2 jobs and 2 queries?

[Becko]

Hi Guys,

Two of the jobs I have on at the moment are causing me a bit of a conundrum on how to resolve them, so I thought I'd drop them on here to get your thoughts....

Job 1. I'm moving an 80a 17th edition DB 7m away from suppliers isolator, what size cable, can't find it in the regs? I'm thinking 16mm with separate 16mm CPC.

Job 2. I have 8 floodlights with 1000w lamps in (so 8000w total load). Fed by C50 MCB onto 16mm SWA, dropping down to 6mm at the columns. The impedence readings start off at 0.91ohms and get progressively worse along the 200m run to 1.25ohms. Any suggestions on how to resolve this without digging in a new SWA? RCD at each post maybe?

 

[SirKit Breaker]

Q1. Install 25mm tails and 16mm earth. Also fit a 60a switchfuse within 3 meters of the cutout to comply with DNO requirements
Q2, Check all the connections to make sure they are all tight and clean before getting in too deep. You dont say how long the cable run is which would help.

Cheers...........Howard

 

[Engineer54]

Q2, Check all the connections to make sure they are all tight and clean before getting in too deep. You dont say how long the cable run is which would help.

Cheers...........Howard

Errrr!!.... i think you'll find he said ''along the 200m run''

 

[IQ Electrical]

I think you're probably stuck with adding RCD protection to the circuit.

Even a BS88 40A at 5 second disconnection has an 80% value of only 1.08 Ohms.

Your C 50 comes in at an 80% value of 0.37 Ohms.

 

[SirKit Breaker]

Errrr!!.... i think you'll find he said ''along the 200m run''

So he did.