Do Wylex RCBO's fit as a replacement for NSB MCB's?

HappyHippyDad · Nov 1, 2022

I may well need to change all the MCB's for RCBO's in this board (see picture).

Do Wylex RCBO's fit in this board? It is currently fitted with NSB MCB's.

Also, Wylex seem to do a few different RCBO's. Do they all fit, especially the new compact range?

[ElectriciansForums.net] Do Wylex RCBO's fit as a replacement for NSB MCB's?

I'll expand a little on the problem. Customer goes away on holiday, power cut, RCD trips, fridge and freezer defrost.

My thoughts are that the combined earth leakage in the property from all the appliances being switched on at once (when the power comes back on) are tripping the RCD. I realise it could be some sort of Mains-bourne disturbance but I think that combined earth leakage is more likely.

WallaceP · Nov 1, 2022

I am not sure but at the cost and effort to replace all the rcbos I would look at just fitting a new board. I know wylex modules are a nightmare between all the different ranges

timhoward · Nov 1, 2022

In general my understanding is that NHX are compatible with older NSB devices.
This chart suggests that NHXS RCBO's would therefore also be compatible.

I also recently found this interesting snippet:
( WYLEX NHX Series MCB Technical Details - Free 2020 Guide - https://electrical-assistance.co.uk/wylex-nhx-mcb-sizes-specs/ )

westward10 · Nov 1, 2022

Email Wylex with the board part no that will say yes or no.

richy3333 · Nov 1, 2022

No they dont fit. I tried it. Stick a Fusebox CU in, will be much cheaper

newfutile · Nov 1, 2022

Contactum do not own wylex , electricum own both and voles as well.
i have asked wylex technical before and they replied as such:

No you would need the NSBS6-B/1 which are still available, you can’t mix match the NSB and NHX together on the same busbar, please note if the cat number of the consumer unit you have starts ‘NS’ and they are the very old style NSB MCB’s then the NSBS RCBO’s will not fit and there would be nothing now, if you have a unit where the cat no starts ‘NH’ then the NSBS6-B/1 will fit no problem.

telectrix · Nov 1, 2022

change the whole CU. keep the rip out for spares.

finally after a month in hospital i can acces laptop and have a screen that i can see that is not more ads than contentent. bliiis.

timhoward · Nov 1, 2022

I agree that changing the board is a far better idea.

Mainly out of academic interest....

newfutile said:
No you would need the NSBS6-B/1 which are still available, you can’t mix match the NSB and NHX together on the same busbar, please note if the cat number of the consumer unit you have starts ‘NS’ and they are the very old style NSB MCB’s then the NSBS RCBO’s will not fit and there would be nothing now, if you have a unit where the cat no starts ‘NH’ then the NSBS6-B/1 will fit no problem.

The board above is an "NH". Most questions on this topic are about putting RCBO's in older NS boards.
I think the opposite to normal has already happened, someone has loaded up an NH board with NSB devices, as per Wylex's comment above.
(You can even still get a metal front for that NH board to turn it into an NM806)

I have an email from Wylex somewhere clarifying that the NSB and NHX on same busbar thing is entirely about a slight dimension difference causing the lid to sit wrong and otherwise they are fine together. In reality I remember not being able to reproduce this.

richy3333 said:
No they dont fit. I tried it. Stick a Fusebox CU in, will be much cheaper

Are you sure that was an NH board you tried it in? I have the exact opposite memory. I could be wrong though!

Also note that TLC say this:

grumpyjohn01 · Nov 1, 2022

timhoward said:
In general my understanding is that NHX are compatible with older NSB devices.
This chart suggests that NHXS RCBO's would therefore also be compatible.

View attachment 103225

I also recently found this interesting snippet:
( WYLEX NHX Series MCB Technical Details - Free 2020 Guide - https://electrical-assistance.co.uk/wylex-nhx-mcb-sizes-specs/ )

View attachment 103226

Despite that chart which I have seen before, I have personally fitted dozens of boards in the mid 00's (so well before 2018) that had the 'cage' type busbar, I think , if memory serves, that they were special order populated boards for social housing projects.

grumpyjohn01 · Nov 1, 2022

There are definitely 2 types of RCBO available in the 'full height' format (confusingly iirc both with NHX part numbers. ) and only 1 fits the balcony busbars properly although the cover is then hard to fit as it is slightly mis aligned. The compact types definitely do not fit.
Go with what others say and fit a Fusebox!!

LewisM · Nov 1, 2022

You should fit a new Wylex one, I fitted one yesterday for the first time, I was really impressed with it good quality metal and the main switch with double screws are rcbos are extremely solid

Pretty Mouth · Nov 1, 2022

HappyHippyDad said:
I'll expand a little on the problem. Customer goes away on holiday, power cut, RCD trips, fridge and freezer defrost.

My thoughts are that the combined earth leakage in the property from all the appliances being switched on at once (when the power comes back on) are tripping the RCD. I realise it could be some sort of Mains-bourne disturbance but I think that combined earth leakage is more likely.

How does your customer know that a) there was a power cut and b) the RCD tripping coincided with it?

timhoward · Nov 1, 2022

I think before I started talking about changing the board, I'd be looking at a global IR L+N to E and a ramp test of the RCD to confirm current earth leakage level (or clamp meter).
It could be as simple as one outside light full of water.

Pretty Mouth · Nov 1, 2022

timhoward said:
I think before I started talking about changing the board, I'd be looking at a global IR L+N to E and a ramp test of the RCD to confirm current earth leakage level (or clamp meter).
It could be as simple as one outside light full of water.

I'd be looking for something like this too. Intentional earth leakage causing RCDs to trip is rare in domestic, at least in my experience. Outside lights full of water, on the other hand, I find a lot of these!

timhoward · Nov 1, 2022

LewisM said:
You should fit a new Wylex one, I fitted one yesterday for the first time, I was really impressed with it good quality metal and the main switch with double screws are rcbos are extremely solid

I like the quiet and subtle way you posted a picture containing a brand new AFDD without reference to it at all!

Do Wylex RCBO's fit as a replacement for NSB MCB's?

HappyHippyDad

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WallaceP

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timhoward

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westward10

richy3333

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newfutile

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telectrix

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timhoward

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grumpyjohn01

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grumpyjohn01

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LewisM

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Pretty Mouth

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timhoward

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Pretty Mouth

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timhoward

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