Low voltage 3 wire fireplace need to hook up to zwave switch

I have a 3 wire low voltage fireplace switch. The 3 wires are as follows: red-hot, white-neutral, Green- Ground. Now the problem is the wiring scheme would work for any smart switch but since it’s low voltage it will not power up the switch. There is no alternate power near by. Any help or suggestions is greatly appreciated.

I was able to get this to work by using a relay. Remotec has one. Issues that have to be overcome:

  1. All relays out there require 120v power. I had to run power from a nearby wall socket to the low-voltage switch. This requires an electrician (or confidence in your own skills). Help from a friend (electrician) showed how easy this is to do if you know building code and stuff. As has been mentioned in other posts: do it right and keep it legal.
  2. The Remotec relay is great but it is “almost” a standard gang switch shape. I had to dremel a metal gang wall plate to fit the relay. Finally, I had to “adjust” the mount to make it flush. Below is the end result; you can see I have some touch up painting to do.

Good luck

I also used a remotec zfm80. It also supports an external switch, so I mounted mine inside the fireplace which had a 120 ac outlet, and used an external switch to control it.
The nice thing about this relay is that it has a feature that allows you to set the maximum run time, thus preventing the fireplace from remaining on F O R E V E R.
I wrote a custom device type to expose this function.

If I get an electrician in to get me power then wouldn’t I be able to use a regular z wave switch? I would just need a 120v power to get the switch online.

You need a relay, not a switch.

Mike what is the significance between the delay and switch. I apologize but for me I would like to understand how a relay can replace my switch. Plus I would still like a manual override if needed.

If you have a gas fireplace with a switch now…there is 120v power available inside the unit like Mike Mentioned. Just get a flashlight and raise the lower grill. You will see that the electronics of the unit are plugged into a built-in powerstrip or AC power is available somewhere for the fireplace to function.
Your current “switch” that turns on the fireplace is completing a DC circuit for control. All it does is connect the white and red that you described to close the circuit and allow the gas fireplace to operate.
A Z-Wave “switch” is used to control 120v AC power for lights, etc. Z-Wave switches require 120v power to function. So they cannot be used for a DC circuit like your fireplace control.
A Z-Wave relay uses 120v AC power to open/close a DC “switch” or contact. There are several relays that are compatible with SmartThings. I used a different relay but wired it exactly like Mike described. Also, I wired my relay underneath in series with the existing wall switch. This way the existing wall switch must also be turned on for the fireplace to work. Or you could wire the relay in parallel with the existing switch to have a manual override.
I hope this helps…

The only advantage of my implementation is that the button (as shown in my picture) is also a on/off switch that never gets out of sync. I was going to do something like Mike described with the relay but my wife complained that she didn’t want zwave to override the switch (be in a state where the fire was off but the switch was on). Likewise she did not want the fire on when the switch was off. My solution is MUCH more complicated but the wife is happy.

That being said; I will be looking at Mike’s code. The forced timer is a nice feature I did know existed.

Thanks a lot everyone. I will get a relay hopefully this week and an electrician to help with the wiring. Mike I would love to use your app as a great safety feature. Thanks for the helping me out tremendously.

When you get a relay make sure it is a “dry contact” relay (the line you are switching is not powered by the relay.). If you just get any relay and send 110v to your milivolt valve you will damage it and have to replace it. E.g. The remotech zfm 80 is a dry contact relay

Thanks pizzinini I will make sure it is a dry contact relay.

@neal10791 what I wrote is a device driver for the remotec ZFM 80, it isn’t a dedicated smart app.
That code will not work with any other dry contact relay since it specifically takes advantage of the special features in the remotec.

The way I wired mine:
Momentary action wall switch --> (external switch input) remotec zfm80 (dry contact relay out) --> fireplace

The way this works is that the switch or ST can turn on/off the fireplace, nothing gets out of sync.
Actually these days the wife just says “Alexa, turn on the fireplace…”

I will be buying the remotec so I can use the information provided. I know what you mean about alexa. I have her opening doors, garages, lights, and mode changes since I got her. I still have yet to find someone who has developed a device for my rachio sprinkler system. I am also hoping for Ac commands with the nest.

Does anyone know where you can get a Remotech zfm 80. my search online shows out of stock everywhere. Hope this switch isn’t discontinued!

I had the same issue, I gave up and purchased: MIMOLite - Z-wave Mulit-Input/Output Dry Contact Bridge

It came with a power plug attached already, too. I didn’t have to cut an older power cable in half. :slight_smile:

It’s not quite as functional, as it can become desynced from the switch, but that doesn’t bother me.

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Sorry to dredge up this old topic but Leviton DZS15 Switch claims to work with low voltage, does that mean it could replace a fireplace switch?

Could you provide a wiring diagram of how that would look with the switch in parallel for manual override?

Just find the two wires going to the physical switch and wire your relay across these. So if either the switch or relay closes the fireplace will turn on.
You need to wire in series with one of the wires to the manual switch if you want to have a “cutoff” switch. If they are in series both must be closed to turn on the fireplace.
I hope this helps.

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Very helpful - would you have time to draw it out for me? (Still new to this and need to visualize it, though I am sure it’s very simple!) I have a dry contact (Linear) that doesn’t have the switch input like the Remotec that doesn’t seem to exist anymore. Thanks again!

@Mike_Maxwell - I hope you have a few minutes to assist me. I have installed the ZFM 80 as you have but I am a little lost on the device driver part. Can you help?