Hi Guys

I have a 6kw solis hybrid machine for 8months now. Been very happy with it. I have 10 x 550w panels on a single pv side as it is within the limits of the mppt. Pic attached to show pv voltage and current. I have noticed the positive pv cable gets very hot to the point that the mc4 plug is showing signs of melting. I don't think this is normal? I've up onto the roof and the positive cable is not hot at all coming from the panels. It's only hot between the DC db box and the inverter?

The pv is a 6mm pv cable and is around 12 meters of cable from panels to inverter. To resolve this should I split the panels and use the 2nd input?

Edited May 1, 20242 yr by cp69

If it's getting hot that means there is a loose connection. In the same way even an AC cable gets hot if there is a partial connection. Even 4mm cable can handle up to 25A DC. So it's important to check all the connections even the MC4. The MC4s if not crimped properly can also cause a lot of heat...

Check all the connections (MC4 to fuse holder to Surge protector) on the hot line ... You will find the culprit.

Edited May 1, 20242 yr by Steve87

15 minutes ago, cp69 said:

Hi Guys

I have a 6kw solis hybrid machine for 8months now. Been very happy with it. I have 10 x 550w panels on a single pv side as it is within the limits of the mppt. Pic attached to show pv voltage and current. I have noticed the positive pv cable gets very hot to the point that the mc4 plug is showing signs of melting. I don't think this is normal? I've up onto the roof and the positive cable is not hot at all coming from the panels. It's only hot between the DC db box and the inverter?

The pv is a 6mm pv cable and is around 12 meters of cable from panels to inverter. To resolve this should I split the panels and use the 2nd input?

Is the cable between the inverter and DC DB hot on the whole run?

Using 5 panels per MPPT or the 10 in series will have the same current in the wiring to inverter.

If the MC4 gets hot perhaps expect a lower quality connector used or wrong crimping.

Sorry @Steve87 Split second timing.

 

Edited May 1, 20242 yr by Scorp007
spelling

Aaah brilliant, gave the cable a yank at the mc4 connection(after turning off the entire system obviously) and it pulled out so obviously a bad crimping job by me. Replaced and sorted. I'll actually do a little yank test on all the connections on the new DC and AC combiner boxes to make sure all is happy

Thanks guys. Legends!!

Edited May 1, 20242 yr by cp69

Happy days man...Happy power...This should also be part of commissioning testing. Most ppl just connect & see some functionality then move on. I spend 1 full day touching cables & feeling temps, checking connections...It's very important because this is such a small fix & worth doing whilst you on site. 

 

What i normally do before connecting the array to the inverter i do a short curcuit test/ string then the guys feel every mc4 connector for hot spots. I use a 4pole 1200v 32A Tomzen isolator with top and bottom contacts bridged out and mc4 pos top mc4 neg bottom.I purchased a Seaward irradiance meter from Action Instruments then i calculate the ISC for each string for optimal performance.