Mc4 connectors

[SunEagle]

Just watched a YouTube video of a guy from renogy which is supposed to be a good company using branch connectors to connect 4 strings together with no fuses ... now you guys are confusing me

The requirement for fusing when you have more than 2 parallel strings is from the National Electric Code. It is also a smart action because it will save your good panels (or strings) if you have a short circuit in one of the other panels or strings.

If the guy from renogy chooses not to follow the code that is his problem. If he chooses to tell people to not to follow the code or to not follow a safe practice, that can lead to a liability action against him and his company should someone get hurt following those directions.

You can do what you want but I choose to instruct those members of this Forum to stay safe and follow all code requirements for their locations.

[Szabie]

I realise that and totally agree with you guys

[bcroe]

Was just wondering is ther a limit to how many panels you can join up in parellel using mc4 Y branch connectors before using a combiner box

I regard those MC4 Y connectors like cheap jumper cables, which may turn out to have entirely too small wire
gauge for the job. They can be useful for light duty work. At night I have added a few to a string of panels, with
the third port covered by a dummy plug. I can plug a volt meter into the 3rd port during daylight to measure the
system; have tracked down bad panels this way. Another ap here is to use a SINGLE return wire for a PAIR of
strings facing opposite directions and never receiving high power at the same time. The other polarity leads are
brought separately to fuses.

I would never expect them to handle anything like 40A; approaching 20A I would be checking them for any heat
buildup under max load. Any significant temp will destroy them in time. And don't leave MC4s exposed to the
weather as the non precious metal contacts will deteriorate quickly. Short unused panels. Bruce Roe