Volt drop

[Maxstone89]

Hi,

Im a fairly new sparky,
So just wanted to get a little idea as im not 100% sure,
Im adding 12m of 1.5mm cable in trunking into a conservatory from a fcu of the ring main the volt drop for this part would be 4.5v so i may need to up the cable size. But what i need to know or confirm is what would i take the ring main volt drop as, as if it was a short run it would be no problem. ? Any suggestions would be helpful and of coarse i will follow it up with my own research when i get a sort of idea.

 

[ian.settle1]

[COLOR=rgba(0, 0, 0, 0.701961)]Hi,[/COLOR][COLOR=rgba(0, 0, 0, 0.701961)]
[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Im a fairly new sparky,[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]So just wanted to get a little idea as im not 100% sure,[/COLOR]
[COLOR=rgba(0, 0, 0, 0.701961)]Im adding 12m of 1.5mm cable in trunking into a conservatory from a fcu of the ring main the volt drop for this part would be 4.5v so i may need to up the cable size. But what i need to know or confirm is what would i take the ring main volt drop as, as if it was a short run it would be no problem. ? Any suggestions would be helpful and of coarse i will follow it up with my own research when i get a sort of idea.[/COLOR]

??????

 

[Maxstone89]

Hi,

Im a fairly new sparky,
So just wanted to get a little idea as im not 100% sure,
Im adding 12m of 1.5mm cable in trunking into a conservatory from a fcu of the ring main the volt drop for this part would be 4.5v so i may need to up the cable size. But what i need to know or confirm is what would i take the ring main volt drop as, as if it was a short run it would be no problem. ? Any suggestions would be helpful and of coarse i will follow it up with my own research when i get a sort of idea.

 

[Maxstone89]

Sorry, corrected

 

[ImpededLoop]

Hi and welcome.

Firstly 4.5V sounds very high for 12m of 1.5mm. You've maybe made an error there.

You can calculate the length of the ring final by measuring r1 or r2 (end to end of live or the cpc). You can then calculate the cable length by finding the ohms per metre for the cable size that's been installed.

 

[Darkwood]

Can you show your calculation method so we can correct it, or use copper as a conductor because 4.5v for 12m of 1.5 is definately wrong, if you think about it your lighting in your house would have a max' length of about 16m before it failed its VD if in 1.5...!

 

[Maxstone89]

29x12x13 %1000 =4.524v
mV/a/m-Meter-Amp
In trunking

 

[E.E.I]

Would the total load actually be 13A?

 

[Maxstone89]

Upto yes as its 3x double sockets

 

[Maxstone89]

So has a 13 amp fuse in it

 

[davesparks]

Would the total load actually be 13A?

It's unknown and variable for a socket circuit so use the OCPD rating to cover

 

[Maxstone89]

It's unknown and variable for a socket circuit so use the OCPD rating to cover

OCPD meaning??

 

[Darkwood]

I understand the high VD now, just from a design point of view can I query how the conservatory is been heated, will it be likely to have a heater plugged in?

ps Over Current Protective Device OCPD

 

[Maxstone89]

So the 13 amp fuse basically would be the ocpd , never heard of it being said as ocpd
No heater no....?

 

[Darkwood]

You have to add the VD you calculated for the radial spur to the VD calculated for the ringmain, if this does not comply for the ring then redesign your circuit or increase the cable.

Volts drop is always calculated from source to end point but where you fuse down mid point you calculate each section and add together.