Light Switch Boxes

[Gareth Ellis]

To save space the walls are thin, about 2" , 5mm ply with 1.5" stud in the middle., as we are using 12v lighting the switch boxes dont need to be closed in the back, but I am using house switches as I like the fell better than rv switches.

As te ply is so thin, the wings on teh LV boxes would not grop as they are designed for 1/2 dry wall, so I laser cut back plates and glued them in place.

Here are the winged LV box frames I am using https://amzn.to/43IIq7S

Here are the switches I am using

Double https://amzn.to/3IRN0sw

Tripple https://amzn.to/43k9B9f

[DeMac]

The 120v switches you selected are rated for a maximum of 15A & 120v. You won't exceed the voltage rating at 12v but you might exceed the Amperage rating, depending on your lighting load.

Be sure to switch the (+) conductors and not the (-) conductors.

The "Auto Grounding" feature is designed with a self-grounding clip for automatic connection in a properly grounded metal wall box. Grounding also requires a third (dedicated ground) conductor. Without the aformentioned components, the switch will remain ungrounded.

[Gareth Ellis]

Thanks fot the information, I am not worried about the grounding clips as none of the 12v system is grounded. I ran seperate negative wires for all house 12v items so for sure will only be switching the positives.

I did some calcs, and a 12amp switch would potentially switch 140W @12v, my led lights are 9w each and the largest string is 6 so 54W total.

It is really good to be aware of these things though so always appreciate additional information.

[HamSkoolie]

MAKE SURE that those AC switches are rated for DC. AC, because it alternates, doesn't have a high a potential for arcing. DC, because it does not alternate (thus it is constant with no off time) is very prone to arcing.


This is a SAFETY issue and while many may have good experiences, YOU may not. ALSO, if you ever have an issue your insurance claim is very likely to be denied if they have any way at all to point to th use of AC rated switches.

[Gareth Ellis]

This is a very valid point,

I will ensure that the switches I use are low voltage DC compatable,

Leviton has a nice range

https://images.thdstatic.com/catalog...b28ebdb069.pdf


This is a SAFETY issue and while many may have good experiences, YOU may not. ALSO, if you ever have an issue your insurance claim is very likely to be denied if they have any way at all to point to th use of AC rated switches.[/QUOTE]

[HamSkoolie]

Originally Posted by Gareth Ellis

This is a very valid point,

I will ensure that the switches I use are low voltage DC compatable,

Leviton has a nice range

https://images.thdstatic.com/catalog...b28ebdb069.pdf

There you go. I'll be keeping that link for my own use since I wasn't aware Leviton had a line of 24V AC/DC devices and my gal is wanting the square household looking stuff.
Thanks!

[Rucker]

Originally Posted by Gareth Ellis

To save space the walls are thin, about 2" , 5mm ply with 1.5" stud in the middle., as we are using 12v lighting the switch boxes dont need to be closed in the back, but I am using house switches as I like the fell better than rv switches.

As te ply is so thin, the wings on teh LV boxes would not grop as they are designed for 1/2 dry wall, so I laser cut back plates and glued them in place.

Here are the winged LV box frames I am using https://amzn.to/43IIq7S

Here are the switches I am using

Double https://amzn.to/3IRN0sw

Tripple https://amzn.to/43k9B9f

Your work on your bus is a very slick! Quality work!

Regarding switches, others have already pointed out it's best to use switches rated for DC. I don't think there's a magic formula for determining whether a particular AC switch rated for x volts and y current will work for a given DC circuit. Some suggest derating the switch by as much as 20x (especially if you are up there in amps).

For my own comfort, I use only switches explicitly rated for the DC volts and amps anticipated.

I would say with light loads at the typical skoolie amp ranges for lights, the most common problem you'll see is a switch failing prematurely, or acting flaky because the mechanism's contacts have been pitted from arcing. Your fuses won't protect against arcing, by the way.

The most risky use of AC-only rated switches on a DC circuit would be anything with an inrush current-typically, DC motors like blowers, fans, or compressors in DC fridges.

