industrial control panel wire ampacity
industrial control panel wire ampacity
(OP)
does the table in 310.16 referencing conductors installed in free air apply to the interior of an unventilated motor starter panel, if the conductors are not installed in wiring duct.





RE: industrial control panel wire ampacity
RE: industrial control panel wire ampacity
RE: industrial control panel wire ampacity
Internal wiring of a power circuit shall not be smaller than 14 AWG and shall be determined by .....(lots of stuff left out here)...UL table 28.1.
As it happens, table 28.1 is very similar, but not identical to, NEC table 310.15(B)(16), which is for conductors in a raceway, not free air.
If the panel is unventilated, you also have the issue to derating due to temperature.
EE
RE: industrial control panel wire ampacity
According to ABB Switchgear Manual ch. "Temperature rise in enclosed switchgear cubicles" dT=Pv/a/Am where : dT= temperature difference above the ambient [oC]
Pv=power loss with allowance for load factor
[allowance factor= 0.5-0.8 usually]
a= Heat transfer coefficient max 6 min 3 w/m^2/K
Am=heat-dissipating surface area of the cubicle.
The lateral all-around surface and the roof surface[m^2].
See also:
http://
For heat loss from different electrical devices see:
http://ww
RE: industrial control panel wire ampacity
Neil
RE: industrial control panel wire ampacity
Another issue in the difference is that (IIRC) UL508A requires that the wires be rated 90degC and can thus be sized that way, whereas most of the common tables used in the NEC for installations are for 75degC.
But you have to remember, the NEC is for an INSTALLATION, UL508A is for an ASSEMBLY. If you have a UL508A listed panel, the wiring inside of it has ALREADY been approved by UL (theoretically) and from an NEC standpoint, the contractor installing it need not be concerned. If you were assembling your own panel in the field without the benefit of getting a UL508A listing however, then the NEC rules would apply.
But I think we have gone back and forth on this in this forum several times and I don't think there is a consensus. The only real consensus is that the AHJ is the final authority and can, if he insists, require the internal wiring to be changed even after being shown that it's acceptable under the different rules. It happens.
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