RCBO's replacing MCB's

[Bud1975]

Hi guys,

I am quite new to all this and I have a number of questions running through my head. One of them being.....

Do most RCBO's fit into the space occupied by an MCB to enable that circuit to be RCD protected as I have seen posts to suggest this might be possible? (Of course this would be a much cheaper option than fitting a seperate RCD unit or even a new consumer unit)

 

[alanl]

Generally, yes.

 

[Bud1975]

Generally, yes.

So simply if a customer wants an addition etc to a circuit or circuits that does not have RCD protection then first (easiest) port of call is to see if an RCBO would replace the current MCB? (If the unit has MCB's that is)

Many thanks

 

[rodney12]

Yes that's correct

 

[Bud1975]

Yes that's correct

Thanks Rodney12 that's helpful to know. I presume it might be best to get the same make RCBO as the consumer units and MCB's to be sure of their compatbility though?

 

[rodney12]

Yeh if at all possible, otherwise you may have to take an MCB out and pop down to wholesalers with it to try and compare to one that will fit

 

[Bud1975]

Yeh if at all possible, otherwise you may have to take an MCB out and pop down to wholesalers with it to try and compare to one that will fit

Thanks mate

 

[white armour]

Hi Bud1975, be aware that most RCBOs are physically bigger that the MCB. Sometimes it is quite difficult to get the RCBO in due to the lack of space around the top of the consumer unit, also if there is a "rats nest" of cabling it is again difficult to get the RCBO into the space.

Regards wa

 

[Geordie Spark]

Hi Bud1975, be aware that most RCBOs are physically bigger that the MCB. Sometimes it is quite difficult to get the RCBO in due to the lack of space around the top of the consumer unit, also if there is a "rats nest" of cabling it is again difficult to get the RCBO into the space.

Regards wa

Yes, RCBOs tend to be taller than MCBs so you need to be sure that you have enough room at the top of the CU to get them in.

That said, there is at least one manufacturer who makes RCBOs the same size as MCBs - I think it's BG, but I'm not sure.

 

[Glen Stimson]

That said, there is at least one manufacturer who makes RCBOs the same size as MCBs - I think it's BG, but I'm not sure.

GE do aswell in B or C type

 

[white armour]

Also think Protek do a smaller type RCBO, have seen them advertised but not "in the flesh".

Regards wa

 

[GLENNSPARK]

Sector fit a volex board as will marbo (which are the same parent company as volex).........

 

[Bud1975]

Thanks for all your replies guys it is all helpful and gives me a really good point to start with.

I have just seen the following link.... Electrical Components Direct Ltd Compact RCBO Mini RCBO Circuit Breakers which shows a "compact mini RCBO" by ECD although one of the customer comments said he was suprised to see this was an MK product.

Anyone fitted a "mini RCBO"? The link states it's perfect for industrial work but how about domestic? Struggling to find other compact RCBO's at the moment so will keep looking.

Regards

 

[malcolmsanford]

White Armour is spot on. in an industrial 3 phase board you will have room to change your MCB to an RCBO, the only problems you normally face in this scenario is that the RCBO leads sometimes need extending.

I would normally in a domestic situation use the existing MCB in the CU to feed a small enclosure that would house the RCBO, this is piggy backed to the CU and then wire the new circuit, or altered circuit into the RCBO.

I havel ost account the number of times you waste time as WA says trying to get an RCBO into a CU that is 1 not designed for it 2 is chocka blocked

 

[Bud1975]

White Armour is spot on. in an industrial 3 phase board you will have room to change your MCB to an RCBO, the only problems you normally face in this scenario is that the RCBO leads sometimes need extending.

I would normally in a domestic situation use the existing MCB in the CU to feed a small enclosure that would house the RCBO, this is piggy backed to the CU and then wire the new circuit, or altered circuit into the RCBO.

I havel ost account the number of times you waste time as WA says trying to get an RCBO into a CU that is 1 not designed for it 2 is chocka blocked

Have you tried these new "compact mini" RCBO's? Would they fit better than a normal standard RCBO?

Also to piggyback the CU fed by the MCB would you fit an RCBO or just an RCD as the old MCB would give the overload protection wouldn't it? Sorry I'm quite new to all this and your adivse is very much appreciated.

 

[GLENNSPARK]

If you have a scenario lets say a new kitchen ring and the existing dis board is a bs3036 (a common scenario) then what you can do is to use a garage board with rcd and 2 ways 1 for the cooker and the other for the ring/radial for the points. You would typically wire this sub board of one of the fuses in the existing board this will give you rcd protection on any new work you have carried out and thus comply with the current edition of BS7671.......

 

[malcolmsanford]

If you have to be careful Glen doing that mate as some of the older BS 3036 boards are limited to just 30amps, so you may be overloading it.

Yes Bud1975 you could just use an RCD and the overload would be covered by the FUSE/MCB.

 

[GLENNSPARK]

If you have to be careful Glen doing that mate as some of the older BS 3036 boards are limited to just 30amps, so you may be overloading it.

Yes Bud1975 you could just use an RCD and the overload would be covered by the FUSE/MCB.

My boss uses a henley but i dont know: no overcurrent protection on the tails see........you cant just rely on the bullit can you.........

 

[malcolmsanford]

Well you can if your not exceeding 3 metres. Have a look at reg 433.3.1 (i) for overload as this will then (ii) will direct you to reg 434.2.1 regarding fault protection.

 

[GLENNSPARK]

Well you can if your not exceeding 3 metres. Have a look at reg 433.3.1 (i) for overload as this will then (ii) will direct you to reg 434.2.1 regarding fault protection.

Yes....with a few restrictions such as fire and/or explosion. thanks Malcolm.