Can I use VOELCB as Main isolation switch

[SUNRAY]

All theoretically true. However, I can't say that I've ever heard of any sort of switch (at least, one screwed to a wall) spontaneously 'swithching itself back on', have you?

Having said that , if I had to remove/replace the installation-side 'tails' of a 'switched off' VOELCB, I would probably use insulated tools and wear gloves, 'just in case' the disturbance affected the switch mechanism. Other than then, I personally think that the risk of a screwed-to-the-wall VOELCB spontaneously switching itself back on is probably close to zero.

It will.

As I wrote to Flameport, I have no idea, but it's certainly not impossible that they were designed (per some relevant Standard) to have contact separation which would today be regarded as adequate for isolation. For what it's worth, my experience is that, in general, ancient switching devices often had relatively massive contact separation.

However, there are some very risk-averse people around (even in this forum) and, provided they are "fully informed", it's for them to make personal decisions with which they are comfortable.

Kind Regards, John

This is why most switch gear is up for on, to avoid the chances of something falling on it or its own weight putting it back on.

I don't recall working on more than one with the cover off but that one had a double contact, ie a pivoting bar that made contact at both ends and a substaantialspring, it required pushing a locking button to allow it to be switched on and almost a hair trigger to flick it off. I feel the contact separation would have easily been ½" twice.

EDIT: Thinking on I found this one: https://www.diynot.com/diy/media/untitled.15082/ which has a very different contact arrangement. If the link doesn't work the thread is 'Freds New Flat'

 

[flameport]

was/is the 'relevant product standard'

The standard was BS842, the most recent version being from 1965, and the majority of what's in it is based on the original 1939 version.
Nothing in it specifies anything about contact gap or mechanical design of the contacts, and it's not stated that it's even suitable for isolation.

There is a preview here which includes the contents. https://knowledge.bsigroup.com/prod...rth-leakage-circuit-breakers/standard/preview

In any event, these devices are 40+ years old at best, and in many cases much older, haven't been operated for decades or ever, and the risk of mechanical or electrical failure is very real.

 

[JohnW2]

This is why most switch gear is up for on, to avoid the chances of something falling on it or its own weight putting it back on.

Quite so, in general - at least in this country and in 'recent'(decades) times, but by no means always. The switchfuses feeding the distribution circuits I inherited in my house were enormous MEM things,of which this was one ..

.

I don't recall working on more than one with the cover off but that one had a double contact, ie a pivoting bar that made contact at both ends and a substaantialspring, it required pushing a locking button to allow it to be switched on and almost a hair trigger to flick it off. I feel the contact separation would have easily been ½" twice.

As I said, albeit on the basis of relatively little experience, I've got the impression that 'ancient' switchgear tended to have 'fairly massive' contact separation.

Kind Regards, John

 

[JohnW2]

The standard was BS842, the most recent version being from 1965, and the majority of what's in it is based on the original 1939 version.
Nothing in it specifies anything about contact gap or mechanical design of the contacts, and it's not stated that it's even suitable for isolation. There is a preview here which includes the contents. ....

Thanks. If it says anything about contact design/separation, it would presumably be in section 15 ("Construction") and/or 16 ("Operating Mechanism") on pages 3 and 4 respectively, but the preview only goes as far as page 2.

In any event, these devices are 40+ years old at best, and in many cases much older, haven't been operated for decades or ever, ...

Indeed

and the risk of mechanical or electrical failure is very real.

Again true - but if it successfully disconnects the supply (as proved by testing) then, as I have said, I would think it extremely improbable that it would subsequently spontaneously switch itself back on.

The only potential risk at all exists during the very brief periods during which the installation-side 'tails' are being disconnected/reconnected and, as I've said, one could use insulated tools and gloves for those operations for added protection/reassurance.

As I've also said, opinions will undoubtedly vary, as will the degree of people's risk-aversion, but provided the OP is adequately informed, it's really for him to reach a decision with which he is comfortable.

Kind Regards, John

 

[SUNRAY]

Quite so, in general - at least in this country and in 'recent'(decades) times, but by no means always. The switchfuses feeding the distribution circuits I inherited in my house were enormous MEM things,of which this was one ..

.View attachment 293086View attachment 293087

As I said, albeit on the basis of relatively little experience, I've got the impression that 'ancient' switchgear tended to have 'fairly massive' contact separation.

Kind Regards, John

I had one of those when I moved into this house; 2x 30A cooker and ring, 2x 5A lights, original from 1965. Added to that a couple of single wylexes; 30A for shower, 45A submain to granny annex.
I actually thought about the wylex boxes after posting, where the main switches are 'up off' but the RCD mains switch version was 'up on'

However to add to the confusion that did change at some point and I did have one of each in my home

 

[Stuart981]

Me again chaps.
One further question if I may. If I were to carry out the modification as detailed below would it be reportable work as per building regs.

