Electricians Help (Simple question)

[Mike Henderson]

Allen, Yeah, I did the same thing when I wired my shop. I ran 220 service with big wire from my main box to a sub box at the shop, with a 50 amp breaker in the main box. Then I ran oversized wire to the outlets and put in a bunch of different circuits. While this is not code (Barry, don't flog me for this), I put 20 amp breakers in the sub box but used the standard 15 amp convenience outlets, and wired only a few outlets to each breaker (for the inspection, I had 15 amp breakers in the sub box). I also separated the outlets - that is, sequential outlets are always on different circuits, in an attempt to minimize the chance of using two tools at the same time on the same circuit. And I put in lots of outlets.

Since I work in the shop by myself, the peak load is the one tool that I'm using. The only time I have two tools running is when one of the neighborhood kids wants to do something (like sand something). I let them go at it while I continue my work. Otherwise, it's one tool at a time, so the 50 amp breaker to the sub box is plenty big.

Good luck on your wiring.

Mike

[Allen Grimes]

Thats how it will be for me for a while. I mean the one tool at a time thing. At least until I get a DC system. Though I do plan on hiring people to help me out in the future.

[Gil Jones]

This is a very good wiring manual!
http://www.amazon.com/gp/product/156...lance&n=283155

[Allen Grimes]

Hey thanks Gil,

Thats not the kind of book that I had in mind when I was asking about electricity books, but now that you brought it to my attention it is definately a book that I want.

[Dev Emch]

>> My neighbor says it saves electricity,

I don't think this was addressed. Changing from 120 to 240 does not reduce your electical bill. You pay your bill based on Kilowatt Hours. Watts are calculated by multiplying the voltage times the amps. As an example, a 120 volt 10amp motor is 1200 watts. The same motor if converted to 240 volts will draw 1/2 the amps so the calculation is 240 volts times 5 amp which equals 1200 watts. In other words, the watts are the same, therefore the Kilowatt Hours are the same no matter how the motor is wired.

Twinkle twinkle little star.....

........... Power equals I squared R.....

[Dick Strauss]

Yes, you will save electricity. However, it will be a very small amount.

If memory serves me correctly it goes like this...

1. assume we need 1100W/1Ph power for a machine.
2. assume we need a 50ft wire run from the breaker to the machine
3. assume no heating of wire (20*C constant)
4. we can get 1100W by 10A/110V or 5A/220V
5. resistance for copper wire is roughly:
10g .00118/ft or 0.059ohms/50ft
12g .00187/ft or 0.094ohms/50ft
6. Power loss is I squared R (R from the wire only)
7. Power losses are roughly as follows:
10A/110V/10g...5.9W
5A/220V/10g...1.5W
10A/110V/12g...9.4W
5A/220V/12g...2.4W

So you'd save about 4.4W with a 10g wire and 7W with a 12g wire. I don't know about you but I wouldn't notice this small amount given our bills are always in kWH.

This is why power companies transmit power at such high voltages (500kV+) over long distances. Higher voltages mean less current and much less total power loss due to line resistances.

My numbers might not be exactly correct but they should be in the right ballpark...

[Stephen Dixon]

The motor uses exactly the same amount of electricity, however, there is some slight amount of extra power lost in the house wiring for 115 V circuits. This is VERY small though, and would take a very expensive meter to be able to read it, I doubt you would see the difference on your electric bill.
Steve

[Dev Emch]

The motor uses exactly the same amount of electricity, however, there is some slight amount of extra power lost in the house wiring for 115 V circuits. This is VERY small though, and would take a very expensive meter to be able to read it, I doubt you would see the difference on your electric bill.
Steve

And if I take that same wire and stuff it into a plastic, insulated conduit and fill that conduit with liquid nigrogen, then how much power will be expended by this highly efficient transmission line?

[Jim Dunn]

Dev, you building a ray gun there??

[Barry O'Mahony]

While this is not code (Barry, don't flog me for this), I put 20 amp breakers in the sub box but used the standard 15 amp convenience outlets, and wired only a few outlets to each breaker (for the inspection, I had 15 amp breakers in the sub box).

Mike, this is OK according to the NEC as long as you use 12 AWG wire, and there is more than just a single receptacle on the circuit; i.e., on a 20A branch, if there is just one single receptacle on it, it must be a 20A. If it is a standard tandem receptacle, or if there are multiple receptacles, then they may be either 15A or 20A.

Just don't put 14 AWG wire on a 20A branch! The bozo electrician my General Contractor hired on my house remodel did that in some places. I'm still finding and fixing mistakes that guy did; the GC doesn't use him anymore.

[Mike Henderson]

Yep, Barry, that's exactly what I did - I wired all the convenience outlets with 12 gauge wire, and I have multiple outlets on a single circuit.

Glad to know that I'm legal! Thanks for the code reading.

Mike