Correct use of nominal voltages

[mshields]

I was recently reviewing article 210 paragragh 12 of the NEC both in the 2002 and 2005 codes (also looked at the predicted verbage for 2008). I noticed that 2002, this pargragh referred to circuits rated 125V. In 2005, among other changes to this paragragh, they changed 125V to 120V. This prompted me to wonder when one should use which?

And for that matter, what about 110V?

 

[bphgravity]

Section 220.5(A) provides some guidance for what nominal voltages to use for calculation purposes. Also see the Article 100 definition for voltage, nominal.

NEMA ratings of electrical devices and motors are not at "nominal" values, ie the 125V use in the 2002 NEC. A circuit is not rated at 125V while the receptacle connected to that circuit likely is. The 2005 NEC clarifies the circuit rating is based on nominal values not NEMA ratings.

110V doesn't exist anymore...

 

[ryan_618]

A cord and plug connected motor...

A 120V circuit supplies a 125V receptacle for the 115V motor.

 

[mshields]

awesome - thanks

awesome - thanks

But what's the story with 110V and when did it become obsolete?

 

[LarryFine]

But what's the story with 110V and when did it become obsolete?

Not to mention 115v, 117v, and 118v, all of which I've seen on older equipment.

 

[mshields]

115, 117 118v

115, 117 118v

So were these equipment ratings prior to NEMA defining what they should be?

 

[mshields]

Penguin thing

Penguin thing

By the way Ryan - my 10 year daughter happened to be looking over my shoulder a while back while I reading a thread. She thought the penguin thing was quite a hoot!

 

[jim dungar]

I believe the use of the current nominal voltages (120, 208, 240, 480, 600) were first promoted by ANSI as far back as the 60's.

I remember getting marked down on a test (back in 1975) for calling a system 110/220 instead of 120/240.

 

[ryan_618]

By the way Ryan - my 10 year daughter happened to be looking over my shoulder a while back while I reading a thread. She thought the penguin thing was quite a hoot!

My 7 year old daughter likes it too.