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How hot is too hot for PV array wire?
#11
When in doubt, go larger gauge wire Wink Bigger is always safer, in this instance
Proceed with caution. Knowledge is Power! Literally! Cool 
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#12
(02-21-2020, 12:43 AM)Korishan Wrote: When in doubt, go larger gauge wire  Wink  Bigger is always safer, in this instance
A light bulb clicked on in my dim brain...  and I remembered that I have unused Midnite Classic temp probes (since Batrium does the battery temps) so I've place a couple of them on the wiring inside the access boxs.     I have modbus access to the Classic data so I can monitor/record the amps vs temp and will see what happens as spring approaches - and I can report back with some actual data/graphs Smile

FYI - I do appreciate your comments - don't want you to think I'm ignoring them. I think I just want to see temps before jumping. If it stays under 50C/122F then I don't think I'll be 'that worried'. If it goes over that then....
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#13
Taking steps to monitor the temps is a good one. Maybe you'll find that it only gets warm at certain times and for short periods.
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#14
quote from ajw22:
My conservative gut feeling would be: ~60C perfectly safe, ~75C concerning but safe
quote from korishan:
When in doubt, go larger gauge wire Wink Bigger is always safer, in this instance

Both have a plus one from me.
You have one roof, what do you care about those extra amps if you can lower your charge at sunny days?
You won't even have use or storage for them, please go and be safe.

40c is nice and friendly to touch...50 you can hold, 60 is uncomfortable....
70 to touch:...your nerves will warn you, you can hold it, but...
80 is not comfortably on touch.
110c dry you can touch and grab for short period, but dry (old) wood can catch fire! at 110c
I can give you samples enough about dry wood smoldering at 80!!!!Celcius.
6 hours is to long, 4 hours can be safe.
Gut (proved) feeling and experience
Heat is building up in the wood, it will go slowly to ?chare? black bbq cole

Side note: my roof is built in 1886, old and dry, average sunny summer day, 12 hours of sun?
Go bigger on cables and lower your amps, increase volt: drop temp.

My two cents
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#15
@100kwh-hunter  - thanks for the comments.

I've placed Midnite Classic temp sensors at 3 different wire locations and I'm starting to get data.    The ambient is 13C/55F. Here's my web monitor and I've circled the related power / wire temps by color.  

RED -  3/4" EMT with 4 x 6AWG wires.  Each pair carries 1 set of 3s5p 285w panels for 4275w maximum.  That's 4275 * 2 = 8550w in 1 conduit.
GREEN - 3/4" EMT with 2 x 6AWG wires.  1 pair of 3s5p 285w panels for 4275w maximum in its own conduit. 
BLUE -   Control Box where 3 x 4AWG wires tie into negative bus for battery.   This is the Classic 150's output to the battery - 61a+65a+62a = 188a right now with 80a/controller = 240a max.


Today is highest yet -  RED Classic #1 + #2 are getting 3369/46.1a + 3601/43.9a yielding 46.1C within the 3/4 EMT.     

Notice the 'low' MPPT voltages causing high amps (46.1a + 43.9a).     Maybe sunny and cool (60F outside) is causing this.   MPPT voltage should be in 90s - e.g. 90-97v as summer approaches - which means the amps shouldn't get much higher than they are today.  
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#16
Based on your factors:
- the measurements you made (best indicator!)
- your 105C rated cable
- NEC code tables for your cable
- the conduit is metal not plastic
- the cable run part with about 45 amps is not in the sun or in the (hot) roof cavity it's underfloor
- the conduit run is not enclosed in insulation
you're going to be fine & you seem to have a good margin before limits or dangerous conditions
Running off solar, DIY & electronics fan :-)
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#17
Gathered some more data on 12.8kw PV array.   Its spring so I'm routinely getting 50+kwh and 10kw peaks. 

EMT1: = combined amps of the 2 sets of 6awg wire in EMT conduit #1.
Wire    = highest deg C of the wire in EMT conduit #1.    


Looks like its holding <= 50C/122F so far.   So its not an emergency.    We'll see what summer brings.....
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#18
The temps have continued upward to 55C, 56C, 57C and its still spring so I rewired things today!

I took the 4 x 6 AWG wires in the original 3/4 EMT conduit and paired them up... this give an effective wire size of 3AWG and reduces the total amps inside the conduit to 50a.

Then I ran a new pair of 6 AWG in a new 3/4 EMT conduit alongside the original.

What I've learned is that running 4 x 6 AWG inside a single 3/4 EMT conduit at 50a per pair (100a total) is too much heat. A single pair of 6 AWG it's own 3/4 conduit tops out at 40C (so far) instead of 56C carrying the 50a.

Note: We're talking a 60ft run of EMT under the house with ambient temp of 15C - 25C.
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#19
You would think the metal EMT would keep the wire cool. Altho, I suppose it does under the house. But once you get above ground and away from the heatsink (of the earth) it heats back up.

I'll have to keep this in mind when I set mine up. Thanks for doing the leg work for us Wink
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