Ring main help

[Mark.W]

Hi

I was wondering if someone could give me some guidance on a ring main please?
The ring consists of 21 CCTV columns drawing 5A each. The total length of the ring will be 1600m.

Is there a calculation I can use to calculate correct cable size and breaker rating?

Many Thanks
Mark

 

[telectrix]

you know the load so start with a cable that can handle that. then work out your csa from calculation. mV/A/m needs to be determined from Amps and length. then size cable accordingly.

 

[trev]

Insulting behaviour reproted. Incidentally, if you don't know how to design a circuit then you're in the wrong job mate. Anyway, enjoy the rest of your time here because I suspect it won't be long

 

[Mark.W]

Thanks telectrix

I know how to do cable calcs but it's working out the ringmain. I know the rule of thumb of 100ft per circuit incorporating sockets etc etc but never installed a ringmain of this size! Can't find anything in regs book either?!?

 

[Octopus]

1600 m circuit. Wow

 

[Sintra]

Thread cleaned up and reopened. Please keep all replies on topic and civil.

 

[Leesparkykent]

Is a ring final circuit the best way to approach this in the 1st place?

 

[bigdavs83]

A kilometre and a half!! Quite the circuit. Is it for a car park or a yard or similar?

 

[Leesparkykent]

Gone silent?

 

[davesparks]

Is a ring final circuit the best way to approach this in the 1st place?

Probably not, but a ring distribution (ringmain) circuit might be a sensible approach.
If the layout of the site is favourable then it might help with the ridiculous voltage drop.

 

[Leesparkykent]

Probably not, but a ring distribution (ringmain) circuit might be a sensible approach.
If the layout of the site is favourable then it might help with the ridiculous voltage drop.

well we may never know as the OP doesn't seem to be replying even though he's been logged on.

 

[davesparks]

Hi

I was wondering if someone could give me some guidance on a ring main please?
The ring consists of 21 CCTV columns drawing 5A each. The total length of the ring will be 1600m.

Is there a calculation I can use to calculate correct cable size and breaker rating?

Many Thanks
Mark

I tried to reply earlier but the thread was locked, apparently someone has been abusive or something?

The OCPD rating can be calculated the same as any other circuit, you work out Ib then select an appropriate OCPD. If it is a ringmain (distribution cct) you want then an HRC fuse might be a better idea than a circuit breaker.

Your cable size will almost certainly be dictated by the VD rather than the CCC of the cables. There is a formula in the regs somewhere for calculating the VD of a ring circuit.

 

[davesparks]

well we may never know as the OP doesn't seem to be replying even though he's been logged on.

I hope he does come back, I've played around with designing ring circuits like this before and it would be interesting to see other sensible opinions on this.

 

[Leesparkykent]

I hope he does come back, I've played around with designing ring circuits like this before and it would be interesting to see other sensible opinions on this.

Like you said if the layout is favourable then it could be beneficial.

 

[Sintra]

I tried to reply earlier but the thread was locked, apparently someone has been abusive or something?

The OCPD rating can be calculated the same as any other circuit, you work out Ib then select an appropriate OCPD. If it is a ringmain (distribution cct) you want then an HRC fuse might be a better idea than a circuit breaker.

Your cable size will almost certainly be dictated by the VD rather than the CCC of the cables. There is a formula in the regs somewhere for calculating the VD of a ring circuit.

Formula for VD on a ring is
mV/A/M x ib x L / 1000 / 4