Best Way to Add RCD Protection?

[macman81]

I have a Wylex NS1104 CU which was installed about 9 years ago. If I understand correctly, there is no built-in RCD protection on this model.
On that basis, I would like to add some RCD protection on the 4 power circuits (up, down, kitchen, cellar). These currently all seem to have 32A MCB's fitted-serial no. NSB32). Whats the best way of going about this-can I just fit Wylex 32A RCBO's as a straight swap for the MCB's, or is there a better way of doing it? Would it be better to put in-line RCD's on each circuit?
The rest of the system was rewired at the same time and is in good condition so I don't want to do anything too radical, but I feel the RCD protection is worth having.

 

[FingRinal]

I think Wylex RCBOs are Type C so overload protection would need to be verified. Also, changing the protective device raises the Part P spectre.

 

[luminaire]

I think Wylex RCBOs are Type C so overload protection would need to be verified. Also, changing the protective device raises the Part P spectre.

Wylex do both type B & C. So if you were wanting to change say a 32A MCB to a 32A RCBO it would be NSBS32-B1. Whereas a 'C' curve would just be NSBS32.
Hope that clears it up for you.

 

[RF Lighting]

Wylex do both type B & C.

Not according to their catalogue

 

[macman81]

Thanks for the advice, but I'm not clear on the difference between B type and C type though-please could someone explain this further? All my existing MCB's are (I think) B type, for example, serial no. NSB06 B6 on the lighting circuits.
On the subject of MCB's. I read another post which said that using C type MCB's on lighting circuits may lead to them tripping whenever a bulb blows. This happens on mine almost every time-not a problem, just inconvenient, but should I be using C type instead?

 

[JohnD]

C type are more resistant to tripping on a momentary surge.

however if you have a problem with blowing light bulbs causing tripping, change to energy saving bulbs (CFLs). As well as saving you money and lasting for years, they do not trip MCBs when they fail.

 

[macman81]

Thanks, so (physically speaking), B and C are interchangeable? I am changing to CFL's, just working my way round as the old ones fail.
Going back to my original query about RCBO's, so should I be looking to fit B or C type, given that my existing MCB's are B type?

 

[GaryMo]

Wylex do both type B & C.

Not according to their catalogue

I've installed Wylex Type B RCBO's though they're a real pig to get hold of.

 

[GaryMo]

I'm not clear on the difference between B type and C type though-please could someone explain this further?

Type B instantaneous trip between 3-5 x In
eg for a B20 between 60A and 100A

Type C instantaneous trip between 5-10 x In
eg for a C20 between 100A and 200A

Type D instantaneous trip between 10-20 x In
eg for a D20 between 200A and 400A

Big problem would be maximum permissible earth loop impedance for the circuits.

B20 would be 230/(20 x 5) = 2.3ohms (1.84ohms 80% corrected)
C20 would be 230/(20x10) = 1.15ohms (0.92ohms 80% corrected)
D20 would be 230/(20x20) = 0.575ohms (0.46ohms 80% corrected)

230v used as per BS7671:2008

 

[GaryMo]

Thanks, so (physically speaking), B and C are interchangeable? I am changing to CFL's, just working my way round as the old ones fail.
Going back to my original query about RCBO's, so should I be looking to fit B or C type, given that my existing MCB's are B type?

Yes they're interchangeable. It would be my preference to source a Type B.

 

[macman81]

Thanks, could I just get clarification on one more point? Are the Wylex RCBO's (part no. NSBS32/1) compatible with my Wylex NS consumer unit as well as the newer NH units? TLC's website says they fit both NH and NS, but when I asked them to confirm this, they said they couldn't tell me and referred me to Wylex...Wylex (rather vaguely) said they would not fit NS boards and I needed to use the 2 pole versions (NSBS32/2), however I can't do this as I want to convert 4 circuits and there isn't enough space on the CU.

 

[macman81]

Can anyone help on this one please?

 

[securespark]

Only to say ring Wylex again & double-check:

0161 998 5454 Ask for Wylex Technical.