Great deep dive Mark. I like to use one DC isolater per string anyway so you can run a partial system if needed. I also double loop inside the rotary isolator to reduce the spark for longer life. We all have our own ways.

Fanatastic Mark, at last a technically literate presentation of solar installation risks thanx 10^6. FWIW I am astounded at the Industry's cavalier approach to Electrical safety. As you rightly point out, such practices as trivialising isolation methods by disconnecting MC4s (they were not designed for such treatment) is criminally negligent and would never be tolerated in the ac world (I come from an industrial Petrochem background where safe working practices are paramount). IMHO I believe that there should be no connector joints in solar cables from the panel down to the nearest accessible ground junction box. The solar panels should be connected using a continuous length (cutting off the supplied MC4 and making off with a professional shrouded crimp butt joint. The argument being, "if it aint there, it can't go wrong". Solar panels are installed, fit and forget. In the rare event removal for maintenance is needed, then cut the cable and remake a new butt joint. Its particularly important not to have hidden connectors, beneath tiles etc. As for Isolating switches for ELV

Good stuff, thank you Would love to see a video about proper use of branches, how many volts, current etc.

Hello Mark, keep up the good work

Let’s dive into the key takeaways from Mark’s video, offering practical insights into proper solar connector termination and the critical role of DC isolators.🔌

Awesome detail

Hi, thanks for the interesting video. What are your thoughts of DC isolators with SolarEdge inverters? They have built in DC isolation and I think SolarEdge say to not use an external DC isolator, previously they gave me the reason as being to reduce arc faults. Also obviously when switched off SolarEdge have their 'safe dc' feature with optimisers making only 1v.

I have just setup a PV System here in Italy and still have to do the final install. I have to say for all the standards most of which we are expected to pay for to read (thus ensuring poorer quality) when I first looked at MC4 connectors I was quite upset by there obvious inadequacy for the job. Then came the MCCBs and where to put the combiner boxes. Endless searching, another big secret. So now they are near the roof. Still I have 300 VDC in the down wires, which seems like insanity to me. Any visiting fireman needs to switch all this off. So batteries and inverters instinct told me to put it all in a well ventilated dry celler with no flamible material. However I want one power off button when a fireman enters the house it should isolate everything. It should interrupt a 12 volt safety line that will then cut all MCCBs DC AC the lot. DC being cut as close to the panels as absolutely possible. So far I have only found shunt releases that trip when 12 volts is applied. Obviously this is not fail safe. As somebody said above there is a lot of dangerous elements to be sorted out in this area. No I am not a qualified electrician but I have done safety work on robotic production lines (tomdehavas dot com) so this stuff is a lot simpler. However it is made more difficult when Standards that should be free are charged for. It's one thing when you write a book but quite another when governments who should be helping us improve deny us information we need to comply with or charge large amounts of money. Smart people like Mark know that he has a job because he is good at it and he proves it by teaching others. Dumb people get some scraps of knowledge and then try to keep them secret instead of helping make the world a better place. Should only qualified people be allowed to do electrical installations. My life experience tell me that not all qualified people are good at their work and not all unqualified people are not good at theirs. We should give free education to people in useful skills and we should learn to ask when we don't know something and we should understand our limits. Instinctively we do I think but school makes slow learners feel bad. That's wrong. Just an aside there. Sorry ;-) Anyone know where I can find a shunt release that cuts off the MCCB when 12vdc ceases to be applied? Gee it's pouring with rain here and I have MC4 connectors out in that Aaaagh. Best wishes

If moisture ingress is a particularly common failure point for MC4 connectors, is it worth packing them with dielectric grease? I know it shouldn't be necessary, but as a layered defence against moisture ingress throughout the life of the connection? Maybe the termination issue for isolators is related to the use of non-maintenance-free terminals and expecting them to last for decades? I wonder if the isolators and SPDs of the future will have either MC4 connectors or Wago-style lever terminals? I do wonder how many mating cycles these MC4 connectors are rated for and if this has been taken into account when the guidelines are suggesting that they are used for isolation.

thanks!

So after isolating a dc isolator abd the ac supply, is it safe to start disconecting the panels or can you still get arcing as there still generating ? Thanks

Do you put pin crimps on the cable when you terminate into a DC isolator or just strip and insert the stranded cable into the isolator terminals ?

Just watching your "dark side of solar" link. My God it really shows that these systems are not for civilian use!! I'm OK because I have a reasonable knowledge but even I wasn't aware of the horros of the MC4s. Its not about the right crimp tools and depth guages. MC4s should not be sold. Back in the old days when AC became the domestic system it was an absolutely right choice. They even talked about 1000VDC down wires. It's insane. 48 VDC would be a reasonable limit for home use and the loss in the cabling is surely worth it. I haven't done the calculations. I lose 10% because of my roof angle anyway and a watt or two per meter of cable wouldn't be a tragedy for the added safety.

im sorry MARK these mc4 connectors are rubbish and in a year ive had several failing by overheating and burn out i prefer crimped and soldered with shrink wrap on joints with dc double pole breakers on each string so eliminating them. its worth checking pane junction box internal connections jimmy 84 auld electrician from dc age

AND BTW WATCH YOUR HAND WITH THAT RING IVE SEEN FINGERS LOST

cant wait until wago make these you would be finished in 20 seconds