Voltage drop

[dokkan1080]

Today I saw a swa 2.5mm run from a consumer unit to a garage shed about 45m (eyeballed it) from a 16amp breaker....

to a double socket then a fused spur to a led light fixture. Voltage drop would be :

15X16X45/1000
=10.8volts

which complies but I guess its pretty close with power circuits being 5 %, but as it has a light on it shouldn't it have been with in 3%?

 

[davesparks]

What is the voltage rating of the LED light fitting?
3% is a generic figure applied in the absence of specific data for the lighting installed.
In this situation you can look at the voltage eating of the specific light and establish what the maximum allowable voltage drop for it would be. I expect it will be fine with a 5% drop.

 

[Dustydazzler]

OP have you physical tested the voltage at the garage ? I would be surprised if it’s below the usual 230-240 range...

 

[radiohead]

In practice the true volt drop will depend on the actual load drawn from the double socket, the light itself will have a negligible effect.

 

[DefyG]

Agreed as above in the absence of more specific data, but from a design perspective 3% is the target for a lighting circuit.

 

[dokkan1080]

OP have you physical tested the voltage at the garage ? I would be surprised if it’s below the usual 230-240 range...

No just observed it and had a bit of a think about it, wasnt my job to add anything to it... xD

 

[timmy88]

Today I saw a swa 2.5mm run from a consumer unit to a garage shed about 45m (eyeballed it) from a 16amp breaker....

to a double socket then a fused spur to a led light fixture. Voltage drop would be :

15X16X45/1000
=10.8volts

which complies but I guess its pretty close with power circuits being 5 %, but as it has a light on it shouldn't it have been with in 3%?

perhaps you should put a voltage regulator

 

[Simon47]

Something else to consider ...
Some, but definitely not all, LED fittings (or rather the SMPS inside) are multi-voltage - will run on anything from something like 90V to 260V. For U0 of 240V, that's a heck of a lot of volt drop before it's affected For a lamp holder you couldn't use that justification, but for a permanently wired fitting it could be reasonable. For others, they might not be multi-voltage, but will still provide constant light output over a significant range.
Lets face it, the regs were drawn up in the days when a small change in voltage would make a significant difference to the light put out by an incandescent lamp.