street lighting

[beaver74]

hi all after some advice for volt drop on a lenght of lighting

7 bolards with low energy lamps 50w max
160m long
all lamp evenly set out
now i am thinking that volt drop will be worked out by

1st lamp 350w (7 lamps) 20metres
2nd lamp 300w (6 lamps) 40metres
3rd lamp 250w (5 lamps) 60mtres

does this look right to you all

cheers

 

[Guest123]

Hi.

You have your total length as 160M, but totalling the other measurments only gives 120M. Where is the other 40M from???

 

[beaver74]

Hi.

You have your total length as 160M, but totalling the other measurments only gives 120M. Where is the other 40M from???

sorry first 40 metres to 1st lamp

 

[Sintra]

You need to know the mV/A/m of the cable you are using, the total load in Amps and the length of the run in meters and multiply together.

 

[Guest123]

I get you.

Your loadings seem fine. It's always best to work out the VD for this type of install in seperate parts and then totalling the VD of all of these parts to get the actual total VD.

To work it out as one long run with the total loading applied would be wrong as it would assume the current to be the same in each section of the circuit....which it isn't and you would end up with a calc telling you to install a 35mm or something.

Obviously this will be an underground install so dont forget your factor for that.

Also a little thing that is often forgotten is the bit of cable from the cut-out at the bottom of the lamp to the head at the top, probably not an issue for you with bollards though.


HTH.

 

[beaver74]

I get you.

Your loadings seem fine. It's always best to work out the VD for this type of install in seperate parts and then totalling the VD of all of these parts to get the actual total VD.

To work it out as one long run with the total loading applied would be wrong as it would assume the current to be the same in each section of the circuit....which it isn't and you would end up with a calc telling you to install a 35mm or something.

Obviously this will be an underground install so dont forget your factor for that.

Also a little thing that is often forgotten is the bit of cable from the cut-out at the bottom of the lamp to the head at the top, probably not an issue for you with bollards though.


HTH.

what got me thinking was when i worked the last lamp for 100w at 160m it gave 2.5 with max load of 3.88A but i will be protecting with a 6A.i take it I can take account of the fact this piece can not be overloaded as we would a flex of a pendant on a 10A breaker
cheers

 

[Guest123]

i take it I can take account of the fact this piece can not be overloaded as we would a flex of a pendant on a 10A breaker
cheers

Ordinarily I would say yes...but, is there a chance of alteration/addition in the future??? if so then maybe worth future proofing.

 

[beaver74]

Ordinarily I would say yes...but, is there a chance of alteration/addition in the future??? if so then maybe worth future proofing.

no more expasion as at the end of property
how would you suggest calculating v/drop per lamp
mv/A/m x load in current leg x lenthcheers

 

[Guest123]

Ok.

Total load in cable from DB to lamp 1 = 900W/230V = 3.91A.

Total load in cable from lamp 1 to lamp 2 = 550W/230V = 2.39A

Total load in cable from lamp 2 to lamp 3 = 250W/230V = 1.08A.


Let us assume a 4mm cable It = 37A, mV/A/M = 11.

VD1 = 11 x 3.91 x 40 / 1000 = 1.72V

VD2 = 11 x 2.39 x 20 / 1000 = 0.52V

VD3 = 11 x 1.08 x 40 / 1000 = 0.47V


VD total = 1.72 + 0.52 + 0.47 = 2.71V

Permissable VD = 3% of 230V - 6.9V so 4mm is ok.


Have I read your circuit lengths right????

 

[beaver74]

Ok.

Total load in cable from DB to lamp 1 = 900W/230V = 3.91A.

Total load in cable from lamp 1 to lamp 2 = 550W/230V = 2.39A

Total load in cable from lamp 2 to lamp 3 = 250W/230V = 1.08A.


Let us assume a 4mm cable It = 37A, mV/A/M = 11.

VD1 = 11 x 3.91 x 40 / 1000 = 1.72V

VD2 = 11 x 2.39 x 20 / 1000 = 0.52V

VD3 = 11 x 1.08 x 40 / 1000 = 0.47V


VD total = 1.72 + 0.52 + 0.47 = 2.71V

Permissable VD = 3% of 230V - 6.9V so 4mm is ok.

cheers bud

 

[ian.settle1]

Ok.

Total load in cable from DB to lamp 1 = 900W/230V = 3.91A.

Total load in cable from lamp 1 to lamp 2 = 550W/230V = 2.39A

Total load in cable from lamp 2 to lamp 3 = 250W/230V = 1.08A.


Let us assume a 4mm cable It = 37A, mV/A/M = 11.

VD1 = 11 x 3.91 x 40 / 1000 = 1.72V

VD2 = 11 x 2.39 x 20 / 1000 = 0.52V

VD3 = 11 x 1.08 x 40 / 1000 = 0.47V

VD total = 1.72 + 0.52 + 0.47 = 2.71V

Permissable VD = 3% of 230V - 6.9V so 4mm is ok.


Have I read your circuit lengths right????

What happend to the other 4 bollards as the original said 7 bollards?

 

[Guest123]

What happend to the other 4 bollards as the original said 7 bollards?

I was a bit confused by that too, as he goes on to say lamp 1, lamp 2, lamp 3.

I took it as 3 columns with multiple lamps on each.