Cable size and a lesson

[bunnydrops]

Hi, I'm from the states where wire is measured in gauges; 10,12,14 etc. And of course, we run 120V. At the farm here in Thailand, I have a small 2000w pump that I need to put in about 60 meters from the house. I went to look for wire but can't make heads or tails. I found some wire around the house. Written on it

300/400 V 70ํ* VAF 2x1 SQ.MM TIS11

First off, what size wire do I need (as written on the cable) and second, if you have the time, explain what that means.

Thanks for making me a little wiser.

[Crossy]

Ok a 2kW pump isn't exactly 'small'

Assuming 4 x full load current at start we're looking at 32A. At 60m that's going to need cable 6mm² if we allow a 10% volt drop on starting.

The cable you have is VAF is a flat PVC insulated and sheathed cable http://www.bangkokcable.com/product/backoffice/file_upload/131007_31-300!300V%2070C%20VAF%202C.pdf of 2 cores, 1mm² each (2x1 sq.mm) TIS11 is the Thai Industrial Standard to which it is made. This cable is intended for indoor use and is not flexible (fixed wiring only).

The "mm²" is the cross-section in square mm, equivalent to your AWG, there are conversion tables on the net if you need to get an idea of comparison. Unlike AWG, the bigger the number, the fatter the cable.

Assuming you're running outside you are going to need an NYY type cable http://www.bangkokcable.com/product/backoffice/file_upload/131007_34-450!750V%2070C%20NYY-2C.pdf of 6mm². NYY can be buried in the ground but will need protection from gardening activities or run it on poles.

Something like "450/750V 70^oC NYY 2x6 sq.mm", show that to your electrical chap and you'll get the right stuff. It will not be cheap!

If you put it on poles you could get away with a VCT cable, same as above but replace NYY with VCT. This cable is really intended to be used as appliance flex but will be a lot cheaper and does last quite well even exposed to sunlight (the enemy of anything PVC). Don't be tempted to bury this type of cable. Our outside street lights are wired in VCT and it's showing no sign of stress after 4 years of full sun.

You should put a ground rod at the pump (to save running 3 core cable) and place an RCD (GFCI) at the supply end to protect your gardener when he cuts the cable.

[bunnydrops]

WOW' Thanks for that. I'm whole lot wiser now. Over head is OK here--- and since I'm the gardener, I will take your advice. We use two meter ground rods in the States. Is that what you recommend?

[Crossy]

Copper-clad steel rods are cheap enough so bash in a 2m one at the pump.

EDIT

A quick re-visit to the calculations, since the run current of the pump will be about 8A we can actually get away with a 4mm² cable and still keep under 10% volt drop on start, cost saving

If your pump can handle a 16% undervolt on start then 2.5mm² would do (just), but by the time you've factored in the drop between the transformer and the house it's going to be on the line and will possibly reduce the life of your pump motor. But if the budget is tight ...