Surge Protection for HVAC Equipment: A Necessity for Cold Climate Heat Pumps

Clint Rabe, P.E.

Clint‘s background designing both mechanical and electrical systems allows him to bring a unique perspective to the design and construction process while helping him to identify potential project opportunities and pitfalls. Clint’s collaborative approach to the construction process is evident as he works to bring all parties to the table in developing the right project solutions. His conscientious and hardworking approach reinforces his personal commitment to making each project a success.

With a push towards decarbonization, more mechanical designs will include the use of cold-climate heat pumps in the Midwest, which use sophisticated electronics to control their operation. These on-board electronics adjust compressor speeds, coordinating fan operation, and optimizing performance across various conditions. However, these electronics are vulnerable to damage from power surges, which can occur due to lightning strikes, utility events, or internal sources within a facility.

Protection Against Power Surges

Power surges involve brief spikes in voltage that can lead to damaging of sensitive components.

Surge protectors are used to divert excess current away from the appliance and into the ground. An HVAC surge protector is connected to the power lines and ground of a heat pump system. It prevents damage caused by power surges, although its effectiveness can degrade over time. Some surge protectors include a fuse that breaks the circuit if the protection becomes compromised.

HVAC-specific surge protectors are important as they safeguard against surges originating within a facility and offer an additional layer of protection.

It’s important to remember that surge protectors cannot defend against direct lightning strikes or persistent over-voltage from an unstable grid. Installing HVAC surge protectors involves connecting them to the outdoor disconnect of the heat pump circuit. They are typically low-maintenance and can be checked during routine servicing. Surge protectors benefit both facility owners and contractors by reducing the risk of equipment damage, costly repairs, and callbacks.

How HVAC Surge Protectors Work

HVAC surge protectors can utilize metal oxide varistors (MOVs) that have varying resistance based on voltage.

When the voltage surpasses a certain threshold, the resistance drops, allowing the surge current to be directed away from the equipment. One might also see those incorporating both MOVs and gas discharge tubes (GDTs) that are specifically designed for the HVAC systems.

We’d encourage surge protectors that would be able to withstand multiple power surges, extreme temperatures, and humidity, especially since a number of these heat pumps are installed on roof tops. The nominal discharge current rating from UL (Underwriters Laboratories) is a great place to start for evaluation along with other reliable performance ratings.

A surge protector containing both an MOV and a GDT provides response to an incoming surge, while the high-flow path provided by the GDT slows the degradation of the MOV and extends the useful life of the device.

Our Recommendation On HVAC-Specific Surge Protection

Contractors can offer surge protection as an add-on service during new installations, service calls, or preventive maintenance visits.

Despite the initial expense, surge protection devices can provide long-term benefits and showcases that company’s commitment to quality and to reduce call backs to fix equipment, which everyone appreciates.