10-3 Direct Burial wiring question

[mjncad]

Now for my personal experience, I would put it all in conduit even though you have UF rated cable.

In general, putting jacketed conductor bundles (e.g. Romex, etc) inside conduit is not recommended as the extra jacketing hinders heat dissipation. I'm not sure what code says about putting Romex in conduit; but I'll bet it's not encouraged.

 

[Ken45101]

Just remember that when running 220 on three wires and then splitting 2 110 legs off, the "neutral" is now handling the current sum of both legs, presuming both are used at the same time. Something to think about if you plan to max out the circuit. The neutral and ground should only be joined at the main box where the grounding rods are located.

No, that's not the way it works if properly wired. CurlyDave is correct.

When you have equal loads on both sides, the neutral current is balanced out and the neutral has zero current. If the loads are unbalanced, then the neutral will only carry the difference. For example, one side has a 20 amp load and the other side has a 15 amp load, the neutral will only carry 5 amps.

As long as you actually have 220 at the end, it's fine. Now if you wired it wrong and connected both hot wires to the same side of the feed, then yes, your neutral current would be too high, but you would have zero voltage between the two hot wires and 110 to ground on both.

To the OP: Yes, three wires without ground sounds strange.

Also consider voltage drop over that distance. If you are planning on using a 20 amp load, especially a motor, you probably need heavier wire. There are calculators that will give you the voltage drop at various currents and wire lengths.

Ken

 

[ray66v]

only thing you'd have problems with is connections to outlets, which are hard to connect using stranded wire without losing some of the strands.

There are premium "back wire" switches and receptacles. They allow you to insert the wire from the back, under a plate, and then it is tightened securely with the side screws.

That's all I use now.

They work fine with stranded wire.

They do cost about twice what the cheapo ones cost.

Curly Dave is also correct as usual. :thumbsup:

 

[firemanpat2910]

not to hijack but this thread seems to have electrical knowledge and little safety police bs. I am at work with a slow computer and i need a quick reference, want to run a 4 amp 220 volt irrigation pump. have direct bury 14 gauge wire already at the farm. how long of a run can I do, and be "safe" there is no code worries, there will be no other load on the circiut, 4 amp 220 motor 14 gauge wire already paid for, just need to know how long I can run the wire vs how far I have to plumb the irrigation.. thanks google searches took me to nothing but adds, i just need a simple chart,

 

[rambler]

240v, copper wire #14, max 4 amp load, should be good for about 280 feet.

You are on your own for 'startupload' of an electric pump, if it's trying to draw more to start up, etc. Might or might not affect your motor life, breakers popping, etc.

Drops to about 140 feet if at 8 amps, for example.

--->Paul

 

[firemanpat2910]

thanks ! that saves alot time.

 

[aczlan]

You are on your own for 'startupload' of an electric pump, if it's trying to draw more to start up, etc. Might or might not affect your motor life, breakers popping, etc.l

A "Start Kit" might help with that. It has a capacitor to help with the surge load at the motor startup

Aaron Z

 

[woodlandfarms]

As this was my thread I will follow and HiJack further cause there are so many smart people here.

I know little about wells. We had one at 100 feet but now we are on city water. I have the pump (It went into the well - the bullet shaped kind of pump).

So 2 questions.

1st, the old pump is 220 with 4 wires. The 4th wire, I am told by a neighbor, is for startup. Can someone explain what this does? There is a control box, and frankly I have no clue how all this works. Anyone give me a laymans explanation/

Second, the well is around 400 ft from the house. Plus another 100 feet down. That is 500 ft on a 10 guage wire. How is this possible? Or is it something to do with 220 not falling off as fast as 110?

Carl

 

[mjncad]

Carl:

It may not be the most accurate way of understanding electricity; but think of volts as the electrical equivalent of pressure, and amps the electrical equivalent of volume.

A 220VAC load will generally have half the AMP requirements as a 110VAC circuit, and vice-versa.

So depending on the pump's AMP requirements, a #10 AWG could very well be all that is required. Also in-rush current (a.k.a. start-up current) can be significantly higher for the fraction of a second during motor start-up; but a slow-blow circuit breaker or fuse is designed to handle the overload for that very brief period of time before tripping.

Regarding capacitor's; I think of them in this manner. A battery stores electrical energy with the intent of a slow discharge to maximize the amount of time a device can be used. A capacitor on the other hand is designed to briefly store a charge and dump it rapidly on demand. Think of a capacitor as the electrical equivalent of a fighter jet's after-burners.

 

[Ken45101]

As noted, using 220 cuts the current in half which reduces the losses in the wire. Furthermore, as a percentage of the voltage, since the voltage has doubled and the current has halved, the drop in the line is only 1/4th as much percentage wise.

To put into numbers, say you were running 110 and required 10 amps of current. If the wire resistance was 2 ohms, the voltage drop in the line would be 20 volts (amps x resistance). That's a 20% (roughly) voltage drop and likely to be too low for the motor. However, if you run 220 with the same wire, the current is only 5 amps and the voltage drop in the line is 10 volts (amps x resistance). Now you are getting 210 volts at the motor, which is only a 5% drop and is acceptable.

Ken