220 wire size Hello buickanddeere and T-Bone

Can some one tell me per the national electrical code what size wire you need for 220 at a set amps for a distance of 40 ft.

I need to run 3 220 lines for my new a/c unit.

Outside unit needs 40 amps. Inside unit needs 1- 60 amp and 1- 30 amp.

I am thinking I will need 30 amp 10/2 with ground
40 amp 8/2 with ground
and
60 amp 6/2 with ground
But would like to make sure before I go buy the wire.

This is a 3.5 ton heat pump.

The out side unit.
I have cinder blocks mortared together and the center filled with dirt. On top of this I have a 4" poured in place slab with the a/c unit set on this. I have it raised with the blocks to prevent mower from hitting unit and keeps it out of the dirt/grass level.

The unit is 220 and is marked min circuit amps 23 and max overload protection of 40 amps so I installed a single breaker box on the house next to the unit with a 40 amp breaker in it and a whip to the unit.
It is about 38 ft from the house 200 amp service entrance.

The inside unit is just on the other side of the wall from the outside unit. 4 or 5 ft at most separate the two units.

The inside unit is also a 220 unit and is marked min circuit amps 7.8/7.8 and max over current protection of 15/15.
BUT I have a 15kw backup elect. heater coil added to this inside unit for the really cold days since it is a heat pump. The heater coil is made to fit this unit. It came with 2 breakers pre wired to the heater coils. It also has a plug that you plug into the blower unit to provide elect. to the unit.
The wiring diagram for the heater coil says…….
Kilowatts 10.6/14.25
Volts; PH; HZ. 208/240/1/60
Heater Amps 50.96
The breakers are marked 10kA 120/240V
One of the breakers is marked 30 on the switch and the other is marked 60. This unit is also about 38 ft from the house 200 amp service entrance.

I think by the time I go around corners and into the units to hook up I will be at 45 to 50 ft max wire length.

I will be running the wire in conduit under the house to the inside unit closet area and then from here I will have the outside unit wire enter the back of the box through the wall and the inside unit wires enter the unit. I am waiting to see what size wire I need before buying conduit so I can get one big enough.

The link is to a picture of the inside unit breaker panel. If you click on the bottom right of picture it will explode to a size you can see all detail.

Thanks for the help.
John

• breaker picture

John

I think you are looking at it wrong.

The fan (unit) is 7.8 min and 15 amps max. I take this to mean it is about a 10 amp fan. The heater coil is 50.96 amps so lets say 51 amps.

51 amps + 10 amps = 61 amps
To get breakers to be at 80% use you will need about 76.5 amps worth of breakers.
I have 90 amps. A 60 and a 30. Guess a 50 and a 30 would have worked but this is what they put in it.
The heater has 3 coils.
2 are run by the 60 amp braker and 1 is run by the 30 amp breaker.

The fan can be run by either breaker so that it will run in heat pump mode or heater mode.

In fact if you look at it this way you really need 90 amps to cover every situation because either breaker will run the fan.

90 amps x .80 = 72 amps
72 amps - 10 amps for fan on 1 breaker - 10 amps for fan on other breaker - 51 amps for the heater = only 1 amp over.

From what I have read and found out here I feel my wire choices will work.

Thanks for the help.

Next..... ..
The 40 amps is for the outside unit. I have a single 220 breaker box mounted on the outside of the house next to the compressor with a whip going to the unit.
There will be a matching 40 amp breaker in the house 200 amp box.

Thanks.

I'm with BD, more info on the inside unit or air handler as well as distance from load center.

The OS unit, 2-#8awg, 1-#10 neutral, and a #10??? bond ground wire if EPVC, no bond wire if EMT. The neutral will be needed for LV control circuits.

A fused disconnect with-in unit sight is also required. I seam to remember a no more than 6ft rule here for some reason.

A 2" thick concrete pad 4" larger than the condensor unit size is required for the unit to sit on. They use a different term for the concrete pad that I can't remember but most inspectors won't pass anything but concrete or concrete paving blocks layed tightly.

I'm unsure of the minimum bond wire size. Just been to long ago.

T_Bone