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T775J ELECTRONIC REMOTE TEMPERATURE CONTROLLER
63-2248—4
13
SENSED
TEMPERATURE = 78
o
F
CALIBRATION
SETPOINT 75
o
F
DEAD BAND
DEAD BAND
MODULATION
HEATING MODE
THROTTLING
RANGE
THROTTLING
RANGE
* DEADBAND IS 1/8 OF THE THROTTLING RANGE
* DEADBAND IS 1/8 OF THE THROTTLING RANGE
COOLING MODE
CALIBRATION
SETPOINT 81
o
F
SENSED
TEMPERATURE = 78
o
F
M2149C
MODULATION
MODULATION
MODULATION
MODULATION
Fig. 17. Explanation of calibration setpoints for heating and cooling modes.
DESCRIPTION/OPERATION
Control Algorithm
Reset Control
The T775J operates as a reset controller with two sensor
inputs. The outdoor sensor is designated Sensor B and the
control medium sensor is Sensor A. Sensor B is wired to pins
7 and 8 of the input terminal block, while Sensor A is wired to
pins 1 and 2. The T775J is capable of providing modulating or
relay outputs for reset control. Each stage of the T775J has its
own independent setpoint that can be configured to operate in
the cooling or heating mode. The mode of operation for each
stage is user determined by the programming keys.
For reset control with two outputs, one of which is modulating,
the modulating output will be designated as stage 1 on the
LCD display. Although the modulating output is designated as
stage 1, it can be programmed to energize after the second
stage is energized.
The T775J offers four different reset configurations and an
adjustable reset ratio between 30 to 1 and 1 to 30.
The reset ratio expresses the amount of change in the
heating or cooling medium control point caused by a change
in the outdoor temperature. It is the ratio of outdoor
temperature change to heating or cooling control point
change (Sensor B/Sensor A). The reset ratio can be an
inverse ratio (when the outdoor temperature goes down, the
control point goes up) or a direct ratio (when the outdoor