You would think that I could use the cam switch as a simple two pole manual transfer switch but NOOOOOO!

I bought the switch purely for A/C service (switching from shore to inverter power). ( Sorry, did not notice that DC service was being considered.) Anyway, I found no documentation but a youtube video showing someone who had actually made jumper wires and connected the output terminals externally (2-4, 6-8, 10-12). (at 10min 50 sec)

My intention was to accomplish this in offgriddle's post:

Looked like it would work, but bulky and rather clumsy looking. Upon closer inspection of the switch, I realised it was easy to strip off an extra inch or so from the insulation and slide the wire right through to tie the output terminals together. The 3 wires clamp very securely and send power out to the NMD90 10/2 cable for the trailer's 30A A/C system. The power sources each connect to the separate input terminals.

When I say goof proof I mean safe separation of switchable power sources , always either/or, never both.

Looks like this blue sea switch comes with the outputs already joined:

Blue sea makes (sells) many DC battery switches. Multi-pole and multi-position. https://www.bluesea.com/products/category/11/Manual_Battery_Switches
It is best not to use an AC switch on DC circuits, in general.

chrisski said:

asked for a 45 amp or 30 amp dc limit. Anyway, ‘should be’ is not good enough for me

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Typical de-rate from AC to DC (if you dare) would be 2.5- 5% of AC rating. Which makes them unusable for DC imho

Levo said:

Looks like this blue sea switch comes with the outputs already joined:

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Look up user roadtoad- he utilized this style of switch very well. There are German, Japanese, USA, snd ?Singapore versions of this style of switch that are more expensive but more quality devices.

I like the version that switches two sources that have three poles. 1-off-2.
Because it can switch two sources with three conductors I think it’s a convenient way to solve the shorepower and inverter N-G bond issue in mobile applications where the bare/green/ground might become energized.

That switch is designed as a reversing switch for motors. Some of them have unexpected wire locations. I don’t recall the thread but a couple months back there were several posts identifying the contacts and switching functions.

chrisski said:

I did not realize you wanted dc.

I emailed blue sea who contacted Schneider about those, and Schneider said they should be good. I can‘t remember if i asked for a 45 amp or 30 amp dc limit. Anyway, ‘should be’ is not good enough for me in a Rv install, so i did not buy those. I had planned on using this to switch solar panels to a circuit breaker prior to the SCC where four panels would be in parallel at 24 amps with a 30 amp circuit breaker, or four panels in series at 6 amps with a 10 amp circuit breaker. I abandoned that plan.

AFIK, all these different website switches I looked at that were similar looking are AC switches, although some are deceptively labeled with things like 120 volts and 65 amps, but makes no mention of DC, and sometimes there is no description.

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I believe the "lack of description" leads the unknowing down the path to what is known as "a fire of known origin".

I agree, "should be" is not good enough.

I purchased a similar rotary switch but not for transfer. I will be wiring it in as an inverter bypass (therefore AC only). My inverter has a built-in transfer switch but if I need to take it off line, I can't pass AC through.

With that said, as long as these are rated for the voltage, and you don't plan to switch under load, the rating is fine for AC or DC. It's when switching under load that you have to worry about DC rating, specifically.

DerpsyDoodler said:

With that said, as long as these are rated for the voltage, and you don't plan to switch under load, the rating is fine for AC or DC. It's when switching under load that you have to worry about DC rating, specifically.

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I am not an expert; decades ago I was an electronic technician, not an engineer.

With my solar panel build, I have seen the DC arc 1/4” at 48 volts and 2.5 amps as I’m bringing the leads into measure a open circuit amperage of the string. I would not want to use the ac switch I linked for DC for that reason. I would go to sleep wondering if the current would arc across the closed switch, especially as the DC votlage got higher.

i may be going overboard, but to each his own.

chrisski said:

I am not an expert; decades ago I was an electronic technician, not an engineer.

With my solar panel build, I have seen the DC arc 1/4” at 48 volts and 2.5 amps as I’m bringing the leads into measure a open circuit amperage of the string. I would not want to use the ac switch I linked for DC for that reason. I would go to sleep wondering if the current would arc across the closed switch, especially as the DC votlage got higher.

i may be going overboard, but to each his own.

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Good point. Maybe an expert can chime in and correct my blunder.

DerpsyDoodler said:

Good point. Maybe an expert can chime in and correct my blunder.

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I wish i had that switch. I’d hook panels up one at a time in series until I got to the point it arced across the switch. I’d give up after 6, about 130 volts for an open circuit amperage test.

chrisski said:

I wish i had that switch. I’d hook panels up one at a time in series until I got to the point it arced across the switch. I’d give up after 6, about 130 volts for an open circuit amperage test.

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Well, the thing is, the terminals are insulated from each other. They would have to arc around the plastic. This is less likely. That said, there is a formula for arc length though I don't know it off the top of my head. Fair enough to do more research on the matter. If it were me implementing it, I certainly would.

I do believe/hope most responsible manufacturers utilize known information and perform the tests required to certify their products at the appropriate AC and/or DC ratings.
If it is not UL listed and/or approved, it probably isn't the best product to move electricity through a home.

All bets are off when a product is designed and built by a group of money hungry folks on the other side of the Pacific who have no worries about being held responsible. They can't see the smoke from where they are.