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Thermostat Connection
The thermostat connection is 24 volt AC. Only connect the thermostat a er all other
work is complete, and the entire heating system is thoroughly purged of air. The
thermostat is connected to the terminals T1 and T2 on the control circuit board (see Fig. 4). In
zoned systems, the end switches of all the zone valves may be connected in parallel and
hooked up to the thermostat connection on the control board. For a typical system (see Fig. 5).
Thermostats described as "Power Stealing" or as "Parasitic Thermostats"
must not be used.
Thermostat Anticipator
The thermostat anticipator setting recommended is 0.2 amps. Failure to correctly adjust this
setting may result in unsatisfactory comfort conditions, and could result in damage to the
thermostat.
This setting may have to be adjusted slightly to ideally match the boiler control system to the
thermostat, as well as overcome the normal inertia of the radiation system. A setting to low
will be characterized by a short cycle, which does not allow the room temperature to be
satis ed before the boiler shuts down. A setting too high will be characterized by a long cycle,
which allows the room temperature to rise too high before the boiler shuts down. Adjustments
should be made to the setting, if required, but should not exceed 0.1 amps per adjustment.
Newer electronic thermostats typically have provisions for the cycle length, and type of
heating system. The instructions for the thermostat should be followed.
In zoned systems where the thermostat is controlling a zone valve, or circulation pump and not
the boiler, the anticipator should be set to match the current draw of the zone valve being used.
Temperature Control Setting (Aquastat)
The boiler has a temperature control knob know as an aquastat on the lower le corner of the
control board. This sets the maximum temperature that the boiler will operate at. The internal
control system monitors the water temperature in the tank and modulates the heating
elements to maintain the water temperature. Note that the setting on the knob only sets the
maximum temperature, it is normal for the boiler to operate at lower temperatures than this
setting at times, this is especially true in the spring and fall when it is not so cold outside. The
actual temperature setting you need to set it to will be determined by the type of
heating system the boiler is installed in. The range of the aquastat is from 10 to 54º C (50
to 130º F).
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