Warm-water capture reduces the need for duct heaters in the air handling system, resulting in significant energy savings.

PMA innovation and teamwork have achieved significant energy savings for a client in southern Florida. PMA served as owner’s representative services on multiple facilities including new air handling units, updates to the central utility plant and airlocks, and upgrades to its building and environmental management systems.

Attaining the very tight temperature and humidity control for manufacturing required fine-tuning the various environments and processes required. Each process uses all outside air to cool the space and the air is exhausted back outside after one pass through the system. In southern Florida, where temperatures and humidity can exceed 90 degrees, the air has to move through the air conditioner, be dehumidified by the 40-degree cold water from the chiller plant and enter the manufacturing space at about 50 degrees. While the air is at the right humidity, it is still too cold for the room.

Before PMA came on the scene, electric heaters in the ductwork worked year-round to heat the air-conditioned air. As PMA worked with the client to install the expansion of the chiller system, the team suggested using a heat exchanger and adding a hot water coil inside the new air handlers to reduce the need for the duct heaters. By capturing the warm water that leaves the cooling coils, the overall power bill is reduced and the return on investment will be less than two years for just one air handler. There are between four to five air handlers to be replaced or added to the system in the next year.

How does it work?

The warm water that leaves the air handlers is diverted through the heat exchanger, where it is routed to the third set of coils back inside the air handler that warms up the air just before the air leaves the unit. By doing this, the warm water does most of the work of the duct heaters but does not add any additional energy costs to the daily operations. While the duct heaters will still be in place and help the warm water system as needed, they won’t have to run as much. Since the plant is in a location with mild winters it can take advantage of this ‘free’ heat year-round.

The piping for the heat exchanger runs on the same rack at the chilled water (much smaller pipe!), and the whole system runs on a 1 HP pump. The good news is the savings will grow, and the power bill will decrease even more reducing the need for fossil fuels. Capturing the heat that was formerly expelled as an unused by-product has turned into a plus for the environment!