Another Shed Supply Question With A Twist

[Darrenm200]

Briwire,

If I wanted RCD protection at the house end I could of used the RCD side of the house CU but having done a bit of research on the forum the general concensus is to put the RCD protection at the shed end not at the house end. Judging by RF's reaction I guess I'm right.

In terms of using three core SWA it's not just about saving a few quid, it's more to do with the overall size of the cable and how much of a git it is to work with. Plus as the armour has the capacity to provide the CPC there is no real (official) need to have three core apart from a failsafe approach (in case the armour corodes, gets broken etc).

RF correct me if i'm wrong at any point.

RF as you've joined in the discussion what do you think to my original question??? All comments appreciated.

 

[holmslaw]

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[ban-all-sheds]

Curious to know why you think that's preferable. It will cost more, as another enclosure will be needed, and if you're in the shed and it trips you'll have to walk back to the house to reset it.

And if you don't use a separate RCD, but just come off an MCB on the RCD side of the main board then a fault in the shed will take out the house, and you may find that you have to go out to the shed to sort out a problem before you can get the house back on....

 

[holmslaw]

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[ban-all-sheds]

It gives a bit of extra protection to someone chopping into the cable.

The cable is armoured.

You speak as if tripping is a daiy occurrence, my exterior electrics are on a 30mA rcd in the house and it has'nt tripped in 20+ years - and yes it does work.

I could with as much justification say that you speak as if someone chopping through the cable is more likely than a leaky outdoor appliance.

If you really want to protect the cable as well then the right way to go is a 300-500mA time delay at the house end, and a normal 30mA in the shed.

 

[holmslaw]

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[plugwash]

putting in a time delay RCD to protect the cable seems like overkill to me.

The chances of the cable getting dug through should be pretty damn low and even if it is dug through the spade will hit the armour first causing a dead short when it hits the live and hence taking out the MCB.

 

[holmslaw]

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[ban-all-sheds]

I don't have any leaky outdoor appliances, the rest of your post is nonsense. First you say I don't need an rcd for the cable and then you say I should fit another one.

If you really want to protect the cable as well then the right way to go is a 300-500mA time delay at the house end, and a normal 30mA in the shed.

 

[holmslaw]

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[ban-all-sheds]

You don't need personal protection from chopping through a cable with earthed armour.

Tell me - have you, through all your time, been putting every circuit you install on an RCD?

People are far more likely to need that protection with cables in their houses than they are with buried armoured ones, so if you've not been RCD protecting everything then you have been operating completely illogically and with absolutely no understanding of priorities.

 

[plugwash]

the spade will hit the armour first causing a dead short when it hits the live and hence taking out the MCB.

Could just clip the side and go through swa and neutral.

It could, and you might end up with a N-E fault or a broken neutral, nothing immediately dangerous.

The important point is that you won't hit live without hitting earth first so your spade will not remain live.

 

[holmslaw]

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[RF Lighting]

[Well I'll tell you what we could do I'll cut half way through the cable swa and the neutral. I'll then invite you to chop through the cable between the fault position and the shed with your stainless steel spade. If your lucky the mcb might trip if your unlucky your dead.

I'm so certain it will still be safe, I'll quite happily be the spade holder.

I've never seen an MCB fail to operate under fault conditions.

 

[holmslaw]

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