I am having a grain bin erected and need to power it.

I have a 100 amp service at the pole. The grain bin in 250' away from the pole.

I will have a second grain in built next year right next to it. So, I'd like to size the wire to run it once or run a pair of feeder wires so I don't have to come back next year.

Each grain bin consists of the following: 1) Fan with a 10HP, 230v single phase 2) Unload auger with two identical motors - 7.5hp single phase 230v

Grand total, I'll be powering two 10hp and four 7.5hp.

What wire do I need to run from the pole to the bin(s)?

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    Do you plan to run everything at once? If so, you probably don't have enough power at your pole -- 50HP is 37.3kW, which at 230V will need 162A – Nate S - Reinstate Monica Sep 20 at 16:56
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    Oh wait, where in the world are you? If you're in North America, where the 230 (really 240V) comes from combining both 120V phases, then the above is true, but if you're somewhere else where you have two independent phases of 230V, then you might have enough power (since you'd really have 2x100A at 230V). – Nate S - Reinstate Monica Sep 20 at 17:00
  • Do you need to run the fan and the auger at the same time? – Harper - Reinstate Monica Sep 20 at 17:03
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    @NateStrickland, elsewhere in the world 100A at 230V is still 23kW, just the supply is a single phase and a neutral. – Jasen Sep 21 at 2:17
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    code requires the largest motor to be sized at 125% plus the sum of the other motors. , the size of the conductors will need to be upsized to reduce voltage drop code recommends 3% for the feeder and a max of 5% but this is just a recommendation not a requirement. With this large of a load and distance I would use transformers to jump the voltage up to 600v at the panel then at the grain elevator another transformer to drop the voltage from 600 back down to 240v this will allow smaller wiring to be used. I have saved more than the cost of the transformers with long runs sometimes many times. – Ed Beal Sep 22 at 9:18

Your worst case scenario on the SERVICE is the 2 x 7-1/2HP 230V single phase motors on one bin while being unloaded, with the 10HP on the other one running the blower. 7-1/2HP 230V single phase motors are 40A each, the 10HP is 50A. You have 130A of load here. You cannot run that on a 100A service, continuous or not. So the wire size is moot.

But IF you get your service upgraded to let's say, 200A when you get the 2nd bin installed next year, then ASSuming you have a separate run from the service panel to each bin, the max worst case load would be 80A on each run, conductors must be 125%, so you size for 100A. You would need #3 Copper cable (if you can even find it), or #1 Aluminum, before de-rating for voltage drop (which I'm not going to do for you) so I would go one size larger.

If you try to do one cable run out to the first bin, then sub-feed off to the 2nd one later, you will need 2/0 (Cu or Al because of a sizing anomaly), 3/0 if there is voltage drop at that distance. That will be a LOT more difficult to run, I'd do it with separate smaller runs.

  • 125% of the largest motor plus the sum of the rest of the motors is the code requirement for multiple motors but I would agree even 1 bin with these motors are two large for a 100 amp service. 50+ 12.5+40+40= 142.5 amps for 1 now if the auger can be interlocked not to run at the same time 1 bin could be powered on a 100a 240v service. – Ed Beal Sep 22 at 9:31

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