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Discuss Garage Re-wire, Need to pick some brains! in the Industrial Electrician Talk area at ElectriciansForums.net

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Blue2Bits

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I am just in the process of a new re-wire for a family friend in her garage. She has in the house a consumer unit with a 32A MCB with 4mm twin & earth cable feeding the garage. In the garage I have installed a radial circuit with three double socket outlets which I am thinking of backing up with a 20A MCB. Then also a twin tube fluorescent (100 watts max) obviously backed up with a 6A MCB. The radial is wired in 2.5mm twin & earth, with the lighting circuit in 1.5mm twin & earth. How would I terminate the incoming 4mm cable. Do I use a consumer unit box or just a 2 way inclosure?
No cowboy, recently qualified electrician except inspection & testing.

Many thanks
:confused:
 
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12345aob

  • Thread Starter Thread Starter
  • #2
what about rcd protction? and how you gona cert it? what quals you got?
 
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Blue2Bits

  • Thread Starter Thread Starter
  • #3
Hi

2330 Levels 1,2 & 3 & 16th edition. There is an RCD on the main consumer unit in the house. Also my electrical manager at work will pop round to do all the relevant testing and certificates.

Many Thanks
 
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uksel

  • Thread Starter Thread Starter
  • #5
would you not use a 16A breaker for the radial buddy?
 
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adamh

  • Thread Starter Thread Starter
  • #6
either go straight into the board or get a rotary isolator to go into 1st and yeh i would agree with the 2way garage unit rcd main switch

have you worked out the drop?
 
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uksel

  • Thread Starter Thread Starter
  • #7
he's got a 4mm tw+e cable, so he can run the cable for a maximum of 34.9 Metres and a load of no more than 25Amps/5999Watts

in this circumstance there will be a 4% (or 9 volts) drop along the run for the supply
 
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adamh

  • Thread Starter Thread Starter
  • #8
so his 32amp breaker at the first db is overated?
 
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uksel

  • Thread Starter Thread Starter
  • #9
ah, oui monsieur! tres bien,

put a 25A breaker in...
 
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Blue2Bits

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  • #10
Cheers for all your help men.

Managed to source a Siemens consumer unit from one of the lads at work. Will have two 16A radial Circuits, one on a single socket outlet for the dryer (2650 watts) and the other for just a standard radial circuit. Then I am thinking of two 6A mcbs for the lights. Flood lights to take into consideration, as well as the internal light (120 watts) max. Somebody has commented on my 32A breaker which feeds the garage. If I change the 4mm T&E to 6mm would I be able to keep my 32A mcb? And also if the house consumer unit has a main RCD I thought you couldn't install two RCD's in one circuit?

Many Thanks agin
 
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uksel

  • Thread Starter Thread Starter
  • #11
if you up the cable you're covered for at least 23 metres according to table 7.1 in the on site guide (16th edition i'm afraid), and depending on your readings for Zs and the house earthing arrangements you could go up to 39 metres.

i'm of the belief that you can install two RCD's in one circuit, though you should apply positive discrimination, ie. following an RCD with 30mA sensitivity with an RCD that has 10mA sensitivity, or 100mA followed by 30mA is advised. or if there is some distance between the circuits (resulting in a higher earth fault loop path or feeding circuits outside the equipotential zone) then you can add an RCD to ensure you have a tripping time of less than 0.4 seconds for your sockets.
 
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