621899R Nordyne Relay N/C 15Amp 

Zettler relay. Single pole single throw (SPST), normally closed (NC), 4.9FLA/15A RES. 10A 28VDC coil activates a 15A 277VAC switch. Two large terminals, two small terminals. Zettler part number AZ2280-1B-24A. 1/2HP 250VAC. Replaces Nordyne 621899 & 6218990. 

Video below shows how a simple relay works.