Is it acceptable to use a standard wall switch for a low amperage DC application?

[Andrewr05]

For clarification in this instance "low amperage" means under 10Amps.

Please answer the poll above

 

[PotusGobbleBottom]

What is low amperage??

 

[timselectric]

Voltage is the more important factor.

 

[Andrewr05]

What is low amperage??

Under 10Amps.

The switches in my case will all be for lighting.

 

[PotusGobbleBottom]

Under 10Amps.

The switches in my case will all be for lighting.

I would keep it under 12 amps and use it.
The real consideration in my OPINION is the difference between AC and DCs arc potential at specific voltages. Make sure and educate yourself on why this specific scenario may work and find out what wouldnt work. Knowledge is power.

 

[Bop]

Quite common in Australia for us to use standard wall switches in offgrid use- All switches can handle AC or DC use- BUT- there are limitations in their use...

When switching DC- you have to stay well under their AC voltage rating but can handle up to their maximum current level
(this is because of DC arcing on switching off- the AC will cross its zero voltage point multiple times a second and break an arc, but DC doesn't have a 'zero crossing point' and will sustain an arc indefinitely (this is a bad thing and can cause fires) so the opening gap must be large enough to break the arc- this means the maximum switching voltage for DC is lower than the AC voltage rating...
(this is often marked in non mains switches- light switches usually don't show this because they assume that they will always be used on mains electricity)
eg

One limitation on DC is when you are switching highly inductive loads- these can cause high voltage spikes on switching off- this has to be accounted for when switching DC loads (and AC) loads and will require derating the switch for both current and voltage limits...

 

[Andrewr05]

I know you don't want to be pulling any high load circuits through a standard house switch.

How about something like a motor starter toggle switch?
Would that work better if I were to have a higher amperage load that needed to be switched?

This question is largely irrelevant anyways, because I most likely won't, It's mostly just going to be low amperage lighting.

 

[Supervstech]

I voted no, because the question isnt specific enough.

"Low amperage" is such a wide range of possibilities.
And the voltage plays a huge part of the answer as well.

Would it work on a 12vDC system for switching some 12v LED house lights?
Most likely...

Unless the house is 2000sqft, and all LED lighting for entire house goes through the switch...

See...
It is difficult to answer.

 

[Bop]

For a high amperage load, either use a appropriately rated switch for that particular load, or an appropriately rated relay/contactor switched by a lower rated switch so it doesn't have to handle the load...

 

[Andrewr05]

I voted no, because the question isnt specific enough.

"Low amperage" is such a wide range of possibilities.
And the voltage plays a huge part of the answer as well.

Would it work on a 12vDC system for switching some 12v LED house lights?
Most likely...

Unless the house is 2000sqft, and all LED lighting for entire house goes through the switch...

See...
It is difficult to answer.

I clarified above.

 

[Partimewages]

I voted no since there was not a specification that approved it.

 

[Q-Dog]

My thinking is to get one with the loudest click I can find. I would test at least one to failure before I used it.

Eagle used to make DC rated wall switches.

 

[Hedges]

I've done it.

My stepson bought a car, and the fan thermostat wasn't working.
I grabbed an AC light switch and wired it up under the hood, so he could just pop the hood and turn it on before driving.
His friends laughed at it. He removed it. He overheated the car.

I've also used an AC circuit breaker to protect motor on an EV. Well, not just any EV, I'm talking almost 50 years ago. I mounted an automotive starting battery on a bicycle, and machined a pully into the HV commutator of a Dynamotor, set up belt drive. It worked, with 30A breaker protecting motor if overloaded. I think I put a capacitor across it.

Yeah, that's the ticket! Make an RC snubber to protect the contacts of your switch, especially for inductive loads.

 

[sunworshipper]

When a switch rated for AC applications is used in DC circuits, the current rating of the switch is the same. The DC voltage limit is usually much lower, typically 1/3 of the AC rating - 120VAC RMS (170V peak) rated switch can be used in 170/3 or about 56V DC. The reason for the derating the voltage spec is that it is easier to sustain a spark/arc created by a DC current.

 

[McKravitts]

Unless otherwisw specified by the mnufacturer, a commonly used "rule of thumb" is that switch contacts, relay contacts, contactor contacts and small circuit breaker contacts, that are marked "AC only" can in fact be used on DC up to the rated AC current but only at about 10% of the rated voltage.
The DC current can not exeed the rated AC current.

Further restrictions apply for inductive/capacitive loads.

 

[Andrewr05]

When a switch rated for AC applications is used in DC circuits, the current rating of the switch is the same. The DC voltage limit is usually much lower, typically 1/3 of the AC rating - 120VAC RMS (170V peak) rated switch can be used in 170/3 or about 56V DC. The reason for the derating the voltage spec is that it is easier to sustain a spark/arc created by a DC current.

Unless otherwisw specified by the mnufacturer, a commonly used "rule of thumb" is that switch contacts, relay contacts, contactor contacts and small circuit breaker contacts, that are marked "AC only" can in fact be used on DC up to the rated AC current but only at about 10% of the rated voltage.
The DC current can not exeed the rated AC current.

Further restrictions apply for inductive/capacitive loads.

So, unless you're doing something above the standard 15a rating of a normal US lightswitch then a 12v load is "okay"?

That's likely every application I can even conceive of at my office grid cabin, even running multiple lights off one string.

 

[Checkthisout]

I have several 120V a/c snap switches switching 12V dc lighting circuits.

It's a non-issue.

They make some awesome DC lights that work amazing but I don't want to use cheeseball RV type switches.

 

[Andrewr05]

I have several 120V a/c snap switches switching 12V dc lighting circuits.

It's a non-issue.

They make some awesome DC lights that work amazing but I don't want to use cheeseball RV type switches.

That was my problem, I don't necessarily have anything wrong with those style switches, but they just seemed odd to me and gimmicky.

 

[Bop]

For offgrid household use, there are DC led bulbs that can be used in standard household lamp holders (both BC and ES are available) and run directly off the battery bank- in fact I use them here myself...
These are two different types I use- one is the standard 'looks like a standard LED bulb' and the other is one designed for 'fancy lamps' like a table lamp and bedside table lamps... (or if you had any lamp with exposed bulbs like a chandelier or the like)- both are available in various colour ranges from 'incandescent' yellow to 'blue-white' so you can choose your desired colour...

Runs off 12v-85v, DC or AC...

And yes, I use normal Australian light switches on them...


(despite appearances- the 230v mains powerpoints are totally separate and just 'cross' behind the roof support in flexi-dute- the light switch and light are totally independent and are currently running at 12vdc from the battery bank...)

I use 'blue/white for the workshop side, but 'incandescent yellow' in the living quarters as it is too 'white' for my tastes but the 'blue/white' is better when you need to see details...

 

[Andrewr05]

Sweet, I'm happy to hear that those all work for you on a normal light switch.

That's actually what I bought as well already.
I bought some 12v rated lightbulbs and few e26 style wall sconces for more directional lighting and then a bunch of 12v string lights for everywhere else.