Smart mcb?

[Aragorn84]

I would use a proper contactor from a trusted brand, and leave the chinesium to switching the contactor supply.

Infact, this is exactly what i've done with my EV charger. A Sonoff device switches the supply to the controller in the charge unit (which controls the main contactor), but never actually sees any of the charging current.

Get yourself a contactor from a trusted make (schneider/merlin gerin, hager, eaton etc), install it into a suitable enclosure, and use something like a Sonoff to switch it on and off.

 

[JohnW2]

Not necessarily true, the "smart" device could trip on 33 Amp and start the OFF ON OFF ON cycle while the normal MCB will not trip unless the overload current is several times 32 Amp.

I don't wish to supporet the product in any way, but what you've suggested seems to be just 'out of the air' speculation.

lightbeing's point was surely one in relation to safety - i.e. that if the device were used in series with a convention ('trusted') MCB, then that MCB would operate in any situation in which one expected/wanted it to operate and, if it did, it would put a stop to any attempts at "OFF ON OFF ON cyclling" that the device might otherwise attempt (i.e. there would be no risk of the circuit being re-energised until the 'trusted' MCB was reset)?

Having said that, as I said (and many others have subsequently agreed), it seems inappropriate for the OP to use any sort of MCB when what is needed is just a WiFi-operated switch/relay/contactor.

Kind Regards, John

 

[bernardgreen]

How could the "trusted" MCB trip if the "smart" MCB tripped before the "trusted" MCB could trip ?

 

[JohnW2]

How could the "trusted" MCB trip if the "smart" MCB tripped before the "trusted" MCB could trip ?

It couldn't, but if the current weren't high enough for one to 'want it to trip', why would that be a problem?

What you describe could (if it happened) be a 'nuisance', but I'm not sure why you are speculating that the device would trip at a much lower current than one would expect (for an MCB of its rating) before attempting to auto-re-set?

I must say that I'm wondering how this 'auto-re-setting' could be engineered, given that it requires a non-trivial amount of force to manually re-set an MCB.

Kind Regards, John

 

[oceansoul]

Auto recloser's are a thing. They are usually found in HV distribution networks, and will automatically reclose a CB in the event of a fault. The number of reclose attempt is usually programmed and if the fault is still present the CB will remain in tripped state. So not off-on-off-on indefinitely. Obviously these HV networks are designed with auto recloser's in mind. I didn't realise they were a thing for LV MCB's but it appears that Schneider do make them. https://uk.rs-online.com/mobile/amp...ZFb6lhxoifTBGZtlSawaAg5xEALw_wcB&gclsrc=aw.ds

I suspect thats what the 'smart' WiFi MCB is trying to imitate. In domestic LV environment I can think of no reason one would need this feature, nor are domestic LV systems designed for it. In the OPs case a simple WiFi relay (Sonoff etc) would suffice, although you'd have to ask the question what are they trying to achieve by switching off the MCB each day?

 

[JohnW2]

Auto recloser's are a thing. They are usually found in HV distribution networks, and will automatically reclose a CB in the event of a fault. The number of reclose attempt is usually programmed and if the fault is still present the CB will remain in tripped state. So not off-on-off-on indefinitely. Obviously these HV networks are designed with auto recloser's in mind.

Indeed - the electricity supply to my house knows all about these HV auto-reclosers

I didn't realise they were a thing for LV MCB's but it appears that Schneider do make them. ... I suspect thats what the 'smart' WiFi MCB is trying to imitate. In domestic LV environment I can think of no reason one would need this feature, nor are domestic LV systems designed for it.

Indeed - but, as you say, why on earth would it ever be needed in a domestic (or, come to that, many other) environment? One doesn't really get 'nuisance' trips of MCBs and transient faults resulting in 'correct' operation of an MCB must be extremely rare. Even if I scrape the barrel of my mind for possible situations in which it might serve a purpose, I end up thinking about scenarios in which it would really be safer for 'auto-reclosing' not to happen.

In the OPs case a simple WiFi relay (Sonoff etc) would suffice, although you'd have to ask the question what are they trying to achieve by switching off the MCB each day?

Indeed - that's what I, followed by many others, have been saying.

Kind Regards, John

 

[bernardgreen]

An auto recloser limited to one reclose attempt could be useful on domestic lighting circuits to restore lighting after a lamp has blown and the plasma short in that lamp has tripped the MCB.

 

[JohnW2]

An auto recloser limited to one reclose attempt could be useful on domestic lighting circuits to restore lighting after a lamp has blown and the plasma short in that lamp has tripped the MCB.

Well, for me, that could certainly have been said in the past, but since I moved away from incandescent bulbs (before which it was a common occurrence), I can't recall any occasion on which death of a bulb/lamp (CFL or LED) had caused an MCB to trip.

What worries me most about auto-resetting MCBs (in domestic etc. environments) is that the devices we're talking about are generally the only means of isolation (alone) of the circuit concerned - so is there something one can do to make absolute certain that it can't try to re-set whilst one thinks the circuit is isolated and 'dead'. I would have expected that your view about risk-taking would make you also very nervous about that!

Kind Regards, John

 

[Harry Bloomfield]

Since this is the make I am using, I can say yes you need the hub to connect anything to a PC, Phone, or internet. There are some in the range like the light switches and sockets that can connect to a remote control without using the hub, but they don't report if switched on or off, all you know is you asked it to switch on or off, not if it actually responded.

