Is 1/2 in EMT acceptable 5 THHN (10AWG) wires?

[jeremylmartin]

I ran 1/2 in EMT from the roof to the inverter. System is 9.9kw in two strings using SolarEdge optimizers and inverter. So there are 5 (10 AWG) wires in the conduit (2 for each string and a ground). The strings are evenly split with 18 275 watt panels on each string (total of 4,950 watts per string). Per all my original calculations this was fine. The fill chart for the 1/2 EMT was almost maxed with the 5 THHN 10 AWG but acceptable. However, now I am second guessing. The run is through the attic about 25 feet and then down the wall in the garage another 5 feet. So 30 feet total run in the 1/2 in EMT. Is the acceptable? Will it overheat in the conduit? Would it be worth all the hassle of changing out to 3/4 inch EMT?

[inetdog]

I ran 1/2 in EMT from the roof to the inverter. System is 9.9kw in two strings using SolarEdge optimizers and inverter. So there are 5 (10 AWG) wires in the conduit (2 for each string and a ground). The strings are evenly split with 18 275 watt panels on each string (total of 4,950 watts per string). Per all my original calculations this was fine. The fill chart for the 1/2 EMT was almost maxed with the 5 THHN 10 AWG but acceptable. However, now I am second guessing. The run is through the attic about 25 feet and then down the wall in the garage another 5 feet. So 30 feet total run in the 1/2 in EMT. Is the acceptable? Will it overheat in the conduit? Would it be worth all the hassle of changing out to 3/4 inch EMT?

The fill chart is primarily for being able to pull the wires without damage. If you have a simple pull, then 1/2 would be OK, especially if using Simpull (R) wire or equivalent lubrication.
But the main heating issue would be the ampacity derating, which would not depend on the size of the conduit at all.

When you figure for attic temperature and four Current Carrying Conductors (CCCs) your 10 AWG should still have enough capacity for the string DC amps, but check it out formally if you have not done the calculation.
Putting some of the run on the roof with and additional temperature penalty might take it out of compliance.

[Sunking]

Ditto you have more than 3 current carrying conductors which means you have to derate capacity. Not to worry the Inspector will Red Flag you, then you get to do it over again with larger conduit and wires if it does not meet code.