How iZone AC Systems Work

The iZone AC control strategies have been developed of 30 years to provide the best possible temperature control with the lowest running costs at a reasonable cost

The different strategies the control the the systems operate are described below

The zone dampers operate as an independent control system as follows:

The most basic operation of the zones is the open / close function. As the name implies when a zone is opened it will drive open to its (MAX) maximum open position. When a zone is closed it will drive to its (MIN) minimum closed position

If the MAX is set to 100% the damper will drive until the motor hits the MAX micro switch inside the actuator which cuts off power to the motor. If the MIN is set to 0% the damper will drive until the motor hits MIN micro switch and cuts off power to the motor.

When the iZone system is reset or the power is cycled to the C225 module the zone motors will all drive fully open to fully closed several times. This is done to record the time in milliseconds for each damper to drive fully open and fully closed

This timing is used when driving to positions other than fully open or fully closed. ie 75% open and 25% closed. See damper timing option for more information

The dampers will drive for different times to achieve different percentages closed. These percentages are based approximately on the performance of the zone dampers and a calculation is performed to approximate the airflow percentage not the damper blade position

For this reason it may be observed that the motor drives less or more to achieve a similar percentage airflow change depending where on the operating curve the damper blade is at that time. The iZone system uses the fully open and fully closed micro switches as reset and reference points for the position of the damper blade

Within the configuration of the iZone system is a facility for the technician to balance both MAX and MIN air quantities. These balance settings are independent from the Zone Air Flow MAC and MIN settings in the GUI for the end users to adjust

For example if a Balance MAX has been set to 75% the Zone Air flows can still be adjusted between 100% and 0% however at 100% the zone will only be 75% open and the technician's air balance will not be affected

Standard electronic constant control allows the installer to configure any number of electronic constant zones. Please note any zone nominated as an electronic constant cannot be used for temperature control

If there are no zones or a fixed ducted constants (outlet with no zone) the installer can select 0 constants

If there is 1 electronic constant the iZone system will look for all open zones to add up to the equivalent of at least one zone open to 100%

For example Zone 1 = 25% open, Zone 2 = 35% open, Zone 3 = 10% open. The constant zone will automatically open to 30% to take the total system up to the equivalent of 1 zone 100% open. As the non constant zones open and close the constant will react automatically to maintain the 1 zone 100% open rule

On larger systems or where finer control of the electronic constant is required two or more electronic constant zones can be configured. The operation of two electronic constants is described below in the example:

The two electronic constants will operate in order Constant 1 followed by Constant 2 and will close in reverse order. The iZone system will look for all open zones to add up to the equivalent of at least two zones both 100% open

If the zones are as follows Zone 1 = 25% open, Zone 2 = 35% open, Zone 3 = 90%, Zone 4 = 0% open, Zone 5 = 0% open, Zone 6 = 0% open. The total of all the open zones is 150% or 1.5 zones fully open. Electronic constant 1 will open to 50% and electronic constant 2 will remain closed

Advanced electronic constant control provides finer control of the constant zones and helps to improve conditions when one or two small zones are the only non constant zones being used. The area of each zone needs input into the configuration along with a minimum area that must be open at all times. (This is labelled as the "Area to be covered by constant”)

For the purpose of its calculations the iZone system assumes that a zone that is 80% open is supplying 80% of the air to this zone so if it is an 18m2 zone, only 14.4m2 is considered to be active at 80%

For example:

Zone 1 = 13m2 @ 20% open, Zone 2 = 12m2 @ 30% open, Zone 3 = 20m2@ 0% open, Zone 4 = 11m2@ 90% open, Zone 5 = 22m2@ 10% open, Zone 6 = 18m2@ 0% open. The Area to be covered by a single constant is 38m2 (This should be determined by the system designer). In this example the amount of active zones will be the calculated as follows:

The equivalent of 18.3m2 is active and the minimum area to be covered as stated above is 38m2

Therefore:

38 - 18.3 = 19.7m2 (required to be served by the constant zone)

19.7/38 = 0.52

The constant zone will open approximately or 52% to ensure the equivalent of 38m2 is being maintained

While this is method is not 100% accurate the areas of the constant and zones can be manipulated to achieve satisfactory outcome

