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When using 10-2 wire for a 3 wire dryer can the neutral wire be the uninsulated ground wire or does it have to be insulated?

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December 03, 2012 11:58PM

You need 10-3 PLUS ground for this 220v application. The ground

is the only uninsulated wire. If you did it with 10-2, I would

suggest re-doing it correctly ASAP. That leaves you without a

neutral and potential for supply to go through grounding wire to

breaker box (or through a person to ground, causing

electrocution).

Clarification: you do not need three current-carrying conductors

for all 220 v applications. There is no neutral in 220, so you only

need two "hot" leads and a bare safety grounding wire. If the

appliance (as here, a dryer) actually needs 110 in addition to 220,

then yes, you need 10/3 cable, plus grounding wire.

First of all the word "shield" in electricity refers to blocking

magnetic flux. What you meant to say is "insulated" which means to

block conductivity. When #?-2 NM w/ Ground wire is used in a 240

volt circiut, there is no neutral conductor. You're connecting the

black and white wires hot and the bare wire as equipment ground in

the distribution panel. On the dryer a 3 wire cord is connected

with the neutral and ground terminals jumpered, so that the ground

wire ran to the dryer serves as both ground and neutral. This is

how dryers have been wired for many years in most of North America.

Electrically this works because ground and neutral have the same

electrical potential. Technically, however, it's wrong because a

ground wire shouldn't be used as a normally current carrying

conductor, and in the case of a dryer, the motor and control

circuits are 120 volt, causing a small current flow in the ground

conductor with a 3 wire supply.

The real question is: Does a residential dryer require a

separate neutral conductor or just a ground conductor? The same

question asked differently does a residential dryer require a #10-2

or #10-3 supply cable?

The answer is: If this is an existing dryer supply, a #10-2

cable with a 3 prong cord will work just as well as it has for

decades, but if this is a new installation, a #10-3 cable and a 4

prong cord is required to abide with current laws.


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