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I want to put 6 300w LED flood lights around a tennis court positioned centre and corners. The cable run is approx. 80 meters. I have a 1.5mm rubber external cable in free air mounted along the top of the mesh fence. 1800w at 240v should give me 7.5a which is within the cable rating but how do i account for voltage losses raising the current draw?
 
When you say rubber cable, do you mean H07RN-F??
 
Will the tennis court be used by members of the public?
Insurances will dictate the lights be put in by a qualified electrician and tested properly.

Not really a DIY job IMO.
 
OK, so normal logic would suggest that if you joined the dots A-B-C-D-E-F you end up with a radial circuit and whatever the calculated volt drop is (which I’ll happily look up for you after my bacon…) BUT as you’re doing a perimeter then you may as well rejoin A to F and make it a ring, in which case your losses are far less.
 
OK, so normal logic would suggest that if you joined the dots A-B-C-D-E-F you end up with a radial circuit and whatever the calculated volt drop is (which I’ll happily look up for you after my bacon…) BUT as you’re doing a perimeter then you may as well rejoin A to F and make it a ring, in which case your losses are far less.
I intend to join up A with F to close the loop. The lights are 300W 1.36A. Full loop is approx. 80m. Enjoy your bacon butty!
 
Actually, having just done the maths, you’ll HAVE to make it a ring anyway to keep within allowable tolerances.
 
I intend to join up A with F to close the loop. The lights are 300W 1.36A. Full loop is approx. 80m. Enjoy your bacon butty!

Actually, having just done the maths, you’ll HAVE to make it a ring anyway to keep within allowable tolerances.
OK will do - what will be the expected current load so I can select the size of fuse (I have a local fuse box as well as the breaker)?
 
Double check the manufacturers instructions regarding the type of protective device required, you may require a C type to allow for in rush currents of the LED driver. This will have a knock on effect regarding the impedance of the circuit.
 
One thing to be aware of is the simultaneous switch-on surge of 1800W at the same time which can run to several times the rated current. You should check the manufacturer's recommendation to see what they suggest, but you might need something like a 16A C-curve MCB (with RCD protection, of course, as it is outdoors).

Otherwise you might look at having two separately switched circuits for 3 lights at a time, etc.

EDIT: Just beaten to it by @Strima !
 
If we keep the maths simple - 1800W is basically 10A. 1.5mm H07 has a voltage drop of 32mV per Amp per Metre. Therefore, 0.032 x 10 x 80 = a voltage drop of 25.6v at the final light, which exceeds the minimum tolerance of 3%. Make a ring and that changes to 6.4v - which is just under the magic figure of 6.9v

As for sizing of breaker, the max allowance of 1.5mm H07 is only 17A anyway. Conductor resistance is 0.0133Ω /m therefore for a ring you'll have an R1R2 value of something in the region of 0.53Ω - a C16 RCBO will give you around 0.6 ohms worth 'to play with' on final figures..... so basically hope the origin of that circuit isn't too far from the origin of supply to start with!!
 
Wondering how I got a slightly different R1+R2....!
1.5mm^2 H07RN-F : 32mV/A/m from same page as you = 32 milliohms / m
(80m x 32) / 1000 = 2.56 ohms r1+r2 (both same size) if a radial
R1+R2 for ring = 2.56/4 = 0.64 ohms
Brain not working!
 
Wondering how I got a slightly different R1+R2....!
1.5mm^2 H07RN-F : 32mV/A/m from same page as you = 32 milliohms / m
(80m x 32) / 1000 = 2.56 ohms r1+r2 (both same size) if a radial
R1+R2 for ring = 2.56/4 = 0.64 ohms
Brain not working!
We probably both forgot to add the Sunday correction factors.
 
I would say that while the regs still say 3% for lighting, really for LEDs 5% is adequate, in fact, I suspect that for the same brightness change in LED versus filament lights the old 3% would be closer to 9% now.

But the limit on R1+R2 for something like a 16A C MCB is significant and only likely to be met with a "lollipop" (ring fed from 'radial') and even then it might need 2.5mm for the feed depending on length.

In terms of cables the OP might want to consider NYY-J just because it is likely to stay stiff/straight along the fence route without masses of cable ties, so might look a bit better.

Finally that sort of a load is likely to burn out a 10A light switch fairly soon, I would be inclined to use at least a 20A DP switch instead.
 
My reflection is that this one really needs someone with a loop tester to advise on the earth loop measurement at the origin before proceeding with the circuit design.
If the OP doesn't have a loop tester (as most diy folk won't) he'll need at least a few minutes of a friendly local sparks time. That may of course reveal the entire place is TT which changes things again.
(BTW I'm in Shropshire so PM me if you want me to take a quick look)

My hunch is that using a 2.5mm ring of H07RN-F is more likely to satisfy the type C breaker's max earth loop as the R1+R2 would be around 0.38 ohms. The NYY-J suggestion is a nice idea and I agree would look neater. (even lower R1+R2 for that too)
 

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