Use a 240v switch in a 12v circuit?

[JohnW2]

The back EMF from an inductive load can be absorbed by a contact suppressor fitted across the switch contacts.

Indeed - or a diode (sometimes with a small series resistor) across the inductive load (common when semiconductors feed inductive loads such as relay coils).

Kind Regards, John

 

[quokka]

All this talk of DC vs AC rating, inductive spikes and AC crossover is very interesting, but are we forgetting the context and over-engineering this a bit?

The OP is just talking about a pump for his home garden. For pesticide and fertiliser, right? Used a few times a year?
In a 12V motor application, the lifetime may be lower than in resistive-load AC applications, but I very much doubt that this will ever be a problem in real life.
Its not going on the Mars Rover.

 

[Monkeh]

All this talk of DC vs AC rating, inductive spikes and AC crossover is very interesting, but are we forgetting the context and over-engineering this a bit?

The OP is just talking about a pump for his home garden. For pesticide and fertiliser, right? Used a few times a year?
In a 12V motor application, the lifetime may be lower than in resistive-load AC applications, but I very much doubt that this will ever be a problem in real life.
Its not going on the Mars Rover.

Or the cheap switch might not extinguish the arc and melt.

Do it right (or at least try to) or go home.

 

[quokka]

Or the cheap switch might not extinguish the arc and melt.

Really? he was talking about a 10A mains power rated switch, not some cheap microswitch.

Do it right (or at least try to) or go home.

Why? Try a bit of risk-return analysis here. Its more a question of economics than electrics. An electricians job needs to be reliable because a return call-out is expensive. But for DIY in the garden, the economics are different. It is better to save an hour or two of farting about now, by using the parts at hand, and accept a small chance of needing to do it again later.
Worst case if the switch fails he can twist the wires together to finish the spraying job .

 

[bernardgreen]

Worst case if the switch fails he can twist the wires together to finish the spraying job .

And if it fails short circuit ( contacts welded ) he can get a spanner to disconnect the battery.

 

[ban-all-sheds]

And all this whilst riding a machine with an unofficial lash-up modification with a pump, tank, wiring and loose switches dangling about which could start chopping bits off him.