must be using a communication protocol, and not just a contact, so I don't think a simple contact in parallel with the remote would work. I believe this would require a piece of zigbee hardware that knows the communication protocol of the water heater remote interface.

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  • 9 months later...

I did call the Navien tech support number to see if there was some method for turning on the recirc. pump separate from the programmed time on the remote. They said the only way to recirculate the water separate from the timer would be to put on an external recirc. pump.

I later thought about putting a relay on the switched wire for the pump. The relay would switch the pump wire from the current wire to a (12v?) supply when on. This should allow a programmable contact to switch the pump to 'on' at any time; otherwise it would operate as normal. I suspect this might void the warranty...

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  • 4 weeks later...

Ideally, I would like to have all the functions available through C4 (pump on/off, set temp, set pump schedule, heater power on/off). But just having the ability to turn on the pump from a C4 switch is the biggest desire. I meant to look into this over the holiday break, but didn't get to it. Possibly this weekend...

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  • 1 month later...

Hi Sparks67,

I think the model I have (CR240A) is a little older than the models shown in the link you provided and doesn't have some of the features you mentioned. I have one unit, and it has one wired remote -- no way for it to know which location is using the water. An interface to C4 could fix all that...

When the schedule has the recirc. pump running, the hot water arrival time at all locations is great -- within a few seconds. But when the pump hasn't run for a while (don't want it running all the time -- wastes heat), it can take several minutes for the hot water to reach certain locations. I've come to the conclusion that my plumber hooked up the loop to go to the far side of the house first, before arriving at the kitchen, which is much closer to the water heater. I may see if it's possible to reverse the loop.

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That, in itself, sounds reasonable considering the pump pushes water to the farthest point from the heater and forces it back through the circuit. What I don't agree with is this desire to schedule the pump. Mine runs 24/7 because you never know when a someone wakes at 3am and needs to wash. Those Grundfos pumps are low current draw to begin with...

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That, in itself, sounds reasonable considering the pump pushes water to the farthest point from the heater and forces it back through the circuit. What I don't agree with is this desire to schedule the pump. Mine runs 24/7 because you never know when a someone wakes at 3am and needs to wash. Those Grundfos pumps are low current draw to begin with...

Hmm, I really didn't think about this. I guess it is still going to be "on demand" no matter what. So it doesn't mean I am going to be using a ton of gas or electricity because I leave it on all the time. They probably had to add scheduling for energy star certification or something.

Does this sound right? If I'm not using hot water 24/7, my gas usage shouldn't go up too much, and because the pump is high efficiency leaving the recirc on all the time shouldn't be a big deal either?

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