Honeywell R7426C Operating Overview, Return Air Offset RetOffs P.20, Minimum Position Minpos P.14

R7426A,B,C TEMPERATURE CONTROLLER WITH AND WITHOUT REAL TIME CLOCK

Y (%)

100

UNOCCUPIED

OCCUPIED

	SOFFS	SOFFS	T (°C)
Xph		Xpc

CTRPH CTRPC

Fig. 5. Night cycle NightLow and NightHigh

The night cycle program automatically cycles between the user selected upper and lower limits and turns on full heating or cooling with forced return air recirculation or full energy recovery whenever the limits are reached. The switching hysteresis is fixed to 1 K.

This function can be disabled for heating and/or cooling by setting NightLow and/or NightHigh to OFF.

Calibration of Temperature Sensors T1CAL, T2CAL, or T3CAL (P.17...P.19)

The controllers include a calibration setting and are factory calibrated. In case of an offset as a result of long wiring lengths the temperature sensor inputs (T1, T2, and T3) can be adjusted separately by the control parameters T1CAL, T2CAL and T3CAL.

Return Air Offset RetOffs (P.20)

The control parameter RetOffs is available only on R7426B,C controllers and is used to activate economizer mode (RetOffs

≠OFF) for mixed air damper (Y1CTRF = 0) or energy recovery system control (Y1CTRF = 1).

If the main temperature sensor (T1) is installed in the exhaust air, the control parameter RetOffs should be set to 0. In applications with the main sensor installed in the room and with a constant offset between room and exhaust air conditions, this offset value can be adjusted within 0...5 K by the control parameter RetOffs. This will be added to the actual measured room temperature value to simulate exhaust air conditions.

The economizer mode is disabled if the value of the control parameter RetOffs is programmed to OFF or if no outdoor air temperature sensor is connected.

Minimum Position MINPOS (P.14)

The control parameter adjustment MINPOS is available on R7426B,C controllers only and determines the minimum open position to which an outdoor air damper actuator can be driven from the controller. In mixed air damper applications it maintains the minimum outdoor air damper setting, even though the temperature input condition calls for a fully closed position.

If the controller is in OFF mode, the time schedule program overrides the minimum position by the ON/OFF input for plant/system shut off and the damper is driven into the fully closed position at OFF condition together with the heating and cooling valve actuators.

Runtimex, x = Y1, Y2, or Y3 (P.21...P.23)

The control parameters Runtimex (x = Y1 for R7426A; x = Y1, Y2 or Y3 for R7426B) are available only on R7426A, B controllers.

The controller converts the deviation signal to a proportional output pulse which drives the actuators depending on the Runtimex parameter value.

An automatic synchronization function ensures correct positioning of the actuators. The run time for synchronization is derived by control parameter Runtimex multiplied by 1.25.

By selection of the output to pwm mode, the pulse-width modulated output is suitable for driving electric heat current valves and is controlled from the heating signal. The total cycle time is set by the control parameter Runtimex.

OPERATING OVERVIEW

Display and Operation Elements

The MicroniK 200 user interface is described in Fig. 6.

NOTE: Pushing the + or - button increments/decrements values or scrolls through the parameter list:

•pushing one time: single step

•pushing without release: automatically inc./dec. or scroll

•after 3 sec pushing without release: fast automatically increment/decrement or scroll

DISPLAY			CONTROLLER MODE
FREEZE PROTECTION	TIME*	OFF	NIGHT* STANDBY COMFORT
	Date Off
LOW BATTERY*	°C % rh		min sec K	ENGINEERING UNITS
MoTuWeTh Fr		SaSu H1 H2 H3		VALUE
	WEEKDAYS / GROUPS*		HOLIDAY SCHEDULE TYPES*

*ON CONTROLLERS WITH REAL-TIME CLOCKS, ONLY.

PUSH BUTTONS

SELECTION OR ESCAPE

ADJUSTMENT OR SELECTION

PARAMETER / VALUE

CONFIRMATION

Fig. 6. User interface

11 EN1B-0203GE51 R0507C