Shelly FAQ

The Shelly Support Group on Facebook is great! It’s a accessible way to quickly get answers to your questions.

Since I joined the Facebook group, I’ve seen quite a lot of questions pass by. I’ve also noticed that lots of similar questions keep coming back every now and then.

Triggered by this post by Marc I decided to write a sort of Frequently Asked Questions (FAQ) for Shelly devices. I not only want to thank anyone who responsed to this topic with frequently asked questions, but all the super helpful members of the Facebook group. And of course a big shout out to the Shelly/Allterco staff designing these devices and assisting their users!

Can I ask my question in a different language? ¶

The “official”/general Shelly Support Group explicitly states that members must communicate in English.

If you have issues communicating in English, because it’s not your mother tongue, you may want search for a group in your own language. Note that these aren’t necessarily recognised as official support groups by Shelly/Allterco.

But I don’t understand English, can I ask my question in French/Spanish/Italian/German/…? ¶

Have a look at the previous section.

How do I wire/install my Shelly? ¶

Each shelly comes with a manual that has the default wiring diagram included. Follow this manual or give this manual to your (licensed) electrician to properly wire the Shelly.

If you lost the manual, you can have a look at the Shelly Knowledge Base.
For example, here you’ll find the wiring diagrams for the Shelly 2.5.

Mains power can kill you or burn your house down if handled improperly. If you don’t have experience or aren’t comfortable with wiring mains powered electricity, I’d advise consulting a (licensed) electrician.

I don’t understand the wiring diagrams ¶

If you’re uncomfortable reading wiring diagrams or working with mains electricity, I’d advise consulting a (licensed) electrician.

Also have a look at my Intro into Shelly article.

1. It’s always important to verify that you’re looking at the correct diagram before wiring or powering the Shelly.
   This diagram is for when the Shelly is powered with mains electricity: 110-240V AC (Alternating Current).
   Make sure you use the correct diagram if you’re using 24V DC (Direct Current)! The wiring differs and you may need to move the jumper.
2. Live wire. Also known as Hot or Line.
   Usually coloured brown, red or black. Always check your local code and/or verify with a multimeter!
   This is the wire that will hurt (and potentially kill) you if you touch it.
   Connect this with any of the L-terminals (see 4) on the Shelly.
   You’ll also need to connect your switch (see 5) to a Live wire.
   Keep in mind that the Shelly (and the connected load) will be protected by this Live wire’s breaker. If you’re borrowing a Live wire from elsewhere because you didn’t have a Live wire available at the location you’re installing the Shelly, the Shelly and the load might end up at a different circuit (and thus behind a different breaker).
3. Neutral wire.
   Usually coloured blue or white. Always check your local code and/or verify with a multimeter!
   If your house is wired in a multi-phase setup without Neutral (e.g., 3x230V), you may not be able to install a Shelly because you’re lacking the Neutral.
   Connect Neutral to the N-terminal (not required but advised for Dimmer2 and 1L).
4. The L-terminals on the Shelly are internally bridged.
   This means that it doesn’t matter whether you wire the incoming Live wire or the wire running to the switch to either L or L1.
   There are 2 reasons for having the internally bridged terminals and its important you understand the reasoning behind it:
   • Wiring a switch.
     You’ll often install the Shelly behind a switch within the install/junction box. Those boxes are often already cramped and adding extra wires and Wago’s/wire nuts will make things even more cramped.
     You can save one Wago/wire nut by feeding the switch input from the Shelly’s 2nd L-terminal instead of splitting the incoming Live wire using a Wago/wire nut and then wiring the Shelly and switch.
   • Splitting the load.
     Most of the Shelly’s are rated for a max. load of 16A and will be installed in a 16A circuit. They have a single output in which you can thus plug a device that draws maximum 16A.
     However, the Shelly 2.5 can output a maximum of 10A per channel, or 20A in total, provided you use the correct wiring and the Shelly is installed in a circuit that allows a 20A power draw (e.g. with a 24A breaker). However, the screw terminals in the Shelly are rated for ‘only’ 16A. By connecting the Live wire to 2 L-terminals – using a Wago to split the incoming Live wire into 2 wires of the same length – the incoming power will be distributed evenly accross the 2 terminals, thus keeping it within the 16A limit.
     Note that you need to use the correct wire size to carry these loads. Always make sure you follow your local building/electrician codes.
   • Daisy chaining Shelly’s (don’t do this!).
     In theory, you could use the spare Live terminal to feed another Shelly, that feeds another Shelly via its spare Live terminal, that feeds another Shelly via its spare Live terminal, … You get the drill.
     Whilst you’re “safe” as long as the total power draw at the first Shelly doesn’t exceed its rating, it should be obvious that this is a very bad idea. So don’t do this!
5. A switch is not required when installing a Shelly.
   If you don’t need a physical switch controlling the Shelly state, you don’t have to wire one.
   You’ll still be able to control the Shelly using the app or web interface.
   If you’re not using the same Live wire for powering the Shelly and feeding the switch, make sure you’re not mixing phases!
6. The output (O) will carry the switched Live for the load you’re controlling via the Shelly.
7. This circle-with-a-cross is the symbol for a lamp in electrical diagrams.
   You can use the Shelly for much more than just controlling lights. So interpret this symbol as the “load” you’re controlling with the switched live output from the Shelly on one side and a Neutral connection on the other.

Which L-terminal do I need to use? ¶

Read §4 in the previous section, or read this document.

The wiring diagram states I need to wire Live to L1, why do people wire it to L? ¶

Read above.

