Honeywell R7426A - User Manual

To Next Page

PRODUCT DATA

63- 2565

® U.S. Registered Trademark

R7426A,B,C,D

Temperature and

Universal Input Controllers

TIME-INDEPENDENT CONTROLLERS

APPLICATION

R7426A,B,C Temperature Controllers use direct digital control

technology to provide more accurate and efficient operation of

heating, ventilation and air conditioning (HVAC) systems.

Parameters are preset for plug and play operation and provide

different control strategies for optimum system performance.

The controller performs proportional or proportional plus

integral (P+I) control and covers all space, supply air or water

flow applications within the specified ranges of 32°F to 122°F

(0°C to 50°C) or 32°F to 266°F (0°C to 130°C). Standard

Pt 1000 or NTC 20K ohm temperature sensors can be used.

The modern design with its easy to operate user interface and

LCD allows complete flexibility of control system design,

accurate parameter setting, and display of actual temperature

values, setpoints and outputs.

The R7426D Universal Input Controller covers all space or

discharge air humidity control applications and special

applications, such as pressure control, within 0 to 10 Vdc input

ranges. The controller provides input span adjustment to

match the transmitter output specification.

FEATURES

• Selectable proportional, proportional plus integral

(P+I), or (R7426D only) proportional plus integral plus

derivative (P+I+D) control.

• Pre-programmed control parameters.

• Digital parameter setting.

• Selectable direct/reverse acting output.

• 24 Vac power supply.

R7426A,B,C

• 3 inputs for temperature sensors.

• Automatic sensor type identification of Pt 1000 or

NTC 20K ohm.

• 3 digital inputs for plant/system On/Off, occupancy

(alternatively summer/winter changeover) and freeze

protection.

• Dehumidification control via humidity deviation input.

• Selectable floating output functions:

— Floating.

— 2, 3, 4, 6 or 15 stage On/Off (TRIAC).

— Pulse width modulation (PWM).

• Analog outputs 0/2 to 10Vdc selectable.

• Start-up routine.

• Space/supply limit or cascade control.

• Sequence control of heating, mixed air damper or

energy recovery system and cooling.

R7426D

• 2 analog inputs 0 to 10Vdc for transmitters.

• Control output monitoring and manual output signal

override.

• Master/submaster cascade control.

• Main variable control and optional high/low limit control.

• Input span adjustment.

• Temperature compensation input.

• Optional remote setpoint adjustment.

Contents

Application ....................................................................... 1

Features ........................................................................... 1

Specifications ................................................................... 2

Ordering Information ........................................................ 2

Installation ........................................................................ 3

Operation ......................................................................... 4

Operating Overview ......................................................... 8

Appendix .......................................................................... 10

Control And Configuration Parameters ....................... 10

Parameter Details ....................................................... 12

Other manuals for Honeywell R7426A

Product Data20 pages

Need help?

Do you have a question about the Honeywell R7426A and is the answer not in the manual?

Overview

The Honeywell R7426A,B,C,D Temperature and Universal Input Controllers are time-independent controllers designed for precise management of HVAC systems. These devices leverage direct digital control technology to ensure accurate and efficient operation.

Function Description

The R7426A,B,C Temperature Controllers are primarily used for heating, ventilation, and air conditioning (HVAC) systems. They offer proportional (P) or proportional plus integral (P+I) control, covering a wide range of space, supply air, or water flow applications. These controllers are compatible with standard Pt 1000 or NTC 20K ohm temperature sensors.

The R7426D Universal Input Controller is designed for space or discharge air humidity control and other special applications, such as pressure control, using 0 to 10 Vdc input ranges. It provides input span adjustment to match various transmitter output specifications.

All models feature selectable control actions: proportional, proportional plus integral (P+I), or (for R7426D only) proportional plus integral plus derivative (P+I+D) control. They come with pre-programmed control parameters for plug-and-play operation and offer digital parameter setting. Outputs can be configured for direct or reverse action, and the controllers operate on a 24 Vac power supply.

R7426A,B,C Specific Features:

These models include three inputs for temperature sensors, with automatic identification of Pt 1000 or NTC 20K ohm types. They also have three digital inputs for plant/system On/Off, occupancy (which can also serve as summer/winter changeover), and freeze protection. Dehumidification control is possible via a humidity deviation input.

Output functions are highly versatile, offering selectable floating output, 2, 3, 4, 6, or 15 stage On/Off (TRIAC) control, pulse width modulation (PWM), and analog outputs selectable between 0/2 to 10Vdc. The controllers incorporate a start-up routine and support space/supply limit or cascade control. They can manage sequence control for heating, mixed air dampers or energy recovery systems, and cooling.

R7426D Specific Features:

The R7426D model provides two analog inputs for transmitters, allowing for master/submaster cascade control or main and optional high/low limit control. It includes a temperature compensation input for main setpoint reset and an analog output for deviation signals. Control output monitoring and manual output signal override are also available.

Usage Features

The controllers are designed with an easy-to-operate user interface and an LCD, providing flexibility in control system design, accurate parameter setting, and clear display of actual temperature values, setpoints, and outputs.

Control Point / Setpoint Adjustment (CPATYP):

The control or setpoint can be adjusted using an internal or external potentiometer connected to the CPA/SPA input. The type of CPA/SPA is selected via the CPATYP control parameter.

