Installation of max. 5A cable protection switch

[TNa]

I am curious to hear how others have followed this installation instruction.

" ⚠️CAUTION! The Device and the load current circuit has to be secured by a
cable protection switch in accordance with EN60898-1 (tripping characteristic
B or C, max. 5 A rated current, min. 6 kA interrupting rating, energy limiting
class 3)."

 

Which device did u use for protection (brand, rating, existing or newly installed)?

Did you change the max load of an existing circuit? Or wire a new circuit?

[Heinz]

@supportadmin Who can we ask for this ? 

[thgoebel]

EN60898-1 is for automatic circuit breakers only. If not, microfuses (e.g. 5x20mm) could be used. But this is not declared by the manufacturer…

[Martin_]

Hi, just installed one and came here to see what people say.

I really like it, and it has some really good things about it!

However.

This is potentially a huge issue, I don’t think anyone has installed this device correctly, as this is not a standard fuse.

 

I would have to return the 2 i bought as it’s impossible to pull new extra wires for me or lower the existing fuse that much.

 

This would mean changing the fuse in the electrical panel (or pull new cables to the device from the panel), and also that whole group would now be limited to 5A (230x5 = 1150W) max instead of a “normal” 10A fuse with 2300W.

Is this really correct? 
Or has the 5A maximum for the switch relay perhaps accidentally followed the max fuse for the device?

 

5A max fuse for the internal switch relay could easily be worked around (extra relay) but the circuit fuse is a different thing.

Edited July 18 by Martin_

[tvbshelly]

The device supply and the switching relay output are connected to the same L in this device according to the schematics.

I think that since the relay is only designed for 5A switching current, the entire device must therefore be protected with a maximum of 5A, so that in case of a fault the circuit breaker (LS) switches off before the relay / internal cabling / device generate damage.

[Martin_]

4 hours ago, tvbshelly said:

The device supply and the switching relay output are connected to the same L in this device according to the schematics.

I think that since the relay is only designed for 5A switching current, the entire device must therefore be protected with a maximum of 5A, so that in case of a fault the circuit breaker (LS) switches off before the relay / internal cabling / device generate damage.

Hi!

It's actually usual that devices have a relay that doesn't support the same A as the main fuse.

See for example the Shelly 1PM Mini Gen3, it supports 10A main fuse but max 8A switching for the relay.

 https://www.shelly.com/en-es/products/product-overview/shelly-1-pm-mini-gen3#node-darrkgp14cqg0

 

[tvbshelly]

The Wall Display seems to be special here, because 5A is required as an external protection. Perhaps it is just a coincidence that the relay also only allows 5A.

External protection:	5 A, tripping characteristic B or C,
	6 kA interrupting rating,
	Energy limiting class 3

Max switching current AC:	5A

[Martin_]

18 hours ago, tvbshelly said:

The Wall Display seems to be special here, because 5A is required as an external protection. Perhaps it is just a coincidence that the relay also only allows 5A.

External protection:	5 A, tripping characteristic B or C,
	6 kA interrupting rating,
	Energy limiting class 3

Max switching current AC:	5A

Yes, in this case it's a coincidence (read design decision) that the relay and device needs 5A fuse.

I have worked as an electrician for 10 years and as electrical consultant for 15 years and have never installed a 5A fuse except for special circuits for certain devices mounted in electrical panels.

I would assume based on my experience that this makes this device a no go in 100% of homes (have you ever seen a 5A fuse in a home?)

The great thing with this would be to change a normal wall switch with this and be able to control all devices in the home!

 

New builds and for people that can redo their electrical panels or pull dedicated cables this would work for, but if correct this is a huge error in design and eliminates almost all easy installations in existing homes.

If i change the fuse to 5A, outlets will have a maximum load of 1150W, that would not handle a vacuum starting due to inrush currents for the motor starting, even if the rated W of the vacuum is lower then 1150W.

Edited July 19 by Martin_

[tvbshelly]

58 minutes ago, Martin_ said:

would assume based on my experience that this makes this device a no go in 100% of homes (have you ever seen a 5A fuse in a home?)

To be honest, no. B16A and B10A is typical here, B25 for specific installations like PV, rarely 6A. I. I have only ever seen 5A in industrial cabinets.

I see the main problem in the fact that most users don't even read or understand the circuit breaker requirement and simply use the installed breaker because they are simply replacing a switch with the wall display. Unfortunately, it only becomes a problem when something really bad happens and then, for example, an insurance company checks why the electrotechnical standard was not complied with.

