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Messages - Victor

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Section 9: Study Guide Review Questions / Question 8 nominal voltage
« on: April 04, 2014, 04:51:18 PM »
In question 8 on page 151, the question is to find max wire run distance for a PV output circuit from combiner box to inverter for a 2% voltage drop.  The given solution uses 240 V for the nominal voltage, however the DC voltage in that circuit appears to be (14 modules) X (29.5 V Vmp) = 413 V.

Why does the example use THWN for the rooftop source circuit in conduit?  I thought THWN was more appropriate for circuits in conduit after leaving the roof and USE-2 was more appropriate for source circuits on the roof.  Also, due to high temperatures on rooftop, wouldn't USE-2 be more appropriate?

Section 2: Verify System Design / Re: Calculating Conductor Ampacity
« on: April 02, 2014, 08:34:15 AM »
I think the reason that 10 AWG is needed is because the 14 A fuse could allow a 14A fault current into this circuit, but the 12 AWG wire selected in Step 4 only has a conditions of use adjusted ampacity of 13.92 A.

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