Switch for solar panel circuit

[seadrift]

I am planning a solar installation and want to include a switch in the #10 or #8 wire between solar panels and controller (2x100w, 24 foot round-trip panels to batteries; yes, fused). Most marine switches seem to have pretty flimsy terminal screws for #8 wire. Conversely, an on/off battery switch seems like overkill, What do others use?

[jeepbluetj]

Small battery switch is fine. Or put into your charge buss via an appropriately sized breaker. You need fuse or breaker on the battery side anyway

[seadrift]

I considered a breaker close to battery, but prefer to be able to disconnect before the controller. So...$25 for the smallest battery switch...

[Colin A]

You can use a Cole Hersee Disconnect switch I know some styles are marine rated.
Battery-Related Products | Master Disconnect Switches | Cole Hersee - Littelfuse

[noelex 77]

For occasional disconnect (which is all the solar circuit should need) removing the fuse can be a viable option to disconnect the circuit, especially with an ANL fuse that can be easily swung out of the way.

Circuit Breakers are ideal acting as switch and a fuse, but finding suitable DC ratings that will accept large diameter cable can be a challenge.

[seadrift]

Thanks; perhaps disconnecting at the battery is best - it takes the charge controller off too.

[FlyingCloud1937]

or just use a proper switching breaker.
C-Series White Toggle Circuit Breaker - Single Pole 20 Amp - Blue Sea Systems


Will handle up to a #4 wire, anything larger, just wire it to a back plane.

Lloyd

Originally Posted by seadrift

Thanks; perhaps disconnecting at the battery is best - it takes the charge controller off too.

[sailorboy1]

I just remove the fuse, which is installed in the bottom of the controller. Only do it when need to work on the system, which the only time I have had to do was in the Fall when I take the panel down for storage.

[btrayfors]

It's a good idea to have a disconnect on BOTH the battery side of the controller and on the solar panel side. Since both of these need also to have CPD's (fuse or breaker), it's often convenient to just install a breaker on each side of the controller.

DO NOT disconnect the battery side while the panels are feeding current to the controller. Some controllers may be damaged, just as would an alternator if you disconnected the battery with the engine running (unless you shut off the field current first).

Bill

[Golden Echo]

Originally Posted by seadrift

I am planning a solar installation and want to include a switch in the #10 or #8 wire between solar panels and controller (2x100w, 24 foot round-trip panels to batteries; yes, fused). Most marine switches seem to have pretty flimsy terminal screws for #8 wire. Conversely, an on/off battery switch seems like overkill, What do others use?

I have a single 135 watt panel wired to a trolling motor plug. When I need to disconnect the panel I unplug it. Works like a charm.

[sparrowhawk1]

you can get a 50 amp circuit breaker from Amazon for $13 if you're going to use 10 gauge wire you're supposed to use a 30 amp fuse

[noelex 77]

Originally Posted by sparrowhawk1

you can get a 50 amp circuit breaker from Amazon for $13 if you're going to use 10 gauge wire you're supposed to use a 30 amp fuse

Attachment 75819

I am a little wary of these cheap circuit breakers. It is important that the interrupt capacity is adequate. The other problem is that some of these circuit breakers become unusable after a short. Also be aware of the maximum voltage rating if using them on the upstream side.

I am probably over conservative, but it is difficult to know the quality control, whether they meet the specs, or even what the specs are in some cases.

Large solar arrays run large cabling and there can be some serious consequences of a short, particularly with lithium batteries that can release a lot of energy quickly.

With the high voltage panels, or series connection also consider that you may be getting up to potentially lethal voltages (this is often defined as 50v+)


Blue seas makes a higher quality version of the circuit breakers, but they are expensive.
285-Series Circuit Breaker - Surface Mount 50A - Blue Sea Systems
Or:
187-Series Circuit Breaker - Surface Mount 50A - Blue Sea Systems

Both of these are only rated to 48v so they are not suitable on the upstream side of high voltage panels.

[Colin A]

As said before the Carling C series will handle the current and voltage and have 1/4 20 studs for attaching wire. If you shop around you can find them at a decent price. If you look at the home solar sites you can also get DIN rail mount Fuse holders with disconnects they tend to be a little pricey thou.

[skipmac]

Originally Posted by btrayfors

It's a good idea to have a disconnect on BOTH the battery side of the controller and on the solar panel side. Since both of these need also to have CPD's (fuse or breaker

Hi Bill,

Glad you mentioned this point as it's something I've been thinking about as I finish the rewire of my boat. I plan to run alternator, solar and wind power outputs to a common bus and from there to a terminal fuse block on the battery. So that end of the hot wires will be protected but what about the other end?

For example, I have a 120 amp alternator and if the hot wire on that is shorted before it reaches the battery terminal fuse then that's a problem as well. But first, quick look at fuse options for that amperage I don't see any inline fuses that will work and installing a fuse block is not really the cleanest solution for my location. Maybe a terminal fuse on the stuc on the back of the alternator? Any other suggestions?

[Dsanduril]

There really isn't a point to a breaker/fuse on the panel side, there is an absolute need at the battery end. A short from battery to ground/negative can lead to tremendous currents and requires a breaker with a high AIC.

Solar panels, on the other hand, are current limiting devices by nature. If a panel is rated at 8A it will put about 9A into a dead short. So what size breaker do you put in for that condition? 8.5A? There really is no breaker or fuse you can put in to protect against a panel to ground short because the current will not increase above Isc. If you size a breaker/fuse at even just 110% of normal current it will never open/trip.