Using a 120V Alternating Relay with 208V Loads

Alternating Relays


Can I use an Alternating Relay with one input voltage value to control multiple loads at a different voltage?


Normally, a 120V Alternating Relay is used with 120V loads. However, there is a way to have certain versions control 208V loads. 

To use a 120V SPDT ARP120A6 or ARP120A6R SPDT Alternating Relay to switch 208V loads, use the following diagram:

Diagram: Using a Macromatic Alternating Relay to switch 208V loads
  • A double pole Control Switch must be used
  • The 120V input voltage between L1 & N is connected to Pins 3 & 4 to power the Alternating Relay
  • L1 & L2 is the 208V voltage for the two outputs
  • One contact of the Control Switch must be connected between L1 & Pin 5 to signal the Alternating Relay to switch to the other position when it opens.
  • The other contact of the Control Switch must be connected between L1 & Pin 1 to control either Load.
  • All connections to Pins 1, 4 & 5 must be from the same phase.
  • Do NOT put a jumper between Pins 1 & 5 that is normally used with SPDT Alternating Relays.

NOTE: this discussion will only work on 208/120V systems with a neutral wire. For other applications, please contact Macromatic Technical Support at 800-238-7474.

There is no way to make a 120V ARP120A3 or ARP120A3R DPDT Cross-Wired Alternating Relay work with 208V loads.  A Cross-Wired Alternating Relay requires both the input voltage & load voltage to be the same.  If you want to switch a 208V load, you must purchase & use a 240V Alternating Relay.

For more information, please contact Macromatic.