Discuss Volt drop on outside lighting in the Electrical Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

A

allybally

I got called to a job this afternoon, it's outside lighting, about a 1000w of lamps on the whole circuit, and when trying to quote for it done a few calcs and the volts drop is massive, it's 24 volts, the circuit is run in 3 core 4mm swa, and is 300m in length, now I know that it's well over the allowed 3% allowed, but after reading into the regs a bit I've found a reg- 525.100 would this apply, the max measured Zs is 2.43 and is on a 10 amp rcbo, so given that disconnection times will be satisfied can I disregard the volt drop as safety is not affected?


many thanks in advance
 
Like I said quick calcs, even still well over, snd back to my question does that reg apply?
 
If its failed on volt drop then its extremely unlikely the circuit will comply with max Zs, however it will depend on how you calculated volt drop…load all lumped at one end will not give the most accurate value as already stated. I believe if the manufacturers minimum voltages are met at most onerous position and Zs is ok, then you are good to go
 
I was called to sort an issue with the rcbo keep going down and to replace all lamps and ballasts if they need it, I just don't want to touch it if the volt drop is too high, I'll have to have another measure and go back to the drawing board, many thanks for now
 
I don't think that high VD would put me off the work particularly if, as Zebra says, its within the lighting manufacturer's spec.

As this circuit is on an RCBO, have you determined whether it's tripping on overcurrent or earth leakage?
 
You aren't clear about whether this is an existing circuit or a circuit you are quoting to install.

If existing then measure the voltage at the intake and the voltage at the end of the circuit when fully loaded and find out exactly what the volt drop is rather than doing rough calculations.

If this is a circuit you are quoting to install from scratch then do an accurate calculation and adjust your cable size to achieve the correct volt drop, not forgetting that you can start with a bigger cable and reduce the CSA of the more distant legs of the circuit if the distribution of the load allows.
 
There's a dead short on live-earth,

So it's just a matter of locating the fault, which should be easy if, as you say, it's a dead short, and then doing the repair. Don't think I'd worry about the volt drop.

Yes, volt drop can be measured, although I guess it would best be done by measuring at the supply end and the load end at the same time, to avoid errors due to variations in supply voltage.
 
Might have made a mistake!!! It's been a while, the ballasts on 21 lights have a PF of 0.36
 
Right this is what I have, 3 x twin lamp posts, and 21 single lamp posts, all sodium, thanks

Ok, so what's the spec for each lamp (Watts, VA, PF)? Are they all the same or are there two different types?
Is the circuit in one run, or is it branched?
What are the distances from the origin to the lamps?

If it's complicated, you might need to do a diagram to convey the information.
 

Reply to Volt drop on outside lighting in the Electrical Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
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

Electrical Forum

Welcome to the Electrical Forum at ElectriciansForums.net. The friendliest electrical forum online. General electrical questions and answers can be found in the electrical forum.
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock