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 > One More Solar question

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Twistedlarch

Cottage Grove, OR.

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Posted: 04/25/20 03:33pm Link  |  Quote  |  Print  |  Notify Moderator

Still working/planning out my Solar set up and another question has surfaced.

I have installed a 40 amp DC circuit breaker between my controller and batteries, should I install another circuit breaker between the panels and the controller? Should this 2nd breaker also be a 40 amp or a 30 amp? I have a max panel output of 23 amps.

Thanks again!
Brian

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Posted: 04/25/20 03:43pm Link  |  Quote  |  Print  |  Notify Moderator

Yes for the CB and follow any connect/disconnect sequencing required by your CC. 30A is fine as is 40A provided the wiring is rated for 40A.


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time2roll

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Posted: 04/25/20 03:52pm Link  |  Quote  |  Print  |  Notify Moderator

You don't need any fuse or breaker on the connection from panels to the controller. You can short the wires and no harm will come of it.

Although a breaker can serve a switch to cut power to the controller for service.


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Gdetrailer

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Posted: 04/25/20 04:21pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

You don't need any fuse or breaker on the connection from panels to the controller. You can short the wires and no harm will come of it.

Although a breaker can serve a switch to cut power to the controller for service.


[emoticon] [emoticon]

You cannot make THAT "ASSUMPTION".

Granted, the panel might "fold back" some when heated, but the reality is it IS rated to provide a certain max amount of current at max illumination..

It would totally depend on the WIRE GA between the panel and controller, OP says panels rated for 23A, one WOULD want to have a min wire ga to handle 23A at peak sun in the event of the controller or a wiring short.

12 Ga is typically rated for 20A circuits but in reality most likely would want 10 ga as a minimum wire size which is typically rated for 30A if you really want to go through life without fuses on power sources..

If one used 18 ga "zip" cord, then that WOULD be a potential fire hazard with no fuse.

Good electrical rule of thumb, when in doubt, FUSE IT!

Fuses are cheap compared to your RV OR YOUR LIFE..

You can buy a new RV, but you cannot buy a new life when dead.

pianotuna

Regina, SK, Canada

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Posted: 04/25/20 04:52pm Link  |  Quote  |  Print  |  Notify Moderator

Panels-->breaker or fuse-->controller-->fuse or breaker near the battery bank (inches if possible).

Why? Because many controllers require the battery to be connected before the panels.

Operate without battery bank and it may let out the magic blue smoke.


Regards, Don
My ride is a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

time2roll

Southern California

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Posted: 04/25/20 05:10pm Link  |  Quote  |  Print  |  Notify Moderator

Panels have an Isc rating. No way will they produce more than that.
Most certainly every solar set up should have wire to easily handle the Isc rating and most go double or more to reduce voltage losses.
12 gauge will handle 45 amps with 105C insulation unbundled. Again nobody will use this wire due to voltage drop.
18 gauge will go 20 amps and probably have so much resistance it would survive just fine. Again nobody is installing #18 wire to feed 23 amps of solar to the controller.
If you have doubts, short the wires all day in the bright sun before you install. The only heat you will see is from the sun hitting the wires.

Boon Docker

Mountain Foothills of Southern Alberta

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Posted: 04/25/20 06:18pm Link  |  Quote  |  Print  |  Notify Moderator

pianotuna wrote:

Panels-->breaker or fuse-->controller-->fuse or breaker near the battery bank (inches if possible).

Why? Because many controllers require the battery to be connected before the panels.

Operate without battery bank and it may let out the magic blue smoke.


^ Best advice.

Twistedlarch

Cottage Grove, OR.

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Posted: 04/25/20 07:11pm Link  |  Quote  |  Print  |  Notify Moderator

2 panels came with 12 AWG, one came with 10 AWG from the manufacture. All three panels are 100 watts and 5.64 amps each. I have planned for four panels but am running with three for now.

Panel wires 10/12 AWG
10/12 AWG to combiner box.
8 AWG from box to controller to batteries.
Controller is within 5 feet of the batteries (per manufactures specs).

I've got a 30 amp breaker on order!

Thank you all for your help!
Brian

beemerphile1

Ohio

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Posted: 04/25/20 08:02pm Link  |  Quote  |  Print  |  Notify Moderator

I put a single breaker between the panels and controller. It allows use as an on/off switch also as the panels should not feed the controller if batteries are disconnected. The size of the breaker should be decided according to the gauge of the wiring.


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Boon Docker

Mountain Foothills of Southern Alberta

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Posted: 04/25/20 11:17pm Link  |  Quote  |  Print  |  Notify Moderator

^
A breaker between the panels and controller is exactly the same as what I did and for the same reason as beemerphile1

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