Honeywell R7426B - Page 7

R7426A,B,C,D TEMPERATURE AND UNIVERSAL INPUT CONTROLLERS
7 63-2565
Dehumidification Control (Humidity Deviation Input)
Dehumidification control is available
only
on the R7426B,C
controllers (three outputs). Use it to connect a humidity
controller. The R7426 compares the deviation input signal
from the humidity controller (Xwrh) with the temperature
control cooling deviation signal (Xwc). The signal with the
highest cooling demand is used to control cooling output (O2).
Table 5. Freeze Protection Actions.
Table 6. Frost Recovery.
Output Functions
The controller provides a choice of output signals suitable for
operating a range of final control devices. Suitability is based
on the parameter setting of OMode and OxMode (where x is
1, 2 or 3) parameters.
R7426A and R7426B
FLOATING VALVE OR DAMPER ACTUATORS (FLOATING MODE)
Parameter setting for Heating/Cooling Control Outputs:
OMode is 0; OxMode (where x is 1, 2 or 3) is 0.
The controller converts the deviation signal to a proportional
output pulse which drives the actuators depending on the
Runtimex (where x is O1, O2 or O3) parameter value.
An automatic synchronization function ensures correct
actuator positioning. This is performed by periodically running
all actuators to the closed position. Synchronization run time
is derived by control parameter Runtimex (where x is O1, O2
or O3) multiplied by 1.25.
Synchronization by the controller is initiated:
• After power up reset (initial start).
• After 250 control steps with control output below 5 percent.
• If plant/system On/Off input is switched to Off.
ELECTRIC HEAT CURRENT VALVE (PWM OUTPUT)
PWM output is suitable for driving electric heat current valves.
It is controlled from the heating signal. The interval or total
cycle time is set by parameter Runtimex (where x is O1 or O3).
EXAMPLE:With 60 percent Output Signal and Motor
Runtimex (where x is O1 or O3) set to 50 sec,
OMode is 0, OxMode (where x is 1 or 3) is 3.
2-STAGE ON/OFF SEQUENCE CONTROL
The R7426A,B controllers convert the output signal into a
2-stage On/Off sequence output signal suitable for operating
relays. Two relays can be connected to provide sequence
control of two stages (such as electric heat stages).
Parameter setting for Output Switching Position:
• OMode is 0.
• OxMode (where x is 1, 2 or 3) is 1.
3-STAGE BINARY ON/OFF SEQUENCE CONTROL
The R7426A,B controllers convert the heating signal into a
3-stage binary On/Off sequence.
Parameter setting for Output Switching Position:
• OMode is 0.
• OxMode (where x is 1 or 3) is 2.
Outputs for R7426B only
4-STAGE ON/OFF ELECTRIC HEATING OR COOLING
When OMode is 2, the O3/O1 output sequence is controlled from
the heating signal and O2 is controlled from the cooling signal.
When OMode is 3 the O3/O1 output sequence is controlled from
the cooling signal and O2 is controlled from the heating signal.
For temperature control sequence, see Temperature
Sequence Control with Heating, Mixed Air Dampers and
Cooling section.
NOTES:
— Mixed air damper operation is not available.
— Output O2 operates in accordance with O2Mode.
6-STAGE ON/OFF SEQUENCE CONTROL HEATING OR COOLING
The output sequence of O3/O2/O1 is controlled from one
output signal. (See Main Temperature Control or R7426A
Cascade Control.)
15-STAGE BINARY ON/OFF ELECTRIC HEATING AND COOLING
The output sequence of O3/O1 is controlled from the heating
signal. The output sequence of O2 is controlled from the
cooling signal (see Temperature Sequence Control with
Heating, Mixed Air Dampers and Cooling section). O2 output
is operated in accordance with O2Mode.
NOTE: The mixed air damper operation is not available.
Fig. 8. 15-stage binary on/off electric heating and cooling.
Model
Output Function Freeze Protection Action
DIR/
REVO1
Su/Wi
Changeover
Outputs (in percent)
O1 O2 O3.
R7426A Dir — 0 ——
Rev — 100 ——
Cho Cooling 0 ——
Cho Heating 100 ——
R7426B —— 00100
R7426C 0 0 100
Model
Conditions of
Outdoor
Temperature (I03) Frost Recovery
R7426A
R7426B
R7426C
Greater than 43°F
(6°C) or I03 not
connected
Main temperature control
Less than 43°F (6°C) Setpoint W1 temporarily
raised by Xp1 and linearly
decreased to normal value
over approximately 10 min
M17452
POWER
STEP 1 ON
STEP 2 ON
STEP 14 ON
STEP 15 ON
ON
OFF
O3/O1
4 SIGNAL SEQUENCE
OF O3/O1 OUT1/OUT2
4.5 11
6.5 13
89 95.5 100%
6.5 13