How To: Controlling Millivolt Ignition Gas Fireplace

[lawsonad]

Hub: C8-Pro running 2.4.3.137
Device: Remotec ZFM-80US (Z-Wave)

Overview:

The gas fireplace is one of the last things in my house to get smart control via my Hubitat hub and integration with Apple HomeKit. I have been nervous to attempt as not to want to mess with anything dealing with natural gas in the house. However, after talking with the my fireplace technician that does maintenance on the insert, he assured me there are failsafes in place to prevent gas flow say when the smart switch is acticated and the pilot light is out.

After doing some searches, many have used ZEN smart relays but these require install under the insert and need a 110V AC plug nearby to power the smart relay. I wanted to do everything at the wall where the simple switch was installed to control the millivolt operation. After doing some research with ChatGPT I found the following option which checked all my boxes. The smart switch acts as both a physical switch and smart remote all in on unit which was important. I did not want to get into a siutation where the physca switch and relay were out of sorts. It's powered by 110V in-wall AC that I used from a nearby powered switch in the same area.

Wiring Setup:

I followed the "Figure 2" wiring diagram from the manual, only difference was I omitted the external physical switch which was not needed. The physical button on the smart remote itself is perfect.

• Black (hot) → L
• White (neutral) → N
• Millivolt TH / TP → Relay Load / Relay Load (polarity doesn't matter)

Final Install:

Including the Remotec ZFM-80US on my Hubitat was painless, it picked up a built-in Hubitat "Remotec ZFM-80" driver which has been working well.

[CuriousB]

There are some special rules in the NEC if you commingle low voltage and line voltage wires.

1. all devices and connections ( wire nuts) must be in an approved junction box. No open air connections.
2. all low voltage wires inside that junction box must have 600V insulation. Wire gauge can be less than 14AWG but insulation must be 600V.

[Pantheon]

Don't the low voltage and 120v have to be separated into separate or divided boxes?

[lawsonad]

Don't the low voltage and 120v have to be separated into separate or divided boxes?

Yes, the double gang box you see in the photo has a low-voltage divider to separate the low and high voltage sides of the same box.

[CuriousB]

No but they can be. If they are separate then the LV side doesn't need to follow the 600V insulation rule. A common scheme would be to run 600V wires off of the devce and into a sperate LV cavity and then class 2 wiring practices can be used, a lower voltage wiring.

My main point is you can't have these devices just dangling around the gas valve and wire nuts on lines in the open. Anything line voltage needs to be in a box. no exceptions.

This is why I lean to the ZEN58 suggestion above. You can plug a 12-24V AC or DC power plug into your terminal strip and then all the wiring is low voltage and not subject to the Class 1 wiring restrictions. I think that is your easiest path forward.