AHTx3d1
This controller is used in conjunction with an AHU controller (version AHU3d4 or later) to control a Thermal Wheel and Evaporative Cooler. The controller is based on a Re-Scalable Driver module and includes many configuration parameters which need to be defined when commissioning the overall system. The release notes for the Dessicant Wheel and Regenerative Heater Controller should also be consulted. Doorway pages have been created to aid the setting up of the complete Dessicant AHU control solution.
The AHU controller provides the control and interlock of the Supply and Extract fans and the primary control functions for heating and cooling demands these operate as for a standard AHU controller. The AHU Heat and cool demands are transmitted over the network to the Thermal Wheel Controller, it is these demand signals which define the action of the Controller.
The Controller consists of two Dual re-scaleable drivers, each accepting both heat and cool demands, one pair is used to control the Speed of the Thermal Wheel and the other the demand level for the Evaporative Cooler.
Single re-scale channel
The controller contains four of these function blocks, designated A, B, C and D. The configuration variables which define the re-scale functions are found in a block starting at C170. A block diagram of the complete controller.
The Thermal Wheel will only need to operate over a specified range of the input heat demand. this range is set using config variables AIMX (A block Input MaXimum) and AIMN(A block Input MiNimum) . The output from the re-scale block normally 0 to 100% is also scalable by setting the output scale parameters AOMX (A block Output MaXimum) and AOMN(A block Output MiNimum). So if the Thermal wheel needs to run from zero speed at a heat demand of 30% up to 80% of maximum speed for a heat demand of 65% the re-scale parameters would be set as
AIMX 65 AOMX 80
AIMN 30 AOMN 0
Some modes of operation need to delay the operation of the Wheel to enable the surface of the exposed wheel to be dried before the wheel starts turning. A delay may be introduced after the re-scale module by setting ADLY in minutes.
The operation of the Wheel is defined for cooling demand in the same way but using the B block re-scale function with parameters BIMX, BIMN, BOMX, BOMN and BDLY. So to increase the wheel speed from zero to maximum as the cooling demand varies from 10% to 40% the settings would be
BIMX 40 BOMX 100
BIMN 10 BOMN 0
Note input values above BIMX will produce an output response limited by BOMX. As before the controller provides the option of specifying a delay before the output is passed to the driver.
The outputs from the both these re-scale blocks are passed to the first channel of the universal driver (normally the heating channel), it is expected that in this application the driver output will be a 0-10V analogue output but the other output driver options are available.
If a temperature sensor is fitted, the sensor must be positioned to measure the supply air onto the thermal wheel. When the AHU is in heating mode the Wheel will not run if the temperature measured is greater than the Return Air temperature as measured by the AHU.
The Evaporative Cooler is used to cool the Supply Air stream. This is controlled in a similar manner to the speed of the wheel. The re-scale parameters are set on block C for heating demands and on block D for cooling demands, configuration variables C180-C189.
The Evaporative Cooler uses the second channel of the universal driver (normally used for cooling outputs) and the full range of driver types is available. The Evaporative cooler will only operate when the AHU fans are running.
The Thermal Wheel/Evap Cooler controller is registered to the AHU like any standard AHU
sub module. It takes an address space normally occupied by an Actuator controller.
new issue see config tables.