Why did they provide multiple L-terminals anyway? ¶

Read above.

How do I install my Shelly in a 2-way (hotel switch) / 3-way / n-way setup? ¶

A 2-way/3-way/…/n-way switch setup virtually acts as a single switch. Toggling any of the connected switches will result in a toggle of the final output to the load (e.g. a lamp).

With the exception of the Shelly 1L, the Shelly should always be installed between the final switch and the load. You will need access to Live and Neutral (not required for Dimmer2) to power the Shelly as well as the Switched Live from the switch and the Live feed of the load.

Have a look at these wiring examples for some examples of 2-way and 3-way wiring, as well as some less common setups.

What about multiple momentary switches / buttons? ¶

That’s a lot easier compared to a n-way setup.

Wire all momentary switches in parallel. All switches are fed by the same Live wire and their outputs are all connected with the same wire to the Shelly’s SW-terminal.

Make sure you don’t forget to set the Button Type on the Shelly to Momentary Switch.

Shouldn’t the DC wiring diagram show + wired to L and - to N? ¶

If you official wiring diagram shows + wired to N and - to L (and the Shelly case also reflects this), you can be certain that it’s supposed to be wired this way!

Note that it doesn’t really matter if you reverse the polarity when powering the Shelly with Alternating Current (AC) as electricity flows in both directions (it alternates).
Direct Current (DC), however, doesn’t have this characteristic. Regardless off whether you’re talking about conventional current flow (from + to -) or electron flow (from - to +), we can agree that electricty flow in one direction. This also means that reversing the polarity will try to push electricity the wrong way, eventually damaging your Shelly.

So don’t freewheel and follow the wiring diagram!

But isn’t + in DC the same as L in AC and - the same as N? ¶

Read above.

So don’t freewheel and follow the wiring diagram!

My Shelly reports a temperature of __°C/__°F, is this too hot? ¶

As long as the temperature filling the blanks in the question above is below 95°C (±200°F), you’re fine!

The reported temperature is the temperature of the core of the onboard CPU.
It isn’t abnormal for electronics under load to reach temperatures of 70-80°C (40-50°C above ambient temperature).
Think about the laptop you’re holding on your lap. The internal temperature of the chips often reaches near 80-90°C under load. Graphics cards often reach much higher temperatures, which is why they’re equiped with big cooling fans (or even water cooling).

Most of the Shelly’s have overtemperature protection built-in. Once the chip temperature reaches around 95°C, the Shelly will turn off. Also, the materials used to house the Shelly can withstand temperatures well above 100°C.

The chip temperature is dependant on the ambient temperature, the amount of cooling it gets and the load passing through the Shelly.
Don’t cram the Shelly in a tiny junction box but allow it some breathing room to release its heat. Also make sure you don’t overpower the Shelly. Stay within the limits mentioned in the user manual. And ofcourse don’t install the Shelly in a black box in direct sunlight.

My Shelly is reaching 70°C, it’s going to burst into flames! ¶

No, calm down!
Read the section above.

How do I configure the Shelly H&T to report real-time? ¶

In short: you can’t.

The Shelly H&T is designed as a battery powered device. Battery powered devices have one drawback: the battery drains :O

To save the battery (and your wallet) the H&T goes into hybernation. The whole device is powered down, with the exception of some small circuitry connected to the temperature and humidity sensors. Only when the temperature/humdity treshold is exceeded, the Shelly H&T wakes up and connects to your WiFi network to report its readings.
Connecting to WiFi consumes most of the energy.

You can decrease the tresholds, which will cause the H&T to wake up more often. This will drain the battery faster.

If you get the USB power supply for the H&T (and check the option in the device settings), the H&T will report every 10 minutes regardless of changs in temp/hum. In-between, the Shelly H&T will still hibernate and thus be ‘offline’.

Why can’t I get my H&T to report real-time? ¶

The main reason is most likely that the device was designed to be battery powered and that the USB power supply was added afterwards.

Another reason is that the chip heats up when it’s active.
This will inevitably skew the measurements, causing the device to become basically useless.

Also read the section above.

Where can I buy the Shelly 4Pro? ¶

You can’t.

The Shelly 4Pro is no longer produced and there’s no more stock.
A Shelly 4Pro Plus is being developed, but there’s no ETA (estimated time of arrival) on this device.

When will the Shelly 4Pro Plus be released? ¶

See the question below

When will the Shelly XYZ be released? ¶

Whenever Shelly/Allterco is happy with the product.

Would you rather have a rushed product, full of manufacturing mistakes, faulty hardware or software bugs?
I guess not…

So have some patience and trust in the expertise of the product development team.

Hey @Dimitar, please read my question/issue/… ¶

Please don’t.
Just don’t.

I’m still stuck installing my Shelly, I need assistance ¶

Include as much information as possible when requesting assistance.
Make sure you’re able to not only explain your problem, but also the troubleshooting you’ve already done.

• Include pictures of your installation and a diagram of how you installed the Shelly (even if you’re convinced you followed the user manual).
• What load did you connect (e.g. which type of lamps), what’s the wattage, how did you configure the Shelly, …
  In case of the Dimmer: which dimming mode did you select, did you wire the Neutral wire (also for 1L), are you using a bypass (also for 1L)?
• Are you powering the Shelly with mains voltage or a DC power supply?
  What voltage?
  Did you move the jumper?

And don’t forget to follow the rules of the FB group!
E.g., if you’re posting in the English Support Group, make sure you’re posting in English!