Relay 24 V appliance
Most relays have their ratings written on them. You can also find all the information you need in the datasheet for that relay. Search for the part-nr in your favorite search engine. 

You need to find a relay that can handle at least 24Volt DC. Not AC as relays can handle a much higher voltage at AC than they can at DC. 

You also need to check how maximum current your appliance draws. Make sure the relay is rated for at least that amount of Amps.

For example; the picture below shows a relay that's rated for 10A and 30VDC