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

 

[Mark.W]

Hi guys, sorry for my outburst earlier! It is not like me to do that at all! The layout is favourable, it runs round the perimeter of a solar park

 

[Darkwood]

Something sounds so wrong here..

What voltage are the cctv running on?
Is 5amp at a SELV or does each column have a mains as in the ring you are supplying.
What is demanding this 5Amps - surely all columns cannot be demnding this at the same time ....

Lots more info please

 

[tazz]

Most external cctv are suppied with 230v, then selved down to 12v 2amps (aprox 30w)......therefore your mains supply in is in mA not amps.

 

[DPG]

Agree with Tazz, I bet the OP has listed the DC current consumption rather than the AC supply consumption. Daz

 

[telectrix]

if he has then it will be the most over specced rfc ever. just imagine a few cctv cameras powered by a 95mm rfc.

 

[Mark.W]

Sorry guys the info I've been given from Smart Integrated is that the require a 5A supply to each column. I will try and get all the required info to you rather than cause all this confusion

 

[dean.diy]

should be fun squeezing the 95mm cable into a junction box from the Celestial Kingdom. Have to say this, not everyone who comes on knows everything about everything. Maybe they do but just looking for friendly confirmation.

 

[davesparks]

should be fun squeezing the 95mm cable into a junction box from the Celestial Kingdom. .

Not sure what you mean here? Why would you terminate the 95 in to a joint box? It would either be breach jointed for each column and brought up to a cutout in a smaller cable, or if there is space each 95 could be brought into the column and terminated in to a cutout.

 

[Engineer54]

I'm not quite understanding why you would connect all these CCTV column's to a single circuit, especially when that single circuit is going to be 1600 metres long by having to follow the perimeter fencing . The other drawback would be, if you lose power to that circuit, (for whatever reason) you've lost every perimeter security CCTV camera on the project... A bad design all round to my mind. I would have thought at least 4 circuits, that ''don't'' follow the whole perimeter to get to the section that each circuit is supplying...

 

[ian.settle1]

I'm not quite understanding why you would connect all these CCTV column's to a single circuit, especially when that single circuit is going to be 1600 metres long by having to follow the perimeter fencing . The other drawback would be, if you lose power to that circuit, (for whatever reason) you've lost every perimeter security CCTV camera on the project... A bad design all round to my mind. I would have thought at least 4 circuits, that ''don't'' follow the whole perimeter to get to the section that each circuit is supplying...

Or if there are local buildings near each camera supply them from them

 

[Marvo]

Most external cctv are suppied with 230v, then selved down to 12v 2amps (aprox 30w)......therefore your mains supply in is in mA not amps.

........I bet the OP has listed the DC current consumption rather than the AC supply consumption. Daz

....the info I've been given from Smart Integrated is that the require a 5A supply

They've probably stated a 5 Amp supply as a generic requirement because this is the smallest circuit you'd normally run as a final circuit. Find the actual real-life consumption of the cameras and work from that, preferably actually go to a site where there are some working and measure the running current for half an hour using a clamp meter with a max-hold facility. Once you've established the real current requirement work out you're cable size from that. I'm betting if the layout is conducive to installing a ring final then you'll probably get away with a 6mm cable.

I think your real problem is going to working out an over-current protection scheme that meets the fault disconnect times required.

 

[GB.Kayak]

I'm not quite understanding why you would connect all these CCTV column's to a single circuit, especially when that single circuit is going to be 1600 metres long by having to follow the perimeter fencing . The other drawback would be, if you lose power to that circuit, (for whatever reason) you've lost every perimeter security CCTV camera on the project... A bad design all round to my mind. I would have thought at least 4 circuits, that ''don't'' follow the whole perimeter to get to the section that each circuit is supplying...

Surely, if redundancy with maximum coverage is required, then 4 circuits that don't follow the whole perimeter would leave large portions of the perimeter without coverage in the event of a fault. If the cameras are intended to watch the inside of the perimeter then this may not be a problem as cameras from another section may have sufficiently good coverage if their view is unobstructed; however, if the system is intended to cover approach to the perimeter then it is even less likely that coverage will be adequate. Equally, depending on the expected threat which these cameras are intended to counter, it may be that the cables for the 4 circuits should take different routes around the perimeter and should serve every 4th CCTV post. It is interesting how such a simple 'requirement' is after all not so simple. Clearly the topology of the network and routeing of the cable may either have been taken into account, and the OP is designing one of a number of similar circuits, or it may be beneficial to his cable calculations to reduce the length of run or the load or both. Clearly the other aspect of design hinted at earlier is the issue of diversity. One assumes that all the cameras will be 'on' and transmitting a signal at all times but that if they have motor driven positioning, not every camera will be panning and tilting at the same time; therefore diversity may also play a part in the reduction of circuit load. So many questions without answers!

 

[Engineer54]

Think you misunderstood me. I'm basically saying that routing of these say 4 circuits should be kept to a minimum and not just follow the perimeter fence. There are several alternatives to adequately supply these CCTV columns, but using a single circuit that comes in at 1600 metres wouldn't be my first choice. As you point out, there are far too many questions left up in the air regarding this installation...

 

[GB.Kayak]

Think you misunderstood me. I'm basically saying that routing of these say 4 circuits should be kept to a minimum and not just follow the perimeter fence. There are several alternatives to adequately supply these CCTV columns, but using a single circuit that comes in at 1600 metres wouldn't be my first choice. As you point out, there are far too many questions left up in the air regarding this installation...

It certainly makes things challenging on the volt drop and circuit resistance for effective ADS!

 

[Geordie Spark]

Think you misunderstood me. I'm basically saying that routing of these say 4 circuits should be kept to a minimum and not just follow the perimeter fence. There are several alternatives to adequately supply these CCTV columns, but using a single circuit that comes in at 1600 metres wouldn't be my first choice. As you point out, there are far too many questions left up in the air regarding this installation...

You being misunderstood Eng.?????

I find that hard to believe.

Anyway, here's a little song for you from a bunch of Geordie lads. https://www.youtube.com/watch?v=vstNm5xzuKM