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hammerhead 08-18-2005 03:44 AM

20amp circuit
Does the NEC allow for 3 5000btu 4.9amp window air conditioners to be running on the same 20amp circuit? Since 4.9x3=14.7amp a 20amp should be fine with this load...right? Or does each A/C require a dedicated circuit?

Teetorbilt 08-18-2005 11:00 PM

What is your start load? By code, all should be on their own circuits.

hammerhead 08-19-2005 07:36 AM

The load will be exactly the 3 a/c's (around 15amps). It will only be used for them and only them. The way I see it 15amps on a 20amps line isn't exceeding the circuit load.
Why would each need to have their one dedicated circuit? Is it because they draw a lot of current when they startup?
(I'm new to electricity, so I will ask a lot of dumb questions).:rolleyes:
Now most important, as I don't want to be an electric outlaw :D. Will this be allowed by NEC, or will it be against code?:eek:

Thanks for the reply.

Teetorbilt 08-19-2005 10:16 PM

They will draw about 30% more on start. Plan your wiring on all of them starting at once + a safety margin.

Take a system that I installed just a few days ago. 17 hundred BTU/ 1-1/2 ton. Start is 17A, run is 11A.

The specs should be somewhere in the units. Oversizing wiring doesn't cost much more and prevents housefires.

Speedy Petey 08-20-2005 08:10 PM


Originally Posted by Teetorbilt
What is your start load?

Start load is not a concern. This is taken into account and the breaker can handle it.
Also, if the locked rotor current (LRC) is not given it is assumed to be six times the rated load current (RLC).


Originally Posted by Teetorbilt
By code, all should be on their own circuits.

Not necessarily. For a room a/c the load must not exceed 80% of the branch circuit where no other loads are supplied. This is provided the load is less than 40 amps.
If the a/c will share a branch circuit with lighting or other appliances the load of the a/c is limited to 50% of the branch circuit.
These requirements are for a single room a/c. IMO another a/c is not "other appliances" and the sum of the ratings of the a/c's can be used.
As long as the three a/c's are not more than 80% of the 20 amp circuit, 16 amps, then they can all share a common circuit. I will say that single receptacles must be used so that nothing else can be plugged into this circuit.

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