Forum Electric: Electrical forum, Electrical engineering, electrician, power plant, energetics,wires

mpriester · Joined: 31 Jul 2006 Posts: 3

I am trying to install sprinklers that are far away from a power source, however the water is coming from the well and there is 3 phase there. I only see 3 conductors and the ground that is buried under the service boxes. I do not see any neutral.

I am only going to run a sprinkler timer on the 110 single phase. Is it possible to use a 110-117 leg from the 3 phase (i'll test it to get the correct leg) and run the neutral from the timer to ground instead of having a real neutral?

yanici · Joined: 15 Jul 2006 Posts: 208

Sorry, but what you want to do is definately a code violation, as well (no pun) as dangerous. The ground wire is there only to carry fault current, not to be used as a neutral. You'll need to do it some other way.

mpriester · Joined: 31 Jul 2006 Posts: 3

OK I have looked into this more and this is what I have come up with.

It is 350 ft from the 3phase to the location I need power located.
I don't need an enormous amount of power but would like to run some lights etc.

Run 220 single phase from the 3 phase setup over #8 either thwn in 1 inch conduit or direct burial, either way only need 2 conductors. At the 3 phase location install a shutoff with 8 amp fuses (The max draw on this size wire at this distance) .

At the remote location, install a GFCI breaker (just to be safe - it is outside) and then install a 220-110 power regulator (transformer)
http://appliances.safeshopper.com/88/478.htm?959

This will give me 110 volts and cleanup any voltage drop that has occured.
I can connect the Sprinkler timer to this location and run very short 24v wires 18gauge to the valves as well as have some extra power for lights.

Install a new ground at the remote location and it should be safe and legal.

Does this sound like it will work?

I am going to run water line and electrical in the same trench. I know they are required to be at least 18" deep, but should they have a minimun space between the water and conduit runs? Vertically or Horiz? Planning on using a trencher not a backhoe.

Thanks for you advice.

yanici · Joined: 15 Jul 2006 Posts: 208

Let's start with the wire. #8 sounds good but you'll also need to pull a #10 green ground wire with it.

18 " deep is good, but you'll have to check with local authority to see if you can put in same trench with water. They may have a minimum spaceing required.

You'll need to have a 2 pole disconnect at the 3 phase end to protect the wire from overcurrent. A small circuit breaker box with a 2 pole 20 amp breaker would work.

At the other end a 2pole non-fused disconnect (it's already protected from overcurrent at the 3 phase end) will be needed before the wire goes to the transformer.

Out of the transformer you'll need black, one white(neutral), and one green to connect to a small circuit breaker box. The box will have a 1 pole 20 amp main. Then you can have your GFCI breaker off of it.

All your ground wires need to be connected together and also to any metalic boxes, fittings and transformer. You will also need to run a #10 ground wire from these grounds to an 8 foot ground rod. Also, be sure to ground the x2 (neutral) connection at the transformer.

None of this will be possible if you are overloading the circuit at the 3 phase end. You must be positive that there is ample spare capacity to start with.

fearfakter · Joined: 23 May 2006 Posts: 30

You havent stated what size wire is feeding the 3 phase pump and the ampacity of the 3 phase pump. you may be able to use a transformer at the pump site to derive your 110volt circuits, or have you checked this this already?

fearfakter

mpriester · Joined: 31 Jul 2006 Posts: 3

I did check it with the local planning commission and they gave me permits to do it.

The incoming 3 phase is on 30 amp fuses. It feeds a 7.5 HP submersible for ag use at this location but we no longer farm, so the pump is not used. The 3 phase is just sitting there.

Only putting in a 20 amp fuse for this feed so I won't be overloading anything.

What I am ending up with is 220 over #8 THHN and a #10 Ground run to a remote transformer 2KVA where I can get 110 and a neutral. Disconnects at both ends and a ground rod installed at the transformer end and both ground rods connected.

My county inspector looked at the install plans and agreed this was OK to do. So thanks to all who helped me get to where I was going on this.