DC rated relay used to switch 240v AC

[Jagman]

Hi all,

As above, the million dollar question is can I use a typical automotive 12v relay to switch 240v ? The coil side of the relay will be switched by 12v with the 240v only running through the contacts. I have spent the last hour on the web looking for some info regarding this but so far have found nothing !! Please shed some light on this one for me !!

Regards

 

[crutschow]

Likely not safely. An automotive relay contacts are spaced to switch 12V. Switching 240V could cause arc-over and relay failure.

 

[KeepItSimpleStupid]

Relays have AC and DC ratings. Relays have max voltage ratings (so do fuses). Relays have currents that they can switch and currents that they can pass. Relays have inductive load ratings.

Here is a common example of a wrongly used (non-foolproof) switch that's common everywhere. The slide directional control switch on a ceiling fan. For long life, it is required to move the position when the motor is stopped.

 

[tcmtech]

Depends on the relay but if it was one of the modular high current types used in the engine compartment then the odds are yes it will handle 240 VAC on the contacts just fine.

 

[Timescope]

Use a 240v rated relay. Most of the automotive relays I have seen have one contact connected to the metal frame of the relay so the isolation is not adequate.

Timescope

 

[panic mode]

read the datasheet. automotive relays are only rated to switch DC loads at voltages that are 30V or less.

 

[dr pepper]

To answer your question, you can switch a load with a 12v relay, but not an automotive one, you need a relay with a 12v coil and ac 240 rated contacts, which are plentiful in supply.