Do I need a solar diconnect?

Hi,

I'm just ordering the last few things I need to finish my project and I was wondering if there is any other reason to install a solar disconnect except for the practicality of it? I'm hesitant to spend any extra money because I already spent more then I planned. Is there any actual difference between just unscrewing the solar input cables from the SCC and switching off a breaker between the SCC and PV?

I couldn't find any definite answer to this question. I was thinking that maybe if you just unscrew them, you need to also cover the panels with some sheet or something. If you have a breaker, it's probably not necessary. But I just need this clarified.

I might be willing to spend a 15-30 € just for the practicality, but the problem is I will have the cables pre-made for my custom measurements. And I see there might be a problem if I need the guy to make too many connections and cuts. It's hard to calculate upfront how much cm exactly do I need and if there are too many connection, more things might be a little bit off in length and it might become an issue.

Thanks

Jan

Small solar array it may not be necessary other than for convenience. Large array yes you will want a disconnect and likely a combiner box. JMHO

1 Or 2 strings? No need. Larger areays need fuses on each string. If you're not doing any kind of grid tie then it's not required by law. If you use a combiner box, that will already have disconnects built in.

Required? No.
Needed for a single or double string array? Handy but no.
Required for 3+ strings? No, but it's really useful for troubleshooting and repairs later.

JanC said:

Hi,

I'm just ordering the last few things I need to finish my project and I was wondering if there is any other reason to install a solar disconnect except for the practicality of it? I'm hesitant to spend any extra money because I already spent more then I planned. Is there any actual difference between just unscrewing the solar input cables from the SCC and switching off a breaker between the SCC and PV?

I couldn't find any definite answer to this question. I was thinking that maybe if you just unscrew them, you need to also cover the panels with some sheet or something. If you have a breaker, it's probably not necessary. But I just need this clarified.

I might be willing to spend a 15-30 € just for the practicality, but the problem is I will have the cables pre-made for my custom measurements. And I see there might be a problem if I need the guy to make too many connections and cuts. It's hard to calculate upfront how much cm exactly do I need and if there are too many connection, more things might be a little bit off in length and it might become an issue.

Thanks

Jan

Click to expand...

Already replied to your pm, but since you've made a post too, might as well leave a comment here for other folks with a similar dilemma.

Personally, I'd recommend getting a properly rated DC double pole isolator circuit breaker in between the SCC and the PV side.

It's just a really convenient way to separate the PV side from your system right there on the spot, for whatever reason you need to.

As I've mentioned in pm, try to avoid disconnecting the DC circuit breaker under load. The way I do it is to disable the 'enable charger' via Victron App and then proceed to disconnect the DC circuit breaker before working on the system or on the PV side of things.

While it might not be technically necessary for a small PV, it's essential overall IMO. Very useful and practical.

Never too safe, it's best to get used to the good practice right from the get-go.

You really want a disconnect between everything. If something goes wrong, turning a switch is much easier than trying to unhook cables, pull plugs, etc.

If everything goes perfectly and no experimenting/testing necessary? Sure.

Otherwise you might very much wish you had the capability to easily disconnect. Problems seem to fluster many of us and a wrong move by a stressed individual can be expensive or downright hazardous. Guessing so many of us end up spending more than the plan, but safety of yourself and others?

An electrical arc can occur where you may not think one would happen; for instance potentially involving capacitors in an inverter, etc…

Some places require a disconnect for an inspected install so that firemen can cut the electricity if there is a response to a fire at a location. Even if it is a smaller set-up I would suggest it. I use them to protect my Inverter/Batteries against Lightning Storms when we have them (which is A LOT where I live in the summer) When I first setup my system last year, I had ground lightning for the first 7 days straight, if the panels got hit then I would need to replace them, but at least I wouldn't need to replace the expensive parts (Batteries/Inverter) - One hit was SO CLOSE that 4 of my security cameras got smoked, and a few emporia switches, also my Ground Fault plugs were tripped (ALSO, A highly suggested safety item, especially if you hook to pumps) . A ground will NOT protect against even close lightning strikes. A quick disconnect is so convenient, even for several 100 watt panels.
Important note: MAKE SURE THAT THE WIRING IN THE SWITCH IS CORRECT for "your" use!!!
These 2 switches look the same but they are NOT! Wiring can vary based on setup:
This one did NOT work for me:
This one DID work for Me:

I have a disconnect on each array, just so I don't have to unscrew the wires when I want to fiddle with things.

I'm a compulsive fiddler.

Okay, you convinced me. I ordered this https://www.amazon.com/Low-voltage-...0658&sprefix=dc+breaker+double,aps,225&sr=8-3
and this https://www.amazon.com/Awclub-Trans...ribution+protection+box&qid=1675080770&sr=8-5

Thanks for all the advice.

I guess you could keep some of these around, but my nine Imo pv switches are much safer to use.

They spark when you cut live twincore wires ... been there done that

I use the disconnect mostly when I am cleaning battery terminals. So that the charge controller doesn't receive voltage while it is powered down. Very handy. I believe the charge controller would go bye bye if it received voltage from the panels while not powered on from the batteries.

JanC said:

Okay, you convinced me. I ordered this https://www.amazon.com/Low-voltage-Miniature-Circuit-Breaker-Panels/dp/B0746DLP7S/ref=mp_s_a_1_3?crid=2N4Y64P4BEVNC&keywords=dc+double+pole+circuit+breaker&qid=1675080658&sprefix=dc+breaker+double,aps,225&sr=8-3
and this https://www.amazon.com/Awclub-Trans...ribution+protection+box&qid=1675080770&sr=8-5

Thanks for all the advice.

Click to expand...

Would just like to mention, that the DC circuit breaker you've linked here is a polarized one. From my understanding of this, in order to work properly it is important to make sure your solar positive cable is installed on the + side of the double pole circuit breaker, and similarly, the negative to negative.

Hope it helps.

Best,
D.

You can't turn off the sun. So definitely have the breaker and watch the polarity as mentioned above.

Also note MC4 connectors are not intended to be disconnected under load.

JanC said:

Okay, you convinced me. I ordered this https://www.amazon.com/Low-voltage-Miniature-Circuit-Breaker-Panels/dp/B0746DLP7S/ref=mp_s_a_1_3?crid=2N4Y64P4BEVNC&keywords=dc+double+pole+circuit+breaker&qid=1675080658&sprefix=dc+breaker+double,aps,225&sr=8-3
and this https://www.amazon.com/Awclub-Trans...ribution+protection+box&qid=1675080770&sr=8-5

Thanks for all the advice.

Click to expand...

I use both these on system as well.

Where does it say and/or how can it be determined that the breaker sold by Walfront, linked to by the OP, is polarized?

For example, the Chtaixi breaker, linked below, that looks just like the Walfront breaker, including the fact that the terminals are marked pos and neg, specifically says:

"Polarity Marked
This DC MCB has no polarity requirement in use, and the positive and negative poles can be inverted.'