ECN Forum Forums Code Related Discussion NEC & other Code issues NEMA configurations for receptacles/plugs

IT dosen't sound like you are asking the right questions. THis forum is chock full of Professionals. In my 45 years in the industry I do not remember any major changes in NEMA Configurations.

If I could remember the name of that plug system... the plugs had 3 pins that looked somewhat rounded like the NEMA locking plugs.

A google search popped up so-called solar receptacles without any mentioned standards, simple flat round pin sockets with two different pin diameters.

440.62 does not limit the size of a room air conditioner to 40 Amps or to 250 Volts.




BTW, even though it doesn't apply, 440-62 has remained basically unchanged since it was added in the 1975 Code.
(Before the addition of Article 440 in the 1971 NEC, the info for Room AC's was in "Appliances", Article 422(F) Provisions for Room Air Conditioners)

NEC 440.62 says that the voltage is limited to 250 V or less, single phase and the current is limited to 40 A or less.

It seems to me that a 277-V, single-phase supply would violate NEC 440.62.

2005 NEC 440.60 states that if the supply voltage is over 250 V, then NEC 440.62 DOES NOT apply.

Larry

All it is saying is that if it is over 250V or over 40A, then the "Single Motor Unit" method of determining the sizing of the branch circuit conductors and overcurrent protection can't be used.

Because motors briefly draw a large current at startup, and then much less current while running, the code in some circumstances will allow a bigger-then-normal circuit breaker on a motor circuit to account for the startup surge. The 250V, 40A test is simply a test to determine which rules you are required to use to determine the wire and OCPD sizing, not a limit on what voltage can be used to power an A/C unit.


[This message has been edited by SolarPowered (edited 09-25-2006).]

Thanks for the replies. It has been so long since I posted that I didn't remember the context of the NEC code 440.62.

What I really would like to know about the NEC code is about 440.60:

The provisions of Part VII cover equipment rated not over 250 volts, single phase, and such equipment shall be permitted to be cord-and-attachment-plug-connected.

A room air conditioner that is rated three phase or rated over 250 volts shall be directly connected to a wiring method recognized in Chapter 3, and provisions of Part VII shall not apply.


Does this say that a room AC with 277-V supply must be hard-wired and not attached with cord and plug?

Tammy, I would not go quite that far. I think you can make a case, though, that things be rated for their use.

Ordinary plugs, and receptacles, are not rated as a disconnecting means for larger loads and higher voltages. There are exceptions; one company ("Meltric" I think) makes such connectors as their primary business. There are others that incorporate a switch in the receptacle, so you actually 'turn it off' as you begin to remove the plug.

Looking at the code, we see that cords and plugs are allowed to be the disconnecting means for only the smalest of motors. This does not mean you cannot use cords on larger stuff; it only means that there must be an additional disconnecting means.

So, using your air conditioner example, I would say that the receptacle would need to have a switch controlling it.

John you remember correctly Meltric makes great disconect rated receptacles.