Voltage Drop for Well Pump

With respect to overlooking something... I would say so. The cost of doing what you propose is far greater over the long run then the cost in wire. The energy spent keeping the cores of both tansformers magnetized will eat up many many watts on a full time basis.

North of 60,

Thanks for the reply, I left out that the control scheme will be such that the transformers are energized only when the pump is running, and being small transformers, (2kva or less) I believed that cost of electricity would be small compared to cost of copper.

thanks again,

corona

Hey...

You mentioned putting the controller at the well head. As such, you would need to leave the circuit energized all the time. Or are you going to use a second starter at the source end that will energize the feeder to the transformer and then send the start signal to the pump? Sounds like this is getting overly complicated for naught.

For that sort of distance on the sheep station, we'd run an aerial sub main using cheaper uninsulated conductors and have a switchboard at the pump head.

The once only install cost to "do it properly" (and without complication) by far outweighs the complexity of multiple transformers and such.

Have you considered a solar array or wind turbine with battery storage. I hear there are some pretty attractive subsidues in your part of the world at present for the alternatives.

"... 160 ft. in well. Power source is 3300 ft. from well. Just using simple voltage drop calculations and using 7000 ft. of run I figure a #4cu. would work...."

Just out of curiosity, how are you getting 7000' from this? Are you thinking you have to count the circuit as a line and return as separate runs? If so, not you don't. It's one drop from source to motor, 3460 feet. 5A at 3460 ft. still comes out as 4AWG for a 4.3% VD, I was just curious why you used 7000'.

10,400' #4 THHN, probably about $1 per foot, $10,400 cost, plus conduit etc.

If you stepped up to 480V 1 phase (because that transformer is easy to buy), you could drop down to 10AWG wire. Two transformers, 1500VA CPTs (easiest to implement and capable of high inrush), including fuses and fuse holders, figure around $250 each, $500. 10,400' #10AWG THHN, probably $0.40/ft, $4,160, plus transformers, $4,660 total.

Less than half the cost using transformers. But you gotta really want that well pump to spend even that much on powering it. I would consider solar for something like that.

Hey there JR... you might want to rethink this. For the VD calc, 7000' is the value of interest. The VD has to be measured on the full circuit length, IE. from the source to the load then back again.

JRaef:

I suppose the best way to explain why 7000ft. instead of 3460ft. would be to have you examine Kirchhoff's second law, however your final outcome coincides with my calculations. And your statement about really wanting that pump is also correct, the pump in question is in eastern Washington, dry arid conditions, sometimes water is rare. I haven't considered solar, and I will research this aspect.

Thanks, Corona88

You're in great solar country, so that could be a good direction for further research.

Just curious. Is there any elevation change from the well head to your end use for the water?

Fredski,

Thanks for viewing and commenting my thread. Yes there is an elevation change, from the well head to the water destination, (which is also the power source) is 3300 ft. run and uphill 80 ft. So from the pump (which is already installed and being run via generator) approx. 240 ft. of head. The system will pump into a cistrern and float switches will control on/off functions.

Thanks again for the look.

Corona

You're really putting this little .5HP motor to work. I'm not completely familiar with your neck of the woods. I was concerned for the possibility of freezing a line that travels over a half mile. I wondered if it was subterranean or surface. I know a lot of people use solar and a storage tank close to the well head. They store 200-300 gallons (make use of the solar when you can even if your home storage is full) and use gravity or a second pump to transport the water to its end point.

I know if this was my project my last choice would be running a 3000' electrical service. I almost certainly would go solar/reservoir. I think once you cost it all out (including service life of your conduit and all the possible scenarios of it being damaged by cars, trucks, vandals, wayward missiles, etc). That's quite a long run! A lot could go wrong.