Zone temperature control requires the respective zones to be set to "Climate" and uses the iZone sensors to modulate the zone dampers to maintain the zone set point. Critical to the control of the zone temperatures is the supply air sensor (CDTS) which is used to invert the operation of the zone dampers when operating in heating and to avoid hot or cold air being blown into a zone when the the system first starts. The zone temperature control strategies use the following parameters for control:

As selected by the user

As measured by the zone sensor. The displayed value takes into account any calibration offsets from the configuration menu

As measured by the CDTS sensor

Open

Open

By default the iZone system will use the in-duct energy to control zone temperatures

This feature uses the hot or cold air in the ductwork when the AC system has cycled off to move the zone towards set point

An example of this working would be as follows:

A double storey home is served by a single ducted AC system and is running in heating. When the upper level reaches set point the zone closes, however the lower level is not at set point and the system continues to heat the lower level

Because of stratification the hot air from the lower level rises up the stair void and the upper level ACT increase by SP +2oC. When the lower level reaches set point the system cycles off and the SA temperature drops below the SP on the upper level

The upper level zone damper will open and will use the cooler SA in the duct to try and reduce the temperature in the upper level down to its set point

This strategy works in reverse in a cooling, where the iZone system uses warm air in the ductwork to heat up any zones which have over shot their set point to the negative

Within the configuration this use of in-duct can be disabled. When disabled the iZone system will only allow the zones to open when running in heat mode if the ACT < SP and in cool mode if the ACT > SP

The following description will cover the strategy for most ducted air conditioning units using C325 AC unit modules

Please note all brands are slightly different and some do not have the full range of control options available for the iZone system

For these systems please see the configuration section for the type of unit you are applying the CUCM to

Similarly these strategies do not apply to the Temperzone units

The iZone provides and receives the same basic information that is normally exchanged between the proprietary AC unit controller and the FCU 

Based on the output data from the iZone system, the AC unit utilises their own internal strategies to determine how to control the evaporator fan, compressor, inverter, reversing valve, condenser fans, condensate pump and all other peripheral controls and safety systems associated with the AC unit

In addition all delay and run on timers are controlled by the AC unit. iZone plays no part it the control of these sub-systems.

The iZone system offers various option for the sensor to control the AC unit as follows:

• R/Air - Return air sensor

• Master - The customer can select any sensor in the system to control the AC unit

• Zones - iZone selects the most appropriate sensor to the AC unit.

• RF - Uses a single wireless iZone sensor to control an AC unit which has no zones

How to select the control sensor options?

The strategies for each sensor type are detailed below:

This option uses the return air sensor that is built into the AC unit. In this option the iZone system does not provide an Actual temp ACT to the AC unit

This option is not available on some brands which do not incorporate an RA sensor. RA is the factory default sensor on the iZone system

Because this is a single sensing point it will provide an approximate average temperature for all the zones

The AC unit runs independently of the zones and may result in the AC unit cycling off before or after individual zones have reached their set points

When the AC unit is being controlled via the RA sensor, the iZone system can only display the AC unit set point in 1oC increments and the controlling range of the AC unit will perform the same as when the proprietary AC unit controller is connected

When "Master" is selected the iZone system populates an icon on the touch screen and the App for the end user to manually select which sensor they would like to control the AC unit

The end user can manually change the Master sensor at any time by changing the X on the screen to a ✔

The AC unit will be controlled by the set point and actual temperatures from the selected Master Sensor

If the Master zone is accidentally closed the zone damper will be held in the fully open position and the AC unit will continue to be controlled by the Master Sensor

When in Master Sensor option the AC unit will display in 0.5oC increments and will control within a range of approximately +/- 1oC depending on the brand of AC unit

When "Zones" is selected the iZone system scans all the zone sensors, which are in "Climate" mode, and selects the sensor that is furthest from set point, as the sensor to control the AC unit

As the zones get closer to set point the controlling sensor may move around until the last sensor reaches set point. The system performs this scan approximately every 3 minutes

If there is a mixture of "Open" zones and "Climate" zones the AC unit will be controlled by the Climate zone that is furthest from set point as described above

However if there are only "Open" zones and all the "Climate" zones have been closed the AC unit will be controlled via its return air sensor as per RA - Return Air Sensor above

If a "Climate" zone is activated the iZone will automatically revert back to controlling from "Zones"

When in Zones option the AC unit will display in 0.5oC increments and will control within a range of approximately +/- 1oC depending on the brand of AC unit

Controlling from Zones will typically provide the lowest running costs and the most accurate temperature control of all the sensor option

The RF option is used for a ducted system with no zones

While it is feasible to run a system with no zones via the units RA sensor it may be preferable to have a wireless sensor (CRFS#) located within the conditioned space to improve control and also to enable in duct temperature display for this systems

When setting up the CRFS# move the zone dial to "R" or "F" on the selector switch

This option is only available on wireless CRFS# sensors

When in Zones option the AC unit will display in 0.5oC increments and will control within a range of approximately +/- 1oC depending on the brand of AC unit. The button on the sensor can be used to turn the AC system on and off

On the iZone control panel or App the customer can manually control the available fan speeds.

