Ring Main/ Volt drop

[LJC]

Can anyone tell me where I'm going wrong.....

Common knowledge 100m is max for ring final!!!!

Im trying to work out volt drop for said length and I am way off where I need to be.......

singles/trunking............15x32x100/1000=48v

Yet if I put a radial in ....15x16x100/1000=12

Can anyone tell me wether the volt drop calc is different for ring final as even the osg says 100m ring is ok

Many thanks in advance
liam

 

[SimpleSimon]

Pretty sure that rings are an exception to the rule so not to worry too much, but I'm sorry I don't know the logical explanation.

 

[Sintra]

For a ring formula is

mV/A/M x ib x L / 1000 / 4


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[IQ Electrical]

Can anyone tell me where I'm going wrong.....

Common knowledge 100m is max for ring final!!!!

Im trying to work out volt drop for said length and I am way off where I need to be.......

singles/trunking............15x32x100/1000=48v

Yet if I put a radial in ....15x16x100/1000=12

Can anyone tell me wether the volt drop calc is different for ring final as even the osg says 100m ring is ok

Many thanks in advance
liam

The OSG describes a floor area of 100M^2, the limiting factor of volt drop on a conventional ring with 20A allowed for load is around 127 Metres in length (IIRC)

 

[LJC]

So as normal then divide by 4?..........Doing 2391 at minute and even the lecturer could not tell me...... what does that say?

 

[Johno]

I don't know about the 100m of cable for a ring thing, as said before you may be confused with floor area.

But as for the volt drop it is 2 x 2.5mm cable = 5mm

 

[Sintra]

It doesn't quite work like that on a ring.

L = 4 x max vd x 1000 / ib x mV/A/M


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