Any 240v power outage sensors?

I have an outdoor hot tub that is run off of a gfci protected 240 volt circuit.

I came out the other night to find the gfci was tripped with no obvious cause.

I'm looking to monitor the power status downstream of the gfci so that I can prevent a possible freeze up in the winter.

Does anyone know of a device similar to the Ring extender that will switch to internal battery power when mains is lost? It has to run on 240v, as there is no neutral at the tub, only 2 hots and a ground.

I'm about 99% sure that's a no. Closest I can think would be to use something like the GE outdoor smart switch for 240v and use something like Device Watchdog to alert if it stops reporting in.

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It’s pretty easy to build one though.


I was thinking in the space of buy and install. With enough money and time...anything could be built :grin:


True dat!

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How about an alarmed water temp sensor?

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So how much spare time do you have @aaiyar ? :rofl: :rofl:

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I have a floating temp sensor now but its not very accurate. I suppose I can set a rule for it, but it may be a day or 2 before the temp drops enough to trigger, especially in summer months.

I think i will poke around the circuit board fuses with my dmm and see if there is anything low voltage that i can connect to a Fibaro Smart Implant and monitor that for going offline.

Here's a simple DIY solution that works in situations like this (I make use of this approach in a couple places).

  1. Run one of the two hots through a current switch like this one:
    RIBXGTF - Functional Devices, Inc.

  2. Connect the terminals of the current switch to any Hubitat-compatible contact sensor that supports external terminals. Such contact sensors are made by Ecolink and GoControl. As long as there is current, the contact sensor will register as closed. If the GFCI pops, the absence of current will make the contact sensor register as open.

Note: Don't run both the hots through the current sensor switch. Because they cancel each other out, so the contact sensor will always register as open.


Thanks. I didn't know there were RIB current switches.

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Awesome. This is exactly what I need. Thanks.

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Not as much as I would like. Although, I am finding that taking short breaks to check out the community keeps me functioning better!


This current switch won't work. I clamped it around one of the hots and had my meter on the outputs. I tested it and found my hot tub must not draw the required 0.35 amps at rest. When the heater or one of the pumps turn on, the solid state switch in this current switch closes, but it opens when the pump or heater turns off.

It's a great switch though. I think im going keep it and use it for monitoring my main sump pump.

I might have to resort to temperature monitoring for now.

This will work but you actually only really need to put the clamps on one 220 leg although you could do both... but if it is out both legs will be out.

As a side note i use this to tell me when dryer is done but not the hot tub. For the tub i use a

Ecowitt wn34bl to alert me when temp drops below 100f