My daughter just bought a house that has a window set up to take a large
window ac unit, with a 220 plug installed below it. (that is the only
electric plug near the window) She wants to put a smaller ac unit in that
window, that has a normal 110V plug. What is the easiest (safe) way of
converting that 220 plug to a 110 one?
Is there such a thing as a converter plug that would plug into the 220
receptacle with a 110 plug on the reverse side?
The most practical way to do it is: assuming the outlet is on a dedicated
circuit, it will be connected to a double pole breaker in your panel. Remove
the double pole and install two single pole breakers, either 15 or 20 amp
depending upon the size of the wire you have. Connect the black wire to one
of the breakers and the white wire to the neutral bar which will have many
other white wires attached to it. The second breaker is just there to fill
the void. Before turning the breaker on, replace the outlet with a 15 or 20
amp 120 volt outlet that corresponds with the size of the breaker you used.
First, let's use correct terminology: it's 120V and 240V, not 110V and 220V.
The easiest and safest way to convert this from 240V to 120V is to replace the
240V breaker with two 120V breakers, and replace the 240V receptacle with a
Check the sheathing of the cable to see what the wire size is. It will be
marked something like "AWG 12/2" or "AWG 10/2", indicating 12- or 10-gauge
wire respectively. The "/2" part means two conductors.
Size your replacement circuit breakers according to the size of the wire: AWG
14 requires 15 amp breakers *maximum*; for AWG 12, 20 amp; for AWG 10, 30 amp.
The size of the 120V window A/C you can use is limited by the breaker and the
wire; specifically, the current rating (amps) of the unit must not exceed 80%
of the rating of the breaker. So with, say, AWG 12 wire and a 20A breaker,
you're limited to a unit that draws 16A at 120V.
The 240V breaker will have two wires attached to it, most likely black and
white. (If they're black and *red*, STOP - following advice does not apply,
and we can address that in a different post if need be.) Turn off the breaker
and disconnect both wires. Remove the breaker, and replace it with two 120V
breakers. Turn them both off. Connect the black wire to one of the 120V
breakers, and the white wire to the neutral bus bar in the breaker box. (It's
the long bar with screw terminals and a whole bunch of other white wires
connected to them.) The other 120V breaker will be unused - it's there to fill
the rest of the empty space left when you removed the 240V breaker.
Then replace the receptacle with a 120V receptacle. Connect the black wire to
the gold-colored screw terminal, the white wire to the silver-colored screw
terminal, and the bare wire to the green screw terminal.
No, there is not. 120V circuits require a neutral conductor, which is usually
absent in 240V circuits.
Doug Miller (alphageek at milmac dot com)
Depending on the age of a piece of equipment, it may be labeled for
110/220v, 115/230v, 120/240v.. the voltages have crept upwards over
the years.. I'm actually used to actually seeing 125v/250v.. (or in
the case of 3phase 120/208Y, 125/213 or so.. ) I've also seen stuff
labeled for 117v.
The 1965 NEC handbook that I have in front of me, in the space of 2 pages,
refers to 110/220v, 115/230v, and 120/208v systems, as well as DC systems.
-- Welcome My Son, Welcome To The Machine --
Bob Vaughan | techie @ tantivy.net |
You must look and see if there is a neutral (white) wire in the box. (4
wires- black, red, white, bare)
If there is then you can replace the 240V outlet with a 120 V outlet.
Connect the white, black, and bare ground wire to the outlet. Cap off the
red wire in the box. (Or the red and black hots could be used on a 'split'
duplex outlet where top outlet for the AC and the bottom outlet for
If there is no neutral (white) wire then there is no 'legal' way to do this
without running a new cable.
There almost certainly is. The likely possibilities are black + white + bare,
and black + white + red + bare. Anything else would be *very* odd. The real
question is whether there is a red wire or not.
Doug Miller (alphageek at milmac dot com)
True - I was probably thinking more along the lines of range wire which was
black-red- bare or maybe it was 2 blacks and bare in my old house built in
I had forgotten that even in my newer house ('98) my central AC is wired
with 10-2/g with the white wire covered in black tape and used as one of the
Think about what you just said...........
Are you getting tired or just that stupid? I will assume you are just
tired. There is ALWAYS a white wire in ALL cable, whether it's NM,
UF, BX, or any other cable. The only way there would not be a white
wire would be is the circuit was run thru steel or pvc conduit.
Fishing another white wire thru conduit would be pretty easy unless
someone overloaded the pipe with wires. Or, if the conduit contains
two black wires, some localities allow one of the black wired to be
wrapped with white vinyl tape on both ends (being sure to use the same
wire of course).
After than, it's simply a matter of connecting the white to the
neutral in the box, replacing the dual breaker with a single, and
installing a standard receptacle in the outlet box. Of course
applying the proper size breaker and receptacle to match the wire.
Assuming your wire is at least a 12 gauge, use a 20amp breaker and
receptacle. If it's 14 gauge (doubtful), Then you may want to rewire.
If it's a 10 gauge, still use a 20A breaker and receptacle. but you'll
have a bitch of a time wrapping the wires around the receptacle
Honestly, if your knowledge of electricity is limited enough to think that
you could use a plug adapter of some kind to solve your problem you should
hire someone to do it. All of the advice given is good and would work, but
it doesn't sound to me that you should go anywhere near a service panel that
has the cover removed.
It's not so much that a thing isn't available. It's called a step-down
transformer. It's just that it's not practical. Here is a page with several
selections of such devices made to convert European 240 volt outlets to US
Out of curiousity,what size BTU is your daughter looking to install? If
it is more than 13,000 BTU, chances are you can get a 220V unit.
Otherwise anything smaller will probably be made to operate on 110V.
As was discussed in other threads, a 220V unit uses about the same
power as a 110V unit. However the 220V unit might be a tad more
efficient due to the reduced current draw.
Yes, as soon as you remove that panel, a giant bolt of lightning is
going to jump out and kill you, your family, your neighbors, and burn
down the whole city. You damn well better buy stock in a funeral
business and write a will before opening that panel
On Thu, 07 Jul 2005 01:53:21 -0500, firstname.lastname@example.org
Wiring isn't what I'd call "difficult" but it does take care. Get
yourself a decent reference--I've found "Wiring Simplified" to be Good
Enough most things, with a copy of the NEC for when I need to do
something more substantial, but YMMV and some folks like bigger books
with larger type and more pictures.
Study the job at hand carefully before you proceed, and decide whether
or not YOU are comfortable doing it.
As I said, it's not everyone's thing. If you don't feel comfortable
doing the job, don't be ashamed to get help from a more experienced
friend or hire a pro.
If yer gonna have to pay a real electrician it would be better to buy a 220
volt air conditioner. It probably would be easy to rewire for 110v for
somebody that knows what they are doing. There are too many unknowns to try
to explain it.
I've heard of marking wires at both ends with the correct color tape. You
electricians know about that don't you?
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