Wylex NH range Consumer Unit RCD+4,RCD+4,MS+2

[macabethiel]

I have an old Wylex Consumer unit in my garage and the RCB is failing I know it is an issue on these units having replaced mine about 6 years ago.
The unit is obsolete so cant get a replacement RCB module.

I have bought a replacement unit that has Split Load and 2 seperate RCB units so if you get a trip it does not switch everything off.

As I have fish tanks in my Garage extension,pond pumps, freezers etc etc the twin RCB seemed a good idea.

I am a little mystified by the split load section on the consumer unit as it has a B6 30ma NHXSBSB06 connector with a pair of fly leads attached one is a thin white lead and the other is a purple-blueish lead.

I am hoping there are some electicians that can point me in the right direction as it is marked with live outgoing and neutral outgoing.

I have fitted about 6 consumer units over the last 25 years or so and am pretty competent but this modern unit is a new one for me.

Have we any electrician members who can just clarify this bit I guess its some sort of RCBO or similar.

From what I can make out the white lead is the earth connection and the Purpleishblue fly lead is for connecting to the neutral bar then the Live outgoing and Neutral outgoing can be used on my freezer supply or similar.
Presumably this having a white fly lead checks the earth continuity somehow?
A search on U tube etc has not shown me a similar unit.

No lectures please on my competence.LOL

[rayf3262]

Originally Posted by macabethiel

I am a little mystified by the split load section on the consumer unit as it has a B6 30ma NHXSBSB06 connector with a pair of fly leads attached one is a thin white lead and the other is a purple-blueish lead.

I am hoping there are some electicians that can point me in the right direction as it is marked with live outgoing and neutral outgoing.


Have we any electrician members who can just clarify this bit I guess its some sort of RCBO or similar.

From what I can make out the white lead is the earth connection and the Purpleishblue fly lead is for connecting to the neutral bar then the Live outgoing and Neutral outgoing can be used on my freezer supply or similar.
Presumably this having a white fly lead checks the earth continuity somehow?
A search on U tube etc has not shown me a similar unit.

No lectures please on my competence.LOL

Yes it is an RCBO.
The white wire is normally referred to as a "functional earth" an should be connected to the CPC bar in the CU.
The blue wire should be connected to the NON RCD neutral bar.

BTW the B6 RCBO is normally used in a split load CU for the smoke detector circuit.

[macabethiel]

So would it be okay for my freezer then or would I need a bigger one if its 30mA thats not much or is the B6 6 amps ?
I am quite happy to put the freezer on one of the RCB's

[rayf3262]

Originally Posted by macabethiel

So would it be okay for my freezer then or would I need a bigger one if its 30mA thats not much or is the B6 6 amps ?
I am quite happy to put the freezer on one of the RCB's

The 30mA RCCD trip rating is fine, but I would be cautious about the start current of the freezer compressor exceeding the inrush current rating of a B6 MCB. For the most part it may be ok, but caught on the peak of a 50HZ cycle it could just tip it over the edge. It's the uncertainty that's the issue here, you do not want to come home after a weekend away to a soggy mess!
I personally would not put a refrigeration compressor on anything less than a C6 or B10, or more likely a B16.
If you have 2.5mm cable to the freezer socket then its current rating (normally) will be 24A so the maximum size MCB/RCBO feeding that circuit could be 20A. Unless it is a ring final, in which case you can go to 32A.
If the cable is smaller then 2.5mm you should down size the breaker accordingly.

[macabethiel]

Thanks Rayf for your advice the seperate uprated RCBO units are quite pricey so I will probably do as I have done on my existing set up where I installed the consumer unit and have taken a parallel feed to the original garage consumer unit that had only two fused outlets and put the freezer on that with just a straight forward trip fuse.

I will not then bother with the RCBO unit or could I install a normal trip fuse in the slot using the neutral from the non RCB bar to avoid inbalnce problems? That way I could do away with the original consumer unit (an old MK unit).

[solarman216]

What Ray says, except if you have fish tanks and freezers in the garage I would run a non RCB supply to these only, any other sockets in the garage I would have protected as would be the pond pump, unless you have Carp in them in which case I would not, Rick

[solarman216]

Mac beat me to it, Rick

[rayf3262]

the cu you have is probably a high integrity unit, so will have 2 banks of RCCD protected and 2 additional circuits, in your case one of these has the 6A RCBO fitted.
If you have a single radial supply for the freezer there is nothing wrong with fitting a B16 MCB in place of this and running the freezer supply without RCCD protection.
It is quite common practice on refrigeration supplys due to the lottery of random RCCD trips. A B16 MCB should cost no more than 3 quid.
BUT do mark the socket as having no RCCD PROTECTION!

[solarman216]

I have to agree with that, Ray I will pm you, Rick

[macabethiel]

Thanks for your input guys that's put my mind at rest on the RCBO slot.

I use RCB protection on my Aquariums just for personal safety, to be honest if they do trip its not an issue as they are freshwater tropicals. The thermal capacity of the sytems are quite high so even 12 hours of no electricity causes no ills. I use sump filtration so the tank bit is okay as its the sump part that suffers from bacterial loss.

This years subscription is money well spent as usual !

Off to Majorca on Wednesday so will fit the new CU on my return with confidence.

[macabethiel]

Just a thank you to the guys who posted advice my unit is now fitted and fully functional.