Defferent between smart switch and smart Relay switch?

I really do not understand the different between smart switch and smart Relay switch and the usage for each one?


Can you provide some context around this or an example. I might be just me but I’m a bit lost with what you are talking about. Thanks.

Do you mean smart relay switch?

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Yes, Relay* … Sorry.

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In general, a smart switch can only control a device rated for the regions voltage (120, 240), a relay can control a device of any voltage.
The difference internally being the switch takes the existing mains voltage and sends this to the load output.
The relay simply provides the relays contacts (which are not connected to the mains) as outputs.

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Smart switch after installed, is something that you will see, can touch / flip.

Smart relay after install, is to be hide behind your existing switch.

Nothing to be sorry about Fadi! Mike’s reply to you is spot on.

great, thanks for the clarification.

Thanks for the answer Mike, please correct me if I am wrong.

from your answer then if I want to use a switch I need to be careful about the voltage, In Dubai we are using 220-240 Volts, 50 Cycles. If I buy any switch I need to make sure it is working with that. and here I am replacing my old switch with a smart one and I can control it physically and by the smart hub. (what about the amp here ?) is it making any different between if I am putting that smart switch for a light or for water heater?

in the case of the smart relay, I will keep using the same old dumb switch and will put the smart relay switch inside so I can control it to be on-off using the smart hub. What about the original dumb switch? I can still use it to turn the device on/off? not sure how the dumb device status will sync with the smart relay and the hub?
the same question for the relay too, can I use it for lights or water heater. or the power of the device make different?

another question here, regarding the light dimmer. what is the things that I should look to in regards to voltage and power when choosing the right dimmer for my lights in Dubai?


Now we’ve just complicated this by at least one order of magnitude (grin)

In all cases, relay or switch, the devices capacity must not be exceeded, meaning if the relay/switch is rated for 10 amps, you cannot (should not) use it to control a device that requires 20 amps…

All devices have an amperage capacity rated at a specific voltage, some devices are rated in watts.
watts = voltage * current (amps)

So that answers the load question, which also applies to dimmers.
Some dimmers work better than others with LED’s, none work with CFL’s or other tube florescent fixtures.

There are switch/dimmer devices that you install behind and connect to your existing switch, and there are devices that have their own switch included.
The choice here being one of aesthetics and availability.
I have a pretty good idea of whats available in the US, but no idea internationally.

Now, which actual device (switch/relay) that you use depends on the region that your hub is a part of.
If you have a US hub, then your zwave device choices are limited to US devices, which will be 120v, and probably aren’t going to be able to tolerate the 240 mains in UAE.
If you have a UK hub, then you will be OK, so long as you order zwave devices for UK’s zwave frequencies.
I’m not up to speed on all the nuances of international zwave frequencies, but I know there are several, and they aren’t interchangeable.

zigbee uses the same frequency internationally, however the device choices are much slimmer.


Without knowing your full use case and assuming you have a UK hub then look at Fibaro for relays and dimmers. They’re not the cheapest but in terms of support (ST and community) and functionality they are very good.

If you get stuck then have a look at the vesternet web site. They have put some real time into them.

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I just also wanted to mention here that in the Z wave standard there is no difference between a relay, an in wall receptacle, a plug in module, or a wall switch. Anything which can turn the power on/off is a “switch” under the Z wave standard.

Consequently, you will find many manufacturers of Z wave devices who use the term “smart switch” for any of those devices. For example, Fibaro calls their in wall relay “smart switch” where all of the discussion in this thread so far would’ve said that is not a switch.

terminology varies from one region to another

Also, networking aside, the terminology is different in the UK and the US. Most of the description so far have been using US terminology. In the US, people just say “relay.” In the UK, it is more typical to say “relay switch” for the same device. In the US, a “Z wave module” is usually a plug-in. In the UK, a “Z wave module” generally goes inside the wall.

So there is no hard and fast rule for what is a “switch” and what is a “relay,” particularly when you were talking about zwave.

So I would ask instead if there are particular models you have questions about or is there a particular use case that you are considering.


Thanks all, I will be looking for UK hub and Fibaro.
Great information. appreciated. I am actually looking here to automate my villa in Dubai. I started doing a research on ST and the devices I need 2 weeks back.

this is what I need:

  • The sliding Garage door
  • Air Condition Split Units
  • the Light Switches / dimmers for all the lights.
  • the water heater tank
  • curtains
  • motion sensors for the kitchen, bathroom and dressing rooms.
  • Projector screen.
  • the 4 outdoor locks.
  • door bill
  • voice controls
  • touch screens on the wall.
  • 3 outside Security Cameras and 9 inside. (for this I am locking for an IP cameras with NVR) I do not think that this can be connected to the ST.

and this is the results of my research:

  • 1 Samsung Smartthing Hub V2 (UK version)

  • 8 Tado for the 8 Split Units Air Conditions ( (any better device?)

  • 5 Fibaro Dimmer Switch (any better device?)

  • 18 AEOTIC Switch in-wall (any better device?)

  • 12 Samsung Smartthings Motion Sensor (any better device?)

  • 2 Fibaro Relay Switch (any better device?)

  • 2 Amazon Echo 1 for down living room and the other for upper living room. (any better device?)

  • 5 Necleus to be as intercom and Alexa in the office, guest room, master bed room and the kids room. (any better device?)

  • 2 wink relay in the down living room and the upper living room to be as a screen to control the hall house. I am thinking to put 2 IPADS on the wall instead. (any better device?)

  • 2 Logitech Harmony Elite to control, TV, Projector and the home theater. (any better device?)

  • 4 August Smart Locks for the outside doors. (any better device?)

  • 2 Ring Video Doorbell Pro one outside the Garage door and the other for the main door. (any better device?)

  • 5 Fibaro Roller Shutter for the curtains and the projector screen. (any better device?)

I really appreciate any suggestions or any better products than the one I selected above.

I know that automating the following will be challenging:

1- Projector screen,
2- Curtain
3- Heater
4- Split Unit Air Condition.

A reasonable way of dealing with high amperage devices is to use a normal zwave/zigbee switch or appliance outlet, and have it drive the coil of a high amperage relay, in the us these devices are called contactors.
That second relay then directly controls the load of the target device.
something along these lines:

40 amp contactor…

You will obviously need to mount such a device in a project box of some sort as well as doing some mains wiring.