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BOILER OPERATING
TEMPERATURE CONTROL
The operating temperature control for the 300,000
Btu/hr model is located on the control panel, inside
of the top of the unit. The digital electronic
operating temperature control for the 990,000 thru
2,070,000 Btu/hr models is located in the front
control panel, behind the front access door. The
sensing element for the unit's operator is placed in
a bulb well installed in the inlet side of the heat
exchanger front header. The operating sensor for the
digital electronic temperature control may be remote
mounted in the system piping if required. See
"Remote Mounting of Sensor" instructions in this
manual. Carefully obser ve the discharge water
temperature on the initial boiler on cycles. The
location of the temperature sensor will generally
r e q u i r e a l owe r t e m p e r a t u r e s e t p o i n t o n t h e
operating control to achieve the desired discharge
water temperature from the boiler. This sensing
element location allows a boiler operating with a
low to moderate flow rate to sustain longer burner
on cycles, preventing short boiler "ON" cycles
based on high discharge water temperatures. For
example, a boiler operating with a 180°F (82° C)
discharge and a 20°F (11° C) temperature rise would
require approximately a 160°F (71° C) to 165°F
(74° C) set point with the temperature sensor
installed on the inlet side of the heat exchanger. The
exact temperature set point is based on your system's
requirements. Set the control set point(s) to the
desired operating water temperature. Observe the
boiler discharge temperature after each set point
adjustment to insure proper operation.
EMS or REMOTE
THERMOSTAT CONNECTION
TO TERMINAL STRIP
A n E M S , r e m o t e t h e r m o s t a t o r o t h e r r e m o t e
temperature control may be connected to the boiler.
Follow the manufacturers instructions supplied with
the remote thermostat for proper installation and
adjustment. The boiler is equipped with a terminal
strip to allow easy connection of a remote device.
The terminal strip on a 300,000 Btu/hr unit is
located on the control panel. The terminal strip on
a 990,000 thru 2,070,00 Btu/hr unit is located in
the electrical junction box, below the main gas
connection. Connection of a set of dry switching
contacts or a remote thermostat to the R and W
terminals will allow the unit to be switched on and
off by making and breaking the 24 VAC control
circuit.
Remove the jumper between the R and W terminals
on the terminal strip. Refer to the chart in this
section to determine maximum allowable length and
wire gauge recommended to connect the switching
contacts of the remote thermostat to the R and W
terminals on the terminal strip. Connection to the
terminal strip will allow the remote thermostat to
make and break the 24 VAC boiler control circuit
turning the boiler on and off based on the remotely
sensed temperature requirements. Set the boiler
operating temperature control as a high limit when
a remote thermostat or EMS is used as the operating
control.
Terminal Strip
300,000 Btu Models
EMS Terminal Strip
990,000 — 2.070,000 Btu Models
50
FIG. 56
FIG. 57
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