4

I read prior questions and need to follow up before investing thousands in wire.

Starting at barn, need to run power to a sprinkler water pump (TSC model CLLS115) 900 ft away. Pump can run either 220V 10A or 115V 20A.

At water pump location I need pull chain light & 115V recep for sm heater or heat lamp in winter months.

Pump is used 1-2 x's per week for an hour. Barn has 2 unused 220V breakers. My plan to keep wire cost down is to use URD 4g Alum 3 strand wire (2 hots & a neutral) the 2 hots for the 2 sides of 220V & neutral for 115V need.

If I drove a ground rod at pump location for ground needs. The 2 hots for pump with ground & the neutral with a split off 1 of the 220V feeds & ground to a seperate 20A breaker for recep & light.

Upon cable reaching pump area I was told I need a disconnect I had planned on a 30A disco. I had planned to put a subpanel because of 115V need as your article stated.

In your prior question work you stated you needed a 220V breaker & 20A breaker at location. If I did the 220V breaker in panel at pump WOULD I NEED A DISCONNECT SWITCH AT LOCATION? however that would be 2 breakers on 1 -220V circuit or would the breaker at barn be enough?? Do I need disconnect also? If so does cable run into disco first then panel or vise versa? Which one is not necessary or both & where to go with cable first? - thought I would check before investing in disco & panel.

  • Can you please include a link to the previous question? Also, can you please edit the title to better reflect your actual question? Are you just asking about the locations of breakers and disconnect switches? Often the necessity of a disconnect switch depends on the equipment instructions and the jurisdiction – Hari Ganti Apr 30 '18 at 18:02
  • Do you really need 120 at the pump house, or can you run the light and heater off of 240 instead? – ThreePhaseEel Apr 30 '18 at 22:20
3

the "I own a copper mine" version

If you own a copper mine, wire cost is no object. Sell your copper at market and buy aluminum. Assuming we're running just the lump at 10A, and aim to confine voltage drop to the stock-advice 3%, we will need 3/3/3/6 aluminum cable.

If you also want to run an honest 20A of loads in total, we will need 2/0-2/0-2/0-1 cable ($3000).

If you want a full 30A still at 3% voltage drop, you'll need 4/0-4/0-4/0-2/0 cable ($5000) .

We need neutral because you have 120V stuff to run that apparently you cannot source in 240V for some reason.

We need ground because using a ground rod instead does not provide fault current protection. You also need a ground rod.

You will need a disconnect at rhis location . This is as easy as using a subpanel which has a main breaker. Size does not matter as long as it is>= the supply breaker. Remember it must also have separate ground and neutral bars.

The stock advice, no-brainer version

See "I own a copper mine" .

The "I do not own a copper mine" version

in which cost is considered worthy of attention. Ok, 2.4 KW for the pump, somewhat less for heat and light, say we can get this done in 5 KW. 5 KVA transformers are often seen on Craigslist for $100ish, we need two. Probably 480V transformers, if possible get 600V, popular in Canada.

The transformers will be used back to back, to step up transmission voltage, reducing voltage drop dramatically. At the far end, it will give 120/240 split-phase.

Amps will be 10.42@480V or 8.3@600V. We are going for 6% voltage drop at max power since draw will usually be half that (and thus 1/4 the drop).

Either way, #8 Al will suffice or #10 Cu ($500). We only need 2 wires.

Why no neutral? We will be manufacturing neutral locally. Why no ground? Irrelevant since the transformers double isolate the service.

Since our final output transformer has no earth ground reference, we must provide one with a local ground rod. All this would make this a main service in need of a main breaker, and as a main service, neutral would be tied to ground here. The technical term is "separately derived service" .

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.