View Full Version : Installing 220v circuit

Keith Wolf Ent
06-14-2008, 02:52 PM
Hey, I am adding an A/C compressor for central air , need to run 220 for about 75 feet outdoors. Has to be to code - Any ideas on any/all of the following?

1) Can I use plastic conduit or must it be metal? How about flexible metal wrapped (and then NOT enclosed)?

2) Is a 2P 20 Amp 3-wire breaker actually a 40 Amp breaker?

3) Is 10/3 600v the right wire?

4) Need a shutoff box at the compressor unit - any recommendations?

The compressor is a Goodman GSC-14 SEER, the coil is already in the central furnace.


06-14-2008, 03:54 PM
You need help.

2) NO. 20 amps is 20 amps. If the circuit is 240 volts, as opposed to 120, the breaker is 2 poles ( 2 switches) but 20 is 20......and that would not be big enough for most AC.

3) You have to get an electrician to look at the specs and the install manual for your air conditioner, determine what circuit breaker size is required, and the NEC will tell him what size wire to use, based on the amps and the distance.

A fused, or non-fused, disconnect, is a very common and necessary item for an AC install. Even HD would have one. Keep in mind that your local building code may require you to install a 120 volt service outlet adjacent to the outside unit.

How old is the inside coil? When is was installed, was it known that the outside unit would be 13/14 SEER? If not, you CANNOT use it. Also, the GSC 14 is available in R-22 and R-410 versions. Which is yours? Is the indoor coil rated for the refrigerant system you will be using?

Bob NH
06-14-2008, 05:31 PM
You need to look at the installation instructions and the nameplate to determine the wiring and circuit breaker requirement.

The nameplate of the equipment or compressor should be marked with either a "Rated Load Current" or a "Branch Circuit Selection Current". If it is marked with a Branch Circuit Selection Current; that is used to select conductors and circuit breaker or fuses. If there is no marking for Branch Circuit Selection Current then the Rated Load Current should be used. See NEC Article 440.

You can't use NM (Romex) outside. THHN/THWN in PVC conduit is a good choice. You should be able to get it all in 3/4" conduit.

If you need to install a 120 Volt circuit for service you can probably run it in the same conduit. You will have to check the derating due to extra wires in the conduit but it should not be a problem. Derating is from the 90C rating so sizes up to #10 are not affected at all and #8 is derated to 44 Amps.

You can use a flex conduit at the end but not for the whole run.

Speedy Petey
06-15-2008, 06:42 PM
4) Need a shutoff box at the compressor unit - any recommendations?Absolutely. Have an electrician do this job.

Keith Wolf Ent
06-15-2008, 08:28 PM
The coil is R-22, the unit is 30A max. There are multiple service outlets already at the coil - the (refrigerant/return) lines only have to run 10 feet or so. Caught a rattler up there today, after he almost got me mum! :confused:

06-16-2008, 06:49 AM
The coil is R-22,
On case coils and air handlers, you can decode the model number to determine the refrigerant. A final digit 6 incates dual compatible~410 & 22. The "C" in the model GSC.....indicates an R-22 unit, so you are good to go on that score.

Speedy Petey
06-17-2008, 03:56 AM
How many amps will R-22 carry? :p

06-17-2008, 06:37 AM
How many amps will R-22 carry? :p

:)R-22 is not measured in amps....it is measured in cubic dollars!!:)

Speedy Petey
07-07-2008, 06:40 PM
Wow, look. Another gold spammer who rated his spam with 5 stars.