What Is VMF Technology? How Variable Mass Flow Improves HVAC Efficiency
VMF (Variable Mass Flow) technology is an HVAC control system that adjusts compressor output based on real-time demand, reducing energy consumption by 10% to 25% without replacing existing systems.
In this expert Q&A, Francesca Altobelli, Energy Engineering Manager at Budderfly, explains how VMF works, where it performs best, and what Budderfly’s pilot program reveals about its impact.
What is VMF technology?
VMF technology is a smart compressor control that uses variable mass flow to adjust the speed of a compressor. This converts a 3-phase fixed speed compressor to variable speed by modulating the refrigerant flow through an HVAC unit. So instead of making that compressor run at its full cooling power anytime it’s called, it is only running the amount that the controller software, informed by the thermostat, prompts it to do so. That helps us save energy at the compressor level.
What problem does VMF technology solve for?
VMF technology helps us solve the problem of optimizing the amount of power we're using at a given time. Instead of using factory settings full power whenever we need any amount of cooling, we're only using the amount of power we need for the exact amount of cooling that is necessary at a given time.
That helps us generate savings from an HVAC unit that was perhaps not at the lifespan or the condition where it was eligible to be replaced. Instead of taking a whole HVAC unit and putting in a new one (when that existing one was already operating well and at an okay age), we can upgrade the existing unit instead and still see efficiency gains.
What have the results of the pilot been so far?
Budderfly has been piloting VMF technologies over the last year by installing a controller onto our existing non-replaced HVAC units and sub-metering that unit to measure the kilowatt hours used by that unit and compare them against days before the VMF was installed. We're seeing about 20% energy savings at the unit level.
Now that we've done our installs, we've monitored the power via submetering, and we are ready to finish evaluating this technology and bring it to our customers.
VMF technology reduces HVAC energy consumption by 10% to 25% per unit.
What's driving that range and what conditions produce the best savings?
Our pilot installed VMF across units in a variety of climate zones, so we could really hone in on where the technology had the best performance. And we found that in more moderate, less humid regions, we saw the greatest results in terms of energy savings. We also wanted to make sure that the controller could keep up with the dehumidification requirements of a region. A very humid area might not perform as well as a more temperate area.
Our pilot program included 50 HVAC units with VMF tested on it across 23 different sites nationwide, serving a variety of different room types—whether that was a kitchen, a dining room, a shared space, or small rooms and large rooms. And our conclusions came to around 10% to 25% energy savings per unit, depending on the season and various factors.
How does VMF fit into Budderfly's broader story about efficiency and emerging technology?
Budderfly is always looking for a new way to save our customers' energy, and we've done a great job in learning when to replace an old, inefficient HVAC with a new one. But there are many cases where an HVAC unit isn't quite ready, or it's not necessarily a smart decision to take out a newer unit and replace it with another. VMF fits into this by finding more energy saving opportunities without having to add a whole new HVAC unit.
What do you like about working on the pilot programs here at Budderfly?
The pilot programs are exciting because every day is different. We're always finding a new way to save on kilowatt hours, and it's exciting having a different challenge and a different type of engineering to learn every week.
VMF vs Traditional HVAC Operation
Traditional HVAC:
- Runs at fixed or full compressor capacity
- Higher energy waste during partial load
VMF:
- Adjusts compressor output dynamically
- Optimized energy use based on real-time demand
Result: VMF reduces unnecessary energy consumption and extends equipment efficiency without requiring full replacement.