ECN Forum Forums Code Related Discussion NEC & other Code issues Aircondition load

The inspector is sighting 240.4d without understanding that 20 amp on 12cu doesn't apply to airconditioning. Also it's a matter of principal. If you read it it's very clear, no gray area at all. It's right there in black and white.

abode electric...check out article 440-62/4
i think this applies to this.

440.62 is for window or wall AC, ones with cords

abode electric...this is not a wall or window unit. where is the ac unit.are we talking about an outside residential condensing unit.?

Hey if it`s an outdoor unit it should be apiece of cake to feed a #10 if needed.I would if it were me run the circuit and ask for the GC to foot the bill for the wire.If not you rest assured you have a better installation.I`ve personally done the exact same.I didn`t have 10 and ran 12 about a year later I was back running #10.A/c man insisted to the home owner 12 was to small and was the cause of the units problems.A while back I made a comment on a similar install about voltage drop on start up and the lights dimming and rescapt stated this was incorrect if you read this could you explain where it was the wrong conclusion.And the voltage drop wasn`t the cause of dimming lights,I did a search and didn`t find it..Thanks

Adobe, You must have amp'd the A/C unit to come up with the "about 17 amps". Then you say the name plate states 22amp min circuit ampacity. You have to use the name plate rating. So 22amps @ 125% is 27.5amps. You have to run #10. I got this from reading 440-2, " Branch-circuit selection Current" using the last sentence. The 22amps on the name plate does not take into account your 125%.

And to add fuel to the fire: Why is this not considered a continuous load? Some motels I've stayed at the A/C stayed on all the time.

Tom

Here we go again LOL!

Gisbon,

The 22 amp minimum circuit ampacity listed on the nameplate already has the 125% of compressor FLA and 100% of all other loads factored in. The manufacturer has already completed the calculation as per 440.32, it does not need to be repeated again in the field. Abode was just approximating the 17 amp FLA rating. 17.6 amps X 125% equals 22 amps.

If the nameplate states a minimum circuit ampacity of 22 amps, then thats what it is, 22 amps. Table 310.16 lists the ampacity of #12 wire at 25 amps in both the 60 and 75 degree columns. Article 240.4d does not limit the #12 wire to 20 amps for air conditioner loads as per 240.4g.

Yes, the NEC is a minimum standard, but minimum or not, #12 wire is legal for this air conditioner unless high ambient temperature and/or adjacent conductor factors apply. Although voltage drop compensation should be considered if it applies, it is not an NEC requirement, it is only a fine print note in article 210.19a.



[This message has been edited by Matt M (edited 01-29-2003).]