Honeywell R7426C, R7426B, R7426A dimensions Parameter Settings Adjustment

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

Summer / Winter Time Change

AddHour / SubHour (C.16 / C.17)

These configuration parameters are only available on controllers with RTC. The configuration parameter AddHour or SubHour are required to adjust the month for summer/winter time change or vice versa.

The actual clock is incremented by one hour at 2:00 on the last sunday of the month for winter/summer time change (AddHour). The actual clock is decremented by one hour at 2:00 on the last sunday of the month for summer/ winter time change (SubHour).

Prestart Gradients PSTG_H / PSTG_C (C.18 / C.19)

The configuration parameter PSTG_H or PSTG_C are necessary for the optimum start program on controllers with RTC. For heating and cooling applications, these parameters determine the prestart gradient to reach the comfort setpoint at occupancy start.

If the comfort setpoint will be reached earlier or later than expected, the controller corrects the prestart gradient by self- adaption routine to optimize the start cycle.

The optimum start cycle for heating or cooling can be disabled by setting PSTG_H or PSTG_C to 0.

Optimum Start Self Adaption Speed Adapt (C.21: Controller with RTC only)

This parameter is used by the self-adaption routine to optimize the energy consumption during the start cycle. For this optimization, a corrected prestart gradient is calculated once per day. The adaption to the actual prestart gradient for the next optimum start cycle is determined by the self adaption speed Adapt (0% = adaption disabled and 100% = max. adaption speed).

Damper Prestart Time tvd (C.20: Controller with RTC only)

The damper prestart time tvd is active with the optimum start program only and is used to set the time before occupancy start (scheduled comfort mode) at which the output signal Y1 (damper) switches to normal operation to supply fresh air to the space in mixed air applications.

Serial Communication Address Adr (C.22)

The configuration parameter Adr sets the serial communication address.

The serial communication bus allows the connection of the PC-based Operator’s Terminal to one or several controllers. It provides access to all application configuration and control parameters, time schedules, input and output values of the connected controllers and easy setting of these via the bus by mouse click or keyboard.

Default Programming DefProg (C.23)

Setting the control parameter DefProg to 1 resets all control and configuration parameters to defaults (see Table 4 and Table 5). Default programming is indicated by a display of def.

After default programming, the parameter DefProg is reset to 0.

PARAMETER SETTINGS AND

ADJUSTMENT

Main Setpoint W1 (P.01)

The main setpoint is either set by the control parameter W1 or by the external setpoint potentiometer if the configuration parameter CPATYP = 3, 5 or 6.

High/Low Limit Setpoint Wlim (P.02)

For high or low limit control, the control parameter Wlim is used as setpoint.

During limit control, the throttling range Xp2 and reset time tr2 are active.

Limit control will be active only if the T2 temperature signal (control parameter T2ext = 0) is available or alternatively the sensor T1 (control parameter T2ext = 1) is used also for limit control.

For cascade control, the limit setpoint Wlim determines the control point at which the submaster setpoint (Wcas) maintains the limit value and is not shifted anymore by the master control loop.

High or low limit control is in accordance with the con- figuration parameter LimTyp (C.13).

Submaster Setpoint Wcas (P.06)

The R7426A,B,C controllers provide cascade control which uses two control loops, master and submaster to maintain the master setpoint CTRP1. Cascade control will be active if temperature sensor T2 is connected and the control para- meter Wcas is set to any value other than OFF.

This adjustment sets the control point of the submaster control loop, discharge temperature (T2), at zero room temperature deviation. If the room temperature deviates, the submaster setpoint Wcas is automatically altered.

Cascade control is disabled if the submaster setpoint Wcas is set to OFF.

Low limit of CTRP2 is performed if control parameter LimTyp = 0 and high limit of CTRP2 is performed if control parameter LimTyp = 1.

Reset Span Adjustment Rcas (P.07)

The reset span adjustment Rcas determines the reset effect in Kelvin. The submaster setpoint Wcas is altered if the tem- perature (T1) deviates by 50% of the throttling range Xp1.

Throttling Range Xp1 / Xp2 (P.08 / P09)

Proportional band (throttling range Xp) adjustment determines the temperature change, required at the main sensor (T1) and

EN1B-0203GE51 R0507C 8