AIR CONDITIONING, COOLING & VENTILATION
Maximising RTU efficiency with preventative maintenance
Kevin Stockton, director large rooftop unit (RTU) product management, ducted systems, Johnson Controls, and Jason Carter, senior product manager, ducted systems explain the dynamics of RTU preventative maintenance and how smart controls, fault detection and diagnostic tools can further enhance outcomes and extend the life cycle of a unit
T
he US Department of Energy estimates that packaged RTUs account for approximately 60% of commercial HVAC systems in use. Prized for their “workhorse” reputation, RTUs have historically had their maintenance deferred in favor of run-to-failure practices. As facility executives continue to face stringent performance standards and ambitious sustainability goals, advanced preventative maintenance has reemerged as a critical component in maintaining energy efficiency and reducing operational costs.
What is driving the demand for preventative maintenance in RTUs?
Commercial building executives have faced significant changes in recent years. From cost increases, to minimum efficiency requirements, to sweeping adoptions of stringent building performance standards and ambitious decarbonisation goals, many building professionals are now responsible for meeting sustainability metrics in addition to managing operational costs.
Understanding these goals can help to
inform a preventative maintenance strategy that is designed to deliver measurable energy efficiency increases and deliver operational cost savings. A maintenance plan can also help to initiate the development of a carbon reduction strategy and be used to support system retrofit or replacement recommendations with data- informed insights.
What are some examples of RTU preventative maintenance that should be prioritised?
Coils, filters and belts are the components most in need of inspection and periodic changing within the RTU. Without proper maintenance, system inefficiency, early wear, clogging (which can lead to catastrophic failures) and ultimately equipment faults are inevitable. Filters, in particular, provide an easy entry point to demonstrate the value of preventative maintenance, especially when an economizer is in use. Dirty filters add static pressure that the fan must overcome, in addition to creating dirty coils, which reduce the thermal heat transfer. These issues result in a fan and
compressor that must work harder and, in some instances, result in a five to ten percent increase in unused energy.
What role do controls play in RTU maintenance?
Research estimates that transitioning to an RTU with advanced controls can have a payback in just one to four years through operational cost savings and reduced system repairs. Smart controls combine advanced sensors, programmable settings and remote management tools that can be integrated across multiple RTUs and sync multiple locations. Performance and operational insights can be used to inform maintenance and minimize downtime. Additionally, maintenance schedules can be programmed into the system to streamline the process between the facility manager and service contractors. Some packaged rooftop units may already be equipped with smart control-sensing technology. This enables the equipment to seamlessly connect with smart control systems and eliminate the need for programming tools. Dependent on the age and condition of the system, RTUs that are not smart control- enabled may benefit from a minor retrofit to enable connectivity.
What considerations should be made for fault detection and diagnostics?
Fault detection and diagnostics (FDD) tools continuously monitor critical variables such as temperature, pressure and airflow that impact operation and efficiency. Algorithms process this data and deliver real-time alerts that allow facilities teams to pinpoint issues for fast resolution. If service is required, FDD data can be remotely transmitted to the contractor before they arrive onsite to improve service efficiency and reduce downtime.
Is there anything else contractors and technicians should know about preventative maintenance?
When aligned to performance and operational goals, preventative maintenance strategies become a valuable asset well worth the initial investment. Combined with smart controls and fault detection and diagnostic tools, preventative maintenance is streamlined and informed by data-driven insights that can help contractors further strengthen their relationship as an advisor.
18 BUILDING SERVICES & ENVIRONMENTAL ENGINEER MAY 2023
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