Midnite Solar Classic 200 -- why are my battery output wires getting warm?

[x98myers7]

I just wrapped up the install on my Midnite classic. fired it up, set the charge limit amperage to 45amps (only 8ga battery wire currently)

I confirmed the wire is 8/2 MC dual THHN/THWN and the amp rating at 90degC is 55amps for typical ambient temp

at any point I hit 40-45amps of charge current, the wires warm up. They are metal clad and the alum shield is warm to the touch. where the wire lug connects to the bus bar, the wire itself is NOT warm. it's only up near the SCC. so, is that just residual heat coming down off the SCC? the midnite itself is warm, fans running.

 

[Mattb4]

Do you have an infrared thermometer? Warm is a rather subjective measurement. Your skin can be scalded at temperatures over 130F but for a wire that is no big deal.

 

[x98myers7]

I don't. I'll get one ordered.

 

[Samsonite801]

For reference:

https://www.usawire-cable.com/pdfs/nec%20ampacities.pdf

 

[sunshine_eggo]

I just wrapped up the install on my Midnite classic. fired it up, set the charge limit amperage to 45amps (only 8ga battery wire currently)

I confirmed the wire is 8/2 MC dual THHN/THWN and the amp rating at 90degC is 55amps for typical ambient temp

at any point I hit 40-45amps of charge current, the wires warm up. They are metal clad and the alum shield is warm to the touch. where the wire lug connects to the bus bar, the wire itself is NOT warm. it's only up near the SCC. so, is that just residual heat coming down off the SCC? the midnite itself is warm, fans running.

Warm to the touch is a non-issue. Note the rating... 90°C - that's almost boiling. Even 60°C rated wire will be painfully hot to the touch before they exceed their specification.

 

[Texas-Mark]

the alum shield is warm to the touch. where the wire lug connects to the bus bar, the wire itself is NOT warm

Got a picture? What type of lugs? Soldered or crimped? Type of buss bar?

 

[Texas-Mark]

Warm to the touch is a non-issue.

Maybe not an issue for safety, but warm=resistance. And the less resistance the better.

 

[Steve_S]

I use a Classic-200, with 6-AWG and run it to 79A out, the wires get warm but never hot.
Now I do run it into a MNDC250 E-Panel, connections inside the MNDC are Crimped and they also get a little warm but NOT hot when running full throttle.
FYI: They provided screened plug for some of the opening in the classic, use them to allow better airflow.

Classic Manual Page 28:

PV in particular will be capable of producing more current than its name plate rating in extreme situations so the safe minimum wire size should be selected for the PV array maximum short circuit current. Please consult PV manufacturer for specifications. The US National Electrical Code requires 1.56 times the PV short circuit current for wire size on the PV input. Output wire size follows the NEC guidelines. Typical wire size for output is 6AWG for the Classic250 and 4AWG for the Classic200 and 150 but check all de-ratings for your wire type and installation method

Older picture below, it's been updated. and will be revised again as more changes are happening.

 

[Prince Of Darkness]

Generally, 90 degree C Ampacities of cable are not that useful, as most terminals, bussbars etc, are only rated for 75 C Max.\

NEC Ampacities are very, very conservative.

The MN Classic terminal block will accept #4 AWG THHN (NOT fine stranded cable), so you could, perhaps, use larger cable, IMO.

'Luke'

 

[x98myers7]

I am. Picking up some 4ga THHN from Lowes tomorrow. I’ll bump the charge current back to 78amps after that.

 

[x98myers7]

Got a picture? What type of lugs? Soldered or crimped? Type of buss bar?

Crimped, UL listed all copper lugs

 

[John Frum]

Since its 8/2 metal clad, its rated for 55 amps at 90C.
55 amps * .8 fuse headroom = 44.64 amps.

You are pushing it to the max.

 

[x98myers7]

I'm letting it run today. I'm constantly at 45amp limit. it's definitely warm, but i'm not super concerned. the MC is warm to the touch and the wire itself at the busbar feels like ambient.