Question about Air Condition service (240V, 30A)


Old 11-14-11, 08:10 AM
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Question about Air Condition service (240V, 30A)

I was hoping someone on the forum could answer a question for me. I apologize in advance for a rather basic question and any incorrect terminology.

I have a fuse/service disconnect box on the back of my garage that services my air conditioning condenser unit. This box is serviced by a 30A double breaker from the main distribution board.

Attached is a picture of the box. The incoming power enters the box on the lower left and the outgoing power exits the box on the lower right.

I have a couple questions:

1) I'm curious why the wiring to this box doesn't have a neutral ground wire. The wire coming into the box has one white, one grey and oone copper wire. In other 240 service (like a RV hookup), there is typically two hot leads, a green neutral ground and copper earth. Is this typical for an outdoor air conditioning unit? The house is newish (built in 2000) and located in Irvine, where you can't sneeze without planning permission and a code inspection. I'm quite sure this was inspected when I bought the house, so I doubt this isn't up to code.

2) If you look closely at the picture, the installer wrapped the white wires in electrical tape to make them appear black, from where they enter/exit the box to the terminal. I'm wondering if this is a standard practice and what's the purpose?

Thanks in advance for humoring a novice.
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Old 11-14-11, 08:29 AM
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The outside unit only uses 240VAC...not 120/240VAC like a newer dryer, range or as you mentioned an RV hookup. Straight 240 does not need a neutral as all current is carried on the 2 "hots".

The reason for the tape is to designate the white wire as a black (or hot). I've seen heat shrink, black permanent marker and tape all mentioned for this use.
Old 11-14-11, 09:31 AM
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Originally Posted by punuffney View Post
why the wiring to this box doesn't have a neutral ground wire.
It does have a ground - the bare wire. It does not have a neutral wire which would be white. Air conditioning units need only two hot wires and do not require a neutral wire so the installer did not put one in. Water heaters are another common household appliance that do not require a neutral wire.

wrapped the white wires in electrical tape
The black tape is used to re-identify the white wire as black. Wire companies pretty much only manufacture cable in black/white/bare so in some circumstances the code allows an installer to use colored tape, paint, or ink to recolor a wire if he needs to do so in the field.

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