7
11) Connect the electric supply to the boiler as indicated on the wiring diagram. The wiring
must be installed in accordance with the National Electrical Code and any other state and
local codes and the following requirements.
a) Internal wiring is completed at the factory on packaged boilers. External wiring must con
form with the National Electric Code and local codes.
b) Field connections should be protected with a 15 amp fuse.
c) A separate, fused disconnect switch should be installed and located near the unit so that
power can be shut-off for servicing, unless already equipped.
d) Install the room thermostat (not provided) on an inside wall away from cold drafts, windows
or heat from fireplaces, appliances or sunlight. Set the heat anticipator in accordance with
the manufacturer’s instructions. Connect the thermostat leads to the “TT” terminals on the
circulator control.
C. Operational Sequence
1) S Boilers equipped with tankless coil are equipped with a combination aquastat control
which has high and low limits to be set at 180° F and 160° F respectively by the installer.
These settings are nominal and may be adjusted for the particular installation conditions.
A 20° F difference between high and low limit is recommended. The control prioritizes
domestic hot water heating as explained below.
a. When room temperature falls below thermostat setting, thermostat calls for heat starting
the burner and circulating pump. The burner and pump continue to operate until room
heating requirements are satisfied (thermostat setting is reached), or until boiler water
temperature reaches the high limit control temperature setting. If the high limit control
temperature setting is reached, the burner shuts off and the circulating pump continues
to operate until the room heating requirements are satisfied. If the thermostat continues
to call for heat after the boiler water temperature has dropped to approximately 10
degrees below the temperature setting of the high limit control, the oil burner will start
again and the circulating pump will continue to run.
b. The boiler water temperature is normally maintained at 160°F around the tankless coil by
the operating control so that an abundance of hot water is available. If the boiler water
temperature should fall approximately 10 °F below the operating control low limit setting,
the oil burner will be started again by the control (and the circulating pump will be pre
vented from operating) until the operating control setting is satisfied. The operating con-
trol has an adjustable low limit differential setting. The low limit differential setting deter-
mines how high the boiler temperature must rise before the burner turns off and or the
circulator comes on if the thermostat calls for heat. The differential is measured from
10°F below the low limit. See control manufacturer’s literature included in the data pack-
age for detailed wiring, operating and safety instructions.
c. Adjusting the low limit differential to higher values will provide priority to heating domestic
hot water over a greater range of boiler temperature. (Maximum of approximately 25°F
differential measured from 10°F below the low limit setting.)