Addition of small supplementary consumer unit

[Griffmaster]

Hi, could I ask for some advice please.

My main consumer unit has 2 banks of 8 MCB's (16 total) with an 80A RCCD for each bank.

My freezer is on one of the banks along with timed security lights, I have timed lights on both banks.

On a couple of ocassions when a lamp has popped, the RCCD for the bank along with the lamp MCB has tripped taking the freezer also.

Thought about fitting a supplementary garage CU for the freezer to overcome any future lamp popping issues.

Is this considered a reasonable idea and if so where best is the live feed for the supplementary CU to be taken from in the main CU?

Already have a garage type CU 63A RCD/1x16A MCB to hand.

Thanks.

 

[Lurch]

Is this considered a reasonable idea

Possibly. Depends on the existing board arrangement, it might be best to just shuffle the devices round and add an RCBO for the freezer circuit.

Whereabouts in Shropshire are you?

 

[Griffmaster]

Sorry Lurch should have read Staffordshire.

 

[Doc Hudson]

Lights blowing popping MCB's & RCD's?   It may be better to replace the security lamps with LED fittings.  Less power, longer life, if or when they do pop probably far less surge current at the point when they blow. less chance of MCB/RCD tripping.

DOC H.

 

[Griffmaster]

Lights blowing popping MCB's & RCD's?   It mat be better to replace the security lamps with LED fittings.  Less power, longer life, if or when they do pop probably far less surge current at the point when they blow. less chance of MCB/RCD tripping.

DOC H.

As I can be away for 2-3 weeks at a time, would that be as reliable as a separate CU for the freezer?

Some lamps are outdoor 300/500 watt halogens on PIR's.

 

[Doc Hudson]

As I can be away for 2-3 weeks at a time, would that be as reliable as a separate CU for the freezer?

Some lamps are outdoor 300/500 watt halogens on PIR's.

300 & 500watt halogens are an expensive waste of energy to produce light.  Most LEDs have lifespans quoted as 20,000 to 50,000 hours. So with 8760 hours in a year, even if left on 24/7, you should be able to go away for 2years without the lamps blowing. Probably something like a 40w or 50watt LED floodlight would give equivalent sufficient light. And cost you approx. 1/10th of the money per hour that they are on.

Doc H.

 

[NozSpark]

If you're away for 4 weeks at a time then I'd do both...

Reconfigure the CU to have the freezer circuit on a RCBO and replace the power hungry halogen fittings with LED equivalents

IIRC they're attempting to remove halogen lamps from sale in the next couple of years anyway

 

[Lurch]

I've been fitting a lot of LED outdoor lighting to replace halogen floodlights recently. I usually fit 10W for low level/general walkway lighting, 20W for something a bit higher up/bit more light required (patio etc). 50W fittings are good for lighting up the entire frontage/drive/garden/patio from the eaves in one go (assuming you source half decent fittings).

With the street lights being turned off in a lot of areas at night now I have had customers fit LED's so they can be left on all night so no PIR's needed, which is good as they can be a PITA.

 

[Griffmaster]

I like the idea of replacement of the outdoor light fittings with LEDs.

If at all possible, until I can get around to it, I have the vacant garage CU fitted close by to main CU and would like to use this )if I in the short term.

From pic, which would be the best terminal to pick up a live feed from for the garage CU?

 

[Murdoch]

Dare I suggest the one a proper spark does for you?

 

[ProDave]

That picture shows an 8 way board. Do I take it you have two separate 8 way boards then? Are all 8 used in both boards?

Fitting a new CU is not normally a DIY job, I really would not recommend it and personally would not give you a step by step guide how to do it. There is far to much that can go wrong if you don't properly understand what you are doing.

Post a picture of the other bank of 8 circuits please?
 

 

[Griffmaster]

Full picture.

 

[Lurch]

Fitting a new CU is not normally a DIY job, I really would not recommend it and personally would not give you a step by step guide how to do it. There is far to much that can go wrong if you don't properly understand what you are doing.

Concur. Re-arranging that board is the proper way to do the job and it is relatively simple, but not a DIY job. Trying to shove a garage unit in (properly) is no less work and isn't really the correct way of doing it (in this instance).

 

[Doc Hudson]

To answer your question. There are no best terminals in that board for you to pick up a supply from, as if you did I doubt the extended circuit would have adequate protection.

Additional observations. That would appear to be a split load board which could have been configured with some non-RCD, or RCBO protected circuits, but it has been configured with all circuits RCD protected for some reason? I have no major issues with DIY persons who feel competent doing minor DIY electrical alterations at their homes, change lights sockets etc. However any work involving adding, changing, replacing, reconfiguring equipment in and around the fuse box / consumer unit is not a DIY task. As most DIY users don't have access to £500+ worth of test equipment to do the essential earth loop impedance tests, RCD trip time tests, prospective short circuit tests etc. that are vital to ensure the amended installation can operate safely. Plus the current trend of ensuring correct torque on terminal screws and non-combustibility of fuse box enclosures.

Also, as you have already found out, your existing fuse box does not comply with regulation 314.1 which relates to division of the circuits on an installation. Basically you have too many circuits sharing a single RCD. I would think a competent electrician could come and reconfigure that existing board to put one or two RCBO's at the left hand end my the main switch. this would give you circuits that cannot trip off the rest of the installation. RCBO's will probably be approx. £35 +/- £5 dependent upon make.  And a local electrician should have it done within a couple of hours max, (assuming testing all goes correctly). Or may be cheaper than RCBO's. make first MCB non-RCD protected then mount a RCD spur adjacent to the box to protect that circuit. Either way I would not advise this as DIY work.

Doc H. 

 

[Lurch]

Also, as you have already found out, your existing fuse box does not comply with regulation 314.1 which relates to division of the circuits on an installation. Basically you have too many circuits sharing a single RCD.

I take it you didn't get down as far as the 2nd picture?

 

[Griffmaster]

OK thanks all.

Looks like the LED route quicker than I envisaged.

 

[Doc Hudson]

I take it you didn't get down as far as the 2nd picture?

You would be incorrect. One RCD protecting 8 MCB's another RCD protecting 10 MCB's (one blank unused). Still to many circuits sharing a single RCD's in my opinion. As is evident by the OP's original question, i.e. inconvenience when lighting fault takes out freezer circuit.  I was not suggesting the whole installation had a single RCD, merely to many per RCD.

Doc H.

 

[Lurch]

Oh. Not heard that before. Not saying you're wrong, but it depends on what you're doing with those circuits. I mean my house has 20 odd circuits, but a lot of them are radials with 1 or 2 sockets on and the outside lights are spread across 3 circuits. It would be absolutely fine with half that so I could just stick a 5+5 in and be done with it.

On a similar note I did a rewire the other year, large property, 2 double stacked boards (1 each end of the house) so 4 RCD's, each one had 8+ circuits, but again it was split so no circuit did more than a couple of rooms for convenience. Would have been fine with half the amount of circuits.

 

[Murdoch]

This is what I call too many circuits on 1 RCD (yes its a house!)



And yes they have nuisance tripping issues!

 

[Sidewinder]

I think that the interpretation of 314.1 can be very broad.

I think that Utopia is all RCBO's.

I think that a single up front RCD is asking for trouble  :innocent .

Don't ask me what my board is like @ home!!!

Murdoch, that install looks dire!