By Eamonn Ryan
Not all safety devices are created equal. During a recent discussion hosted by Jamie Kitchen with Jörg Saar and John Broughton, the trio explored how manual reset switches and automatic safety devices impact HVAC system reliability. This is part two of a seven-part series.
“Controls manage normal operation; safety devices step in only when conditions threaten the system.” – Saar. Freepik.com
Kitchen illustrated the difference with a simple analogy: “Control is like telling your kids to turn the music down. Safety is when they ignore you, and you pull the plug. Nobody is happy, but it’s necessary.” Saar agreed, highlighting the temperature side: “Alarms are neither controls nor safeties. They tell you something’s wrong but don’t prevent damage. Safety devices physically stop the system before damage occurs.”
Broughton noted that high-pressure cutouts are a common safety intervention, often triggered by blocked condensers, airflow issues, or refrigerant imbalances. “I’ve seen dumpsters or even hedges blocking airflow. It’s rare, but it happens. When the system hits the cutout pressure, the safety device does its job – sometimes creating frustration but preventing worse damage.”
The discussion also addressed manual versus automatic reset mechanisms. Saar explained: “Manual reset can be an annoyance, but it ensures someone evaluates the problem before restarting the system. Automatic reset is more convenient but may not address recurring issues, especially in sensitive applications.” Broughton added, “Compressor overloads often have internal protections without reset buttons. They may trip temporarily and reset once conditions normalise, extending compressor life without requiring immediate intervention.”
Kitchen emphasised the legal and operational importance of safety overrides. “A safety switch cannot be bypassed. Even if the system contains R200 000 worth of product, it’s the last line of defence. It trumps everything else.”
The segment also explored intermediate safety measures, such as thermal overloads and low-pressure cutouts for scroll compressors. Saar explained, “Running a scroll compressor at excessively low pressure or without adequate superheat can destroy it. Low-pressure cutouts protect against that, while thermal overloads provide backup in case of transient issues.”
Ultimately, Kitchen concluded that understanding how controls and safeties interact is critical for system reliability. “Controls maintain operations within normal limits. Safety devices ensure that when things go wrong, the system doesn’t fail catastrophically. Knowing when to use manual reset versus automatic devices can prevent expensive equipment damage and product loss.”
