The relays contact ratings depend on whether they are switching AC or DC, and differ for normally open and normally closed contacts.<\/p>\n\n\n\n
For resistive loads the ratings are:<\/p>\n\n\n\n
Normally open: 5A @ 125VAC, 3A @ 250VAC, 5A @ 30VDC<\/p>\n\n\n\n
Normally closed: 2A @ 125VAC, 1A @ 250VAC, 1A @ 30VDC<\/p>\n\n\n\n
The above ratings are for resistive loads. If you use the board with inductive loads such as motors or solenoids, there will be additional strain placed on the relay contacts by the spark generated when the contact opens. Derate the contacts by 40%.<\/p>\n\n\n\n
If you are driving DC inductive loads (say a contactor with a 24VDC coil) you can reduce the strain on the relay contacts by connecting a diode across the load, cathode to the positive load terminal. This will prevent the spark from forming, at the expense of slowing down the turn-off speed, and allow you to use the relay to the full resistive load rating. A 1N4004 will work fine for any load the relay is able to drive. (Don’t attempt this with AC loads!).<\/p>\n\n\n\n