Garden office electrics

[crappy]

I believe I know where they are getting in. It's a converted barn shed, wooden clad, and there is a strip between the brick wall (it's a foot or so high) and where the cladding starts - it's got some gaps in it.

Agreed, I will invest in more traps as it is a bit swifter on the poor things trying to eek an exitance...like us all

 

[flameport]

a table which said clipped was 65.

That only applies if the cable conductors are operating at 90C. That wont be the case in any domestic installation.

 

[crappy]

That only applies if the cable conductors are operating at 90C. That wont be the case in any domestic installation.

gotcha.

 

[John D v2.0]

Your other problem with circuit protection would be you would need to check the impedance of the earth fault loop and make sure it would trip quickly enough if there was a fault at the shed end of the cable.
Maybe 32A was the most that would trip quick enough. If it's a B32 you don't have much more than 1 ohm and that a third of that can be taken up by the supply.

 

[crappy]

Sorry John, I don't follow.

 

[Taylortwocities]

Sorry John, I don't follow.

Which is why you need an electrician before you go swopping circuit protection devices!

So from an RC point of view, there are two in the circuit

that is bad design. When there is a fault in the outbuilding, there is no guarantee which RCD will trip. Or it could be both.
If the RCD in the house is protecting other circuits then they too will lose power. You know, the freezer full of food, etc…

 

[John D v2.0]

Sorry John, I don't follow.

Basically if a cable is too long, a bigger circuit breaker would not trip in time, or maybe even at all.
Supposing you had a fault on the cable and 160A are flowing, a 32A mcb would trip in a fraction of a second, however with a 63A mcb it would trip after a long period of time and that could easily start a fire or shock someone.
Volt drop and current carrying capacity is not the only consideration.

 

[crappy]

Which is why you need an electrician before you go swopping circuit protection devices!

An incredibly valid point.
I'm a very competent DIY (more so at electronics) but clearly folk like yourself and John who are forced to keep up with the regs do need to step in and a) put me in my place b) charge me for said service.

I do these things because I enjoy it but if I ever end up hurting someone - my kids.... - I'd be looking for a rope and beam.

 

[crappy]

Basically if a cable is too long, a bigger circuit breaker would not trip in time, or maybe even at all.
Supposing you had a fault on the cable and 160A are flowing, a 32A mcb would trip in a fraction of a second, however with a 63A mcb it would trip after a long period of time and that could easily start a fire or shock someone.
Volt drop and current carrying capacity is not the only consideration.

Thank you. I'll leave it as is for now, if it becomes a problem I'll get a pro in.