Circulator relay switch question

[Rick Stanley]

Here's a shot of the inside cover of the ones used on my oil boiler. Can someone look at this and tell me in plain english what each connection shown is for, like what does r/t mean? 6no/ etc? and what the capabilities of this relay are? Like, can it be used to control more than one pump? If so can it give one priority over the other?

Thank You

 

[Jim K in PA]

This is a DPDT (Double Pole, Double Throw) relay. The numbers are the terminal IDs. You have power in (L1 L2), T-stat/control ckt input (R/T G/T C), and output from the relay. Basically you can discriminate between two loads, with either side being either in a off (N/O) or on (N/C) state. Either side can be on, off or a combination. Energizing/De-energizing the relay will reverse those conditions.

Hope that did not confuse.