Is it OK(ish) to treat garage MCBs as switches?

[skotl]

I have a garage CU with three ways, next to the garage door where the light switch is.

I've got into the habit, when leaving the garage, of switching the lights off and flicking the MCBs for the welder and sockets off "just in case*" (I leave the lights MCB on in case the Mrs heads into the garage).

The welder and sockets should not have any (appreciable) load on them when I flick them off so my question is; do MCBs have a lower life expectancy if someone keeps flicking 'em off and on as if they were power switches?

Cheers
===
(* the "just in case" is if I've left anything on so that I know the entire garage is dead when I leave it)

 

[mfarrow]

MCBs should not be used as switches. I think they wrote that into the regulations.

It hasn't stopped people doing it for decades though!

 

[skotl]

MCBs should not be used as switches. I think they wrote that into the regulations.

It hasn't stopped people doing it for decades though!

Oops - you think the concern is switching them when there is a load across them, or is it more basic than that?
I could just stop doing it, I guess

 

[RF Lighting]

The regulations actually write the exact opposite. Circuit breakers are approved for use as isolators as well as functional switching.

 

[JohnW2]

MCBs should not be used as switches. I think they wrote that into the regulations. It hasn't stopped people doing it for decades though!

Oops - you think the concern is switching them when there is a load across them, or is it more basic than that? I could just stop doing it, I guess

Use them for switching under load would clearly be 'even worse' but it's probably 'more basic' than that. Since they are not designed for repeated manual operation,it could be that they would suffer, and their life be reduced, by such a practice. Particularly given that MCBs are effectively untestable, the thought of possibly 'wearing them out' is probably not a very clever idea.

Kind Regards, John

 

[JohnW2]

The regulations actually write the exact opposite. Circuit breakers are approved for use as isolators as well as functional switching.

Interesting. Use as isolators sounds fine (when SP isolation is acceptable), but I'm a little surprised about functional switching, essentially because of what I've recently written here. I wonder what the manufacturers have to say about this?

Kind Regards, John

 

[RF Lighting]

Table 53.2 in the red regs.

It used to be commonplace in factories to see MCB's used as the light switches and I can't remember ever seeing an issue with this arrangement.

 

[EFLImpudence]

And 53.4 in the green. (Don't have yellow yet)

Plus - it specifically states 60898s and 61008/9s are suitable for on-load isolation.
The same as 60947-3s

 

[mfarrow]

The regulations actually write the exact opposite. Circuit breakers are approved for use as isolators as well as functional switching.

I thought the latest amendment had put a stop to people using them as a general switch? I thought I'd read it somewhere at least. Shame it's not on BSOL yet.

 

[mfarrow]

And 53.4 in the green. (Don't have yellow yet)

Plus - it specifically states 60898s and 61008/9s are suitable for on-load isolation.
The same as 60947-3s

Circuit-breakers and RCDs are primarily circuit-protective devices and, as such, they are not intended for
frequent load switching. Infrequent switching of circuit-breakers on-load is admissible for the purposes of
isolation or emergency switching.

 

[EFLImpudence]

Thanks for that.

Did it make it to the book, John?

 

[JohnW2]

And 53.4 in the green. (Don't have yellow yet) ... Plus - it specifically states 60898s and 61008/9s are suitable for on-load isolation. ... The same as 60947-3s

Same (as green) in yellow - 60898, 60947-2, 60947-3, 60669-2-4 and 61009-1, plus all RCDs and 60947-4-1 contactors are OK for all purposes - isolation, emergency switching, functional switching and on-load isolation. I'm still a bit surprisd about the functional switching!

Kind Regards, John

 

[JohnW2]

Circuit-breakers and RCDs are primarily circuit-protective devices and, as such, they are not intended for
frequent load switching. Infrequent switching of circuit-breakers on-load is admissible for the purposes of isolation or emergency switching.

Thanks for that. Did it make it to the book, John?

Ah!!!!!! Yes, it did make it into the BYB, but I missed it because it is referenced not from individual devices but from the column heading of the "Functional Switching" column of the Table - which is a bit silly, given that 'circuit breakers and RCDs' represent only a small proportion of the entries/rows in the Table! The Note actually goes on to say:

... For more frequent duty, the number of operations and load characteristics according to the manufacturer's instructions should be taken into account or an alternative device from those listed as suitable for functional switching in Table 53.4 should be employed

My apologies for overlooking this - but I suppose it does go to show that my very first comments were essentially consistent with what the BYB now says Mind you, the note relates essentially to on-load switching, and therefore does not necessarily relate to essentially off-load switching such as skotl was talking about.

Kind Regards, John

 

[mfarrow]

Mind you, the note relates essentially to on-load switching, and therefore does not necessarily relate to essentially off-load switching such as skotl was talking about.

That's true I guess, I was confused by the reference to light switching earlier (and in my memory) when reviewing the OP's intentions.

I'm glad it's in there, as the cynic in me has always thought DPCs were just the IET telling us there will be changes whether you like it or not, but we need to go through this process to keep people happy.

 

[ban-all-sheds]

This is not a light switch.