Shooting the Breeze
A quiet word about air conditioning for the home:
Selecting an air-conditioning system for your new home is not an easy task. The most important decision is often selecting the right heating and cooling professional. The next is selecting the right type of air conditioner and then there is the control strategy. Our engineering team have provided the information below as a guide to selecting the best air-conditioning system for your project.
Ducted SystemsA concealed ducted system is often the first choice for a home. All system components are concealed within the structure. When selecting a ducted system it is important to understand that manufacturers provide a single point from which the temperature information is gathered.
Mode Selection A home is made up of many rooms and each will have a different heat load characteristic due to the size and location of windows, the size of the room and the position of the sun. A multi-zone temperature control system gathers information form every room and then modulates motorised valves within the ceiling to adjust the airflow to each room. If you want your heating and cooling system to automatically change from heating to cooling when needed the mode selection is best done from a Multi-zone temperature controller to avoid large shifts in indoor temperature. DC Inverter Refrigerant Flow Control A well designed multi-zone temperature control system will adjust the capacity of the air-conditioning unit by working with the manufacturers controls to modulate airflow and refrigerant flow. Refrigerant Flow Modulation is achieved by adjusting the manufacturers system wide temperature target and by influencing the indoor heat exchanger mid-coil temperature. Indoor Airflow Modulation It is also important to select a control system that has the ability to redirect some of the airflow in a bypass mode to avoid the spill or dumping of energy ladened cold or hot air into living areas. Ducted art conditioners are typically three speed fan and almost always the lowest speed to too high over 85% of the operating requirement. It is important to select a control system that works with the unit manufacturers controls to provide better than three speeds of airflow. Key points: 1. Insist on a target temperature for each room 2. Say no to dump or spill rooms 3. If underfloor heating is being used insist on an interlock with the ducted air conditioner. 4. Insist on fault code notification by automated email to reduce servicing costs and return trips when a system fault occurs. |
VRF & VRAFVariable Refrigerant Volume (VRV), Variable Refrigerant Flow (VRF) or Variable Refrigerant and Airflow (VRAF) systems are required when it is difficult or impossible to run ducts to all areas of the home. A system of this type has multiple indoor units connected to a single outdoor unit. The space needed for services is reduced from an air duct to a pipe pair. While these systems provide a significant befit in that less space is lost to services there are a number of issues that need to be addressed in the control system.
Mode Master The outdoor unit provides refrigerant to all indoor units, what this means in practice is that all indoor units must share the same system mode (Cooling, Heating or Ventilation). System manufacturers nominate a single indoor unit as the Mode Master and all other indoors must be a slave to that indoor units setting. The solution to this is for your heating and cooling professional to include a control system that monitors the heating and cooling required for every room and automatically adjusts the system wide mode based on the entire home. Auto Mode Deadband The VRV & VRF manufacturers control system continues to allow refrigerant to flow after a room has reached its set temperature. An unfortunate consequence of this strategy is that when a system is set to Auto Mode the temperature inside the home can drift up to four degrees. To avoid this problem it is important to use a control system that removes the Auto mode function from the unit controls. Key Points: 1. Make sure that every thermal zone or room contributes to system mode selection. 2. Make sure that Auto Mode is not controller by the manufacturers control system. 3. Make sure that if motorised dampers are used with VRV/VRF that each thermal zone or room has a temperature sensor 4 If underfloor heating is being used insist on an interlock between the VRV/VRF and the Hydronic. 5. Insist on fault code harvesting and notification to reduce repair costs, reduce the number of visits by a technician and extend system life. |
What Goes on Your Wall
A heating and cooling system is often the largest capital expense outside of the structure of the home. If you select a multi-zone control system to improve the performance of the heating and cooling system a temperature sensor is required in each room. A range of options are available for temperature sensors including sensors no larger than a $2.00 coin that can be painted the same colour as the wall, a glass capacitive touch room controller with backlighting to show the system operating state or room touchpads that provide access the adjustable parameters like the temperature the room is set to. IF you are including a lighting system the temperature sensor, On/Off and even the adjustment of the set point can be done from the light switch. In some situations heating and cooling installer will offer battery powered sensors. These sensors reduce installation time but to save energy they transmit the temperature data 100 times slower than a wired sensor. Battery powered sensors also require an annual battery change at each sensor for the life of the system.
Key Points:
1. If you are not using a multi-zone temperature control compare the look and feel of the manufacturers controller with other options such as Google Nest.
2. If you are using a multi-zone temperature controller select the sensors for each room as invisible, discreet or styled.
3. Avoid battery powered temperature sensors.
Key Points:
1. If you are not using a multi-zone temperature control compare the look and feel of the manufacturers controller with other options such as Google Nest.
2. If you are using a multi-zone temperature controller select the sensors for each room as invisible, discreet or styled.
3. Avoid battery powered temperature sensors.