Wire Gauge Charts vs Calculators

[Cal]

Glad we're in agreement. There is no breaker requirement for less than 3 strings connected in parallel. That's because breakers in a 2-string system will never trip. The two 15A and the two 30 breakers should be deleted. They serve no purpose other than degrade performance and inject another possibility of failure.

A PV disconnect should however be installed. I use a simple toggle switch. Many people use one breaker as a switch (after combining), knowing it will never trip.

 

[tictag]

There is no breaker requirement for less than 3 strings connected in parallel.

Whilst I entirely agree with you, being the devil's advocate, you could argue such breakers would allow you to disconnect the load from a specific string allowing safer maintenance on that individual string. But, yes, other than perhaps convenience, installing breakers on simple arrays i.e. where the PV cable can easy handle Isc in case of a fault, just adds unnecessary cost and complexity.


This is the big difference between PV lines and battery lines; batteries can generate hundred's if not thousands of Amps in a short circuit fault condition, PV panels/arrays can only ever generate Isc - they have differing characteristics and, therefore, require differing circuit protection features.

 

[Cal]

Whilst I entirely agree with you, being the devil's advocate, you could argue such breakers would allow you to disconnect the load from a specific string allowing safer maintenance on that individual string. But, yes, other than perhaps convenience, installing breakers on simple arrays i.e. where the PV cable can easy handle Isc in case of a fault, just adds unnecessary cost and complexity.

Absolutely, we're in agreement. I did mention in my previous post that it's best to install a switch (or breaker) to disable solar.

This is the big difference between PV lines and battery lines; batteries can generate hundred's if not thousands of Amps in a short circuit fault condition, PV panels/arrays can only ever generate Isc - they have differing characteristics and, therefore, require differing circuit protection features.

Yep, that's because a battery is a voltage source and PV is a current source. In theory a voltage source delivers a voltage independent of current and a current source delivers a current (between Isc and Imp) independent of voltage.