Log cabin supplies

[User567]

190m run SWA underground, supplied from 3p+N 240mm sub main, each cabin total demand is 80A, worked out 35mm but volt drop is about 8%, would this be okay?

 

[pc1966]

For a 80A 3-phase load it is coming in OK, but I have not looked at a single load being 80A for VD.

 

[westward10]

No 8% is not okay. Which cable is 190m long the 240.0 or the 35.0?
If the 35.0 what is the volt drop of the 240.0 because the drop is calculated from the source of supply assuming the 240.0 is from the source of supply.

 

[buzzlightyear]

Multicore 90°C Armoured Thermosetting Insulated Cables​

Tables Apply to: H6942XL, H6943XL, H6944XL, H6945XL, Tuff Sheath,

Voltage:400V

Load:44.34kW / 80A

Length:190m

Method of Installation direct in ground or in ducting in ground

Cable Size:35mm²

 

[James]

Have you applied any diversity? 80A per cabin (19kw) if they are really using that much power then they should be glowing a dull red colour.

 

[westward10]

Multicore 90°C Armoured Thermosetting Insulated Cables​

Tables Apply to: H6942XL, H6943XL, H6944XL, H6945XL, Tuff Sheath,

Voltage:400V

Load:44.34kW / 80A

Length:190m

Method of Installation direct in ground or in ducting in ground

Cable Size:35mm²

For volt drop 35.0 in undersized.

 

[buzzlightyear]

That calculated from Cleveland cables.

 

[pc1966]

That calculated from Cleveland cables.

@westward10 point is that is when you have a balanced 3-phase load so only the losses in L1-L3 are a factor as N current is near-zero, if you have just one cabin drawing 80A then you get double the drop (L & N losses) so I'm guessing that is the 8% mention above, but I have not actually checked it.

But as @James points out 80A seems a lot for a wooden cabin! If heater cooker, and shower all on at once maybe, but allowing a bit of diversity, and/or maybe a priority unit cooker/shower would drop the peak load and make the overall drop acceptable.

 

[Pete999]

190m run SWA underground, supplied from 3p+N 240mm sub main, each cabin total demand is 80A, worked out 35mm but volt drop is about 8%, would this be okay?

noooooooooo

 

[pc1966]

Going up from 35mm to meet drop is going to be expensive. However, it seems 80A draw for a log cabin is quite high, more than many flats have as a supply!

So before sizing the cable to meed VD for 80A on a single phase of the three, are you sure that it really is needing that much?

You don't need to meet VD at the supply OCPD current (though you can find issues with disconnection times if not careful there), nor even at the max permitted by the sum of load OCPDs, but you do need to meet it at all realistic levels of usage. Can you tell us the loads and assumptions you made for the 80A figure?