Use of Shelly Plus 1 to control heated towel rail

Forums › Gadgets, robotics, home automation, electronics (including wearables) › Use of Shelly Plus 1 to control heated towel rail

leaplae

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#316069 13-Sep-2024 12:27

Had an electrician out to replace a breaker today, and asked about him installing a Shelly Plus 1 to control a heated towel rail.

I've mocked up using a spare switch and a bit of cardboard exactly like this example on YouTube: https://youtu.be/mJFSI81m5wo?t=419 and demonstrated to him. He said that he can't install it like that, as it won't meet regulations - the switch has to isolate the circuit or something, so can't have the switch 'off' while the Shelly is 'on'.

Is this really the case? Are there any work arounds? He did say he could wire it differently, so the switch turns the Shelly and the towel rail off, but when in off position the app won't work (as the Shelly won't be powered).

I don't really want to have to do the old tape over the switch trick...

openmedia

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#3281687 13-Sep-2024 12:45

I'm considering the same, but using a momentary switch rather than an on/off switch

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leaplae

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#3281689 13-Sep-2024 12:55

While that would work for something like a light, I'd say it's a bit more difficult for a towel rail as it's not immediately obvious if it's off or on?

eluSiveNZ

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#3281693 13-Sep-2024 13:06

leaplae:

While that would work for something like a light, I'd say it's a bit more difficult for a towel rail as it's not immediately obvious if it's off or on?

You will face the same issue with a standard on/off switch. Assuming you will use automation, the switch could be in the off position and the automation has turned the shelly output on, the switch is still in the off position.

Momentary switches generally have light indicators to show state.

As for your electrician's comments, is the towel rail hard wired to a permenant connection and switch, or is it operated from the wall with the lights switches?

leaplae

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#3281695 13-Sep-2024 13:12

From the wall, with the towel rail cord going into a little hole above the switch (on the faceplate).

lxsw20

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#3281701 13-Sep-2024 13:34

leaplae:

While that would work for something like a light, I'd say it's a bit more difficult for a towel rail as it's not immediately obvious if it's off or on?

Can you put a wall plate in that takes a neon too, so when the shelly/towel rail is on the neon is also glowing.

https://www.tradezone.com.au/product/hpm-excel-red-neon-indicating-mech-red-16006.html

You would have a 3 way plate, switch, neon and power out to the towel rail.

SomeoneSomewhere

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#3281748 13-Sep-2024 15:20

An auto/off/manual switch would be my preferred option for this.

A light switch can't be an isolator and I don't think there's any specific rules that apply to a heated towel rail requiring it to have a dedicated isolator or functional switch, but it's still not really good practice to have a switch that appears to turn something off but can be bypassed electronically.

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sdemler

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#3281776 13-Sep-2024 16:44

Shelly plus 1 is a dry contact relay meaning when it is "on" the load bypasses the shelly circuitry. It's spec'ed to 15 Amps so should be more than enough for tower rail. It's actually the right fit for your use case so I'd look to get some better advice from an electrician experienced at handling relay switches. If you are going down the DIY route it sounds as if you might be a bit new to relays, so if this is your first time mucking with relay switches choose a simple use case that doesn't use much current i.e. a light switch. D

Things to consider :-

1) If you use this with a physical on/off switch the state of the switch will occasionally get out of alignment with the state of circuit, which isn't ideal.

2) There will be a timer switch controlling the element, make sure the shelly is upstream from this circuit

leaplae

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#3281813 13-Sep-2024 17:26

sdemler:

Shelly plus 1 is a dry contact relay meaning when it is "on" the load bypasses the shelly circuitry. It's spec'ed to 15 Amps so should be more than enough for tower rail. It's actually the right fit for your use case so I'd look to get some better advice from an electrician experienced at handling relay switches. If you are going down the DIY route it sounds as if you might be a bit new to relays, so if this is your first time mucking with relay switches choose a simple use case that doesn't use much current i.e. a light switch. D

Things to consider :-

1) If you use this with a physical on/off switch the state of the switch will occasionally get out of alignment with the state of circuit, which isn't ideal.

2) There will be a timer switch controlling the element, make sure the shelly is upstream from this circuit

Thanks for the insights. I did quite a bit of research into which one to get before purchasing, and I've used relays in a few projects prior.

I think the main issue here is that the physical on/off switch may get out of sync. So, it's not obvious that the appliance is 'on' or 'off'. The electrician said it wouldn't be compliant, as after turning the switch to 'off', the shelly could override that and turn it back on.

Not that I think anyone would be 'working' on a heated towel rail, if it breaks then the thing is getting replaced, and the breaker at the panel would be flipped in that case...

Does anyone have any suggestions for electricians in CHCH who are aware of smart relays?

michelangelonz

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#3282102 14-Sep-2024 13:58

What about putting the Shelly after the switch on the face plate that way the face plate switch is the master isolator and the Shelly just does the auto on/off.

JessieB

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#3282144 14-Sep-2024 20:10

I solved this problem in accordance with what your electrician required. This was done separately for the towel rail and the heater using two 16 amp rated smart switches. The physical ordinary 2-gang light switch, used for the light and extractor fan, was then replaced with a 4-gang smart switch. Two of the gangs were connected to the light and the fan, as before. The other two gangs were left physically unconnected, but programmed to operate the smart switches connected to the heater and towel rail.

leaplae

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#3282567 16-Sep-2024 12:28

Decided to keep it simple, and not wire the switch into the Shelly. So when the switch is 'off', both the towel rail and the shelly are off.

Electrician didn't really know what he was doing and put live and neutral into either side of the dry relay. Luckly, the relay was open, and I saw the error before testing using the app.

Took a bit of convincing, but eventually got him to put his meter into continuity mode and cycled it with nothing attached (except for the Shelly power) to show him how it worked. After that we were away.

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johno1234

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#3282575 16-Sep-2024 13:07

leaplae:

I think the main issue here is that the physical on/off switch may get out of sync. So, it's not obvious that the appliance is 'on' or 'off'. The electrician said it wouldn't be compliant, as after turning the switch to 'off', the shelly could override that and turn it back on.

Two way light switches naturally get around the wrong way - is it allowed for light switches but not of other things?

SpookyAwol

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#3287326 28-Sep-2024 18:43

leaplae:

Electrician didn't really know what he was doing and put live and neutral into either side of the dry relay. Luckly, the relay was open, and I saw the error before testing using the app.

I think that really sums it up.....

At the end of the day, its not an isolating switch, it can be either way. As you mention, if someone is working on it then it will be isolated at the switchboard, not just by turning off the switch.....

sdemler

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#3287544 29-Sep-2024 13:07

Your electrician is a bit disappointing! The DIY’er has to supervise the electrician to make sure he doesn’t kill himself. Sigh! Glad you got it working to your satisfaction though - that’s the main thing!

phoenixmarine

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#3308880 14-Nov-2024 10:21

Wow that sounds like the electrician didn't really know what he was doing. In case anyone comes across this thread in the future there should be no reason why you can't just have the Shelly wired into the switch like normal. Yes you could have the switch in the off position but have the relay turned on via the app so not "Isolated" as such but what is the difference to having a simple momentary press mech wired into the Shelly switch. I wonder if he would have been fine with that setup.

Worse case would be to have two switches one down under the towel rail where the towel rail is wired in. This one would basically always stay in the on position and would be fed by the Shelly's relay output. Then the 2nd switch up by the light switch would be connected to the Shelly's input. This should satisfy any electricians issues as you can physically isolate the towel rail should anything go wrong.