Faulty installation practices and a lack of maintenance are the two biggest contributors to poor system performance in refrigeration and air conditioning equipment.
These are the findings of the Leaks, Maintenance and Emissions report released by the Department of Agriculture, Water and the Environment report last month.
This report explores opportunities to reduce emissions from refrigerant leaks and unnecessary electricity consumption.
In most modern economies refrigeration and air conditioning equipment is one of the largest, if not the single largest consumer of electricity.
The implications of the fact that cooling services are consuming more than a fifth of all the electricity generated in Australia is still not widely appreciated.
Electricity production is the largest single source of greenhouse gas emissions in the Australian economy, producing 34 per cent of all emissions in the year ending December 2019.
The International Institute of Refrigeration (IOR) provided a global estimate that ‘Better optimisation, monitoring, and maintenance of cooling equipment has the potential to save 30 giga tonnes (Gt) of CO2eemissions by 2050, contributing a further 38 per cent of savings on those delivered through the planned phase down of high GWP refrigerants agreed at Kigali’.
The IOR estimates optimisation, monitoring and maintenance can reduce total greenhouse gas emissions by 13 per cent.
With more than 50 million individual pieces of RAC equipment employed in the Australian economy, the report provides industry with opportunities to really make a difference.
Most prevalent faults across all RAC equipment are:
- Sub-optimal refrigerant charge (undercharge most common);
- Condenser fouling and restricted airflow;
- Evaporator fouling and restricted airflow;
- Refrigerant contamination, degradation, fractionation, non-condensables and flow;
- Control system faults; and,
- System sizing and equipment location.
Some faults tend to build up over time. These faults include incorrect refrigerant charge, dirty filters, fouled evaporators and condensers, refrigerant contamination, and inappropriate changes to control settings. These faults can be easily addressed and corrected by routine good practice maintenance and monitoring techniques.
Other faults are related to the original design and installation of the system. These faults include undersized ductwork, leaking ductwork, mis-sized or mis-matched equipment, incorrect location or poor equipment control.
These faults tend to be more difficult to address as they cannot be corrected by maintenance alone, and require optimisation, recommissioning or an upgrade to repair the fault or reduce energy waste or the energy penalty.
The report identifies problems and provides solutions including one section of the report which is specific to air conditioning. This section deals with Ducted AC (split and packaged) and central air conditioning (chillers).
Problems identified for this equipment include improper duct sizing, poor fan connection/installation, incorrectly sized or installed dampers, incorrect/no commissioning.
Inefficient ductwork is a system fault that is designed into the system at installation stage. Systems that do not meet the minimum airflow requirements will not operate at their designed efficiency level. Fans work harder and refrigeration systems do not reach their operation potential.
It is not uncommon for a ductwork system in a commercial application to be re-used even when air conditioning systems are replaced or upgraded. The energy penalty occurs for the life of the system and is most impactful at periods of peak load.
On average energy waste is in the five to 10 per cent per annum range and as high as 25 per cent in cases where the system is significantly compromised.
“The installing technician should always check the evaporator airflow rate, and airflows of each outlet against the intended design,” the report said.
Another issued identified in this section of the report is poor filter maintenance.
Comprehensive building studies have shown that filter maintenance is typically not carried out in 25 to 40 per cent of buildings, the report said.
Regular filter inspection and maintenance is recommended by every air-conditioner manufacturer and all HVAC maintenance best practice guides, as well as maintenance standards AS/NZS 3666.2.
A widespread industry problem is insufficient thermal insulation which contributes to serious energy loss.
“In poorly sealed ducts, the effect of leakage can be considerable. Individual workmanship is the greatest variable,” the report said.
“Leakage from the supply duct will reduce the capacity of the system to meet the load (chillers and cooling towers and fans will work harder) and increase power consumption, ducts can sweat (condensation) at leakage points if not adequately insulated.
“Leakage into the return air duct adds to the plant load. Duct leakage faults are very difficult and/or expensive to rectify post installation, particularly for insulated ductwork systems. The energy penalty can exist for the entire service life of the cooling equipment and potentially be re-used when equipment is upgraded or replaced.”
Maintenance strategies can generally be characterised as reactive, preventative or predictive.
Comprehensive maintenance packages that typically bundle preventative and reactive maintenance costs together, may not specifically target energy efficiency and reducing energy costs.
Maintenance procurement can be used to incentivise energy efficiency by including energy targets and key performance indicators in all maintenance contracts.
Traditionally maintenance tasks have been as much about visual and physical inspection - gathering data, assessing information, recording results – as about manually repairing components.
The report points out that advances in digital technologies now provide opportunities for digitalisation of many maintenance tasks, services and solutions.
“Equipment and system data can be automatically recorded on system controllers, relayed by wireless sensor networks, analysed by cloud-based machine learning algorithms and ultimately visualised on mobile computing devices, generating alarms and recommended actions, even providing specialist technical instructions to the maintenance service provider,” the report said.
“This digitalisation of maintenance is disrupting traditional practices and creating new value opportunities, and DA19 terms this technical development as smart maintenance.
“The maintenance activities that deliver both improvements in energy efficiency and reductions in loss of refrigerant charge require skilled technicians with the appropriate licensing, knowledge and understanding that is common and accepted practice in the RAC community.”
Failing to regularly maintain equipment can be costly but owners/employers may not always understand the value of routine maintenance in reducing operating costs and avoiding business disruptions (from break downs).
Routine maintenance (at least annual) is essential for the effective operation of equipment.
A further issue to consider is the rate of innovation across the industry. Modern RAC equipment now utilise microchannel technology, speed controllable compressors, fans and pumps, electronic sensors and components, advanced controls, new refrigerant types and digital communications abilities which can all improve system COP.
The industry is innovative, competitive and technology is constantly improving. Modern equipment has progressively been designed to operate more efficiently with components and refrigerant charges optimised.