A phase protector, also called a phase protection relay or a phase monitoring relay, is an electronic device commonly used with large motors in HVAC systems to prevent damage from power supply issues. If the three-phase currents in your HVAC system aren’t equal, you could end up with a phase imbalance, which could harm your air conditioning system and cause it to perform poorly. Ultimately, these voltage issues could even cause your system to fail, which is where having a phrase protector can really come in handy. In this article, I’ll explain the ins and outs of phase protectors and why they’re important to have in your HVAC system.
*Cost data in this article is sourced from Home Depot.
How Phase Protectors Work
A phase protector checks the power feeding into the three-phase motor in your HVAC system. It continually checks for low or high-voltage, overcurrent, phase loss, phase reversal, and voltage imbalance.
If any of these occur, the protector acts like a circuit breaker to immediately stop power to the motor and prevent damage until you can have an HVAC system inspection performed.
Phase protectors have indicators and alarms to notify you or technicians of problems, preventing costly downtime and repairs.
What Are Some Advantages of Phase Protectors?
Phase protectors offer many benefits to your HVAC system, including the following:
HVAC Protection
Phase protectors effectively prevent your HVAC system’s key components, like its three-phase motor and transformers, from phase imbalances and voltage-related harm. Preventing these damages can help keep your HVAC system running smoothly for years to come.
Reduced Repair Costs
Since phase protectors prevent phase imbalances and damages, they also help prevent any substantial repairs. By cutting off the power to your HVAC motor, you can keep it from doing any damage that’s expensive to fix.
Better Performance
Phase issues can hurt your HVAC system’s performance, leading to higher energy costs. Phase protectors help minimize imbalances and increase your system’s energy efficiency, which leads to better performance.
Are There Any Disadvantages To Phase Protectors?
The main disadvantage to installing a phase protector in your HVAC system is that it comes at a cost. According to Home Depot, most basic models run between $100 and $200, while heavy-duty or advanced models can run into the thousands. Still, this is a small price to pay compared to the repair costs you may face if your phase imbalances go unchecked, so it’s worth considering.
Key Features to Consider
Here are some key features to consider when selecting a phase protector:
Adjustable voltage range to match your motor’s needs
Phase loss detection to prevent single-phasing
Phase reversal protection
Protection from undervoltage and overvoltage conditions
Time delay to prevent restarting too quickly
Voltage imbalance protection
These Items Come With Pre-installed Phase Protectors
Phase protectors typically come pre-installed in industrial equipment, like the following HVAC systems:
- Air compressors
- Chillers that cool the water circulated to air handlers
- Cooling towers that discharge heat from chillers
- Large commercial air handlers that distribute conditioned air
- Water circulation pumps
Phase Protector Installation
Phase protectors are installed alongside motor starters and drives, sometimes on the din rail, and they connect to the three-phase power feeding these motor controls. When a problem is detected, the protector contacts disconnect power to stop the motor, preventing any further damage. You can press a reset button to reconnect power after the issue is fixed.
Many modern motor controllers have built-in phase protection. Check if yours includes it before adding an external protector.
So, Are Phase Protectors Worth It?
For home HVAC systems with large motors, phase protectors are absolutely worth it. Without phase protection, problems like low voltage, phase reversal, or voltage imbalance can quickly ruin motor windings, resulting in poor performance or failure. Replacing these motors costs far more than adding preventive protection, so use phase protectors to help prevent expensive damage to air compressors, chillers, pumps, and other equipment from power issues.
Phase protectors immediately shut down your motor when trouble is detected, preventing any damage. If you want to get the most out of your HVAC system and have it last for years to come, phase protectors are a wise investment for your home’s HVAC system.
FAQs About Phase Protectors
Where are phase protectors installed?
Phase protectors connect to the incoming power before it reaches motor starters or drives so they can monitor the raw power.
What is the typical phase protector price range?
Basic units at Home Depot start around $100 to $200, but more full-featured protectors run $600 to $1,000 or more, depending on amp rating and features.
How are phase protectors reset after tripping?
Simply push an external push button to reconnect power.
Can you add phase protectors to existing HVAC systems?
Yes, you can integrate protectors by disconnecting and rewiring the power and motor leads through the protector.
Do phase protectors prevent all power problems in HVAC systems?
Phase protectors mainly guard against multiphase faults. You’ll need additional surge protection for transients and spikes.
