Garage with some electrics in place

[happyhacker]

I have a garage with a CU with RCB (30Ma) lights and power circuits. It has an armoured cable going to the house CU to a 16A breaker on the MCB side. I think I should get this end connected to an RCBO of 16A and 100ma. Is that right?

PS I know that if a Freezer is connected in the garage there should not really be an RCB in the circuit. Is there a way of using one of the incoming cables (black or grey wire) to feed a power failure back to the house to warn power has gone? I was thinking this could be a neon which goes out or perhaps a buzzer.

 

[securespark]

There should not be a freezer in the garage. They are not to be used in such environments, unless they are rated for such low temperatures.

http://www.which.co.uk/home-and-garden/kitchen/guides/best-freezers-for-your-garage/

 

[ban-all-sheds]

I think I should get this end connected to an RCBO of 16A and 100ma. Is that right?

No - no point to having RCD protection at the house end.

Is there a way of using one of the incoming cables (black or grey wire) to feed a power failure back to the house to warn power has gone?

Is one of the cores not being used for the earth?

 

[happyhacker]

Cores for earth? Yes as I see that the sheath although will be clamped and earthed both ends, it may not be enough resistance to act as a fault earth under certain conditions so I will use one for earth and tie it to the sheath/earth bar. Is it usual to tie the earth wire of the cable to the earth bar(s) or the sheath clamp?

So, all I need at the house CU is a simple MCB unit or simpler, a armoured cable connector with a 2.5mm cable into the CU. At the moment the cable was "bodged" into the CU.

Freezer in the garage, not one there at the moment. Do Freezers have a "lowest environment" temp. then?

 

[PrenticeBoyofDerry]

If the cable supplying the feed to the garage CU is of SWA cable this cable does not need RCD protection, the circuits in the garage may well though.
If the cables in the garage are also mechanically protected they to will need no RCD protection.

The Metal sheath of the SWA should be connected to your earth busbar via an earth conductor at both ends main CU and garage, as also should one of the cores of the the SWA.
So what core colours have you on the SWA cable?
If there is no yellow/green core for earth connection and there is a spare core this should then marked up for identification with green/yellow PVC sleeve and terminated as previously mentioned.
But the other cores of the SWA should also be colour coded correctly to avoid confusion.

 

[ban-all-sheds]

Cores for earth? Yes

In which case

Is there a way of using one of the incoming cables (black or grey wire) to feed a power failure back to the house to warn power has gone?

no - you have no spare core to use.

as I see that the sheath although will be clamped and earthed both ends, it may not be enough resistance to act as a fault earth under certain conditions

"May not be enough resistance"?

AAF.

• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• //www.diynot.com/wiki/electrics:mcb2[/list]
  
  
  

  Is it usual to tie the earth wire of the cable to the earth bar(s) or the sheath clamp?

  //www.diynot.com/wiki/electrics:swa-gland
  
  
  

  So, all I need at the house CU is a simple MCB unit or simpler

  It's already got an MCB.
  
  When you say "or simpler", what do you have in mind?
  
  
  
  

  At the moment the cable was "bodged" into the CU.

  You may be best off getting an electrician. I've you've not worked with SWA before, and if space is limited and/or there's little cable to work with it could all go horribly wrong.
  
  
  

  Freezer in the garage, not one there at the moment. Do Freezers have a "lowest environment" temp. then?

  Why didn't you read the Which? article securespark linked to?

 

[happyhacker]

Thanks all.

OK, so as we are single phase I seem to have the option of tying black to earth (sleeved Y/G) and black to earth or neutral (sleeved appropriatly).

I see the appropriate glands are these but not utilised - don't ask me who fitted it, I don't know.

Yes there is an 16A MCB spare now. A standard 2.5 mm cable out to a metal box adjacent to the CU for terminating the armoured cable will be simpler. I was considering a double socket locally in my hallway fed by the same but of course that would space restrictions on the box (armoured cable + double socket squeezed in) and this is an MCB (and so would need to feed with a RCB in the CU). Keep it simple I think.

Is it acceptable to have long tails from the armoured cable termination box to the CU instead of running a separate 2.5mm short cable between them? I assume the tails would need "wrapping" in something.

I have now looked at all the suggested articles - thanks.

Is there somewhere I can check the csa of the cable as each wire has about 6 twisted strand overall a dia. of about 2mm?

 

[ban-all-sheds]

OK, so as we are single phase I seem to have the option of tying black to earth (sleeved Y/G) and black to earth or neutral (sleeved appropriatly).

Black to earth and black to earth or neutral?

Why do you have the "option" of doing any of those things?

The cable is already installed.

I have a garage with a CU with RCB (30Ma) lights and power circuits. It has an armoured cable going to the house CU to a 16A breaker on the MCB side.

And your repeated talk of "tying" cores to earth shows that you don't truly understand what's going on - please get an electrician.

Yes there is an 16A MCB spare now.

No there isn't.

I have a garage with a CU with RCB (30Ma) lights and power circuits. It has an armoured cable going to the house CU to a 16A breaker on the MCB side.

A standard 2.5 mm cable out to a metal box adjacent to the CU for terminating the armoured cable will be simpler. I was considering a double socket locally in my hallway fed by the same but of course that would space restrictions on the box (armoured cable + double socket squeezed in) and this is an MCB (and so would need to feed with a RCB in the CU). Keep it simple I think.

Is it acceptable to have long tails from the armoured cable termination box to the CU instead of running a separate 2.5mm short cable between them? I assume the tails would need "wrapping" in something.

Please get an electrician.

 

[happyhacker]

No. I shall research the job untill I've got it right then proceed within the rules. Thanks for your time. If I need to post again I will return.