1) Disable the protection functionality on the ELCB as previously discussed in this thread and use it as a shut off switch only .
2) Install a residual current breaker between the shut off switch and the consumer unit.
3) Remove the wired fuses from the old Wylex box and fit miniature circuit breakers in their place.

Regards Stuart

 

[JohnW2]

Me again chaps.
One further question if I may. If I were to carry out the modification as detailed below would it be reportable work as per building regs.
1) Disable the protection functionality on the ELCB as previously discussed in this thread and use it as a shut off switch only .
2) Install a residual current breaker between the shut off switch and the consumer unit.
3) Remove the wired fuses from the old Wylex box and fit miniature circuit breakers in their place.

People may argue, but that would not to my mind represent 'replacing a consumer unit' which is the only relevant thing that would be notifiable.

However, as I suspect you realise, aside from the issue of isolation (which we have discussed at length), to add an RCD and replace the fuses with MCBs is far from the ideal way to go - you should really replace the Wylex box with a modern CU (which has built in RCD protection plus other things) - but that would indisputably be notifiable work.

Would your only reason for proceeding in the manner you suggest be simply to avoid the need for notification, even though it would be far from an ideal solution?

Kind Regards, John

 

[Stuart981]

People may argue, but that would not to my mind represent 'replacing a consumer unit' which is the only relevant thing that would be notifiable.

However, as I suspect you realise, aside from the issue of isolation (which we have discussed at length), to add an RCD and replace the fuses with MCBs is far from the ideal way to go - you should really replace the Wylex box with a modern CU (which has built in RCD protection plus other things) - but that would indisputably be notifiable work.

Would your only reason for proceeding in the manner you suggest be simply to avoid the need for notification, even though it would be far from an ideal solution?

Kind Regards, John

Thanks for that John and yes you are correct. I simply cannot afford to go down the route of an approved tradesman and building control notification but want to make my installation as safe as I can.

 

[flameport]

Remove the wired fuses from the old Wylex box and fit miniature circuit breakers in their place.

What do you hope to achieve by doing that?

 

[JohnW2]

Thanks for that John and yes you are correct. I simply cannot afford to go down the route of an approved tradesman and building control notification but want to make my installation as safe as I can.

That's obviously what I suspected. However, as flameport has implied, changing the fuses to MCB won't make it any safer. The RCD theoretically would make it 'safer' to some extent, but many/most people would probably tell you that you shouldn't really have just one RCD protecting the whole installation - since, if it trips, you will lose power to everything in your installation.

Having said that, I lived for a good few years with just a single, up-front 'catch everything' RCD, without any problems, and my daughter still has such a situation to this day.

Kind Regards, John

 

[Stuart981]

That's obviously what I suspected. However, as flameport has implied, changing the fuses to MCB won't make it any safer. The RCD theoretically would make it 'safer' to some extent, but many/most people would probably tell you that you shouldn't really have just one RCD protecting the whole installation - since, if it trips, you will lose power to everything in your installation.

Having said that, I lived for a good few years with just a single, up-front 'catch everything' RCD, without any problems, and my daughter still has such a situation to this day.

Kind Regards, John

 

[JohnW2]

Stuart, yes, that's what i wrote - but did you have something to say in response?

 

[bernardgreen]

Having said that, I lived for a good few years with just a single, up-front 'catch everything' RCD, without any problems, and my daughter still has such a situation to this day.

In 1980 having two RCDs was considered by the electricity supply company to be un-acceptable. The person sent to connect the supply to our building site declined to make the connection,

A phone call to his boss was made to explain that one RCD was for the caravan we were living in and the other RCD was for the supply to the building site. Pointing out that an accident involving electrical tools on the building site could trip an RCD, With only one RCD this would leave us without power in the caravan when first aid might be needed.

This was accepted as being common sense and the person was sent back the next day to make the connection.

 

[Stuart981]

Stuart, yes, that's what i wrote - but did you have something to say in response?

Thanks for the reply. As you say fitting circuit breakers to the old box adds nothing and they appear to be unavailable anyway. So thinking of fitting an upfront 100 amp 100 mA RCB at this time and then maybe swap over the CU later with MCB's and 30 mA RCB in the box and maybe a surge protector as well if I can run to that.

Regards Stuart

 

[SUNRAY]

In 1980 having two RCDs was considered by the electricity supply company to be un-acceptable. The person sent to connect the supply to our building site declined to make the connection,

A phone call to his boss was made to explain that one RCD was for the caravan we were living in and the other RCD was for the supply to the building site. Pointing out that an accident involving electrical tools on the building site could trip an RCD, With only one RCD this would leave us without power in the caravan when first aid might be needed.

This was accepted as being common sense and the person was sent back the next day to make the connection.

Yes I encountered something similar, ended up with just one RCD... well until SEEBoard guy left the building.