Key Takeaways
- Critical Component: Crankcase heaters prevent refrigerant migration and oil dilution during off-cycles, protecting compressors from flooded starts
- Common Failure Point: Failed crankcase heaters frequently cause tripped breakers and blown fuses, making them essential troubleshooting targets
- Maintenance Oversight: These components are often overlooked during preventative maintenance despite their importance to system reliability
- Wiring Safety: When using auxiliary contacts, ensure heaters power on during compressor off-cycles, not vice versa
It would be really hard for me to count the number of times I have come across a tripped breaker or blown fuse due to a failed crankcase heater.
It makes sense though, a lot of manufacturers don’t provide an auxiliary contact or thermostat to cut its operation when not needed. They are exposed to the elements and varying compressor temperatures contribute to the expansion and contraction of the heater.
What Is a Crankcase Heater?
A crankcase heater is a component in HVAC systems, used to maintain oil temperature above the refrigerant’s saturation point when the system is idle.
This prevents refrigerant migration and oil dilution which can lead to operational issues like unsuccessful compressor start-ups, inadequate lubrication, and liquid slugging.
The heater enhances the HVAC system’s durability and efficiency and should be controlled by a thermostat or pressure switch for optimal operation.
What Does a Crankcase Heater Do?
Crankcase heaters are used to protect the compressor from liquid refrigerant migration during the off cycle and are an important factor in preventing flooded starts. Understanding the refrigeration cycle helps explain why this protection is so critical during system downtime.
In my experience, crankcase heaters are overlooked during preventative maintenance. Finding failed or defective heaters can result in creating legitimate work. This is especially important when preparing systems for seasonal heating maintenance, as a failed crankcase heater discovered in winter can lead to compressor damage.
Diagnosing tricky component failures like crankcase heaters becomes more efficient with proper preparation. Property.com’s ‘Know Before You Go‘ tool gives HVAC pros critical property insights before arriving on-site, including equipment age and maintenance history that can help predict component failures. Join Property.com’s exclusive network to elevate your diagnostic capabilities and customer service.
Also, if you are experiencing a situation with a tripped breaker, inspecting the crankcase heater is not a bad place to begin troubleshooting. This is particularly relevant in heat pump systems with reversing valves, where compressor protection is crucial year-round.
Self-Regulating Solutions
Fortunately, there is a product that doesn’t require extra controls to regulate heat. Universal, self-regulated crankcase heaters are available and they fit various compressor sizes.
Emerson EasyHeat is a great example of this type of heater. These self-regulating models eliminate the need for complex BMS control integration in commercial applications.
✋ Keep In Mind: When wiring in a crankcase heater utilizing auxiliary contacts, ensure that the heater is powered on during the compressor “off” cycle and not vice versa. This is a mistake that has been made by several techs and can leave the compressor unprotected when it needs it most.
🎥 Video Demonstration: Diagnosing and Replacing a Defective Crankcase Heater
This video demonstrates the complete process of diagnosing a defective crankcase heater and shows the replacement procedure:
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