Years after years I am planning to control my outdoor Christmas lights with Node-RED. But never find time. This week it needs to happen. I have bought a Shelly Pro 2 switch, but I am doubting about two things:
I have also a circuit breaker, but I didn't find a diagram/tutorial that explains whether the shelly should be before or after the circuit breaker. I assumed after because when you turn off the circuit breaker, everything (inclusive the shelly) should be switched off:
I can't image your Xmas lights would require 10 amps, I would use the smallest MCB you can get away with. probably 6amps would be more than enough (1.3 kw) There needs to be a fuse before the Shelly.
@E1cid,
Yes you are right, but my description is not good enough. I have installed last summer two outdoor wall outlets, where I have now plugged in my christmas lights. But in summer I can use those two wall outlets for other stuff, so not only used for christmas lights...
Currently the circuit breaker is 16A.
Then L3 i would fuse to 0.5 or 1 amp, as there is no load.
and L1 and L2 I would fuse at 13 amp each (UK spur fusing max capacity. Not sure Of Netherlands fusing in plugs and spurs).
I would run the whole thing of a 25amp MCB (depending on cable size)
This would allow a max capacity similar to Shelly spec. You can then fuse each item from the exterior socket, in UK each plug has a fuse (max capacity 13 amps).
We have mostly circuit breakers of 10A and 16A in our house (here in Belgium). Currently it is 16A which was working fine during summer. So I could replace it by a 10A version for safety, but then it perhaps will turn off often during summer, when I use the outlets for other stuff. But not sure what happens if I try to go (accidentally) above 16A: then the circuit breaker will turn off, but I am then at the limit of the Shelly. Not sure if that is ok for the shelly..
That is not something which is in my english vocabulary
My circuit breaker look like this one, if that is what you mean?
I do despair at the lack of fusing in our continental neighbours electrical systems.
Your first diagram is much better as each outlet is fused. Does Belgium not have a unit to fuse down supplies to lower amps. In UK they are called spurs (switched or unswitched) They are used to go from a 16 amp MCB which may feed power to a shed, to a lower amperage cable for lighting, then there is no need to run a second cable to power a light in the shed.
Ah ok, you guys call that an MCB (Miniature Circuit Breaker). Yes we have a lot of such MCB's in our electrical box. But no fuses/spurs in the switches or wall outlets.
On the Shelly facebook group there is an interesting question:
Genuine question why do Shelly devices that support 16A, only have terminals that support a 1.5 mm² wire? Speaking for Malta, it is standard practice that the wall plugs are wired in 2.5 mm² or 4 mm²
And one of the answers is:
They can handle 16A for brief moments. Not continuous load. No need for 2.5 mm wiring since the Shelly will burn before the cable becomes hot.
Although this comment does not really contain scientifical evidence, I assume there is some thruth in it. From the Shelly site it indeed looks to me that the Shelly 2 pro (without PM) will NOT have a current protection (in contradiction to the Shelly Pro 2 PM):
With devices such as this, which are rated 110/220V, the max 16A current rating is for 110V, for 220V the rating is more like 8-10A or about 1.7kW to 2.2kW.
Although I didn't find some test results (e.g. temperature/current chart), I looks to me that it might be safer to replace my 16A circuit breaker by a 10A version.
Do your appliance plugs have a fuse in them? If so why not wire the Shelly to a plug with a 3A fuse.
If the Shelly is a permanent installation connect the Shelly to a fused outlet with a 3A fuse. Unless you have mega loads of ancient filament Christmas lights this should be OK.
Either way rather than changing the circuit breaker (and the Shelly should definitely go AFTER the MCB) supply the Shelly from a fused supply from the existing socket outlets.
@Buckskin,
Thanks for confirming that! Feels always a bit better...
No they don't. As shown in my second drawing above, it is in fact two regular wall outlets that are connect to the two channels of the Shelly Pro 2. I installed those wall outlets some time ago especially for my christmas lights, but during the summer I have use them to power various other electrical devices. The christmas lights in the winter will be no problem, but I need to make sure I don't burn the Shelly during the summer with my other electrical tools...
As shown in my second drawing above, it is in fact two regular wall outlets that are connect to the two channels of the Shelly Pro 2
In that case if would be advisable to fit a lower current MCB.
If your plugs do not have a fuse in them how to you protect a low current device if it is plugged into a wall socket?
Thanks for the second confirmation. Really appreciated!!
No idea. I have always assumed devices with a CE label have been designed to coope with that kind of situations. Of course not when lightning strikes the net near your house.
Although I always take your feedback very serious, I am going to take your last quote with a grain of salt. Because you guys already freak out when the driving wheel is at the correct side of the car, and that everyone will collide and no one on this planet will survive
Yes based on your feedback it seems that I have only 2 options left:
Convince my wife to call our electrican again to redo everything from scratch, based on some weird standard that is most probably not accepted in most places.
Convince the UK government to call the EU Brexit negotiators again to redo everything from scratch, but this time with some common sense in mind.
I think that the latter option will be much more easier to achieve. So first thing I will do tomorrow morning is call Keir Starmer. Hopefully he can fix it fast, because I really want to control my twinkle lights before next Christmas...
CAUTION For future readers interested in installing a Shelly Pro 2 in a country with normal electricity standards: you can stop reading here! From now on the number of likes will start rising, and people will start joining on a very large scale. They will spread below very useless off-topic information, which they themselves describe as British humor
So on topic advice as others have mentioned, MCB before the shelly to limit the current to shelly outputs to max 16A, or lower if you want to be safe, and perhaps an inline fuse of 1A to provide power to the shelly unit itself in case of a fault on the shelly.
Returning to the serious side for a moment, from what I have read every socket in your house is wired back to the consumer unit (where all the MCBs are) so I am interested to know what current rating the MCBs supplying the SO's are rated at, and are they all the same? (as I couldn't find any info on the subject).
For non EU readers
Apparently Belgium uses an earthed plug & socket (type E) along with France. Type C sockets are now illegal to install. Amazing stuff EU electrical plug info - loads of different types.
10 Amps is a lot of current for Christmas lights. Especially at 220V.
Put the circuit breaker before any loads including the Shelly and size accordingly.
Cheers!
@smcgann99,
Yes I will use 10A MCB before the Shelly, based on all the feedback I read on the Shelly forums. The last thing I want to do, is burn my house down for some twinkle lights.
Yes correct. I didn't mention that above, because I thought that this was common across the globe. But it seems not... We do have limitations about the number of lights and sockets that are allowed per MCB.
What do you mean by rating? This is the info from the manufacturer. Although I see you cannot select english. Not sure if it contains what you need.
What do you mean by rating? This is the info from the manufacturer. Although I see you cannot select english. Not sure if it contains what you need
It did. This bit from the manufacturers specs,
Electric Current
Rated current
16 A
The current rating of the MCB is important for the protection of the wiring following (between the MCB & the SO). In the UK we use a ring circuit rather than radial and every appliance is protected by it's own fuse. Hence the misunderstandings regarding protection of the lights.
Ah really. Never heard about that. Thanks for illuminating me about this!!! Next time I will make sure that I make a better drawing, to make sure everybody is aware of the full setup. Now I completely understand the confusion.
CAUTION 