These are normally High / Medium / Low however some brands to have less speed options and some have more

If set to Fan Speed "Auto" the iZone system will automatically adjust the fan speed depending on the number of zones that are Open or in Climate and the percentage these zones are open

This is a dynamic function and so as zones dampers modulate open and closed the fan speeds will be adjusted. To enable this function the following must be correctly setup in the iZone configuration menu:

• Fan Auto must be enabled

• Fan airflow capacity in litres per second must be recorded

• The number of fan speeds must be recorded: High / Med / Low = 3 speeds

• All zone areas in sq meters must be set

• The constant area must be set

It should be noted that the differences of the average percentage of airflow for each fan speeds are not significant. The changes in air flow are approximately as per the following table:

The iZone system has the following modes to select:

The AC unit will be run in Cool / Cooling mode

The compressor will be controlled by the AC Unit's own protocol

The fan will run as per the AC units factory default setting (continuously or cycle with the compressor) or as set up on in the AC unit field settings

For the best results we recommend the supply air fan runs continuously in Cool Mode

The AC unit will be run in Heat / Heating mode

The compressor will be controlled by the AC Unit's own protocol and will initiate defrost mode as required by the condensing unit

The fan will run as per the AC units factory default setting (continuously or cycle with the compressor) or as set up on in the AC unit field settings

For the best results we recommend the supply air fan cycles on and off with the compressor in Heat Mode

In Vent mode the fan will run continuously and the compressor will not start

The AC unit will be run as per Cool mode however the fan speed will be automatically changed to low speed to maximise moisture removal to dry the supply air

In Auto mode the iZone will automatically change modes between Cool and Heat to satisfy the sensor

There is an Auto mode dead band which can be adjusted in the iZone AC>Config>AC Unit>Auto mode dead band. It is recommended that this Auto mode dead band is set to around 1.5oC (SP +/-1.5oC)

When controlling the AC unit from "Zones," the system will select the majority of zones requesting the same mode. (Cool or Heat)

If the majority changes, the mode will be permitted to change, after the new majority's controlling temperature has exceeded the dead band

If the number of zones requiring cooling and heating are the same (ie. No majority) the system will run in the mode it was last in

For example (See diagram below):

3 zones require cooling and 2 zones require heating the iZone will start running the system in Cool. The zones requiring heating will close when the supply air temperature sensor (CDTS) detects cool air

If the zones requiring cooling reduces to 2 with 1 zone moving from past the set point from cooling to heating and 2 zones still requiring heating the majority of zones will change to heating. The mode will change the mode from Cool to Heat ( provided one of the heating zones is outside the dead band. The zones requiring cooling will close when the supply air temperature sensor (CDTS) detects warm air

After some time the heating zones achieve set point, however the mode remains in heating even though all 5 zones require cooling as they are all within the dead band. After more time one of the zones drifts outside the cooling dead band and the mode changes from Heat to Cool. The zones requiring heating will close when the supply air temperature sensor (CDTS) detects cool air

Unit Auto Off option can be selected or deselected at Config>AC Unit>Unit Auto Off

If this option is selected the AC unit will automatically turn off, after a short delay, when all the zones in the system have been set to the closed position

If the AC unit is turned On at the On / Off button when all zones are set to the closed position, a message will be displayed on the screen advising the user that all the zones are closed and the AC unit will turn off shortly

If a zone is immediately set to open or climate, the AC unit will continue to run as per normal. If no zones are opened or set to climate the AC unit will automatically turn off after a short delay

If Unit Auto Off is enabled it will not turn the AC unit OFF when the zones are in Climate mode even if all zones are satisfied and have closed

This is a unique feature of the iZone system and must be enabled in the AC Unit Configuration to function

