View the thread, titled "Type B and C RCBO's together?" which is posted in Periodic Inspection Reporting & Certification on Electricians Forums.

Hello,

After feeling pleased with myself for installing and testing a new CU ready for my NICEIC inspection, I noticed that one of the RCBO's I bought is a type B where the other circuits are type C, the circuits are:

Heating - 16A type B RCBO
Ring main - 32a type C RCBO
Cooker - 40A type C RCBO
I have another radial circuit which is a socket on a 16A type C RCBO as it is only used for a tumble dryer.

A pretty dumb oversight I know, my question is will I have to replace the type B to match? I read a thread which said most RCBO's are type C and acceptable for domestics and all the readings and tests are within regs, normally I would just buy another one but this inspection is costing a small fortune and if I can get away without changing it then that would be great.
 
Hi,

The ring main is 0.50ohm max is 0.58 for a 32A.
cooker is 0.33 compared with a max of 0.46 for a 40A
other 16A radial is 0.26 max 1.16 (really short leg)

I have checked OSG page 103 Table 2d for above. Is this ok?
 
looks OK to me. possible change just one C type to B type on the ring as the reading is close to the max.
 
what earthing do you have tt tns tncs then have a look in the osg pages 44 -51 hope this help i would hate you to have a revisit
 
If it is your place just say you put the C type in because you are thinking of upgrading the cooker to one with an induction hob and you know that you will need one then.
You might even score some brownie points for showing your knowledge and planning ahead;)

edit: didn't read your first post properly initially thought you had just put a C type on the cooker. Although you can get away with the C's the mcb's at least are recommended for general use in commercial and industrial installations. For the sake of the extra cash i would switch them to B's would be my feeling - you can always keep them for future use and it will save you answering awkward questions on your assessment.
 
Last edited by a moderator:
fair point! and for the purposes of an assesment it is best to not have anything for an assesor to flag up. In reality the RCBO or RCD will break well within the max disconnection time regardless of the Zs being a tad high.
 

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Type B and C RCBO's together?
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