Compact Energy Recovery Ventilator Complements Variable Refrigerant System

Beardsley Design Associates, a firm specializing in sustainable architectural and mechanical design for a variety of commercial and institutional markets, was selected to design the mechanical renovation at the Stanley campus, but there were challenges. The “D” wing of the Stanley facility included some conference rooms and other spaces with outdated baseboard heating, but no cooling or means for fresh air. Built nearly a half century ago, the building had rooftop load restrictions that eliminated the option of installing conventional air handlers on the roof to supply fresh air. Furthermore, a traditional ducted system would have been difficult if not impossible to discreetly install given the existing walls and layout.

Given these circumstances, Beardsley chose a zoned VRF heat pump system for heating and cooling, and Topvex ERVs for fresh air supply. The latter was small enough to install above the ceiling where it is ducted directly to the VRF indoor split (terminal) units that were also installed above the ceiling.

An outdoor VRF heat pump is piped to the indoor split units, supplying refrigerant as need to the individual zones. This combination of space and energy efficient equipment not only brought the spaces up to code, but introduced a whole new level comfort and control to the building spaces.

The fresh air challenges at the Stanley campus are common to many K-12 renovations. Space limitations and rooftop load restrictions often rule out more conventional, centralized HVAC solutions. These are the primary reasons a school might typically opt for a solution like the Topvex that actually fits within the building envelope. But many other benefits apply such as longer equipment life, part-load efficiency, and serviceability.

Electronically commutated motors, or EC-motors as they are commonly called, are the key to the Topvex part-load efficiency, as well as the overall longevity of the unit. EC motors are designed to operate at high efficiency even during low RPM periods and consume an average of 30% less energy than AC motors. The motors are standard on all Topvex units so no separate variable frequency drives (VFDs) are required, which reduces wiring at the jobsite. The motors do not require any greasing and are virtually maintenance-free. They are also quiet, which makes them particularly appealing for above ceiling installations in classrooms and conference rooms.

Bag filters are another unique standard feature of the Topvex unit. The filters are designed with greater surface area so they last longer. When replacement is required a built in pressure transmitter that measures the filter pressure drop alerts personnel via the control panel or Building Management System (BMS). The filters are mounted on guiderails for easy removal and replacement. This is the only maintenance procedure required for the Topvex ERVs, which is a big plus for K-12 campuses where maintenance staff is often limited.

The Stanley campus renovation illustrates the problem-solving potential of the Topvex ERV, particularly with VRF applications.

Schools are expected to provide many decades of service, so investing in high efficiency equipment that also meets stringent indoor air quality standards makes sense. Topvex ERVs are the perfect complement to VRF systems as they provide the necessary ventilation in an energy efficient package that can be located in spaces where most ERVs cannot.

Benjamin Hardy, service technician for Modular Mechanical Service, oversaw the HVAC start-ups at the Stanley campus, and agrees that the combined systems provide an excellent solution for schools and other light commercial projects.