Why is HVAC System Redundancy Necessary?
Redundancy is method of utilizing extra or duplicate HVAC system components to ensure continued operation in the event of primary system failure. For example, if a chiller shuts down, a secondary, redundant chiller automatically takes over, allowing for minimal disruption to operations. Redundancy is necessary for preventing downtime, ensuring continuity, and maintenance, as operations do not have to be interrupted or offline while performing standard service or repairs. HVAC systems can require redundant components for chillers, air handlers, pumps, UPS (Uninterruptible Power Supply) systems, and backup generators.
What Facilities Require HVAC Redundancy?
Redundancy is often mandated in mission-critical or critical infrastructure facilities. It’s required in hospitals with life-saving equipment to preserve patient care, climate and pressure control, and air quality. Redundancy is also a necessary aspect in data center HVAC systems for unit cooling and to meet uptime requirements. Other facilities, such as cleanrooms, laboratories, and pharmaceutical manufacturing, require redundancy to ensure sterile, controlled environments and hazard containment. ASHRAE (American Society of Heating, Refrigerating, and Air Conditioning Engineers) has specific standards that these types of facilities must meet in order to be compliant, such as ASHRAE 170 for healthcare facilities and ASHRAE 90.4 for data centers.
HVAC System Redundancy Methods
There are a variety of methods utilized to achieve redundancy depending on the size and needs of the facility. When planning for redundancy, you should also make sure to consider seasonal impacts. For example, winter increases the strain in heating systems, so your redundancy plan should account for frozen pipes, increased energy demand, and airflow issues.
- N+1: one extra unit to meet the load. N refers to the number of units plus 1 additional as backup. Common in data centers.
- 2N: full system duplication. 2N refers to twice the number of units. Common in high-reliability facilities like hospitals.
- Parallel Redundancy: simultaneous operation of primary and backup units.
- Rotational Redundancy: alternating the operating order of redundant components to ensure no single piece has excessive runtime.
Maintenance for Redundant HVAC Units
60% of HVAC downtime is preventable with proper redundancy. Performing preventative maintenance is crucial to the full HVAC system, not just the redundant units. For the most accurate guidance on service intervals to support the longevity and reliability of your primary and backup system, you should look to ASHRAE. In general, they recommend that systems should be serviced twice a year, once before heating season and once before cooling season to ensure they’re working efficiently when workload is highest. Along with this, filters should be replaced every 6 months or quarterly, depending on the usage of the HVAC unit. In considering ASHRAE 90.4, 170, and 180, it’s also useful to know the Mean Time Between Failures (MTBF), a reliability metric that is useful for maintenance planning. To calculate the MTBF, divide the total operating time (in hours) by the number of failures during that time. For example, if a unit runs for 10,000 hours and has 5 failures, the MTBF would be 2,000 hours. Knowing the MTBF allows you to be proactive with scheduled maintenance and reduce the frequency of failure. The final recommendation for maintenance is to stock backup parts for quick replacement. Some essential parts needed for redundant components include:
Single-point failures in HVAC systems can lead to downtime, compromised air quality, and safety risks in critical facilities. Developing a redundancy plan is crucial to keeping the facilities operational in the event of unit failure or power outages. Performing preventative maintenance and stocking backup parts from LONG PartsPros is also a great way to ensure the efficiency of your HVAC system!