Honeywell T775A Product Data page 7

OPERATION
Control Algorithm
On/Off Control
The T775AC operate with one temperature input supplied by
the remote sensor while T775B,D have two temperature
inputs. The T775A,B,C,D are all capable of providing up to four
stages of on/off control relay outputs. Each controller stage has
its own independent setpoint that can be configured to operate
in either the heating or cooling mode. The mode of operation
for each stage is user-determined by programming keys.
Heating Mode Operation
• Relay outputs energize at the temperature setpoint minus
the differential value.
• Relay outputs de-energize at the temperature setpoint
value.
Cooling Mode Operation
• Relay outputs energize at the temperature setpoint plus
differential value.
• Relay outputs de-energize at the temperature setpoint
value.
EXAMPLE
Using a device with one input and one relay output, the
corresponding load energizes at the following temperatures
based on the initial settings:
• Setpoint: 68°F
• Differential: 2°F
Outputs Energized
Heating Mode: Stage One energizes at 66°F.
Cooling Mode: Stage One energizes at 70°F.
The T775B,D have dual sensor inputs and allow two separate
controllers to exist within one enclosure. Selection of the stage
parameters (operation mode, setpoints, and differentials) is the
same as for a single sensor device after each stage is
assigned its operating sensor. This assignment is hardware
driven via a four position DIP switch. An explanation of the DIP
switch assignments appears in Fig. 9. See Fig. 3 and 4 for the
DIP switch location.
Contact Closure Override Input
The two-terminal input allows the user to override a relay-
energized condition on all outputs. This is done using contact
closure between terminal pins 3 and 4 (TOD). (See Fig. 3 and
4 for location.) This can be achieved manually or by using an
EMS controller or time clock with normally open contacts
(W7505 or S7005, for example).
When this override is active:
— The display shows the number of stages that would be
energized
— The words STAGE ENERGIZED flash on the display.
— Energized stages de-energize until the override returns to
inactive (Off).
T775A,B,C,D REMOTE TEMPERATURE CONTROLLER
°F/°C Selection
A single jumper plug controls °F/°C indication of the displayed
temperature value. See Fig. 3 and 4 for the location of this
jumper. The unit ships with the jumper installed in the °F mode.
To operate the device in the °C mode, remove the jumper.
Replacing the jumper reinstates the °F mode.
NOTES: If, upon removing the jumper plug, the device does
not display °C:
— Remove power from the device.
— Replace power to the device.
DIP Switch Selections
On the T775B,D, DIP switches are provided for assignment of
each relay output stage to its operating sensor. If an individual
switch is depressed to the right—toward its corresponding load
number (1 through 4 on DIP switch)—Sensor B is the
controlling sensor for that output stage. If an individual switch
is depressed to the left, Sensor A is the controlling sensor for
the output stage. An example of the switches and their
corresponding positioning is shown in Fig. 9.
SWITCH
PWB
SWITCH
PWB
A
SIDE VIEW
Fig. 9. DIP switch settings for sensor selection.
Device Setup
1. Determine loads to be controlled and the operating mode
(heat or cool) and enter them in the Device Programming
Worksheet (Table 2).
Table 2. Device Programming Worksheet.
Load 1:
SetPt 1
Diff 1
Load 2:
SetPt 2
Diff 2
Load 3:
SetPt 3
Diff 3
Load 4:
SetPt 4
Diff 4
7
SENSOR A SENSOR B
LOAD 1
LOAD 2
LOAD 1 IS CONTROLLED BY
SENSOR A WHEN SWITCH IS
DEPRESSED ON THE LEFT
LOAD 2 IS CONTROLLED BY
B
SENSOR B WHEN SWITCH IS
DEPRESSED ON THE RIGHT
(AS SHOWN)
On at
Off at
On at
Off at
On at
Off at
On at
Off at
M3292
63-2489—2