Can I use VOELCB as Main isolation switch

[Stuart981]

Hello chaps

I have an old CU that I want to replace with a modern unit. This is a TT system with an earth spike driven into the ground and a voltage operated earth leakage device installed.

My question is on the new installation can I just leave that VOELCB in place so that I don't have to call in the network operator to pull the main fuse.

Thanks in advance - Stuart

 

[conny]

Not an electrician but I'm 99% certain the answer is no.
It is outdated and modern boards must have a 30mA RCD fitted as a minimum.
I could be wrong but an electrician will soon give you the correct answer.

 

[ericmark]

I did, the only down side is likely rated 60 amp, so if you want a larger isolator latter it will need renewing, and the earth rod will now by-pass the unit. I assume something like this without the centre wires, it is just an isolator like any other.

 

[JohnW2]

I have an old CU that I want to replace with a modern unit. This is a TT system with an earth spike driven into the ground and a voltage operated earth leakage device installed. My question is on the new installation can I just leave that VOELCB in place so that I don't have to call in the network operator to pull the main fuse.

As you've been told (and probably already knew) you cannot, and should not, retain the VOELCB functionality as an attempt at 'protection' of your installation and I presume that the modern CU you wish to install will include proper RCD or RCBO protection.

However, if you remove the connection between the VOELCB and the house's earth system, then it will simply become a 'manual isolator'. Hence, IF the (presumably aged) VOELCB is still effective/safe as an isolator, then I would see no theoretical reason why you could not do what you suggest.

The VOELCB probably ought to be eventually changed to a modern isolator, both for reassurance about reliability and because it may well not have a high enough current rating for your present needs. Until such a change were made you would probably need to be prepared for discussions/arguments with anyone inspecting the installation about the presence of the VOELCB (which they may not understand!).

I presume you are aware that replacement of a CU is a 'notifiable' job - which means that, if you want to remain within the law, DIYing it may not be cost-effective?

Kind Regards, John

 

[Stuart981]

Yes thanks for the replies chaps.
Conny - I understand the new CU has residual current protection.
Ericmark - The VOELCB looks similar to the photo. Yes you are right about the rating as the ceramic main fuse holder is embossed 60 amp. No EV charger without an upgrade.

 

[flameport]

can I just leave that VOELCB in place

No, it's obsolete and should have been removed decades ago.

It's not suitable for it's original purpose, and it can't be used as an isolator either.

 

[SUNRAY]

No, it's obsolete and should have been removed decades ago.

It's not suitable for it's original purpose, and it can't be used as an isolator either.

Interesting, I know of an installation with one in every outbuilding (at least a dozen) where the earth arrangements have been removed just leaving them as isolators (within a locked steel enclosure with a small Schneider CU).

 

[JohnW2]

No, it's obsolete and should have been removed decades ago.

I think everyone, including the OP, fully understands that it should have ceased to be used as a protective device decades ago.

It's not suitable for it's original purpose, and it can't be used as an isolator either.

As I said (with all my original emphasis), "IF" it still remains satisfactory as an isolator, I see no reason why it can't be used as such - and whether or not it achieves satisfactory isolation is something that would need to be verified ('checking for dead') even if it were a brand new isolator - so, provided that is done, I see no 'safety' issue.

The situation Sunray describes is exactly what I inherited when I moved into my present house. The connection from CPCs/MET to the installation side of the VOELCB had been removed, but the device itself left there as an isolator.

Kind Regards, John

 

[flameport]

I see no reason why it can't be used as such

The standard to which it was made is not referenced in BS761.
It is not compliant with 537.2 or Table 537.4

 

[JohnW2]

The standard to which it was made is not referenced in BS761.

To again paraphrase that infamous young lady of old, "It wouldn't, would it?"

It is not compliant with 537.2 or Table 537.4

Same comment as above.

However, 537.2.1 allows that a device used for isolation "... shall be of a type for which the isolation function is explicitly recognized by the
relevant product standard or as identified in Table 537.4". We know that it is not "identified in Table 537.4", but since I haven't got a clue as to which was/is the 'relevant product standard' (do you know?), I have no idea as to whether "the isolation function is explicitly recognised" in it for suc devices (do you know?). All I can tell you, for what it's worth, is that when I did have one, at least one electrician did use it 'for isolation'.

In any event, I thought (perhaps wrongly) that the OP was looking for practical advice based on electrical common sense and considerations of safety, rather than education about what current regulations (do not) say about a very obsolete device.

Kind Regards, John

 

[Stuart981]

As you've been told (and probably already knew) you cannot, and should not, retain the VOELCB functionality as an attempt at 'protection' of your installation and I presume that the modern CU you wish to install will include proper RCD or RCBO protection.

However, if you remove the connection between the VOELCB and the house's earth system, then it will simply become a 'manual isolator'. Hence, IF the (presumably aged) VOELCB is still effective/safe as an isolator, then I would see no theoretical reason why you could not do what you suggest.

The VOELCB probably ought to be eventually changed to a modern isolator, both for reassurance about reliability and because it may well not have a high enough current rating for your present needs. Until such a change were made you would probably need to be prepared for discussions/arguments with anyone inspecting the installation about the presence of the VOELCB (which they may not understand!).

I presume you are aware that replacement of a CU is a 'notifiable' job - which means that, if you want to remain within the law, DIYing it may not be cost-effective?

Kind Regards, John

Thanks for that John. I do understand that to do this is not best practice but was looking for confirmation that what I was proposing was actually safe.

 

[JohnW2]

Thanks for that John. I do understand that to do this is not best practice but was looking for confirmation that what I was proposing was actually safe.

You're welcome. As you will understand, that's how I took your question and was the spirit in which I answered. As one might expect, others have felt it more appropriate to point out that, in addition to not being 'best practice', it is also probably non-compliant with current regulations (BS7671), and have used that to imply that you shouldn't do it - but I suspect you already knew all that.

As for safety, as I've pointed out, even if it were a spanking new modern isolator, good practice and common sense (and a desire for self-preservation!) would demand that, after 'switching it off', you undertook recognised "testing for dead" to confirm that things downstream of it were no longer life. If such tests confirm 'dead' after you switch off the VOELCB then, even though it is an ancient switch mechanism, it is (at least, in my opinion) all-but-impossible that it would suddenly 'switch itself back on' again. However, I'm sure that you understand all this, and will come to your own decision as you see fit.

Kind Regards, John

 

[Stuart981]

good practice and common sense (and a desire for self-preservation!) would demand that, after 'switching it off', you undertook recognised "testing for dead"

will do - thanks

 

[plugwash]

What testing for dead won't tell you is whether contacts are seperated by an appropriate isolation gap, or whether they are just barely not touching, and are a bit of vibration away from touching again. A well-designed isolator will be designed such that the switch position provides a positive indication of the position of the contacts.

So "don't use something as an isolator if it wasn't designed to be an isolator" seems like a pretty good principle in general. The question then is were VOELCBs designed to be isolators. I understand some older (pre-BSEN) MCBs were not.

 

[JohnW2]

What testing for dead won't tell you is whether contacts are seperated by an appropriate isolation gap, or whether they are just barely not touching, and are a bit of vibration away from touching again.

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.

A well-designed isolator will be designed such that the switch position provides a positive indication of the position of the contacts.

It will.

So "don't use something as an isolator if it wasn't designed to be an isolator" seems like a pretty good principle in general. The question then is were VOELCBs designed to be isolators. I understand some older (pre-BSEN) MCBs were not.

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