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220V to 110V Q's & A's

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Wiring from 110 to 220

I need to change a plug in outlet from 110to 220 so I can plug in a window AC/Heating unit. What do I have to do?

More than likely, you need to run a brand new wire to the outlet from a new breaker in your box. Unless (which is unlikely) the outlet is the only one on a circuit now.  Let me see if I can explain.

To wire a 220 outlet, a new 220 (double pole) breaker is installed in your box. From this both the black and the white wires will be hot when checked or wired to ground. You are wiring from both sides of the 110 in your box. Going from either line to ground is 110. Going from one side to the other is 220. That is why the breaker in your box is a double one ganged together.

Ok.. so if you are not comfortable with wiring in your service box, leave that to an electrician. But you can run the wire to the outlet yourself.

For an air conditioner, you probably want a 20 amp circuit. So the sire size would be 12 gauge.

You will need a 220, 20 amp outlet. And if you are wiring this separate, go with a new outlet box and leave the old one be. (unless for reasons of "looks" you don't want another outlet there.)

If by some lucky chance the outlet now is the only outlet and fixture on the circuit, you would only need to change the outlet to a 220 outlet and connect the wires in the service breaker box to a 220 breaker. The size of the breaker and the outlet would depend on the present wiring. So if there is 12 gauge there now, you can go with a 20 amp breaker and outlet. If there is only 14 gauge then you would go with a 15 amp outlet and breaker.

Wiring in your service box is dangerous, because even when you turn off the main circuit breaker, the lines coming in attached to the main breaker are live (and bare) So the box is never dead unless the power company shuts off the power.


Wiring from 220 to 110

I was told that you can tap off of a 220 source and make a 110 outlet or fed from that. Is this possible and what would you have to do?

If your 220 circuit has a third wire (a neutral) with it, you can wire either line to the neutral to give you 110. But you can't if it doesn't. (You do NOT want to wire either to the ground, which would give you 110 but is NOT safe)

Often the 220 circuits running to dryers for instance come with a neutral (by code they are required to now) but a straight 220 circuit may not have the neutral.

There are of course a lot of codes written to govern your wiring, and it is always best to check if what you are doing is allowed. Check with your town's building inspector. For instance the dryer line is supposed to be a dedicated line, so you shouldn't tap into that one. (I used it as an example) You are allowed to do wiring in your own home without a license, but you should still follow all codes, they are for our safety.

Wiring from 240

I was told that you could use a 240 feed for a 120 circuit. if this is possible please let me know what do do.Thanks.Also I have a 3 &4 way switch that just stopped working and the tester shows very little power going through it. I'm baffled. I have wired whole houses but never have run into this.

If your 220 circuit has a third wire (a neutral) with it, you can wire either line to the neutral to give you 110. But you can't if it doesn't. (You do NOT want to wire either to the ground, which would give you 110 but is NOT safe)

Often the 220 circuits running to dryers for instance come with a neutral (by code they are required to now) but a straight 220 circuit may not have the neutral.

As for the 3-way 4-way switch, did you check all the connections? If they are all good, I would try replacing the switches. No other idea comes to mind.

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220v convert to 115v? 

I have a 220v outlet for an a/c I would like to convert to a 115v for a new a/c unit. Can this be done with the existing wiring? If so, how? Or is there a plug converter that may step down the voltage and change the plug to accommodate the standard 3-prong?

It is relatively easy, but if you are inexperienced in working in your breaker/fuse box, you should have an electrician do it.

What you need to do, is replace the 220 breaker with a 120 V breaker. In doing so, you will disconnect the white wire from the old breaker and connect it to the common bar. Then at the outlet, remove the 220 V outlet and install a 120 V outlet. The wiring will stay the same, as long as you had, a 20 Amp circuit before and you stick with 20 amps, or had a 15 amp circuit and stick with 15 amps in 120 V.

Self-contained forced air heater

I am going to purchase the above item; however, I must choose between a 120 volt or 240 volt heater depending on the voltage of my power supply. How can I find out what voltage my power supply is? Additionally, what is the difference between single-pole and double-pole? My house is relatively new (less than 3 years old) if that makes any difference.

Most (or all) of your outlets are 120 V AC. That is the standard size with the exceptions for electric ranges, electric dryers, some large air conditioners, etc. In other words large loads.

You can tell when looking at the outlet. If the two openings for the plug are vertical openings, then the outlet is 120V 15 amp circuit. If the left opening has a horizontal slot also (with the ground plug oriented down) then it is a 120V 20 amp outlet. If the right slot has a horizontal slot (only) it is 240 V outlet. That is done so you can't plug the wrong plug into the wrong outlet.

Higher amp rating 240V outlets such as the dryer or oven are different again.

Your house has the capability to have outlets wired at 240V, but it would involve running a new wire from your supply box, etc. So unless you have an outlet already wired for 240V that may be there fore a large air conditioner, you will probably want the 120V unit.

As for your question about poles.. to what are you referring? You may have heard it in reference the the circuit breaker that feeds the outlet you will use. If it is double ganged breaker, i.e. a two pole breaker, than that is a 240V circuit. If the breaker is a single switched, i.e. single pole circuit breaker, the circuit is 120V.

Changing 3 wire to 4 wire outlet

I have a dryer that came with a wire with three prongs. I moved into a house with a four prong 220 outlet. What is the extra prong for? You have two for the power, one for ground, what is the other one for? Also the two prongs are flat, one is round and one is shaped like an L. Which is which? Are all necessary?

Recently the code changed on wiring dryers. Previously when something like the timer needed 110V, it used one of the hot legs and the neutral. This outlet is essentially ungrounded although the chasis ground in the dryer was usually connected to the neutral lead. Which is contrary to every other application... so it was changed.

Now the wire that runs to a dryer has four wires in it. The two hot legs.. (220V across them) the neutral (for 110V items) and the ground; to ground the chassis.

Where does that leave you? You can buy a replacement plug (or pigtail as they are sometimes called) with the four prongs. The two outside ones are the hot leads. The center and lower one are the neutral and the ground (the ground is the round one, the L shaped one is the neutral.) When you wire it, obviously the hots go to the new hots. Then separate the neutral wire from the ground strap on the machine. The ground can then go to the ground and the neutral to the neutral...That all makes sense?

Click here for our Wiring A 3 or 4 Way Switch Article
Click here for our Reverse Polarity Article
Click here for our Electrical Tips Article

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