School at Midnight...."No Class"
School at Midnight...."No Class"
That's what I'm doing at the moment but I'm still a little confused.
The power supply we're using has a 24 Volt, 75 Amp rated output. The input is 208 with a 14.5 amp draw. Based on 725.41(A), I'm guessing the power supply isn't a Class 1 power supply (24 Volts x 75 Amps = 1,800 VA), right?
The power supply I'm using is listed to UL 1012 which is titled "Power Units Other Than Class 2". The UL Standard for Class 2 power supplies is UL 1310. Since it isn't Class 1 by definition of it's VA's, and it doesn't appear to be "Class 2". It must be Class 3...right?
A look at Table 11(B) in Chapter 9 doesn't seem to fit since the incoming power ("Source Voltage) is greater than 150 Volts, or is the term "Source" intended to be the output of the power supply?
When the system looses AC voltage it is then powered from the batteries, which according to 725.121(A)(5) is defined as a Class 2 power source.
Am I generally correct in saying that Class 1 circuits require 600 Volt insulation, where as Class 2 or 3 may permit 300 Volt Insulation.
Someone posted an article from
http://ecmweb.com/mag/electric_making_sense_necs/ from ECM Magazine titled "Making Sense of the NEC's Rules on Industrial Controls" which dates back to 2003. Under "Point's to Remember" the first paragraph hints;
"...If the circuit is an instrumentation circuit and meets the requirements of Art. 727.5, you can use ITC (300V insulation)."
Our customer has spec'd all 300 Volt insulation. They're saying that the cable is "ITC" and therefore falls under 727.5 and I'm telling them that no matter how much lipstick and perfume you put on it...I'm still not kissing it.
Any direction or education you guys can offer is appreciated. To me this is like school at Midnight...."No Class"
