Digital Display
The display is two seven segment LED’s, which are used to display three types of information; Display the current setpoint, using the decimal point on the right hand side to indicate the half degree increment, ie. 22 is 22.0 and 22. is 22.5. Display the current room temperature, when setting the setpoint, the room temperature is shown 10 seconds after the last button is pushed. The displayed sensor temperature range is 10°- 35°C. Display of hours when the timer function is being used.
On/Off Button
A push button switch is used to put the unit into stand-by mode. In stand-by mode, all outputs are off, and all indicators and the display are off. Pressing the on/off button when in stand-by will set the controller into active mode, when all functions are operable.
Mode Selection
A single push button is used to sequentially select the mode. The sequence is as follows, heat and cool, heat only, then cool only. The current mode is indicated by a tri-colour LED, red for heat only, orange for heat and cool, green for cool only. Power up default is the heat and cool mode.
Setpoint
The setpoint is raised or lowered by using the increase or decrease push buttons When the controllers put in stand-by mode, the current setting is stored in memory. The setpoint can be varied in half degree increments and has a range of 15 to 30 degrees Celsius. The power up default is 23°C.
Function Indicator
The current status of the controller is displayed by a Bi-colour LED. The LED is red when the unit is heating, and green when the unit is cooling.
Timer
The timer can have two functions Firstly if the unit is currently in the stand-by mode and the timer button is pushed, it is assumed that the user wants to set a delayed start. If the unit is on and the timer button is pushed it is assumed that the user wants to set a delayed stop. In either mode, the delay can be set by pushing the timer button, one push will cause the display to show “00”, each further push will increment the time by 1 hour, to a maximum of 12 hours, at which point the display returns to “00”. The hours are displayed on the two 7 segment displays. To leave the timer setting routine, pause for 20 seconds with no button push, the last hours shown will be the setting. A LED next to the timer push button indicates when the controller is in the timer mode. When in the delayed stop mode, to see the number of hours remaining, briefly push the timer button. When in a delayed start, the controller will display the hours remaining, and will operate in the heat/cool and fan modes that were last used.
Fan Speed
A single push button is used to sequentially select between the three fan speeds and the auto mode. When the controller is put into stand-by, the current fan selection is stored in memory. When in the auto mode, the fan speed will vary according to the current temperature and the setpoint. In the cool mode, the fan speed increases as the temperature rises above setpoint. In the heat mode, the fan speed increases as the temperature falls below setpoint. Refer to the sequence diagram, figure 1. The “pulse mode” is a 15 second burst on low speed, every 45 seconds. This mode is used to reduce drafts while still maintaining air flow across the sensor. The “pulse mode” feature can be disabled by dip switch 4, instead of pulsing the fan, the fan will remain in the off condition until the temperature decreases to the point where the fan comes on at low speed. When in the heat and cool mode, the last compressor operation determines the fan mode ie. if the compressor last cooled, the fan will be in the cool mode, and vice versa. When the controller goes from dead-band to heating in the reverse cycle mode, the fan switch on is delayed 10 seconds after the compressor starts, this allows the coil to warm up and avoids a cold blast of air. The power up default is auto fan mnAa.
Over-Ride
A set of terminals on the back of the control module allow external switching to be utilised. Voltage free contacts are required and can be from time clocks, manual switches etc. When the contacts close the unit will operate in the last known mode, ie. heat/cool and fan. When the contacts open, the unit will return to the stand-by mode. The on/off push button over rides the external input in the following way; If the unit is in stand-by and the on/off button is pushed, the unit will start. The unit will continue until one of the following happen, the on/off button is used to select stand-by, the internal timer has been set and counted down or the external contacts next go open circuit. If the unit is operating and the on/off button is pushed, the unit will go into stand-by. The unit will remain in stand-by until one of the following happen, the on/off button is pushed, the internal time has been set for a delayed start and counted down or the external contacts next go closed circuit.
Dip-Switches
A six way dip-switch is fitted and is used to select a number of options that are available on all units. switch 1 selects if the external temperature sensor is connected directly to the micro-processor. switch 2 selects if the internal temperature sensor is connected directly to the micro-processor. switch 3 selects the display function. When the switch is on the digital display will only show the desired setpoint when the switch is off, the display will show room temperature as well as setpoint. switch 4 selects the function of the fan in the heating mode when in dead band, with the switch on, the fan will pulse 15 seconds every 45 seconds. Then the switch if off, the fan will
be off in dead band. Used with return air sensor. switch 5 fan run-on timer for electric heaters. Low speed fan will run on for 30 seconds after the unit is switched off. Only when dip switch 6 is set “ON” to on-off control. switch 6 selects the type off relay output function. When switched on the heat relay will come on for heating only and the cooling/compressor relay will come on for cooling only. When the switch is off the heat relay is used to control a reversing valve and the cool/compressor relay will come on in heating and cooling. In built time delays. The controller has a timer function that prevents the compressor from restarting until a minimum of two minutes has elapsed from when it last stopped. This time delay helps prevent fast cycling of the compressor when the setpoint is ramped up and down quickly. When in the compressor/RCV mode, the heat relay will not change over until 2 minutes after the compressor stopped, this delay allows the refrigeration system to equalise before changing over and avoids “gas rush” noise.