OK, a system like yours has a triple aquastat relay mounted on it. It
will have two temperature dials on it, unless it's an electronic
model. In any event, that control maintains the temperature of the hot
water in the boiler independent of circulating control. Each of your
two circulators has a relay which sends 120 volts to it's respective
circulator when that circulator's thermostat calls for heat. If you
turn up and down each thermostat, you should hear it's relay click on
and off. Don't go by the hum of the circulator as that can be
deceiving. Check for each relay clicking on and off as you raise and
lower the thermostats.


RBM, there is a Honeywell box on the from of the system. if i take the
cover off there are two dials insied. One says HI and set on 180 the
other says LO and set on 160. I remeber when the guy put the system in he
told me those dias control the water temberature coming out of the faucet.
Other than that I dont see anything that controls the temperature for the
circulating pumps.