Choosing a 120 or 220 v Air conditioner

lazo177May 3, 2010

Help! live in an apartment building in NYC and have the option of installing either a 120v/10 amp or 220v/4.5 amp air conditioner. The apartment has both 120 or 220 wiring. Both units cost the same. Which would be more efficient and save me money in electric bills? Consider that the unit will only get about 4-5 months of use per year.

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If they have identical cooling capacity there is no real difference.

    Bookmark   May 3, 2010 at 5:36AM
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Given the circumstances as described, I would choose the 240 volt unit. In event of a power brownout, the 240 volt unit might handle it better. And any conductor has voltage drop when in use. Conductor sizing per code helps keep voltage drop within acceptable levels. Higher amperage increases the voltage drop. So the lesser amperage of the 240 volt unit will result in less voltage drop and greater efficiency. In this case, the difference will not be great, but it will exist.

    Bookmark   May 3, 2010 at 7:56AM
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It the AC rated 208-240 or one of these? Is the building 120/208 or 120/240? Do you have a lot of room in your service panel?

When specifying power-hungry, expensive laboratory equipment, I tend to stay away from stuff labeled 208/240 for a 120/208 building. The 120 option on 120 V outlets will do better with voltage reductions than 208/240 appliances powered by 208. The same may be true for AC compressors.

The 120 ac circuit will only require one space in your service panel while the 208/240 will require two. Balancing that, the cable for 208/240 will be less expensive because there is less copper in it. The latter is probably only significant if you have a large distance between the service panel and the AC.

    Bookmark   May 3, 2010 at 2:10PM
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You'll be better off with the 240v and I couldn't describe it any better than bus_driver did.

Is the 240 available within the reach of the electrical cord or will it have to be added?

    Bookmark   May 3, 2010 at 2:39PM
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Hey, thanks for the comments. The AC is 230/208, the building is 240, and the 240 is within reach. The 240 breaker already exist. Anything else?

    Bookmark   May 3, 2010 at 11:03PM
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"So the lesser amperage of the 240 volt unit will result in less voltage drop and greater efficiency."

Providing closer to nominal voltage under starting surges also shortens the start time and results in less equipment heating and wear and tear.

The 240 V unit is very likely to last longer for this reason.

    Bookmark   May 4, 2010 at 10:01AM
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While many people have made points here that are technically correct, the big picture is that you will have about the same installation and operating costs for both systems. Both use the same process to cool air and the amount of cooling is the dominant factor in determining operating costs. The only way you are going to save significant money is by raising the temp a degree or two. All the other considerations are just nibbling around the edges and are only going to amount to a few pennies per day.

    Bookmark   May 4, 2010 at 10:43AM
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If this is a portable aircon that you may take with you when you move, I'd suggest a 120v unit for its easier installation in most other homse and apartments.

If it's to become part of the structure, it makes almost no practical difference for a residential user. Choose on the basis of SEER (efficiency), noise level, serviceability, and reputation for durability, and let the installer worry about the voltage.

    Bookmark   May 4, 2010 at 9:49PM
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