Tekmar 261 2 stage boiler

BDP1858

I have a question about wiring the pumps for the Tekmar 261 I will be installing. I have 2, 199 natural gas, natural draft burnhams injecting into the system loop using primary secondary. Since there is only one pump contact on the controller, do I need to just have all 3 pumps (both boiler pumps, and system pump) going at the same time off the Tekmars call for heat? Instead of wiring the boiler pumps to each boiler. I’m thinking if I don’t, once the tekmar has reached its set point, it will just shut the boiler off completely and leave no way for the boiler pump to purge. Alternatively, is there a post purge on the Burnhams even if the call for heat stops while the boiler is firing?