Has anyone else seen problems with Wylex MCBs? I've had about 5 (all
NSB32s) fail over the last year or so. They work fine until either
tripped or switched-off and then they stay open circuit (or maybe high
resistance) even though the lever latches in the ON position. They're
becoming expensive fuses!

Are any other manufacturer's MCBs interchangeable?

Dave

On Fri, 27 Oct 2006 12:19:05 +0100, NoSpam wrote:

Has anyone else seen problems with Wylex MCBs? I've had about 5 (all
NSB32s) fail over the last year or so. They work fine until either
tripped or switched-off and then they stay open circuit (or maybe high
resistance) even though the lever latches in the ON position. They're
becoming expensive fuses!

Are any other manufacturer's MCBs interchangeable?

Dave

Have you bothered to contact the company .Surely that's the first thing you
should be doing .Did you keep the failed ones .?



Stuart

Stuart wrote:
On Fri, 27 Oct 2006 12:19:05 +0100, NoSpam wrote:

Has anyone else seen problems with Wylex MCBs? I've had about 5 (all
NSB32s) fail over the last year or so. They work fine until either
tripped or switched-off and then they stay open circuit (or maybe high
resistance) even though the lever latches in the ON position. They're
becoming expensive fuses!

Are any other manufacturer's MCBs interchangeable?

Dave

Have you bothered to contact the company .Surely that's the first thing you
should be doing .Did you keep the failed ones .?



Stuart

I exchanged them at the local factors but I suspect they went into the bin.

Dave

In article ,
NoSpam writes:
Has anyone else seen problems with Wylex MCBs? I've had about 5 (all
NSB32s) fail over the last year or so. They work fine until either
tripped or switched-off and then they stay open circuit (or maybe high
resistance) even though the lever latches in the ON position. They're
becoming expensive fuses!

Are you exceeding their breaking capacity?
The PSSC (prospective short circuit current) available at
your supply may be exceeding the current which the Wylex
breakers can break. This is often written on the breakers
in the form M3, M6, M10, etc (3000A, 6000A, 10000A respectively).
Some of the older Wylex breakers designed to plug in to
the older rewirable fuse boxes have rather low breaking
capacities (I think I might have seen as low as 1000A on
the push button ones, and probably only 3000A on the toggle
versions).

--
Andrew Gabriel

NoSpam wrote:
Has anyone else seen problems with Wylex MCBs? I've had about 5 (all
NSB32s) fail over the last year or so. They work fine until either
tripped or switched-off and then they stay open circuit (or maybe high
resistance) even though the lever latches in the ON position. They're
becoming expensive fuses!

I have seen some Proteus MCBs fail like that in the past - they turn on
electrically only some of the time when you turn them on mechanically!
(that makes for a rather perplexing fault finding session!)

Something else to consider: are you in a big town, or very close to the
substation? If so, it could be that your prospective fault current
exceeds the breaking capacity of the MCBs. Most MCBs will only break
fault currents up to 6kA - above that they may fail to break, or expire
in process!

Are any other manufacturer's MCBs interchangeable?

See the recent threads on just this topic.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Andrew Gabriel wrote:

Are you exceeding their breaking capacity?

The OP said

They work fine until either tripped or switched-off and then they
stay open circuit [...]

The "or switched off" bit suggests it's not a breaking capacity issue.

The PSSC (prospective short circuit current) available at
your supply may be exceeding the current which the Wylex
breakers can break. This is often written on the breakers
in the form M3, M6, M10, etc (3000A, 6000A, 10000A respectively).
Some of the older Wylex breakers designed to plug in to
the older rewirable fuse boxes have rather low breaking
capacities (I think I might have seen as low as 1000A on
the push button ones, and probably only 3000A on the toggle
versions).

The NSB type referred to is M6 (6 kA).

I suggest a call or e-mail to Wylex's technical support dept:

Telephone: 01543 438320 Facsimile: 01543 438321 eMail:
wylex[dot]technical[at]electrium[dot]co[dot]uk

--
Andy

Andy Wade wrote:
Andrew Gabriel wrote:

Are you exceeding their breaking capacity?

The OP said

They work fine until either tripped or switched-off and then they
stay open circuit [...]

The "or switched off" bit suggests it's not a breaking capacity issue.

The PSSC (prospective short circuit current) available at
your supply may be exceeding the current which the Wylex
breakers can break. This is often written on the breakers
in the form M3, M6, M10, etc (3000A, 6000A, 10000A respectively).
Some of the older Wylex breakers designed to plug in to
the older rewirable fuse boxes have rather low breaking
capacities (I think I might have seen as low as 1000A on
the push button ones, and probably only 3000A on the toggle
versions).

The NSB type referred to is M6 (6 kA).

I suggest a call or e-mail to Wylex's technical support dept:

Telephone: 01543 438320 Facsimile: 01543 438321 eMail:
wylex[dot]technical[at]electrium[dot]co[dot]uk

Thanks Andy.

Dave

John Rumm wrote:
NoSpam wrote:
Has anyone else seen problems with Wylex MCBs? I've had about 5 (all
NSB32s) fail over the last year or so. They work fine until either
tripped or switched-off and then they stay open circuit (or maybe high
resistance) even though the lever latches in the ON position. They're
becoming expensive fuses!

I have seen some Proteus MCBs fail like that in the past - they turn on
electrically only some of the time when you turn them on mechanically!
(that makes for a rather perplexing fault finding session!)

Absolutely right! The last thing that comes to mind is that the MCB has
failed when it latches in the ON position OK.

Something else to consider: are you in a big town, or very close to the
substation? If so, it could be that your prospective fault current
exceeds the breaking capacity of the MCBs. Most MCBs will only break
fault currents up to 6kA - above that they may fail to break, or expire
in process!

This isn't the problem. Some of the failures have been on circuits which
only have domestic HIFI equipment connected.

Are any other manufacturer's MCBs interchangeable?

See the recent threads on just this topic.

In article ,
NoSpam writes:
John Rumm wrote:
Something else to consider: are you in a big town, or very close to the
substation? If so, it could be that your prospective fault current
exceeds the breaking capacity of the MCBs. Most MCBs will only break
fault currents up to 6kA - above that they may fail to break, or expire
in process!

This isn't the problem. Some of the failures have been on circuits which
only have domestic HIFI equipment connected.

That's irrelvant -- it's the supply impedance which matters
when it comes to exceeding the breaking capacity.

--
Andrew Gabriel

Andrew Gabriel wrote:

In article ,
NoSpam writes:

John Rumm wrote:

Something else to consider: are you in a big town, or very close to the
substation? If so, it could be that your prospective fault current
exceeds the breaking capacity of the MCBs. Most MCBs will only break
fault currents up to 6kA - above that they may fail to break, or expire
in process!


This isn't the problem. Some of the failures have been on circuits which
only have domestic HIFI equipment connected.


That's irrelvant -- it's the supply impedance which matters
when it comes to exceeding the breaking capacity.

I would expect that would only come into play if you have actually
tripped the circuit due to a fault. Simple overcurrent trips or, more
likely given the stated load on the circuit, no trips at all, would not
result in damage to the MCB even with a very stiff supply.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/