A dedicated outdoor air system (DOAS) conditions and dries a building’s ventilation air, and its controls are built around one job that matters intensely in Florida: hitting a low supply-air dewpoint so the ventilation air enters dry. The sequence drives the cooling coil to a dewpoint setpoint, often reheats to a neutral temperature, manages energy recovery, and modulates ventilation to demand — keeping the building dry without wasting energy.
A DOAS exists to take hot, humid Florida outdoor air and deliver it to the building dry, so the space equipment can handle temperature without fighting the moisture load. Its controls are therefore organized around dewpoint — the measure of absolute moisture — not just temperature.
Control the dewpoint of the air leaving the DOAS, and you control how much moisture enters the building with ventilation. That is the whole game in a humid climate.
The core loop drives the DOAS cooling coil to pull the outdoor air down to a low supply-air dewpoint — cold enough to condense out the moisture. A dewpoint or low-limit humidity sensor on the supply air drives the coil valve. As outdoor humidity rises, the coil works harder to hold the dewpoint setpoint.
This deep dehumidification is the work a normal comfort system struggles to do, which is exactly why the DOAS takes it on as its dedicated job. See DOAS for Florida buildings.
Air cooled enough to wring out moisture is cold — too cold to dump into spaces directly. So the DOAS usually reheats it back to a neutral delivery temperature. The control modulates a reheat source to hold that supply temperature.
Efficient designs reheat with recovered or free heat rather than new energy — using a heat-recovery coil, hot gas from the unit’s own refrigeration, or the energy-recovery wheel — so the reheat does not waste what the cooling just spent. The sequence coordinates cool-then-reheat to minimize that penalty.
Most Florida DOAS units include energy recovery — an enthalpy wheel or core that uses the building’s outgoing exhaust to pre-condition incoming outdoor air, removing much of the heat and moisture before the coil even sees it. The controls modulate the recovery device (wheel speed or bypass) to capture energy when useful and avoid it when not.
Energy recovery is often code-required above certain ventilation rates under ASHRAE 90.1, and the controls have to operate it correctly for both the savings and compliance. See ASHRAE 90.1.
The DOAS need not deliver full ventilation when the building is lightly occupied. Tied to CO2 sensors and occupancy, demand-control ventilation modulates the outdoor-air volume to actual need — and since every cubic foot of Florida ventilation air is expensive to dry, not over-ventilating an empty building is a direct saving.
The sequence coordinates DCV with the dewpoint and reheat loops so the unit ramps ventilation to demand while still keeping whatever air it does deliver dry. See demand-control ventilation.
A DOAS with a sloppy sequence — dewpoint setpoint too high, recovery not modulating, reheat wasting energy — either lets the building run damp or burns money doing its job. A tight sequence keeps the building dry at the lowest energy, which in Florida is the difference between a comfortable building and a moldy one.
These loops are commissioned and trended like any critical sequence — see trending and commissioning.
They control the dewpoint (absolute moisture) of the ventilation air the unit delivers — driving the cooling coil to condense out moisture, reheating to a neutral temperature, managing energy recovery, and modulating ventilation to demand. The goal is to deliver dry outdoor air so the building stays dry.
In a humid climate, controlling moisture matters as much as temperature. Dewpoint measures absolute moisture, so controlling the supply-air dewpoint directly controls how much moisture enters the building with ventilation — which temperature alone does not capture.
Air cooled enough to remove moisture is too cold to deliver to spaces, so the DOAS reheats it to a neutral temperature. Efficient designs reheat with recovered or free heat — a recovery wheel, hot gas, or heat-recovery coil — so reheat does not waste the energy the cooling just spent.
Often, yes. ASHRAE 90.1 and the Florida energy code require energy recovery above certain ventilation rates and outdoor-air percentages, which Florida buildings with significant ventilation frequently exceed. The controls must operate the recovery device correctly for both the savings and code compliance.
Suncoast Cold Systems installs, wires, and configures the HVAC controls integral to the mechanical systems we provide — and specifies open protocols (BACnet, Modbus, open supervisory platforms) so you own your building’s controls and data, with no proprietary dealer lock-in. Where a project calls for certified systems integration, we coordinate it within one accountable mechanical scope. Licensed Florida Class A Air Conditioning Contractor (FL #CAC1824642).
The system these controls run.
Demand-based ventilation in depth.
Resetting dewpoint and ventilation to demand.