The system must also have a supply air sensor and temperature controlled zones to benefit from this feature

When this option is enabled the iZone system will make use of the temperature of the air in the ductwork to try and move the zone closer to set-point regardless of the mode the AC unit is set to

For example: If a system is set to run in cooling mode, all zones reach set-point and the compressor cycles off

The air in the ductwork heats up over time as it is located in a hot roof space

Any zone that is set to Climate and is below its set-point will be opened to use this warm air to heat the zone up to it's setpoint

The reverse can occur in winter under the right conditions

The fault history is populated whenever a fault message is sent from the AC unit to the iZone system

It is not a fault with the iZone system (See Messages for notification of faults with the iZone system)

Each AC unit fault will be date and time stamped for future reference

If an AC unit fault does occur it is recommended that the technician connects a proprietary AC unit controller to the system to confirm the fault and the fault code

The AC unit fault history cannot be deleted, edited or reset

By default the iZone system is the Master controller

If any remote controller is connected to the system and attempts to make changes to the settings the iZone system will override the instruction back to the iZone setting

To override this the Master/Slave option in the Config settings can be customised

The Master/Slave settings allows for 3rd party controllers to control some of the air conditioning unit's functions

The functions that can be controlled are as follows:

In the above table the following is applicable.

• On/Off can only be controlled by "iZone"

• Mode can be controlled by both "iZone" and "Other"

• Fan speed can only be controlled by "Other"

• Set point can only be controlled by "iZone"

As well as the AC unit configurable settings there is an array of configurable options are available for the technician to customise each air conditioning system

These options are accessed via Config>Options> and are detailed below

iZone will display a message reminding the user to clean their filters

This function is purely time based and when the message is reset the timer will reset

It is recommend that an appropriate frequency is selected to suit the particular site conditions

Options available to select the frequency of alerts to clean the filters are as follows:

• Disabled (No alert will be displayed to clean the filter)

• 3 months

• 6 months

• 12 months

When this option is selected the iZone will lock the Minimum and Maximum set point temperatures that the user can select in all zones and / or AC unit control if applicable

This option should be used in conjunction with Max SP temp and Min SP temp options

In this option the technician can select the maximum temperature that the user can increase the set point temperature to

Once set the technician must "Lock temps" for this option to take effect

In this option the technician can select the minimum temperature that the user can decrease the set point temperature to

Once set the technician must "Lock temps" for this option to take effect

Scrooge is effectively a placebo effect

When the Scrooge mode is selected it will utilise the Max SP temp and Min SP temp settings to limit the operation of the system between these two values, however, the user will still be able to select the full range on the iZone screen. When in this mode the Actual temp is hidden on the touch screen

Make sure "Lock Temps" is deactivated when Scrooge is activated to ensure it works correctly

To reduce enquires and excessive analysis by the customers it is possible to hide the system actual temperatures by selecting the "Hide actual temp"option

Select this option if you do not want to display the actual temperatures on the screen or App

To reduce enquires and excessive analysis by the customers it is possible to hide the system in-duct temperature by selecting the "Hide inductl temp"option

Select this option if you do not want to display the actual temperatures on the screen or App

On the Modern graphics display > Zone Summary, there is an option to display either the Airflow % or the Actual temp in each zone

If this option is not selected the Zone Summary will display the Airflow % to each zone

If this option is selected the Zone Summary will display the Actual temperature in each zone

Damper timing is the time it takes for the damper to drive from fully open to fully closed

The iZone system uses this timing for positioning the damper blades for percentage control and for damper motor fault detection

The factory default for damper timing is "Auto"

Auto is suitable for iZone damper motors and other motors with current draw that can be detected by the iZone system

In Auto timing mode the system will drive the damper actuators open and closed during initialisation, and will record the drive time for each zone actuator

The recorded times will be used by the system for percentage control and zone fault detection

If the damper motor current draw is too low to be detected by the iZone system (Belimo actuators) then the technician must manually set the damper timing (in seconds)

When a manual setting is used the system will not detect damper faults

Manually set damper timing is a global function for all damper motors on the system so it is not advisable to use damper actuators with different drive times on same iZone system

The iZone system is designed to drive iZone damper actuators (CZDA) and iZone cables (CDC12G) which drive the damper from Open to Closed in a clockwise direction

This is the default setting in the iZone system

If dampers are used that drive Open to Closed in an anti-clockwise direction then the "Reverse dampers" option should be selected

