D
davesparks
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.
L
Leesparkykent
well we may never know as the OP doesn't seem to be replying even though he's been logged on.
D
davesparks
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.
D
davesparks
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.
L
Leesparkykent
Like you said if the layout is favourable then it could be beneficial.
S
Sintra
D
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
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
D
davesparks
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.
E
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...
M
Marvo
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.
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!
Last edited:
E
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...
G
Geordie Spark
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
If they have LED illuminators then driver inrush might be a problem, and although the running current isn't 5A it might be necessary to design as though it was, unless sequential on-delay timers can be fitted.
E
Engineer54
It happens, my fault on occaisians, especially first thing in the mornings before i've had my second wake-up coffee!! lol!!
What would 'work out cheaper'? ... and would it? It is interesting how we all scramble over each other to help one moment, and the next suck our teeth and say get an expert in. Besides which, in my experience consultants borrow your watch to tell you the time and often charge an exorbitant rate to do so!
of course it would work out cheaper the fools are asking for 100amps to feed the pillars not accounting for vd over 1.6km
im guessing around 95mm ring lol
Last edited:
i meant 95mm 4c swa lol was randomly chucking numbers in a random calculator to get 95mm
4% vd at middle of the ring lol
just for a laugh 4c 185mm swa works out at 4% vd over 1600m for a radial
S
Silly Sausage
OFFICIAL SPONSORS
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
Advert
Thread starter
Mark.W
-
Thread Information
Advert
Thread statistics
Advert
TrueNAS JBOD Storage Server
-
-
-
Understanding TrueNAS JBOD Servers: A Comprehensive Guide- Started by Dan
- Replies: 8