Recs for Solar Cut Off Switch?

[Powertour]

Looking for help finding some sort of cut off switch that I can mount on the wall inside my coach next to where the charge controller is currently mounted.

Side note: I'm pretty much hemmed into putting the cut off switch next to the charge controller due to the way the previous owner wired the array into the coach.

Trying to find anything that isn't big &/or big & ugly has proven to be an exercise in futility.

Thanks in advance!

[BFL13]

Reading some articles from Google on this confirms the DC vs AC thing.

I have a couple of questions on the specs of this 12/24 switch, eg:

https://www.princessauto.com/en/detail/12-24v-rotary-battery-master-switch/A-p8437402e

So its says it has a watts rating of 2700w. What does the watts limit have to do with anything? 2700/12= 225 the amps rating, but where is the 2700/24 = 112.5 ?

The 1,000 for 15s is perhaps for inductive loads on and off? I read that switches need to be L or R where L has the huge in-rush current when turned on or off.

And, what does it mean by "polarity" in a switch? This one says it is "positive". (I remember in school they told us that Americans do electricity direction backwards, so would I have to install this the other way around? 🙂 )

I see that I could use my 15a 120v light switch as long as the DC is 15a at no more than 30 volts. Not clear how that fits with gap and speed of switching.

[pianotuna]

Boon Docker,

The gap needs to be larger in a DC rated switch. Faster is better, too.

[markchengr]

I used a Blue Sea battery switch from West Marine in the positive wire between the panels and the controller. Made a sign near the batteries to shut off this switch prior to disconnecting batteries.

[Vintage465]

This is what I did. There is a PV shut off where the #4 cable comes down(top). Then where it come out of the controller it goes thru a 30a circuit breaker that has the re-set switch you can push to open the circuit. They seem to be pretty nice.

[bpounds]

I used this little DC circuit breaker. I'm a bit over on the voltage rating, but I know it isn't going to be an issue. Mounted it on the same panel as the CC. I chose to interrupt the positive lead, because it is good practice, but it make no difference in a non-grounded solar circuit. Just makes me feel better in case something around the panels decides to find a path to ground.

https://www.amazon.com/gp/product/B01H3DKGGE/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&th=1

[Boon_Docker]

Richard:

The main difference between AC and DC switches is the speed at which the contacts open/close when activated. A DC switch is made to open/close quicker that an AC switch. Thus less chance of it arcing.

[pianotuna]

Hi,

On AC power the direction of the voltage changes 30 times a second. On DC it is one way, so an arc requires a larger gap.

Here is a high voltage example:

https://www.youtube.com/watch?v=d3U1yrBI3xc

That is what is happening inside the switch. The arcing causes pitting of the contacts.

RLS7201 wrote:

pianotuna wrote:
BFL13,

With respect, using a switch rated for AC in a DC circuit may lead to arcing.

Don, what are the design characteristics of AC and DC switches that differentiates the two? What inhibits the arching in one design and not the other. Inquiring minds want to know.

Richard

[2oldman]

CapnCampn wrote:
I found it amusing that this "Little" switch is listed with dimensions of 48x36x48 inches in the Amazon technical details.But it is only 9.1 oz... I bet it floats well.

Lol. Yeah, I had a hard time getting it in the basement.

[CapnCampn]

2oldman wrote:
Little disconnect switch

I found it amusing that this "Little" switch is listed with dimensions of 48x36x48 inches in the Amazon technical details.

But it is only 9.1 oz... I bet it floats well.

🙂

[RLS7201]

pianotuna wrote:
BFL13,

With respect, using a switch rated for AC in a DC circuit may lead to arcing.

Don, what are the design characteristics of AC and DC switches that differentiates the two? What inhibits the arching in one design and not the other. Inquiring minds want to know.

Richard

[PNW_Steve]

Boon Docker wrote:
12v inline circuit breaker

This would be appropriate if your array Voc is 24v or less.

For higher voltage arrays the Midnite Solar DC breakers may be a good option.

If you are running an MPPT controller it is very possible for you to exceed the capacity of that breaker. For example: My array is wired 2S3P with panel Voc of about 37 volts. That gives me an array Voc of 74 volts.

[time2roll]

What is the voltage? All parallel panels can be about any DC switch rated for the Isc total. Panels in series sending 50+ volts to the controller needs to be properly rated for the DC voltage.

[Itinerant1]

crcr wrote:

Itinerant1 wrote:
If needing to disconnect panels from system it's as easy as pushing a button.

Actually, you should have two DC breakers like that, one between the solar panels and the controller, and one after the controller, before the inverter, so that you can completely isolate the controller from the system if need be. It looks like that's how this system is wired, and that's how I wired my system.

From the PT controller manual...as an example.

[BFL13]

pianotuna wrote:
BFL13,

With respect, using a switch rated for AC in a DC circuit may lead to arcing.

OK, noted. Deleted that.

[pianotuna]

BFL13,

With respect, using a switch rated for AC in a DC circuit may lead to arcing.