Advanced Technology: Variable Frequency Drive and Demand-Controlled Ventilation

Variable Frequency Drive (VFD) and Demand-Controlled Ventilation (DCV) are two distinct but complementary upgrades that can, when installed together, reduce energy costs by more than $700 per unit/year while still providing optimal levels of ventilation and comfort.

Older HVAC Systems Struggle to Adapt

Older single-zone HVAC systems often lack the ability to regulate the motors and fans that ventilate a space in response to environmental changes like the weather or building occupancy. Instead, California building code requires the air damper to be fixed open wide enough to ventilate to the demands of peak occupancy, no matter how many people are actually inside the building. In addition, the supply fan is required to constantly re-circulate air.

These two conditions add up to an HVAC system that is working hard constantly, wasting energy, ventilating and conditioning air unnecessarily.

How It Works

Return air damper using Demand-Controlled Ventilation.Supply Fan and Variable Frequency Drive.

The VFD upgrade automatically reduces the speed of the supply air fan when the unit is not conditioning indoor air, reducing the energy use of the fan by 60-80%.

The DCV upgrade gives the system the ability to open and close the outside air damper to the position that will provide the ideal amount of ventilation, according to readings from a CO2 sensor.

The Result

Installed together, VFD and DCV will maximize energy savings and reduce installation time and costs. The building is ventilated efficiently, providing fresh air as needed, rather than according to inflexible schedules or assumed occupancy levels. This means lower energy bills, more reliable HVAC system operation, and higher indoor air quality.

We’ve seen businesses that complete VFD and DCV upgrades attain annual savings of about 4,900 kWh and $740 per unit. SCE offers incentives that can create simple payback periods between one and two years.

There may be cases when choosing just one of the upgrades makes sense. Your contractor can help you figure out what path is best for the needs of your building and business.

SCE customers who are already participating in Quality Maintenance or Quality Renovation can ask their current contractor for information on estimated energy savings, incentive amounts, and payback periods for VFD and DCV.

If you’re new to HVAC Optimization, you can find a participating contractor to learn more and determine your eligibility.

Local HVAC contractors who want to expand their services and bring the benefits of VFD and DCV to their customers can find out more by contacting the HVAC Optimization team.