Adding lighting to Garden shed

[Seamus Mcloughlin]

Hi All, I'd like to wire a garden shed for a flouscent light (with switch) a nd I'm wondering what is the best approach, the principle here is I DO NOT want to drill holes out through my house walls from my distribution cabinet . Between my house and my garden shed is a smaller outdoor "structure" hous ing my oil fired burner, it additionally is housing the powered relay circu its for hot water and heating zones (control panel is inside house), power for oil burner initiator and finally powered control panel fo bio-treatment system. While I've not investigated as of writing this post I'm expecting these are runnning off an MCD from the Dist. cabinet in the house. Ideally I'd like to run a spur from an electrical connection in this "boiler house" via reinforced / outdoor cable to the garden shed to po wer the lighing. I understand I'd need to be using IP54 for this job but wo uld I need something like

Is it a bad idea using a spur to feed such a dist. box. ?? Is it a bad idea to "daisy chain" one MCD (feeding boiler house power) wit h another MCD (feeding lighting power to garden shed)

Even thought I'm not a qualified electrician (I'm an electronic engineer), I've worked with other electrical projects in the house (simpler) but I'm n ot sure of the potential pitfalls here ( and of course regulations).

Regards

Seamus

[Tim Watts]

On Thursday 24 October 2013 15:08 Seamus Mcloughlin wrote in uk.d-i-y:

You are introducing another element of risk (run of damp extreior cable and damp accessories) onto a critical (heating) circuit. ie probability of tripping out the heating goes up a non insignificant amount.

[John Rumm]

For the avoidance of doubt, it might help to clarify terms here... I am not familiar with MCD - I suspect you probably mean Miniature Circuit Breaker (MCB) rather than Residual Current Device (RCD) - but it would be handy to know.

It may or may not need to be IP54 - depends on how dry the boiler house is. You may or may not need an additional RCD in the unit, depending on what is feeding the supply to the boiler shed.

How do you plan to take the cable to the shed? If it is to be beried in a trench, then you will need to use Steel Wire Armoured (SWA) cable:

That needs terminating at suitable glands:

Daisy chaining MCBs is fine, but RCDs is usually pointless in most cases.

What you should try to avoid is allowing the addition of a new circuit making nuisance trips of the old circuit more likely - since it sounds like a damp light fitting in the shed could then leave you without heating in the house.

Its a sensible question to ask since wiring outdoor circuits carries more complications and nuance than interior work. You might find it helpful to have a read through:

and then come back with specific questions.