Smart Switch which makes/breakes both Live+Neutral connections


We have some exterior lights where the switch is in an outbuilding which we’d like to be able to control from HA so we can control them from inside the house (the lights are down a dark passage which leads to the outbuilding, so that would be very useful!).

The outbuilding has WiFi + full mains power. We are in the UK.

The switch appears to make/break both the live and neutral wires (I’m not sure if this what would be called a “single throw / dual pole” switch – I think that might be about switching live between two alternatives). Inside the switch the wiring looks like this:

Live + Neutral in at the bottom and out at the top. There’s an LED when the lights are on which is the wiring with the white sheath.

I’ve not been able to find a smart switch which looks appropriate. Does anyone know of one? Even just knowing the correct technical name for this type of switch would be very helpful!

I assume that cutting off the neutral is a safety feature since they are external lights so I’m a bit reluctant to change that aspect – even if it were technically fine/legal to do so.

Ideally we’d like to be able to continue to use the physical switch too (e.g. like a Shelly device would support) but would sacrifice that if need be.

Thanks in advance for any insights!


I’ve seen similar one for my water heater switch
You can install shelly relay or sonoff mini r4/matter for this

Hi, that’s a 20Amp double pole isolator. You need to be mindful of the MCB that’s supplying that circuit as a standard light switch or in all likelihood any smart switch is not going to be rated at 20Amp. If the MCB is a normal 6amp lighting MCB then the isolator has possibly only been installed to allow the neon to indicate if the lights are on and a standard light switch may be able to be used with the neutrals being joined and the switching only on the live conductors. However, there may be some requirement for the neutrals to also be switched, but that’s not possible to establish with the information given.

for a high amp isolator there is this you can look into:

I personally think it is not necessary to switch both the Phase and the Neutral.

But if you really want to, you could install 2 x Shelly 1Plus Mini.

One for the Phase and one for the Neutral - in HA you would have to make sure that both relays are activated/deactivate simultaneously.

That way you could keep the current switch and its functionality - as long as there is enough room for the 2 shellys in the box (looks like it!).

That’s what the parallel actions function is for with automation’s as otherwise it runs them down the list one after the other, I have it setup for a few things with conditional triggers… so many options to optimize things in HA heh.

Thanks everyone for the feedback.

The MCB is a 6A ROH-106B/030 and the total load is 72W + 110W so 24W or about 0.1A @ 240V – but that seems awfully low so I’m not sure I trust my maths! But in any case it seems like the existing 20A switch is not there due to there being anything close to a 20A load, so it’s likely either there just for the LED or due to some regulatory requirement.

According to BS 7671 (at least as summarized here):

outdoor lighting supplied by a single-phase TN-S or TN-C-S system can be isolated by a single-pole device in the line conductor but outdoor lighting supplied by a single-phase TT system should be isolated using a double-pole device.

So it seems like I need to figure out if I have a TN or TT system… I think it may be time to call in a qualified electrician!

Thanks again everyone,

Section 714 applies to public outdoor lighting. It doesn’t apply to any domestic lighting where the supply to the outdoor lighting is fed from within the property itself. If the supply is protected by a 6A breaker, then there is no need to switch the neutral.

EDIT: The fact it is a 6Amp breaker, isn’t the reason the neutrals don’t need to be switched, but rather from the other information I believe that’s the case (The two weren’t mutually exclusive, just wanted to clarify)


From what I’ve gathered recently, some Eu communities require all outdoor switches disconnect both the live and the neutral. The logic baffles mt, but that is the requirement. (Clarification needed, where is this a requirement?)

First, NEVER use any smart switch or relay at its rated power. 75% is my limit. The rated power is usually the rating of the relay itself, but the specs of these relays aren’t clear about the duty cycle.

What you want is a 20 amp double-pole contactor. You control the contactor with a smart switch, and let the contactor handle the high current.

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+100 what Stephen said.

If it’s a ‘nonstandard’ switching device that exceeds the spec of the standard switch or has extra poles etc.

A similarly rated contactor is your friend.

This is a non starter… If it’s a DPST (double pole single throw) you can’t split the poles and switch them independently (don’t care what the poles are connected to, hot neutral, us split phase, whatever…) they MUST be mechanically switched in the same action or it’s no longer DPST

Controlling the poles independently with a computer and network (that can both fail) between them is even worse. Don’t do it

Agree the two shelly solution is a bad idea.


A parallel automation does not mean simultaneous. Close, maybe, but not simultaneous.

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Another solution would be wiring up the relay/switch to a contactor. Seen this one for water heater/pumps

Thanks everyone for your thoughts.

I ended up using a Shelly Pro1 and a 20A double pole contactor as suggested. The switch is a momentary one and the shelly is configured to toggle the output when it is pressed.

Thank you to everyone for your advice.


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If the Shelly’s get out of sync, bad things could happen.

This looks like a good solution, and professional looking. Is the box you used an off-the-shelf utility box?


The box is a Wylex ESE2 Insulated Electrical Circuit Breaker Enclosure - 2 Module, white: