Wylex NN CU Breakers NB Type required

[alb1988]

Got a Wylex NN board installed in April 1990, at some point a bigger shower (Bristan Cheer 8.5kW) has been installed leaving the original NB30 Type 2 as a spare with an NB40 breaker being installed to run the larger shower.
The NB40 breaker keeps tripping, have established the breaker is the issue as trips at a lower level than it should (the shower is the correct size for an NB40 breaker).
As we know, these are obsolete, so eBay will need to be scoured for a replacement as no one else has any stock, tried TLC and the usual obsolete breaker sellers online. Is this a good idea, any idea how to ensure the breaker bought is OK?
Secondly the NB40 breaker is I think from a similar kind of source as the Type has rubbed off (see picture). What Type do I need to source to replace? Type 1 or Type 2?

 

[pc1966]

For a shower there is no surge current so either breaker type is fine.

However, type 2 has a higher "instantaneous" trip point (than type 1) and strictly speaking you should be checking that the cable & earth resistance is low enough for it to trip quickly enough for protection.

Short answer type 1 is safest bet for general replacement, but your board seems to be fitted with type 2 so presumably that was OK for the original installation.
[automerge]1585395647[/automerge]
Quick search shows this supplier. No idea how trustworthy, but they have one:

404 Not Found - Circuit Breakers Online | The place to find any mcb or rcbo that you need!

We specialise in the supply of all circuit breakers mcb's rcbo's and rccb's from very old to modern day circuit breakers.Brands stocked are mem eaton, square d, hager,mk elctric, wylex federal eletric and many more.

circuitbreakersonline.co.uk

 

[alb1988]

Sounds like Type 1 is the safer bet, not know the history or having any details of the install (apart from the date). Type 1 is also easier to find.
Is buying from eBay a good idea? Found this one which seems quite reassuring in their warranty terms.

WYLEX 40A Type 1 Single Pole M6 Circuit Breaker SP 40 Amp MCB~STOTZ KONTAKT~NB40 | eBay

WYLEX Single Pole Circuit Breaker (MCB). M6 - BS 3871. 40 Amp - Type 1. They are then assigned a uniqueidentification serial number for full traceability and warranty records. What Yor Electrical Will Do.

www.ebay.co.uk

 

[pc1966]

I suspect where ever you get one from it will be old/used so it is a bit of pot-luck.

However, more importantly is it is fitted correctly (connections clean and tight, but not too tight) and that you carefully observe it when first used to make sure nothing overheats. For example, check that flipping it really turns the shower on and off, and if you run the shower for, say, 10 minutes while observing the fusebox you don't see any signs of excessive heating, burning smells, etc

Some generally useful guidance can be seen here:

https://www.electricalsafetyfirst.org.uk/media/1258/consumer-unit-connections.pdf

 

[alb1988]

Fantastic. Thank you for the advice.