Cable sizing

[dma.electrical]

I'm trying to work out the size of swa cable i require to supply an office. the office will have 2 x 32A ring mains, 2 x 6A lighting circuits, 1x 20A heating circuit. The lighting circuits total wattage equates to 1800w. The rings will have roughly 8 sockets each. The supply cable will be a 3c SWA clipped direct to a wall so will not be covered. This is a 25m run. I have done various calculations and the answers just dont seem right. From the top of my head i would have thought it would need to be 16mm but the answers say higher

 

[Spa Key]

I'm trying to work out the size of swa cable i require to supply an office. the office will have 2 x 32A ring mains, 2 x 6A lighting circuits, 1x 20A heating circuit. The lighting circuits total wattage equates to 1800w. The rings will have roughly 8 sockets each. The supply cable will be a 3c SWA clipped direct to a wall so will not be covered. This is a 25m run. I have done various calculations and the answers just dont seem right. From the top of my head i would have thought it would need to be 16mm but the answers say higher

I presume you're applying diversity? Will dig out my OSG and see what I get.

 

[dma.electrical]

Yep diversity taken in to account. I have not done the calculation in so long and just need to check.cheers buddy.

 

[Spa Key]

Yep diversity taken in to account. I have not done the calculation in so long and just need to check.cheers buddy.

Yep I get 16mm. What were you thinking it should be?

 

[dma.electrical]

I was getting 25mm or above. must be doing something wrong. could you show me your workings please.

 

[Spa Key]

I was getting 25mm or above. must be doing something wrong. could you show me your workings please.

Tab 4E4B. 16mm clipped direct = 94A.

VD = (2.5*76*25)/1000 = 4.75v.