replacement CU

[ajrobb]

Untitled

• ajrobb
• 25 Apr 2010
• 2

As part of a refurbishment, I'm about to replace this BS3036 fusebox with a CU. There are currently 5 circuits in the 6 slots:

• spare
  5A 1.5mm² downstairs lighting radial
  5A 1.5mm² upstairs lighting (probably radial)
  15A 2.5mm² radial (formerly for immersion heater)
  30A 2.5mm² ring
  30A 10mm² cooker point

I've got the electricity board coming on Friday to fit an isolator switch and the LABC coming next week for Part P pre-work. He wants the new CU installed before he comes.

The bottom fusebox is not connected to the mains and I'll be removing that, along with the wiring for 2 storage heaters.

I'll be removing the ring main from arm's length of the kitchen sink and using the 2.5mm² radial for spur isolator switches to

• cooker hood concealed socket
  gas igniter concealed socket
  washing machine concealed socket
  combination boiler fused spur

This leaves the main ring powering sockets on the other side of a 2.5m wide kitchen and a new socket on the other end wall, over 2m away from the sink.

As you can see, space inside the meter cupboard is a bit limited. The cheapest/simplest replacement appears to be a 6-slot CU with a single 30mA RCD/isolator and 5 MCBs. It looks like these would be rated at 6A for each lighting circuit, 20A for the radial and 32A for the ring. Should I use a 40A MCB for the 10mm² cooker point radial?

Ultimately, it is down to the LABC to accept whatever I put in. However, I would appreciate comments and suggestions.

 

[Lectrician]

To correctly comply with the regs, you cannot use a CU with a single 30mA RCD.

 

[martinxxxxxx]

Better off using 6 RCBOs and a main switch version.

Or better still re-site the unite where it has more space so you can fit a CU that has room to add more ways in the future.

What is the point of doing only half the job?

Martin.

I have an tale of one mis-selling on one of these if anyone is interested. Big co involved.

 

[davelx]

To correctly comply with the regs, you cannot use a CU with a single 30mA RCD.

To correctly comply with BS7671:2008 (aka 17th), yes. But there is no requirement for the OP to comply with the 17th, or indeed any other edition of the regs. The only requirement for him to get his BR completion certificate is for his LABC to be satisfied that he has complied with part P1 of the BR.

Before the 17th was published, 16th edition installations complied with P1. The publishing of the 17th doesn't suddenly make 16th edition installations non-compliant, and as long as his LABC is happy that what he is doing complies with part P1 that is all that is needed.

That being said, if I was doing the job I'd go with martinxxxxxx's suggestion.

 

[ajrobb]

I have found a local supplier with:

• £19.80 Wylex 5-way insulated board with 100 amp switch
  £21.60 Wylex C type 6A RCBO for lighting radial
  £21.60 Wylex C type 6A RCBO for lighting radial
  £21.60 Wylex C type 20A RCBO for kitchen radial
  £21.60 Wylex C type 32A RCBO for socket ring
  £21.60 Wylex C type 40A RCBO for cooker radial

The RCBOs are from their 'extended' range, so I will have to pre-order.

This is a LOT more expensive than a single RCD+5xMCB, but I can see it is a MUCH better solution. I have spoken with an electrician who worked on the original build. He said he struggled to get the cables up the wall into the ceiling plenum. So, I don't fancy trying to move the CU with the cable protection plate and plaster in place.

 

[OwainDIYer]

As you can see, space inside the meter cupboard is a bit limited.

You can stack some CUs vertically with a stacking/linking kit, so you could have 6+6 giving you 12 modules, enough for mainswitch, RCDs and circuits.

Depends on the property but I would always allow spares for electric cooker and shower at least, a future occupant might want them even if you don't.

 

[sergeantash]

Untitled

• ajrobb
• 25 Apr 2010
• 2

I've got the electricity board coming on Friday to fit an isolator switch

Out of curiosity, I assume you have to pay for this if an isolator switch isn't already in situ? If so how much?

 

[bongos]

The RCBOs are from their 'extended' range, so I will have to pre-order.

Order B type RCBOs, not C type. Unless you have alot of high inrush current items like welders and fluoresecent lights all over the place.

This is a LOT more expensive than a single RCD+5xMCB, but I can see it is a MUCH better solution.

More expensive yes but the best solution. Good choice sir!

OOI - are your LABC doing the testing as required for this CU change or are they making you pay additional ca$h (incorrectly) to get someone else to do it?

 

[bongos]

Out of curiosity, I assume you have to pay for this if an isolator switch isn't already in situ? If so how much?

That depends sarge. Some companies will fit it FOC, others want you to pay through the nose. There doens't really seem to be any set level. But I understand a cup of tea and some biscuits can help when they come round...

 

[sergeantash]

Out of curiosity, I assume you have to pay for this if an isolator switch isn't already in situ? If so how much?

That depends sarge. Some companies will fit it FOC, others want you to pay through the nose. There doens't really seem to be any set level. But I understand a cup of tea and some biscuits can help when they come round...

cool thanks mate

 

[ajrobb]

OOI - are your LABC doing the testing as required for this CU change or are they making you pay additional ca$h (incorrectly) to get someone else to do it?

The LABC says they will have to get an electrician in to test the completed work. I have read that in 2006(?) Part P was clarified that it is at the expense of the LA. I have paid over £170 as a notification fee.

Order B type RCBOs, not C type. Unless you have a lot of high inrush current items like welders and fluorescent lights all over the place.

They only offered type C with the Wylex CU. The circuits are quite short, so I hope that type C will trip OK.

Out of curiosity, I assume you have to pay for this if an isolator switch isn't already in situ? If so how much?

Southern Gas are charging £43.50

As you can see, space inside the meter cupboard is a bit limited.

You can stack some CUs vertically with a stacking/linking kit, so you could have 6+6 giving you 12 modules, enough for mainswitch, RCDs and circuits.

Depends on the property but I would always allow spares for electric cooker and shower at least, a future occupant might want them even if you don't.

I get your point, but I don't want tenants adding circuits willy-nilly. It already includes a cooker point, so they have a choice or gas or electric cooker. I am fitting a combination boiler and thermostatic shower, which provides more flow than an electric shower.

 

[garethpa]

try this consumer unit for size

http://cpc.farnell.com/pro-elec/acu10m/consumer-unit-10-way-with-isolator/dp/PL10668

The rcbos are dead cheap too... e.g.:

http://cpc.farnell.com/pro-elec/aub1r-32a/rcbo-single-pole-32a/dp/PL10658


However, you can get them cheaper by adding '10' to the product code in the search box as they are currently on offer.

 

[bongos]

The LABC says they will have to get an electrician in to test the completed work. I have read that in 2006(?) Part P was clarified that it is at the expense of the LA. I have paid over £170 as a notification fee.

An LABC doing what they should! How refreshing.

 

[Steve]

try this consumer unit for size

http://cpc.farnell.com/pro-elec/acu10m/consumer-unit-10-way-with-isolator/dp/PL10668

The rcbos are dead cheap too... e.g.:

http://cpc.farnell.com/pro-elec/aub1r-32a/rcbo-single-pole-32a/dp/PL10658


However, you can get them cheaper by adding '10' to the product code in the search box as they are currently on offer.

Thats real quality stuff mate.

 

[garethpa]

Thats real quality stuff mate.

Have you used it?