Honeywell L6006C Aquasta wiring to a Taco 006-BC4 Hot water Circulator Pump
I looked at the instruction manual for the switch, and it says:


  Switching action is as follows:
  Upon a drop in boiler water temperature (to dial setting,
  less differential), makes R to B burner contact; breaks R to W
  contact, preventing circulator operation. Upon a rise in boiler
  water temperature (to dial setting), breaks R to B burner
  contact, makes R to W circulator contact.


Manual link

That said, I don't know much about how the circulator should work, and what temperatures to set, but if you want the pump to come on when the temperature drops, you would wire it to terminals R and B and if you need it to come on when the temp goes up, it would be terminals R and W.  One is typically meany for heat (B) and the other for a circulator (W), but your installation might be different.