Shelly cannot be accused of not clearly pointing out this circuit breaker requirement. Of course, it is a disappointment that it was not made possible to use a circuit  breaker with at least 10A.

I almost feel that with many motors you get a problem with the inrush on a 5A circuit breaker - since Shelly also allows C Characteristic, this would make it slightly better.

[Martin_]

2 hours ago, tvbshelly said:

I see the main problem in the fact that most users don't even read or understand the circuit breaker requirement and simply use the installed breaker because they are simply replacing a switch with the wall display. Unfortunately, it only becomes a problem when something really bad happens and then, for example, an insurance company checks why the electrotechnical standard was not complied with.

Yes, agree 100% with this, no-one unless "technical" people will understand it or even look for it, but people will install it.

2 hours ago, tvbshelly said:

Shelly cannot be accused of not clearly pointing out this circuit breaker requirement. Of course, it is a disappointment that it was not made possible to use a circuit  breaker with at least 10A.

I really wonder why this made it into the final product and how the conversation went during the design phase.

At least C10A should be the minimum for a main fuse as you say.

[Martin_]

Or, option 2 is to include a small fuse holder, to put infront of the display.

That would be an easy option and cost almost nothing to include, that would secure the installations in an easy way.

[tvbshelly]

Quote

 

5 A, tripping characteristic B or C, 6 kA interrupting rating, Energy limiting class 3

 

I'm not sure whether you can meet the specified requirements with such a fuse ... unfortunately, I'm not familiar with this.

 

[thgoebel]

On 10.6.2024 at 13:48, thgoebel said:

EN60898-1 is for automatic circuit breakers only. If not, microfuses (e.g. 5x20mm) could be used. But this is not declared by the manufacturer…

Some days ago…

[Martin_]

1 hour ago, thgoebel said:

Some days ago…

Hi, missed that post 👍

It's no problem the change a MCB for a micro fuse, but it can be a jungle also, there are different types of them, some a quick and some are slow.

https://www.swe-check.com.au/pages/learn_fuse_markings.php

FF or F type would be sufficient to replace a MCB, but agree that this should be specified in the manual! Then all would be OK as workarounds.

 

 

[tvbshelly]

1 hour ago, thgoebel said:

Some days ago…

Oops, sorry, unfortunately I didn't remember.

[Martin_]

@thgoebel @tvbshelly @TNa

Hello.

I small update regarding the fuse situation.

I have now looked into this regarding the fuse of the device with my electrical calculation software supplier. 

 

I don't know how much you know about fuses (so i will explain it) but there are 2 different things to consider if you have a fuse.

1. Over current = Limits the current output so we don't connect too many things on a fuse.

2. Short circuit = Limits the current when there is a direct short or fault.

 

1. Over current:

If we consider point 1, then this would protect the internal relay of the WD from over current, ex connecting a 10A (2300W)  radiator to the circuit, the internal relay is not made for this load.

 

2. Short circuit:

This is if we get a short (after the relay of the WD)

Now, this is where the mind bending begins, it doesn't matter if you have a 6A or 10A fuse for the WD, the Ik1 (short circuit current) will be the same for both fuses!

It depends on the cable impedance (lets say 1,5mm2 cable) we will get the same trigger time (0.1 s) from the 6A MCB as the 10A MCB, and so the short circuit current going through the WD will be the same!

 

So to summarise:

The 5A in the WD specification is for the internal relay only.

If we limit this load "1" (to under 5A) then there is no problem having a 10A fuse for the display, as the "2" short circuit current will be the same.

 

Therefore:

Shelly could update their specification and make it clear that the maximum load (1) on the internal relay is 5A (over current protection).

And, for short circuit protection (2), that can be 10A (or even 16A MCB) = This enables all installations.

 

Perhaps this would cause confusion, but i don't see it, as almost all their other devices have the same situation.

Ex Shelly 1PM Mini Gen3, maximum switch current is 8A but the fuse is 10A.

 

 

[Martin_]

Here is a calculation for 4, 10 and 16A MCB fuses showing maximum Ik1 short circuit current for each circuit (0,3kA), they are all the same (except for W004)

 

We can see that the biggest impact on maximum short circuit current is the area (mm2) of the cable

(compare calculation W001 and W004, same fuse different cable 1,5mm2 vs 2,5mm2)

As the cable has less resistance the current will be higher when there is a short.

 

But, as you can see, for short circuit protection only, it doesn't matter if you have a 4A, 10A or 16A MCB fuse as the fuse will blow at the same time (0,1 s) so the current will be the same.