The ones I'm using (as reported in another thread) do indicate to Alexa whether on or off. They just connect to a normal wifi router.

 

[bernardgreen]

I would have expected that your view about risk-taking would make you also very nervous about that!

The risks of harm when the lights go out versus the need to manually isolate the circuit when working on it.

I can't recall any occasion on which death of a bulb/lamp (CFL or LED) had caused an MCB to trip.

One string of our village Christmas Lights blew a 20 Amp BS88 fuse, the string has approx 300 LED bayonet cap golf ball lamps which are only one or two Watts each.

One lamp on a different string did go pop with a visible flash when powered up. Maybe these lamps can short circuit long enough to take out a 20 Amp fuse.

Or the fuse had become very "tired", it is 33 years old and lived for 27 years in a power box on the wall of a house.

 

[JohnW2]

The risks of harm when the lights go out versus the need to manually isolate the circuit when working on it.

As I said, my concern with any 'auto-resetting' device would relate to the question of how certain one could be that one had irrevocably "manually isolated" (just) the circuit when working on it. I think I'd probably end up switching off an entire CU - which would be a significant inconvenience.

One string of our village Christmas Lights blew a 20 Amp BS88 fuse, the string has approx 300 LED bayonet cap golf ball lamps which are only one or two Watts each.

I didn't suggest that it never happens, but I can only speak of my own experience. I have a very large number of bulbs/lamps in my house and, when they were all incandescent, it was probably almost a weekly event that one would die and trip an MCB. However, during the last several years (of initially CFLs, now almost all LEDs) I'm not sure that it has happened even once. ... certainly not a reason for even vaguely thinking about the possible benefit of an auto-resetting MCB.

Kind Regards, John

 

[lightbeing]

lightbeing's point was surely one in relation to safety - i.e. that if the device were used in series with a convention ('trusted') MCB, then that MCB would operate in any situation in which one expected/wanted it to operate..

Thanks JW , that is exactly what i meant.

Also, thanks to everyone who has contributed so far.

Now, just to clarify the requirements as to why this setup is needed.

It is not to control a single socket or a device but a means to easily control a whole final ring circuit that services the house bedrooms. Why would anyone want to do that one may ask.

My wife suffers from electro-sensitivity (Electromagnetic hypersensitivity ) due to effects of the mains electricity especially when the room sockets are in pretty close proximity to her when sleeping. So it was suggested (by a therapist, i know this health issue remains contested.) that she should sleep away from any mains sockets and at some distance away from any mains cables running in the walls which is very difficult to achieve unless the final ring circuit (just serving the bedrooms upstairs) is to be switched off every night before retiring to bed.

The house wifi router, and all other essential services are on other mcbs and left unchanged. I hope that clarifies the reason why. Off course this can be inconveniently done manually so I thought we could make our life easier with a smart circuit breaker to in order to easily control that ring circuit and perhaps would add the light circuit too if it turns out to be a sound solution.

Kind regards to all.

 

[ericmark]

From what I remember with high voltage safe working procedure was to short the outputs so even if a auto system tried the make the system live it would fail, spiking the cables for example. This is not the case with low voltage, simply locking the lid on a distribution board is considered as OK, so having a MCB auto reset I would not see as safe.

However I can't see them working very well anyway in a modern metal consumer unit, it would need an aerial outside the consumer unit to work.

You posted while I was writing, the other point is the using you linked to was 63 amp and a ring final is 32 amp.

I would be looking at alitube cable. If it is being sensitive to the RF from 50 Hz then the faraday cage is your friend, metal sockets, ali-tube cable, and plaster board with the foil backing. The last thing you want is any wifi device.

 

[JohnW2]

Thanks JW , that is exactly what i meant.

Thanks for confirming.

Now, just to clarify the requirements as to why this setup is needed. ... It is not to control a single socket or a device but a means to easily control a whole final ring circuit that services the house bedrooms. Why would anyone want to do that one may ask. .... My wife suffers from electro-sensitivity ... which is very difficult to achieve unless the final ring circuit (just serving the bedrooms upstairs) is to be switched off every night before retiring to bed.

I'm sorry to hear about your wife's problems. I think we all understand conceptually what you wanted to do (switch an entire ring circuit by WiFi), but it wasn't apparent "why?" - but you have now explained that.

However, I don't think this alters anything that has already been said. You really don't need a second MCB, of any type. You can keep the existing MCB supplying the circuit and use that to feed a WiFi-controlled switch/contactor/relay (such as have been described), and then have the ring circuit (both ends of ring) originating at the output of that switch/contactor/relay. The only small issue is that feed from existing MCB to it would then have to be 4mm² cable (or, I suppose, two 2.5mm² cables in parallel), since it would be carrying all of the ring's load.

What you would then end up with would, strictly speaking, not be a 'ring final circuit' any more but, rather, a 'lollipop circuit', but that is not really of any consequence.

Kind Regards, John

 

[bsr]

I've been involved with auto reclosers in the rail and energy industry where they are used widely. Typically they hold off for 1-2 seconds and then reclose only once. Useful for things like animals getting fried on rails or wet blown branches causing arcs on hv cables. Said feed circuits always have separate isolation which would be locked and tagged out under a safe system of work. No way would you just isolate the reclosers.