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 jackscanlon 12-31-2010 11:26 AM

Voltage Drop ?

I've installed a floodlight out in my yard 250 ft. from the house. I want to switch it from either the pole or the house and I want an outlet which is always hot at the pole. I like the "coast 3-way" wiring scheme since it will save me an extra 250 ft. conductor for the outlet. My concern is that with certain switch combinations it appears that the hot leg to the lamp could be 750 ft. in length. The light is metal halide pulse start with the ballast rated at 120V and 2.5 amps. Are there any potential light or light fixture performance issues ?

 AllanJ 12-31-2010 11:40 AM

What is a coast 3 way wiring scheme?

You would not need a 750 foot current path.

You need 4 wires from the house to the pole to have 3 way switching of the light and a receptacle that is always live.

You need 3 wires from the house to the pole where the 3 way switching controls both the receptacle and the light at all times.

You need just 2 wires from house to pole where you have a master switch for both light and receptacle at the house and optionally a slave switch that turns the light off at the pole.

To run a reasonably heavy load appliance such as a hedge trimmer, you should use 10 guage wire. For only occasional and small current usage (about 7 amps including the light) you can get away with 12 gauge wire.

For a 15 amp circuit you could run a 14-2 cable for the light 3 way part and a 10-2 for the receptacle and shared neutral.

10 gauge wire: 0.00118 ohms per foot. 12 gauge wire: 0.00187 ohms per foot. The number of volts dropped within the wires from your 120 volts (same number from a 240 volt circuit) equals the number of amperes being drawn times the resistance (in ohms) of the circuit round trip.

 J. V. 12-31-2010 11:55 AM

1 Attachment(s)
Here is an interactive drawing of a California three way switch diagram. I am not certain it's legal as you are switching the neutral. If thats the case (non-compliant) it would be a waste of time to pull wires for it.

I think at one time cal 3 ways were allowed and we sometimes run across one that makes for difficulty figuring out until you understand what you have. I personally would never use a cal 3 way method.

 oleguy74 12-31-2010 11:57 AM

Quote:
 Originally Posted by AllanJ (Post 559704) What is a coast 3 way wiring scheme? You would not need a 750 foot current path. You need 4 wires from the house to the pole to have 3 way switching of the light and a receptacle that is always live. You need 3 wires from the house to the pole where the 3 way switching controls both the receptacle and the light at all times. You need just 2 wires from house to pole where you have a master switch for both light and receptacle at the house and optionally a slave switch that turns the light off at the pole.
for a lite with 3-way and always hot outlet,you need 5 wires.1 neutral,3 hot,one ground.with #10 wire drawing 10 amps you would be at 6 volt drop.if you use a multi-wire ckt and keep load down on the outlet #10 will get you by.

 AllanJ 12-31-2010 12:04 PM

Oops, I did not count the bare wire as one.

 oleguy74 12-31-2010 12:07 PM

Quote:
 Originally Posted by J. V. (Post 559714) Here is an interactive drawing of a California three way switch diagram. I am not certain it's legal as you are switching the neutral. If thats the case (non-compliant) it would be a waste of time to pull wires for it. I think at one time cal 3 ways were allowed and we sometimes run across one that makes for difficulty figuring out until you understand what you have. I personally would never use a cal 3 way method.
not legal beacause you canot switch a neutral.

 jbfan 12-31-2010 12:11 PM

Quote:
 Originally Posted by oleguy74 (Post 559723) not legal beacause you canot switch a neutral.
Agreed!

 Speedy Petey 12-31-2010 12:51 PM

Quote:
 Originally Posted by jackscanlon (Post 559698) I like the "coast 3-way" wiring scheme since it will save me an extra 250 ft. conductor for the outlet.
And other than here no one has told you how <not smart> and unsafe this is??? All to save \$20 worth of wire?

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