air conditioner??

[workingman]

can someone tell me were in the code i can find what conductor to run for an outside ac unit if the nameplate is gone?? also if the nameplate is there do you size the breaker @125% of nameplate?? and do you size the disconnect @115% of the nameplate? I am pretty sure i read the code right but as you all know it can be confusing. thanks for any replies

 

[bdarnell]

Open the unit and find the compressor(s). There should be a nameplate on it. Then find the nameplate on the condenser fan motor(s).

Those are your loads. (Unless there is a crankcase heater or some other attachments that aren't standard)

 

[oliver100]

Start the unit(s), mesure the current and act accordingly.

 

[jtester]

quote by oliver 100

Start the unit(s), mesure the current and act accordingly.

Article 440 doesn't allow this approach to the best of my knowledge. 440.6 for conductor ampacity, and 440.22 for OCPD's both require a nameplate rating. There is no substitute for finding out the manufacturers stated values.

Jim T

 

[oliver100]

There is no substitute for finding out the manufacturers stated values.

Too bad - one nameplate ruining the job and sending the equipment to the garbage.

 

[gndrod]

You might take a look at the main contactor for a clue for sized wiring within the unit and then determine run length drops. The unit may also be a scrolled type (one motor) to make determination easier. Using line ampacity not less than 125% for branch circuit is covering all bets. (440.32) I hope this helps. rbj, Seattle

 

[infinity]

I like Brad's idea. Take the compressor FLA and multiply it by 125% then add the fan FLA. This should be your minimum circuit ampacity. As others have said technically you're required to use the nameplate.

 

[haskindm]

I doubt that an inspector would approve the installation without a nameplae. The unit is probably not useable in most jurisdictions.

 

[tshea]

If this is a used unit, in my book you are sol.

Now if this is a new unit that has been vandalized, the HVAC mech should be responsible to get a new nametag based on the unit info.

If this is a unit that someone sold to the HO then again you are sol. I would walk. There are better jobs with less headaches.

If this is for your house follow Brad's advice.
(As electricains we tend to be more cautious with our own homes...then again some throw caution to the wind :roll:

 

[iwire]

Re: air conditioner??

can someone tell me were in the code i can find what conductor to run for an outside ac unit if the nameplate is gone??

The NEC requires the name plate.

440.3(B) Multimotor and Combination-Load Equipment. Multimotor and combination-load equipment shall be provided with a visible nameplate marked with the maker?s name, the rating in volts, frequency and number of phases, minimum supply circuit conductor ampacity, and the maximum rating of the branch-circuit short-circuit and ground-fault protective device.......

Strictly speaking you can not install the unit without the name plate.