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Richard Cummins
Electrical Manager
Lectrus Corporation
(832) 295-1200
Richard Cummins is Electrical Manager for Lectrus Corporation (formerly Metal Systems), a Chattanooga-based industry leader that engineers and builds fully-integrated, electrical equipment centers, operator centers and custom enclosures for the power, oil & gas...more»»
Arc Fault Testers
Posted by Joseph from Ridgewood, NJ, US on June 9, 2009
Which arc fault tester has been found to work best?
The answer depends upon your specific application. If you are testing 120 VAC 20 amp or 30 amp circuits, we have found that the Fox Meter AS1000 is very good for around $200.00. For more information, please visit: http://www.arcfaulttester.com.
3 Phase Power
Posted by liz from Warner Robins, GA, US on June 7, 2009
In a gas powered 3-phase power generator, is the ground always connected to neutral?
If the generator has a neutral and ground it will need to be connected through the Transfer Switch to the main system where the neutral and ground are connected. Section 700.8(B) in the NEC states that the 3 phase generator is a separately derived system. If the 3 phase generator is connected to a grounding electrode at a remote location, there shall be a sign at the grounding location that identifies all emergency and normal sources connected to the ground at that location.
Central AC
Posted by James from Islip, NY, US on June 7, 2009
Artical 440.32 States that “Branch-circut conductors suppling a single motor-compressor shall have an ampacity not less than 125 percent of either the motor-compressor rated-load current or the branch-circut selection current, whichever is greater.
In my question we are concidering a normal hermeticaly sealed, thermally protected motor normally associated with a residential compressor unit on the outside of a home.
My personal outside compressor unit states that the compressor has a FLA of 18 amps and the fan motor has an FLA of 2 amps. This adds up to 20 amps.
It then states that the minimum supply ampacity should be 25 amps which i can understand since that would be 125% of the FLA of both motors involved.(which is contratictory to Art. 430.24)
Do I then have to add another 125% to their minimum circut ampacity concidering this as what the code says might be the “branch circut selection current”? Even though they state that that the minimum supply circut ampacity should be 25 amps?
An HVAC is not a single motor circuit so Article 440.32 does not apply. There is ampacity in total the compressor motor, the evaporator fan motor, the refrigerant valves, the control relays and 24 VAC transformer which add to the overall power requirements. In my opinion, a 30 amp circuit would be appropriate in your example.
Cable tray
Posted by Denny from Chauvin, LA, US on June 4, 2009
Can I ran 1″ stain steel gas line that will have 60 psi on the top edge of 24″ alum. cable tray?
In our opinion, you can run a one inch stainless gas line above a cable tray provided the gas line is bonded to the cable tray so all metal surfaces are acting as an approved grounding point.
Ampacity of Flexible Cords and Cables
Posted by James from Schenectady, NY, US on June 3, 2009
I have a flexible cable that is marked TYPE SOOW 90 DEG C. To determine its ampacity, do I use Table 400.5A according to the type of cable, or do I use Table 400.5B according to the 90 deg temperature rating. According to the manufacturer, I use 400.5B but I am concerned that will be a violation of the NEC.
I would think that the manufacturer recommends finding the AMPACITY: Based upon an ambient temperature of 30 degrees Celcius per NEC Table 400-5(A), Column A for multiconductor of more than two and column B for two conductor cables.
