Replies

1. 
   DaveRicheson | Jun 19, 2004 11:37pm | #1

   220v/20 amp  is ok on 12/wg. if the length of the run is not overly long.

   Are you talking about a central unit or a window shaker? Either case you need to look at the name plate for voltage and amp ratings.

   If the wirimng is under size orthe voltage drop to great a couple of things will happen. Compressor will not start and/or the breaker will trip on over current. Voltage drop will eventually cause the motor to burn up.

   Basically we need more information than has been provided.

   Dave

1. 
   Tomar | Jun 20, 2004 12:32am | #3

   He actually had two of them installed.  They're window units.  They're both brand new and identical.  He quoted 220volt,20amp out of the 'owner's manual'.  They're both running steady but barely cooling.  He said the guy ran two dedicated circuits, each on their own breakers (they're each about 50' from the panel).  I was just wondering if it might be undersized wire because he said the guy had to run back to the store because he had the wrong receptacles. (after the wiring had already been run).  I haven't seen it so I don't know what gauge he actually ran.  Just a 'longshot' I guess, it just seems funny that they're both brand new and neither is doing the job.

   Edited 6/19/2004 5:47 pm ET by TR

1. 
   DanH | Jun 20, 2004 01:48am | #4

   Maybe he installed them backwards. (:-))

1. 
   Tomar | Jun 20, 2004 03:03am | #6

   Maybe - - I'll ask him if it's cooler outside.

2. 
   Tomar | Jun 20, 2004 03:13am | #7

   I went over and checked it out, the wiring is 12/2 w/g and the breakers are correct.  It seems the problem may be he bought them at the 'Cheapo'.

2. 
   remodelerdw | Jun 20, 2004 06:24am | #8

   Maybe all they're doing is pulling moisture out of the air?

   i.e. they've hit the spot on the humidity / temperature curve where all the unit can do is pull moisture, and they're undersized to move down the curve and have an affect on the air temperature?

   remodeler

   If the units are dripping outside they're working.

1. 
   BillHartmann | Jun 20, 2004 03:04pm | #9

   "If the units are dripping outside they're working."

   Most units nowdays are designed not to drip under "typical" conditions.

   They hold the condensate in a tray and sling it on the condesor coil and use that to help disapate the heat.

1. 
   DanH | Jun 20, 2004 05:44pm | #10

   Yeah, but if you hold your hand where you can feel the air blowing outside, you will feel droplets of water hitting your hand.

2. 
   DanH | Jun 20, 2004 12:06am | #2

   Like Dave says, if the wire is undersize (and the wire itself doesn't burn up as a result), your symptoms will be the compressor overheating and cutting out, or burning out entirely.

   If the compressor seems to be running continuously and it's still not cooling then I'd suspect either bad installation or a defective unit.

3. 
   4Lorn1 | Jun 20, 2004 02:09am | #5

   In most cases 12/2 w/ground will be fine.

   That said I sometimes go ahead and install 10/2 even when voltage drop due to length is not an issue. Reason being that sometimes a small window AC unit is installed in a cottage or remote room of the house to get people through the summer.

   Even if they have central AC this can save money by keeping the large central unit off and just running the smaller unit where the people are. Home offices are particularly good for this.

   Sometimes people figure that during winter central heating will cover the area. They neglect the opportunity to install a combination AC/heat window unit. While this might not work in NE Maine here in Florida or areas with mild falls and springs a combination unit can save money without problems of the plumbing freezing.

   To take advantage of most of these units you need a 30A, circuit run in 10/2. The difference in material costs is minimal. If they, you, ever choose to go with a larger AC or a combination AC/heater the 10/2 makes the change as easy, electricity wise, as changing the breaker and receptacle at either end. An easy 20 minute job. A lot easier than putting in new cable through a crawl space, attic or other festive locations.

4. 
   rjw | Jun 21, 2004 12:24am | #11

   Are you sure its _a_ "220v breaker?" I ask because 220 usually calls for 2 side by side breakers (a "double pole"), although there is at least one manufacturer who makes a double pole that sort of looks like a single breaker.

   Typically, 24,000 btu (= 2 tons) has an FLA 18 ("Full load amps???) and calls for a 30 amp max fuse size, but unless the breaker is tripping, the problem isn't the unit needing more amps.

   But as noted, you need to look at the manufacturer specs for proper breaker sizing.

   Also, note that #12cu is rated for 20 amps.

   ---

   "It is as hard for the good to suspect evil, as it is for the bad to suspect good."

   -- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)

1. 
   Tomar | Jun 21, 2004 02:37am | #12

   It's a 'Square D' breaker.  It's double wide in width but has a single wide switch.  It's 20 amp.

1. 
   IronHelix | Jun 21, 2004 02:20pm | #13

   What is the temperature differential between the ambient air temp and the output vent of the window A/C?   Should be 15 degree at a minimum.....20-25 would be the better.  Check manufacturers spec for confirmation "delta T" differential.

   In my past life....the install on a 24K BTU window unit was wired on 10/2wg with a 220 30 amp breaker as a matter of standard practice. 

   .......................Iron Helix

2. 
   rjw | Jun 21, 2004 03:00pm | #14

   Sounds like the problem isn't with the wiring, although without running actual tests ....

   I think you need an A/C guy.

   BTW, is it a window unit or split/central A/C??

   "It is as hard for the good to suspect evil, as it is for the bad to suspect good."

   -- Marcus Tullius Cicero, statesman, orator, writer (106-43 BCE)

1. 
   Tomar | Jun 22, 2004 12:34am | #15

   Thanks, Bob - - it's a window unit.

1. 
   CapnMac | Jun 22, 2004 01:16am | #16

   Seal up the space the a/c unit is in (hopefully this just means 'close the door').  The unit may just be getting overwhelmed by the air volume available. 

   My 1400 sf house has 11,200 cf of air in it.  My 3 to Carrier central a/c is designed around that much volume (and 12 more pages of calculations). 

   Three tons of a/c is 36,000 btu, an 8000 btu window unit would run all day and not appreciably change the air temp in the whole house (but would make a 16 x 16' bedroom right chilly.

   Just a thought.Occupational hazard of my occupation not being around (sorry Bubba)