Basic Electrical Questions, Please Help

Old 09-01-10, 06:06 PM
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Basic Electrical Questions, Please Help

Hello, here is what I've got, I need someone to explain to me :

#1.what determines the amount of electricity that flows through a circuit? the appliance? The circuit breaker?

Here is why I ask, I have a project. I have a 3 wire, 40 Amp 220v line that a elderly sick man has asked me to wire a 20 amp 220v Air conditioner and a 20 amp 220v HID light too. My question is, can I wire this circuit with a 10 gauge wire, and 2 20Amp receptacles, both are wired for 220. Will the 40 amp line I am considering hooking these 2 receptacles blow up the equipment (AC AND LIGHT). I think what I am attempting to ask is, what determines the electrical current in any giving circuit?

Thank you in advance for your time and advice...
Old 09-01-10, 06:55 PM
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I'll try to give this a shot...

You are asking if you can power a 220v air condition and a 220v light off of one 220v 20amp circuit?

If so, you would need to find out the amperage draw of both the devices. There should be a nameplate on it stating the amperage. If the amperage of both of them exceed 80% of the breaker, it will most likely be overloaded, causing the breaker to trip.

The wire size of #10 is plenty. You could actually use #12 for a 20amp circuit.

I would be careful too about doing electrical work on someone else's home if you are not a electrician. You could be asking for some liability issues if something were to go wrong.

Also, you may need to pull a 4 wire setup, but I'll let a electrician correct me on that if I'm wrong.
Old 09-01-10, 08:16 PM
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I seriously doubt that anywhere in the US of A, except MAYBE in the sticks far from civilization, do you have 220 volts. When I was a kid (I'm 60 years old now) the standard was 117 to 120 volts along with 234 to 240 volts.

What do you mean by a "three wire" line? Is it two "hot" wires and a neutral or is it two hot wires and an equipment ground? Does the circuit breaker have 40 printed on it or are you assuming that two 20 ampere circuit breakers linked together equals 40 amps?

If it is a 40 ampere circuit breaker then the minimum size wire for all parts of the circuit outside of manufactured utilization equipment is #8 copper. You CANNOT use a 20 ampere receptacle on such a circuit.

To answer the question of what determines the amount of current in an electrical circuit it is the voltage applied divided into the resistance of the utilization equipment. In other words, the device that actually "uses" the electricity is the determining factor in how much amperage is used. In practice it is a bit more complicated because of several safety requirements.
Old 09-01-10, 09:04 PM
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I would seriously back away from this one guy. Let the man hire a electrician to do whatever he/you are trying to do here. I dont really understand what you are asking but from what I gather you should not be messing with it. Hope this helps.
Old 09-02-10, 06:40 AM
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It would be much better to have two circuit installed for this purpose.

There a several problems with your proposed solution, along with doing work in someone elses house.
Old 09-03-10, 10:36 AM
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..the fact that it's for a high power HID light and air conditioner raises red flags too. Sounds like the guy wants to grow some 'medicine'..
Old 09-03-10, 11:36 AM
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I draw kind of a funny line - if a person shows a little expertise, I'm usually comfortable with them working on a 120V issue

However, 240 is a whole different animal in my mind and there should be no doubts if you're working with it

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