This is a global function and when selected all dampers in the system will be driven anti-clockwise

The factory default for an integrated iZone / AC system is to close all the zone dampers when the AC is turned off

However it may be desirable for a system to have the damper drive open when the AC system is turned off (for example heat exchange / ventilation systems that use the AC ductwork to distribute the fresh air)

Select this option to drive the dampers fully open when the AC system is turned off

This option allows the technician to select a port to skip on the screen and is particularly useful if a zone port on the C225 or CEXT has been damaged it can be skipped and the subsequent zones moved by one port

This assumes there are spare port available

Select this option, then choose which zone ports you would like to skip

When selected this option displays the status of all zone dampers in the system

The status of dampers will be displayed as follows:

• OK - the zone damper is performing as required.

• Not detected - the iZone system could not detect a zone motor connected to this port or the zone motor/cable/port is faulty

When this option is selected the zone names will be locked and cannot be changed in the zone summary screen

To change a zone name deselect this option in the Configuration>Options and the names are allowed to be changed

When this option is selected a message will appear on the screen asking for a "lockout code"

The user selects their own lockout code (Pin)

The user will be asked to enter the lockout code

The user will be asked to enter the number of days the system can run normally before the lockout is activated

Type in the number of days you require

If you require immediate lockout enter 0 days

When the lockout is activated the AC system is turned off and any attempt to change the system will result in a pop up screen asking the user to enter their code to unlock the system

Once the correct code is input the system will be unlocked and can be used normally

When this option is selected the Min airflow adjustment will be locked at their current settings

The user will still be able to adjust the Max airflow adjustment and will be able to view the Min airflow setting but will not be able to adjust the Min airflow setting

Wireless Sensor

The LED on the wireless sensor has three displays modes

Because the wireless sensors are battery powered the use of the LED is minimised to preserve the battery life

1. LED Blue for 2 seconds when the sensor button is pushed and the zone is set to Climate control.

2. LED Red for 2 seconds when the sensor button is pushed and the zone is set to Closed.

3. LED Blue and Red flashing for 2 seconds when the sensor is not receiving a confirmation message from a paired C225 module

Wired Sensor

The LED on the wired iZone sensors has two display options that can be changed iin the system configuration as follows:

1. LED Option is ON - Blue whenever the associated zone is in Climate Control or Open and Off when the zone is Closed

2. LED Option is OFF - Blue for 2 seconds when the sensor button is pushed and the zone is set to Climate control. Off at all other times

The Ventilation system can be controlled via the air quality sensors in the Nexus+ touch screen

The system can be configured to automatically change speed depending on the level of contaminants measured by the sensors

It is possible to have one or more sensors controlling the system

If a sensor is not selected it will not control the system

The system will respond to the sensor readings as follows:

Relative Humidity (RH)

The fan speed will be controlled to maintain a RH of; set point (SP) +/- 5%. The SP range is between 5%-95%

Volatile Organic Compounds (VOC)

The fan speed will be controlled to maintain a VOC of; set point (SP) +/- 50 ppb. The SP range is between 50-2500ppb

Carbon Dioxide (CO2)

The fan speed will be controlled to maintain a CO2 equivalent of; set point (SP) +/- 100 ppm. The SP range is between 500-1500ppm

Time delay between stages (minutes)

A time delay can be set between stages (changes in fan speed) to prevent the fan from excessive cycling

The default is 3 min but this can be changed to between 3-240 min

The time delay is common for all all stages and sensors

Cycle fan off

If this option is selected the fan will cycle off once all parameters have been below their respective SP for the required time delay between stages

If this option is not selected the fan will run on low speed continuously to provide a minimum level of ventilation

The iZone system has the ability for basic configuration when Auto Configuration is selected

When Auto configuration is selected the iZone system will configure the system as follows:

• The iZone system will make Zone number 1 the Constant zone

• The iZone system will initialise and will detect all the operating zone damper motors

  • The last damper that operates on the system will determine the number of zones for the configuration of No. Zones

  • So for example if there are 10 zones connected to the system and the zone in the Zone 10, C225 port is fault and not detected the iZone system will configure the system to have only 9 zones

• The iZone system will look for wireless sensors that have been paired to the system if a sensor is paired and the zone selector switch has been set it will automatically change the zone type to wireless sensor

*Not available on earlier iZone systems

**Not available on all AC unit brands