In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Larry, try disconnecting the thermostat wires from the aquastat. Watch the boiler then. I should not be constantly banging off the hi limit if no one is calling for heat. Only the aquastat photo came out, and I could not see of you had anyzc/zr contacts coming from another zone relay. Is there water pressure in the boiler? are both zones when calling for heat circulating and returning hot water?
where are you located?