First of all, the number of coil turns is different. The DC resistance of the relay 24VDC coil is very large, and the coil current is equal to the voltage divided by the DC resistance of the coil, so the coil wire is very thin and the number of turns is large; the number of turns of the relay 24VAC coil is relatively small. Second, the power supply is different, the power supply of the relay 24VDC must be DC, and the power supply of the relay 24VAC must be AC.

The relay is an electrical control device, which is an electrical appliance that changes the controlled quantity according to predetermined steps in the electrical output circuit when the input quantity changes to the specified requirement. Relays have a control system and a controlled system, and are usually used in automatic control circuits to perform functions such as automatic adjustment, safety protection, and circuit switching.
The model of the relay is generally composed of the main name code, appearance symbol, dashed line, serial number and anti-characteristic symbol. Secondly, the specification number of the relay is composed of the model number and the specification serial number. The model number and specification number are separated by a slash, and the specification number cannot be used alone.