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View Full Version : Run a 220 line from electrical panal to an outlet


realtree
Jan 26, 2008, 08:56 AM
I would like to run a 220 line from electrical panel
Box to an outlet for a table saw.what for breakers
And what gage wire should I use I will be about 20FT
From panel? The saw motor is a 2hp 1 phase, runs at 3450 rpm
And draws 10.2 amps

Stratmando
Jan 26, 2008, 09:00 AM
2 # 12's(black and black, or black and red, plus green for ground.
Also a 2 pole 20 Amp breaker to match panel.

eleud
Jan 26, 2008, 09:25 AM
I would like to run a 220 line from electrical panel
box to an outlet for a table saw.what for breakers
and what gage wire should I use I will be about 20FT
from panel? The saw motor is a 2hp 1 phase, runs at 3450 rpm
and draws 10.2 amps
10.2 amps is calling for a 40 amp breaker by code your only allowed to use 80% of the load so thererfore you will use a 40 amp double pole breaker and a 8 -2 wire black white ground both black and white wire gets hooked up to the 40 amp 2 pole break

tkrussell
Jan 27, 2008, 08:42 AM
Eleud, please explain why a motor load of 10.2 amps needs a 40 amp breaker and #8 wire?

I will explain how to size this circuit, and show that your advice is incorrect and way off base. If you were an electrical contractor bidding jobs, you won't be in business very long. Over-engineering is a dead giveaway of lack of Code and electrical theory knowledge.

The 2 HP motor, while nameplate states 10.2 amps of running load, you must use Table 430.248 of the NEC to size the circuit size and breaker size.

Being a motor that is cord connected, the motor should have built in thermal overload protection , so that does not need to be considered.

Per table 430.248, a 2 HP motor is to be rated at 12 amps at 230 volts since the supply voltage is actually 240 volts.

Circuit size is to be 125% of 12 amps, or 15 amp rated minimum, so #14 wire is allowed.

The breaker will only be needed for short circuit protection, and can be up to the maximum of 250% of the value in Table 430.248, or 12 * 250 %= 30 amps, for a typical inverse time circuit breaker, which is what is used in every home.

So, this motor circuit for a 2 HP 240 volt motor can be a minimum of #14 wire and be protected by a maximum of a 30 amp breaker.

Oh oh, here we go again, a large breaker protecting a small wire!

Any typical electrician would use #12 wire, which I would do myself, and use a 20 amp breaker, which is fine as long as this size breaker allows the motor to start. Many electricians do not know how to use Article 430 Motors, and cringe when a large breaker is used to protect a smaller wire.

This particular motor typically would not start under any load at all, so a 20 amp breaker most likely will work fine consistently. Once the motor is started and rolling, the breaker will only see the actual 10.2 nameplate amps, and be there for any short circuit event.

Again, I am assuming overload protection is built into the motor. If not, that is another topic, and overload protection is needed, in addition to any circuit breaker. For a motor circuit, any circuit breaker or fuse is only for short circuit protection of the circuit and device, and other devices are needed for overcurrent protection.

Hkstroud is incorrect with his explanation of 10.2 amps being 5 amp per leg. If one were to measure the amps in both wires feeding the motor, the meter will read 10.2 amps on each wire. And the actual running load nor nameplate amps is not to be used to size a motor circuit.

So, Realtree, the best advice you have received is from Strat, use a #12-2 cable, tape both ends of the white wire with color tape, and connect to a 20 amp 2 Pole breaker.

If the motor fails to start using the 20 amp breaker for some reason, this will be evident by the 20 amp breaker tripping at startup, then you may go up to a 30 amp breaker on the #12 wire.