Don't take my word for it though. Here's a nice YouTube demo of the difference:

https://www.youtube.com/watch?v=mQpzwR7wLeo

It should be enough to firmly convince anyone to go back and swap out their AC switches on DC circuits.

[HamSkoolie]

Great video but he's using 120 and 240 volts. that's 10 and 20 times the typical 12VDC system.
It's still an issue but that video may not convince folks with 12VDC gear.


So remember folks, if you have an electrical fire and you used switches (or anything else) not specifically rated for DC..... the insurance company will likely deny the claim. A couple we met had lost their first bus to a fire after a DIRECT lightening strike. Their battery bank (home built lithium) was all the insurance needed to deny their total loss.


We should all strive to use UL listed materials rated for the voltage and type (AC or DC) in all of our build to keep the insurance thieves at bay.

[BarnYardCamp]

OK, several post earlier in this thread, some one mentioned that you should only place the switch on the (+) positive side of the circuit. Since all the switch does is interrupt or complete the circuit, why does this matter? Reason I'm asking is that for my water pump, I would have had to run another 7 feet of wire. That extra 7 feet had me concerned that the wire gage I used was too small. So I used the switch on the negative side.
I did use household switches in 2 places, the water pump and the bathroom light. I'll swap those switches out for DC rated switches when I get my bus back from the mechanic....hopefully soon.

[DeMac]

Originally Posted by HamSkoolie

Great video but he's using 120 and 240 volts. that's 10 and 20 times the typical 12VDC system.
It's still an issue but that video may not convince folks with 12VDC gear.


So remember folks, if you have an electrical fire and you used switches (or anything else) not specifically rated for DC..... the insurance company will likely deny the claim. A couple we met had lost their first bus to a fire after a DIRECT lightening strike. Their battery bank (home built lithium) was all the insurance needed to deny their total loss.


We should all strive to use UL listed materials rated for the voltage and type (AC or DC) in all of our build to keep the insurance thieves at bay.

-----------------------

All of this ⤴
Is Good Stuff


The open back boxes, being used in this thread, are not approved for electrical switching devices, of any sort.

They are approved for use with coax cable, phone/data, audio/video, etc. Not devices with live parts (12v,120v, 277v, etc.)

The AC electrical switches shown, are UL listed & rated to be installed into an enclosed, fire rated, device box.


Most Importantly
The switches' set screw terminals, where the wires terminate, are primarily designed for solid #12 wire. Usually, only 20A devices will accept #10. (Max) Verify each device's max wire size & if the terminals are listed for stranded.


A meticulous builder may be successful using stranded #12 around set screws, listed for use, if practicing the methods discribed in Post #65 of this⚡thread. I encourage stranded-users to also read Posts #69 & #70, thereafter.


There is a better way. Backing up sucks, but if you want safe, make it safe.

[Rucker]

Originally Posted by BarnYardCamp

OK, several post earlier in this thread, some one mentioned that you should only place the switch on the (+) positive side of the circuit. Since all the switch does is interrupt or complete the circuit, why does this matter? Reason I'm asking is that for my water pump, I would have had to run another 7 feet of wire. That extra 7 feet had me concerned that the wire gage I used was too small. So I used the switch on the negative side.
I did use household switches in 2 places, the water pump and the bathroom light. I'll swap those switches out for DC rated switches when I get my bus back from the mechanic....hopefully soon.

Don't know if there's a rule about this.

The practice is to switch the positive lead, for three reasons I can think of. First, with the switch off the device is not energized when are swapping it out or otherwise working on it. No risk of inadvertent grounding/arcing etc. The second is that anyone else coming after you will expect the switch to be on the positive lead. The third is that any short on the line after the device but before the switch may first cause the device to fire up, perhaps without blowing a fuse, but certainly energizing whatever it is shorted to, offering a chance for a zap or a fire.

There may be counterpoints, but I think from the point of view of the third failure mode, it's a safety or shock hazard putting the switch after the device.

