New dwelling 170m away from main supply

[deejaypsy]

Hi guys,
Wondering if you could give me your 2 cents worth?
I have a client who has a farm with 3 phase power.
He wants to build a staff cottage and power a couple of water pumps 170m away from the main installation and nearest DB.
The cottage will employ an electric geyser, and possibly an electric oven, but I will strongly advise gas to save on power consumption. I would be looking at around 40A single phase worst case scenario needed on the cottage end.
After consulting my regs book am i right in saying that if I run single phase this distance, I would require a 35mm 2 core armoured cable to do the job.
If I was to supply 3 phase across this distance then I would only need to run a 10mm 4 core armoured cable to supply 20 amps/ phase, which, if loaded correctly, should supply the necessary power to the cottage and run the pumps. (I don't think the pumps will be 3 phase).
Does this sound about right?
Does anyone have a better idea of how to get power there?
Many thanks

[GCE]

Hi

The other way is to do a step up cable step down transformer - The distance and amperage will not warrant the cost

The 10sqmm x 4c should be sufficient to run 20 amps but be careful on the pump size and start arrangement - A motor, direct on line start up current, can be 6 times higher then run current - It can cause a problem.If I was quoting I would allow for a VSD and if the client does not want the VSD and is prepared to take the chance then so be it - When the motor burns out at least you covered yourself.

People always forget start up current when sizing long lengths of cables and generators for motors.

[deejaypsy]

Yeah, I agree, the step up step down would not warrant the cost to the client.
I will get specs of the pump from my client before I advise anything though.
Thanks for your input