Subpanel Circuit Question

[Jay M]

Eariler this summer I had an air conditioner installed. I happened to look in the subpanel today. The AC is on a double breaker totalling 60 amps. Both the Black and White wire go to the breaker and the bare ground wire goes to the neutral busbar. Obviously, the white wire is being used as the second hot. This is regular romex cable. The gauge is okay, but there's no conduit to use as ground and no fourth wire. Is this acceptable? Shouldn't there be 4 wires? Black and red going to power, while white (neutral) goes to its busbar and bare wire ground going to the ground busbar?

I also have another breaker dedicated solely to a space heater (hard wired). This circuit is wired the same as the AC with only 3 wires. Was this an old way of doing it before ground wires were used or do some appliances just not need ground?

[coloradotrout]

what you are describing is a 220V circuit.

I just had AC installed.. i should take a look at mine.

I think it's OK to wire 220 that way -- I did that for my shop; using

3 wires as you note. I read up on that and had enough evidence to suggest it was OK

But not sure if wiring AC is OK that way; expecially w/ 60 amps. My shop 220 circuits were only 20 amps.

[Jay M]

Right about 220. When I rewired my 3-wire electrical washer cirucuit into a

4-wire, I did so because it was safter (and up to code). To my understanding, the AC (and my space heater) are wired "correctly", however, they don't have the added safety of a ground wire (nor do they meet code color for conductors). I suppose I could rewire them and just run a ground wire to the chasis.

The other issue is that because the panel is a subpanel, both the ground and netural busbars are isolated. Because the romex (for the AC circuit) was black/white/bare, and because the white is being used as hot, that means the bare is neutral. So now, I have a bare wire going to my neutral bus bar which will probably touch the subpanel chasis at some point which means it will also go to the ground busbar which is connected to the chasis. Follow? This is another no no.

[Paul A]

*ALL* appliances need ground. It is what protects you from shock or death if a short occurs in the appliance or its wiring.

Not all appliances need a neutral. If all components are 220 V, there is no need for a neutral. If some require 120v, then a neutral is needed. Some a/c units do not require a neutral and use a completely separate circuit (on a separate breaker) for their 120 needs.

If the bare wire is being used as a ground, then it is on the wrong bus.

If there is a need for a neutral, you have a bigger problem and you are short a conductor in the cable.

[nospam]

What real difference does it make since the Ground buss and the neutral buss are connected to each other in the mail panel box and both are then connected to the wire going to the system ground bar buried in the ground?

[Thomas D. Horne]

Move the bare wire to the Equipment Grounding Conductor (EGC) buss bar that is bonded to the sub panel's enclosing cabinet. In NMC (romex) cable the bare wire may not be used as a neutral [or more properly as a grounded current carrying conductor]. Since the two loads you describe are both 230 volt (nominal) there is no need for a neutral in the circuit.

-- Tom

[Thomas D. Horne]

With the ground conductors attached to the sub panels neutral bar the shell of the appliances and fixtures that those circuits supply will always be at an elevated potential relative to grounded objects. Even with the neutral intact and performing normally these surfaces will have a touch potential equal to the voltage drop caused by the impedance of the neutral in the feeder that supplies the panel.

If anything were to happen to the neutral conductor in the sub panel's feeder that causes it to go open or develop a high impedance then the conductors that are connected to it's neutral buss bar will no longer be grounded current carrying conductors and they will be at an elevated voltage relative to naturally grounded surfaces such as metallic plumbing fixtures, heating ducts, concrete floors, tile walls, and so fourth.

If the neutral is kept isolated from the possibility of human contact by proper installation and maintenance then no harm to the buildings occupants will result. The 120 volt loads served from that panel would still be damaged or destroyed but there is a much lower likelihood of fire or electrocution.

-- Tom

[Paul A]

But first -- check at the equiptment end and verify that the bare wire is being used a a ground, not as a neutral -- that there are *no* 120 v requirements in the equiptment (transformer for controls, for example). If not requirements, move the wire. If there are requirments, run a new line.

[Thomas D. Horne]

Dam it, Why do I always fail to anticipate just how damnably careless some previous installer may have been. Thank you for catching that omission in my advice.

-- Tom

[Stormin Mormon]

With the AC, the black and white carry power, the bare wire is a ground.

220 volts does not use a "neutral".

[NoSpam]

[Jay M]

Thanks to everyone for their help.

Okay, I'll check. So being-used-as-ground means that ground should be going to the chassis of the appliance, right? As far as I can tell, there are no lights or any other gizmos to the AC or the space heater, so I think there's a good chance there is no need for a neutral and so I'll switch the bare wire to the ground busbar. I'll be happy not to have to run new line(s).

BTW, I know that in 3-way switches, you mark the white with red to indicate swtiched hot. In the 240 case I have described, what is the proper way to mark the white wire as hot? Just mark it red?

[Paul A]

Yes and yes (at both ends and any junctions)

[Calvin Henry-Cotnam]

When a white wire is used as a hot (switched or not), it should be marked in some way. You can do this with a permanent marker, a piece of electrical tape (any colour exept white or green!), or if you want to be fancy, a piece of heat shrink tubing.

[Calvin Henry-Cotnam]

If the item uses JUST 220/240 V, then no neutral is needed. An electric range has 120 V items (clock, rotisserie motor, convenience outlet) and must have the neutral.

In our kitchen, we have a cooktop and built in oven. The cooktop is strictly

240 V, so has no neutral. The oven needs both, so it has a neutral.

The A/C is only 240 V. Other items I have worked with that use only 240 V and do not need a neutral include baseboard heaters and pool pumps (pool pumps usually can be wired for either 120 or 240, but in the 240 V configuration, only two lines are needed - no neutral).