[Gareth Ellis]

@ DeMac...I just cant seem to find anything or any jurisdiction that controlls low voltage wiring in motor homes so as I am curious, do you have links from the authority that approves and dissaproves such switch installations in a motor home that specify the approved method of mounting a vehicle 12v switch? The switches and outlet you have shown here is a nice example of a commercial installation to code for a building. Not sure that I have ever seen anything as extravagant as that before in a motor home / RV. The 'open back box' as you describe is for all low voltage applications and is described in the industry as a low voltage mounting bracket. I cant seem to see the difference between the low voltage mounting bracket in this post or a basic rv low voltage switch mounting bracket, as long as the crimped terminals connected to the switch are insulated it is safe.

if not...... you better start re-wiring all your dashboard switches!! ;)



https://amzn.to/43wEhnT

[DeMac]

Juristiction? Authority? Hehe. I'm neither ones parent nor erand boy. Gareth Ellis, we are each our own AHJ. Personal Itegrity is the key.
(Q): What is an AHJ?
(A): See Post #60

We each have free will & each of us choose our level of education. You may disregard our help. Our comments and suggestions are for the sake of fire safety. We are skoolie.net members who are concerened about the other builders here. We help folks build safe, if they want to build safe. But you do you. I can tell that you already know all about fire safety.

Dashboard switches are actually Listed For Use in automotive applications. Check with the manufacturer, not me. The 120v switches you selected were never formally tested for that plate-holder nor the inside of a vehicle. TRUTH. Heck, the plate-holder was made for 1/2" & thicker drywall.(Nobody is gonna enforce these facts upon your build) UL is short for United Laboratories, not FBI or DOJ. Funny stuff. The NFPA is the National Fire Protection Association, they study fires. They're not your local code enforcent agency. Lol.

Please post more photos of your electrical work. We are looking forward to seeing it all come together. 😉

[Polarweasel]

Gareth Ellis: the RVIA has a list of all the standards and agencies relevant to their certifications. If you want references, it’s all there. Most of it is probably paywalled too, but it’s usually not too hard to find copies of standards.

This page is a good starting point:

https://www.rvia.org/node/associatio...pted-standards

[HamSkoolie]

Keep in mind however that while the "standards" of the RVIA are, in fact, standards, they're pretty shoddy standards. Anyone building a custom rig should certainly strive to put the RVIA standards in the dust.


As DeMac has said though, you do you.



Keep in mind however that if you have any insurance claims your choices (any of them) could result in denial of your claim.

What could cause that? Here's a short list:
Not disclosing a wood stove, roof raise, roof deck
Building up your own battery bank from 18650 cells (seen it happen)

Running over weight
Running recaps on your steer axles
Improper drivers license
Using non UL listed components (I've seen it happen to people)
Using components rated for DC but not AC in a DC system and vice versa


One couple I met were in their second bus. The first was a total loss after it burned as result of a DIRECT lightening strike and the insurance company denied their claim based on the fact that they'd built their lithium battery from 18650 cells. They didn't care that the lightening strike would have caused a fire with ANY lithium battery. Because there's was DIY, they decided IT was the cause of the fire, not the millions of volts from the lightening strike.


And then what happens if there's an "issue" (wreck, fire, etc.) and someone, anyone, is seriously injured or killed? Criminal negligence charges are entirely possible whether you really were negligent or not. The hazard to your freedom is real in such a case and defense is expensive..... very expensive. Yes you're entitled to a lawyer provided by the government if you can't afford one but guess who decides if you can afford one....yes that's right, the government. AND those of us who have studied the criminal "justice" system have a name for those government provided attorneys..... public pretender. They will push for you to accept a plea deal because they are almost universally carrying too many cases and have too few resources to effectively defend you and those plea deals are often the best they think they can do for you, their client.


So, you do you, but understand the system within which we all live and make your decisions with the knowledge that right or wrong those decisions can come back to bite you. Right or wrong.