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AHU Controllers 
1. Design:

The AHUCS02 Air Handling Unit (AHU) Controller is a complete digital control system developed by Flexline using Microprocessor technology. It is designed using latest Microchip microprocessor family with flash type program memory.

2. Applications:

The AHU controller can be configured for most air handling configurations by changing internal parameters and settings. For any specific application if the control function cannot be met by standard program features Flexline can alter the program to meet the required functions. Following are the advantages of using the AHUCS02 AHU controller.
  • To reduce energy expenses while keeping occupant comfort its top priority.
  • To control Temperature and Relative Humidity to an accuracy of 0.2°C and 1%RH respectively.
  • It can be used for new HVAC applications.
  • It can also be used for existing applications where complete control is not available.
  • It is available for both chill water type and compressor type AHU’s
  • It can be configured as a standalone operation and communicate on RS422 protocol with a master so that all points can share information with rest of the network.
3. Features:

Supply Power: 230VAC, 0.5A
Input Signals: Isolated Digital Inputs (24V AC or DC) 16 Nos
Output Signals : Relay Outputs SPST 24VDC or 250VAC, 5A 16 Nos
Analog Input Signals: Analog Inputs 0-10VDC 06 Nos
Computer Interface: RS422 Communication port.

Digital Display Unit: The display board consist of following seven segment display units.
  • 3 Digit Common Display for parameter setting and common value display
  • 3 Digit Display for Temperature Display (Range 0 to 99.9°C)
  • 2 Digit Display for Temperature Set Value display (Range 0 to 99°C)
  • 3 Digit Display for Relative Humidity Display (Range 10.0 to 90.0%RH)
  • 2 Digit Display for Relative Humidity Set point display(Range 10 to 90°C)
Alarm display: 23 lamp Indictors are provided to indicate different alarm conditions generated in the controller. Some alarm conditions are generated according to the values entered to the parameters. Other alarms are generated from input conditions. Alarm once activated should be acknowledged by user.

4. Special Features:

The AHUCS02 controller is in-built with a unique feature for %RH Sensing and Control. It can read a Dry Bulb and Wet Bulb temperatures from a Dry Wet type Temperature Transmitter (Product Supplied by Flexline DWTT502410) through the analog inputs and generate the %RH with a 1% accuracy within the range 10 to 90 %RH. The % RH is generated from a Dry Wet Temperature Chart embedded in the Microprocessor.

5. Parameters:

Parameters are values that need to set in order to operate a AHU unit within a narrow band as per user requirement. Parameters can be password protected against unauthorized change. The following values can be set using parameters. Parameters are field calibrated using the four buttons ( Fn-Function, Ent- Enter, Inc- Increment, Dec: Decrement) avaliable on the front panel.
  1. Wet Bulb Temperate – (Read Only)
  2. Temperature Set Point (Recommended Range 10 – 40°C)
  3. Humidity Set Point (Recommended Range 55% - 70%)
  4. Chill Water Valve Command Position. (Read Only)
  5. Password (1 – 999)
  6. Temperature Sensitivity (1% - 10% )
  7. Humidity Sensitivity ( 1% - 10% )
  8. Humidity Water Rate (Makeup Solenoid Timing) (5 – 15 Sec.)
  9. Temperature High Alarm Limit (5% – 50%)
  10. Temperature Low Alarm Limit (5% – 50%)
  11. Humidity Low Alarm Limit (50% - 70%)
  12. Humidity High Alarm Limit (55% - 75%)
  13. Proportional Constant (5 – 90)
  14. Dry Bulb Max. Raw Value
  15. Wet Bulb Max. Raw Value
  16. AHU Communication Address
6. Computer Interface:

The AHU controller is provided with a in-built RS422 port for Computer interfacing. Using RS422 Protocol up to 64 nodes can be connected as a single network to one serial port of a computer.

The netwaork requires 4 core shielded CAT5 cable. The cable can extend up to 500m. The monitoring software is avaliable from Flexline for monitoring and set value changing of AHU units. In addition the RS422 communication protocol is given for the user to develop own interface software. Following are the features avaliable through computer interfacing
  • Dry-Bulb Temperature
  • Wet-Bulb Temperature
  • Relative Humidity
  • RH Set Point
  • Temperature Set Point
  • Digital Status (48 Bit Integer which hold 36 digital signals)
7. Mounting:

The base module can be mounted easily using four mounting screws. Screw termination connectors are provided for connecting inputs and outputs.