Elec. Disconnect box help

[Greg White]

Hi all,

Just a general electrical question, I am installing central air system (230V)and have got a 12 gauge line to the breaker 20A, 2 pole red(hot), black(hot), white(common), copper (grnd). Now I am installing it to a disconnect box (Cutler Hammer). In the box it has screw connections for the 2 ground (1 in from the panel and 1 out to the central air) and then 4 connections (2 in and 2 out) but I have 3 in and 3 out wires. Do I connect the red and black hot together on one side and the white common the other? I think this is right but just need assurance from someone who as done this before.

Cheers,

John

[Doug Miller]

White is neutral. Not "common". That's a DC term.

NO! NO! NO!

The red and black wires are what give you the 240 volts. Connect the two of them together, and you've just short-circuited a 240V circuit. If you're lucky, the breaker will trip before anything catches on fire.

240V devices don't use the neutral (white) wire at all.

The correct hookup is black to one hot terminal, red to the other hot terminal, bare to the ground terminal.

White connects to nothing. You don't even need it.

No offense intended, but....

Why would you think this is right? Please, please, please have "someone who has done this before" do it for you. It's clear that you don't know what you're doing, well enough to do it correctly or safely.

[terry]

xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx Tend to agree:

Although might word it as "Many 240 volt devices do not need the neutral (white) at all."

Just thinking about 230/240 volt items in this house.

No neutral: Hot water heater. Bench saw. Electric baseboard heaters. A few 230 portable power tools (I make sure they are grounded though!). A plug in 230 volt welder.

230 volt items that do also use neutral. Cooking stove. The clothes dryer; although this varies from model to model.

A proper ground is essential for all.

These people who work on the "Connect the red wire to this and the white wire to that ............ etc.(and worse. e.g. connecting the red and black together!!!!!) basis"; clearly do not understand what they are doing. One danger is that a they may just get it to work, but unsafely! The OP should make sure that there is no neutral required by the equipment; if it is, the connection box mentioned may not have sufficient terminals; or 'the neutrals should be connected through', in the Cutler Hammer box, using an approved method. BTW insurance companies are not impressed by fires and electrical hazards that may be due to improper wiring! Do implore; get someone who 'understands' 230/115 volt AC wiring to at least assist!

[Doug Miller]

Those are 240/120 devices, not 240.

[Greg White]

OK I got it now,

I have the wrong cable. The same box is here:

should have gotten the red,black,green cable. Would it be possible to use the whit as a ground since my bare copper ground is thinner than the white?

Cheers,

John

[RBM]

Yes, just mark it green at both ends, although all four conductors should be exactly the same gauge

I should have gotten the red,black,green cable.

[Doug Miller]

Only if it's larger than 6AWG, otherwise not permitted. Code requires continuous green for 6 & smaller.

[Doug Miller]

Not necessarily -- see below.

What's shown in the illustrations at that link is actually individual conductors. Good luck finding premises-wiring cable that's red/black/green.

You can use black/white/bare, just mark the white wire red at each end.

No. Code requires the grounding conductor to have either no insulation, or continuous green insulation. It doesn't meet Code to re-mark a white wire green. The only exception is conductors larger than 6 gauge, which you probably don't have.

You sure about that? It should say on the cable sheath exactly what size the conductors are.

What gauge are the wires, and what is the rating of the breaker you're planning to connect them to?

[RBM]

It's permitted in a multi wire cable, which is what he's using

[mm]

I don't understand their stupid warning on the URL: " You can prepare the wiring for hook-up, but only a skilled contractor should complete the high-voltage wiring. Inexperience can cause electrical shock or damage to your equipment or property. "

I've gotten a hundred shocks from 110AC to 2,000 volts in a tv, to

50,000 volts from a spark plug wire. None of them are as likely to kill as the 220 from the this wiring, but they only mention "electrical shock", not death.

[Doug Miller]

Yes, "where conditions of maintenance and supervision ensure that only qualified persons service the installation." [Article 250.119(B)]

That doesn't apply to *any* residential installation.

[RBM]

Where does it specify that it doesn't apply to any residential installation? My interpretation is: Who has more control than a homeowner to assure that only qualified people work on their equipment. That being said, Greg White in considering connecting red wires to black wires, does defeat my argument

[Doug Miller]

"Where conditions of maintenance and supervision ensure that only qualified persons service the installation."

The Code explicitly defines "qualified person" as "one who has skills and knowledge related to the construction and operation of the electrical equipment and installation and has received safety training on the hazards involved."

In any residence, the installation can be serviced by the homeowner, his half-wit brother-in-law, his alcoholic buddy from work, the neighbor who "knows all about it" but whose actual experience doesn't go beyond changing light bulbs, etc. etc. etc. There is *no* assurance whatever that unqualified persons will not service the installation.

Oh, I dunno, a factory foreman or a building supervisor, perhaps?

Well, there is that, too....

[Stormin Mormon]

The two red wires go on one side of the box, the two blacks on the other side. When you put the connector handle in, the red should connect to the red. The black connects to the black.

Your outdoor unit probably does not use a white wire, so that one gets wire nutted and folded over.

The exposed metal connecter at the bottom of the disconnect connects the green or bare wires.

I've been installing central AC for seven years. I think you're not right.

[Stormin Mormon]

Use the bare for a ground, even if it is thinner. If you start changing colors around, you'll confuse the next guy who works on the device. Use the bare for a ground.

[Doug Miller]

Hold on there a minute. If the circuit is 30A or less, it's a Code violation to use an equipment grounding conductor that's smaller than the ungrounded conductors. (Table 250.122 -- minimum size grounding conductor is 14AWG copper for a 15A circuit, 12AWG at 20A, 10AWG at 30A.) At 40A and higher, it's permitted. We don't know yet what size conductors the OP has. I asked him yesterday, but he hasn't answered.

[terry]

Good point; he may have acquired some #14 AWG (Red, black, white and bare ground) typically used for domestic lighting circuits or low capacity 15 amp maximum outlets???? No good for a 20 amp or 30 amp circuit! Do wish the OP would get someone to assist who knows how to do the work safely and to code. The idea of using the wrong colour especially for ground instead of neutral is 'wacky'. It might not cause an immediate problem but God help the electrician or do it yourself-er who tries to understand what has been 'hooked up' some ten or fifteen years from now.

[RBM]

Your interpretation is probably what they intended, but I'd still maintain from my experience as a contractor having worked in hospitals, nursing homes, factories, office buildings, etc. , the group of mutants that you list, are indeed the same ones I've seen

[RBM]

In his original post, he says he has a "12 gauge line"

[Doug Miller]

LOL -- my experience observing the quality of commercial installations is limited to under-the-floor power wiring in computer rooms, where everything I've ever seen has been first-rate work. I'm sure you've seen quite a bit of stuff that was second-rate, to be charitable.