VRF Enabled Makeup Air – Decarbonization Solution

Blog
Decarbonization

As developers and engineers look for ways to provide improved energy efficiency with their eye on decarbonization, heat pumps are getting a lot of attention.  Both air and water source heat pump technologies deliver exceptional value when addressing these two requirements.  For space conditioning, engineers are getting quite comfortable designing with these technologies, widely incorporating variable refrigerant flow (VRF) and geothermal systems, but how do we address 100% outside air units?

In the multi-unit residential market, where 100% makeup air units (MUA) are required for corridor ventilation, it presents several challenges.  For now, we’re going to look at MUA only, and disregard energy recovery options as I will look at those in a later post.

So, you need 100% outside air and you want to leave the gas line at the street!  The quick solution would be a 100% electric MUA.  Another approach is a packaged air source heat pump (ASHP) AHU with supplementary heat.  These units need 100% redundant heat backup since the ASHP is locked out at ambient temperatures below 10°F.  To avoid these limitations, a more elegant solution is to employ an LG VRF ASHP as the primary source with electric pre-heat.  This solution, we’ll refer to as VRF enabled MUA, takes advantage of the low ambient (-22oF) heating performance of LG VRF equipment.

The VRF enabled MUA is manufactured with an electric pre-heat coil upstream of the ASHP coil.  In heating mode, this coil maintains the air entering the ASHP coil greater than 41oF.  The ASHP provides any additional heat required to deliver neutral conditioned air the building.

On a recent project, we designed a 5,000-cfm MUA for corridor MUA.  The chart below shows a comparison of energy input during heating season for an all-electric solution vs. the VRF enabled MUA.  This chart takes into consideration the degradation of ASHP coefficient of performance (COP, which is the ratio of energy produced to the energy input required) with lower temperatures.  Specifically, the performance data for the 20-TR LG VRF ASHP was used. Clearly, the VRF enabled MUA requires significantly less power input (25-75% reduction) through the entire outdoor temperature range.

The VRF enabled MUA is a viable solution for both new and retrofit applications.  The solution is scalable and can address any size air handler.  Although, not specifically addressed in this post, integrating VRF with energy recovery equipment makes the analysis even more favourable for VRF as it eliminates the requirement for electric preheat.

Recent Projects

Explore Our Projects
Canadian Canoe Museum
Discover how the Canadian Canoe Museum, a unique national heritage centre with over 100 canoes and kayaks on display, embraced innovative HVAC solutions to enhance energy efficiency.
More Details about Canadian Canoe Museum
Capreit 15 Tangreen Project Profile
In collaboration with a mechanical consultant, we overcame significant challenges to upgrade the HVAC system of a residential REIT building.
More Details about Capreit 15 Tangreen Project Profile
Chemtura
To support its growth, Chemtura Corporation constructed a new laboratory in Guelph, Ontario, featuring a sophisticated lab exhaust solution designed by us in collaboration with WalterFedy.
More Details about Chemtura
Folkway Music
Folkway Music, renowned for its vintage and unique guitars, partnered with us to implement a reliable humidification system.
More Details about Folkway Music
Urban Tactical
We collaborated with a design-build contractor to implement advanced ventilation solutions for Urban Tactical, a firing range in Brantford.
More Details about Urban Tactical
Schembri Property Management
Thirty-one Kingsbury Drive in Kitchener, Ontario, is a shell office building built by Schembri Property Management. The consultancy firm of M.A. Bryan Engineering was retained to complete the job.
More Details about Schembri Property Management