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5 Electrical connections (continued)
35
Installation & Service Manual
Locating Temperature Control
Remove the control panel door on the front of the unit in
order to locate and access the temperature control.
Temperature Control Settings
Remove the control panel door on the front of the unit unless
your unit is specified as a boiler only with an outdoor air reset
option. If your unit is a boiler only with an outdoor air reset
option, there are additional controls for this option. They are
explained under Outdoor Air Reset Option, page 37.
The three setting knobs on the temperature control are for Set
point, Differential, and High-Fire Offset (see FIG. 5-4).
Figure 5-4_Temperature Control
Maximum Set Point Determination
The maximum set point for the control is factory set. Boilers
can be set to 240°F max., water heaters are set to 190°F max.,
and specialty state and local codes to 200°F.
These maximum set points are established by cutting the OJ1
and OJ2 jumpers located on the right side of the temperature
controller. The maximum set point is determined as shown
below in Table 5C.
TABLE - 5C
MAXIMUM SET POINT DETERMINATION
OJ1 OJ2
MAX.
SET POINT
Connected Connected 240°F
Cut Connected 190°F
Connected Cut 200°F
Cut Cut 160°F
NOTICE
Anytime that OJ1 is the only jumper cut, a
new overlay is required under the Set Point
knob on the temperature controller because
the scale has changed to a maximum of
190°F.
Anytime the OJ2 jumper is cut (with or
without OJ1), a new overlay is required
under the Set Point knob on the temperature
controller because the scale has changed to a
maximum of 200°F.
Set Point
The Set Point knob specifies the target inlet (or system sensor, if
used) water temperature in degrees, Fahrenheit. After the water
temperature reaches the set point, the temperature control shuts
off the burners.
Differential
The Differential specifies the number of degrees below the set
point that the control will allow the water temperature to drop
before it brings the unit back on again.
High-Fire Offset
The temperature control operates a two-stage firing system. The
two stages are High-Fire and Low-Fire. High-Fire operates all
burners at full rate while Low-Fire operates the burners at
approximately one-half rate.
The High-Fire Offset knob specifies the number of degrees
below set point that the High-Fire stage shuts down. At that
point, the unit will continue to operate at the Low-Fire stage
until the set point is reached.
The High-Fire Offset knob has settings between 0°F and 20°F. If
set at 0°F, the High-Fire Offset is disabled and the unit will
operate the High-Fire stage until the set point is reached and the
temperature control shuts the unit off.
If the High Fire Offset knob is set to 0 or 1, the delay will be
10 seconds; if set to 2 or above the delay will be 120 seconds.
Boiler Application
Standard boiler units are equipped with one inlet water
temperature sensor. An optional sensor is also provided for use
as a remote system sensor. Boilers with the outdoor air reset
option also have an outside air temperature sensor.
Water Heater Application
Water heater units are shipped with an inlet water temperature
sensor and a multi-purpose temperature sensor to be used as a
tank sensor. The inlet water temperature sensor is factory
installed on all water heaters.