Any electricains out there?

[rtbcomp]

Hello MK,

why is that?

Alec

The closer to the supply you fit a protective device the more of the circuit it protects. In this case an RCD at the mains will trip if someone slices the underground cable with a spade. If the RCD was in the shed the cable wouldn't be protected and the guy with the shovel could be killed.

It can be a pain going into the house from the shed if it trips, so put a high trip-current RCD in the house with a more sensitive one in the shed, the latter should trip leaving the former untripped.

 

[rtbcomp]

Also I wouldn't wire the lights through the shed RCD. If it trips due to a fault the last thing you want is to plunged into darkness in a potential emergency situation.

 

[madkayaker]

As above.It is also for fire protection.

 

[piman]

Hello RTB,

yes, in theory but have you ever tried putting a spade through a cable? I am assuming a suitable cable adequately buried.

Incidentally on a similar frame, we came across a hatchet and evidence of a damaged (11Kv) cable when I worked in a copper mine in Zambia years ago (Cable and other theft being rife). No corpse though :-)

Alec

 

[madkayaker]

cables can be damaged by a spade if someone thinks its just hard soil. Worked in a steel mill in Rotherham and one of the old sparks told me of a buzz bar being nicked while stud on a plastic washing up boll

 

[Tractor Man]

Would it be best then to have a 40A 30ma RCD in the workshop and a 100A 100ma one in the house?

The cable is armoured, but as you say its not worth the risk if there is the slightest chance that someone could get hurt if it was cut!

I think I still need to further investigate the condensation issue (probably won't get a chance till the weekend ).

 

[madkayaker]

that would be the best configuration as there is disparity between the two RCD's and still good level of protection on the cable. 100mA is enough to kill (lowest recorded 35mA) A time delayed 30mA would give the protection but can cause nuisance tripping. AS its armor 100mA would be my first choice providing that the armarage is earthed well at both ends.

 

[Tractor Man]

Thanks MK

I think I will have to look into doing this.