Voltage Drop

[russellroberts]

What is the most accurate formula for sizing wire on longer runs for inductive loads?

I've always used the VD=2klI/cm formula.Is this accurate enough for most resi applications? Well pumps etc.?

 

[tom baker]

Re: Voltage Drop

It should be OK, but keep in mind it does not account for power factor of the motor. But for a well if you allow 5% VD end to end (and that is to the pump motor) you'll be fine.

 

[russellroberts]

Re: Voltage Drop

Thanks for the reply Tom,I appreciate it.

 

[tom baker]

Re: Voltage Drop

There was a similar thread to this recently. I should add the motor voltage tolerance by NEMA is +/- 10%. The motor is rated at 230 volts, for a 230 v motor minimum would be 207 V. If you alloow -5% then you have some room for voltage drop if the utility primary is low. Also if it is a 120/240 system your seconday voltage may be 240V. I like to be consertative on well pumps as they are a lot of work to pull. The ones I maintain are 50 or 100 hp, usually set at 200 feet.