Section 2 of the UL508A MTR re-qualification exam tripped me up in a few areas, one being sizing field wiring terminals. If the wire material is not specified, I've been using the largest size wire gauge for a given ampacity between aluminum and copper, since the panel builder does not know what type of wire will be used. So for example, if the required ampacity is 35 A, then I would select a field wire terminal size of 6 AWG, since that covers both copper and aluminum. 8 AWG would only cover copper. Is this the right approach?
UL508A Table 28.1: Copper or Aluminum?
- Thread starter EC Dan
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My copy of UL508a is quite old (I perfer the PDF) but my copy shows both aluminum and copper for 60°C and 75°C, generally speaking if a test question does not specify material the default is copper.
Where are you getting the 35 A from ?
Does the question supply that ? and which column are you using 60°C or 75°C?
Generally speaking the anticipated field wiring will have ampacity of 125 percent of the full-load current rating of the load involved, so you may need to 1.25 X 35A ..
Also
May be a trick question, in some situations you many need to throw away that 35A and go to another table, a terminal or component with a marked horsepower rating can have field wiring having an ampacity of 125 percent of the full-load current from the HP table (50.1) , not of the 35A but from the ampacity corresponding to the horsepower rating from another table.
Hope the helps
The 35 A was an example, but is similar to the test question in which a value is provided. The difference between 60 and 75 deg C columns is often more clear, either it's outright stated or it defaults to below 100 A using 60 deg C and above 100 A using 75 deg C.