consumer board query

[Deansplit]

I need to replace my x3 old 'fuse holding style' consumer boards for modern trip style, but noticed a couple of things while researching them:

1. Why do they come pre loaded with various MCB's? Surely it's best to add whatever amperage you require as there will otherwise be some which are not required, and have to replace with others of different rating? Mine for example is made up of 3 boards - No 1 has 4x5a, 4x30a, 1x32a, No2 has 5x30a, No3 has 6x5a, 1x30a. I'm hoping to combine 1 & 2 into one 15 way boards as they're next to each other so would be neater, but all the 15way board I've looked at don't obviously cater for my circuits!

2. Have the ratings changed? eg. why 6a & 32a - is this what you'd use for a 5a light & 30a ring main circuit?

Thx

 

[ericmark]

Yes the 5A has been replaced with 6A and 30A with 32A the point is to work out sizes required we have to look at three main things.

1) Current carrying capacity of cable in the way it is routed.
2) Loop impedance of cable at the worst point.
3) Current requirement of items on the circuit.

Clearly even if cable able to handle 20A if all it does is feed an immersion heater then 16A is ample.

In the main existing fuse gives a good indication as to size for new MCB. Where items for example a ceiling rose which is rated at 5A are used as a junction box on the circuit we should not in theroy exceed 5A but in practice to raise it to 6A does not really cause a problem.

But the loop impedance is more of a problem. With the fuse if the impedance was a little on the high side it may not technically comply but extending the trip time from 0.4 seconds to 0.5 seconds was unlikely to cause a problem in the grand scheme of things. However with the MCB going just a little over makes a huge difference jumping from 0.01 seconds to 15 seconds as one exceeds the threshold at which the magnetic part of the trip operates. So step 1 has to be to measure the loop impedance.

As to pre-loaded it depends where you buy it from. Firms like screwfix will have a set selection but many electrical whole sale outlets will provide what you require. However be aware they will likely just be slotted into place and you need to check all terminals are torqued to correct setting.

The 314.1 Every installation shall be divided into circuits, as necessary, to: (iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation. Does cause some problems with larger boards. All RCBO is expensive but just two RCD's for 21 MCB's could hardly be considered as complying. A double hight unit with 4 RCD's may be considered as complying but likely one would want at least some circuits with RCBO protection.

Because of these problems selecting the most appropriate method the changing of consumer units requires LABC notification and their charges mean even if you did have the meters required to do all the testing likely it would still be cheaper not to DIY.

 

[plugwash]

I need to replace my x3 old 'fuse holding style' consumer boards for modern trip style, but noticed a couple of things while researching them:

[qupte]1. Why do they come pre loaded with various MCB's? Surely it's best to add whatever amperage you require as there will otherwise be some which are not required, and have to replace with others of different rating?

You can buy them non-loaded if you want, it's just you tend to see deals on the fully loaded ones. I guess selling a complete CU is less hassle than selling an empty CU and a load of breakers seperately.

Plus domestic installs tend to have a fairly similar mix of circuits so you will most likely only have to replace a couple of breakers (if any) when using a fully loaded CU.

2. Have the ratings changed? eg. why 6a & 32a - is this what you'd use for a 5a light & 30a ring main circuit?

Yeah the ratings for MCBs changed slightly with european harmonisation. Fuses which are not harmonised kept the old ratings but it's unusual to use fuses in a domestic CU nowadays.

P.S. You also need to consider what you are going to do about RCD protection.

 

[ban-all-sheds]

I need to replace my x3 old 'fuse holding style' consumer boards for modern trip style,

You can't possibly do this yourself, so why not let your electrician worry about whether it's cheaper to buy CUs and breakers separately, or bundled deals and make changes?

Sure you can tell him how many circuits you want, and whether you want all RCBOs or not, etc, but the actual sourcing of the equipment would be best left to him - it'll be cheaper that way anyway.

 

[PrenticeBoyofDerry]

You can buy them fully loaded if it suits, but you can also buy a variety of boards without the MCB, to configure the way that suits you best.
Here is a link to an unloaded split board, that could suit your purpose.
http://www.tlc-direct.co.uk/Products/CPDS168P.html
You could also go done the full RCBO route if you wanted.

 

[john4703]

You can't possibly do this yourself, so why not let your electrician worry about whether it's cheaper to buy CUs and breakers separately, or bundled deals and make changes?

Why can't he do it himself. If we accept that he owns the house then why should anyone tell him that he needs to pay someone else to do this work? If he can do it himself then why not?

 

[EFLImpudence]

Why can't he do it himself. If we accept that he owns the house then why should anyone tell him that he needs to pay someone else to do this work? If he can do it himself then why not?

Do you know Deansplit has the necessary test equipment without which it is not possible to comply with Part P and therefore illegal.

 

[RF Lighting]

I'm all for DIY, but replacing a consumer unit is NOT a DIY job. Never has been, never will be.

 

[ban-all-sheds]

Why can't he do it himself.

Read his body of work on this forum and tell us you still think he's up for replacing a CU.

If we accept that he owns the house then why should anyone tell him that he needs to pay someone else to do this work?

Property ownership does not grant exemption from laws which apply to activities regarding the property.

If he can do it himself then why not?

If he can then he may.

I do not believe that he can.

 

[scousespark]

The first post in this thread would indicate he would be out of his depth.

Given there are 3 separate boards, I suggest you get an electrician in and ask him/her for an EICR. This will tell you if any work is required on any of your circuits. The alternative is to wait until the new board is fitted and deal with the fallout when circuits no longer work.

 

[kevindgas]

with 3 boards first thing i would be questioning is why? has a bodge up been done before or is one an economy 7 or 10 supplied board? like already sugggested an EICR would be the only sensible route to be sure what is already existing and how safe it actually is!

just this morning i went to do an EICR. only 5 circuits - 2 had overrated MCB's, 1 socket was broken , the heat alarm in the kitchen was missing! and the wiring in the CU was best described as multi colour spaghetti! so never assume anything is safe!

 

[kevindgas]

You can buy them fully loaded if it suits, but you can also buy a variety of boards without the MCB, to configure the way that suits you best.
Here is a link to an unloaded split board, that could suit your purpose.
http://www.tlc-direct.co.uk/Products/CPDS168P.html
You could also go done the full RCBO route if you wanted.

£92 all in is not bad for 16 way board with MCB's to suit

 

[PrenticeBoyofDerry]

£92 all in is not bad for 16 way board with MCB's to suit

It's a little bit more as TLC prices are excluding VAT and there will be a delivery charge, but still a VFM board at about £114.00

 

[kevindgas]

£92 to me as Vat registered