Temperature Sensor Calibration (I01CAL, I02CAL and I03CAL):

To compensate for offsets caused by long wiring lengths, the temperature sensor inputs (I01, I02, and I03) can be individually adjusted using the I01CAL, I02CAL, and I03CAL parameters.

Parameter Selection/Adjustment:

Users can access parameter selection mode by pressing and holding the + and - buttons. Parameters can be scrolled through using +, and SET is used to enter adjustment mode. Values are adjusted with + and -. Changes are saved to EEPROM with SET, or discarded with SEL.

Displaying Actual Values:

In standard display mode, one of six actual values (e.g., main sensor, main setpoint, limit/cascade setpoint, humidity deviation, or outputs) can be selected and displayed by pressing SEL.

Output Manual Overrides:

This mode is particularly useful during installation and setup. Users can display output data selection mode by pressing and holding SET and SEL. Desired parameters are selected with +, and SET enters adjustment mode. Outputs are adjusted with + and -. SET saves the output, while SEL discards changes. To disable manual override, users repeat the selection process and press and hold + and - until rEL is displayed. All overrides should be disabled before exiting manual override.

Operating Modes:

After power-up, the controller version is displayed, followed by the standard display mode. The R7426A,B,C models have four control modes (Off, Night, Unoccupied, Occupied), while the R7426D has Off and On modes (On is represented by the Occupied icon).

Economizer Modes:

Economizer modes are suitable for installations where the main temperature sensor (I01) is in exhaust air or a room with a constant offset to exhaust air. The RetOffs parameter allows programming an offset value (0°F to 9°F) to simulate exhaust air conditions. Economizer mode is disabled if RetOffs is Off or no OAT sensor is connected.

Outside Air Temperature Compensation:

When the I03 sensor is connected, outside air temperature compensation is performed. The Wcomp parameter defines the summer and winter changeover point, while Wi and Su define the degree of compensation. A smoothing filter for OAT input I03 is incorporated to eliminate sudden temperature variations, providing more stable control.

Summer/Winter Changeover Function:

The occupancy input can be used for summer/winter changeover by setting the DIR/REVO1 control parameter to Cho (R7426A only). A potential-free contact between terminals 1 and 4 switches the controller mode between heating (contact open) and cooling (contact closed).

Freeze Protection:

The controllers include freeze protection. When the contact connected to the freeze protection input is opened, specific actions are executed (e.g., output 01 to 0% for Dir, 100% for Rev). A closed contact initiates frost recovery. Freeze protection takes priority over all other control operations.

Output Functions (R7426A and R7426B):

Floating Valve or Damper Actuators (Floating Mode): For heating/cooling control, the controller converts the deviation signal to a proportional output pulse, driving actuators based on the Runtimex parameter. An automatic synchronization function ensures correct actuator positioning by periodically running actuators to the closed position.
Electric Heat Current Valve (PWM Output): Suitable for driving electric heat current valves, controlled from the heating signal. The total cycle time is set by Runtimex.
2-Stage On/Off Sequence Control: Converts the output signal into a 2-stage On/Off sequence for operating relays.
3-Stage Binary On/Off Sequence Control: Converts the heating signal into a 3-stage binary On/Off sequence.
4-Stage On/Off Electric Heating or Cooling (R7426B only): Output sequences are controlled from heating and cooling signals based on OMode settings.
6-Stage On/Off Sequence Control Heating or Cooling: Output sequence of 03/02/01 is controlled from one output signal.
15-Stage Binary On/Off Electric Heating and Cooling: Output sequences are controlled from heating and cooling signals.

Two Position Damper Control (R7426B,C):

If OMode is 4, output signal 01 operates as two-position control: 100% when On/Off input is On, 0% when Off. The start-up routine must be disabled for this function.

Analog Output (R7426C only):

Three dc output control signals are provided for controlling actuators for valves, dampers, or pneumatics. The full output range is 0 to 12 Vdc, software configurable to 2 to 10 Vdc or 0 to 10 Vdc using the ORange parameter.

Maintenance Features

Resetting Parameter Values to Default:

All parameter values can be reset to default settings. This is done by pressing and holding the + and - buttons during power up until the display flashes dEF. The R7426D also has a DefProg (C.23) parameter that, when set to 1, resets parameter values to default.

Time Out:

After approximately 10 minutes of inactivity (no buttons pressed), the controller automatically returns to standard display mode. Inputs not confirmed by the SET button are discarded, and old parameter values are retained.

Error Messages:

Improper sensor inputs trigger error messages to flash on the display, indicating issues such as incorrect main sensor input, no input to a sensor, or incorrect humidity deviation input.

Installation Considerations:

The manual emphasizes careful reading of instructions, checking product ratings for suitability, and installation by a trained, experienced service technician. Post-installation, product operation should be checked.

Wiring:

The manual provides detailed wiring diagrams and instructions, including stripping wire insulation and inserting wires into terminals. It highlights the importance of disconnecting power supply before installation to prevent electrical shock or equipment damage. All wiring must comply with applicable codes, ordinances, and regulations.

Parameter Details:

The manual provides detailed information on all configuration parameters, including their purpose and how they affect control functions. This allows for precise tuning and troubleshooting.

Start-up Routine (C.07):

A start-up routine is provided for R7426B,C controllers to prevent start-up problems. Enabling this routine by setting the Startup parameter to On ensures that, after power-up or an On/Off input signal change to On, the outdoor air and exhaust air damper (O1) will stay in the closed position (0 percent) for approximately 5 minutes before switching to normal operation.