Smart Air Curtain Control for Commercial Entrances

Using door status and temperature conditions to make entrance air curtains operate when the building actually needs them

A commercial entrance is a small part of the building envelope, but it can create a difficult HVAC condition. In a busy shop, showroom, lobby or public building, the door may open dozens or hundreds of times during operating hours. Each opening interrupts the separation between indoor and outdoor air.

An air curtain helps protect that boundary, but only if its control sequence matches the entrance. Running the unit continuously at one fixed condition is simple, yet it ignores whether the door is open, whether heating is required and how the entrance is actually being used. This application focuses on the control layer around the air curtain rather than treating the unit as an isolated fan.

Project Summary

Project Overview: One Entrance, Two Different Control Decisions

The entrance uses an air curtain above the main external door. During busy periods, frequent door opening allows outdoor air to enter the occupied space and conditioned indoor air to escape. Staff near the entrance experience the effect first, but the disturbance can also influence the surrounding HVAC zone.

The project has two related but different questions. First: when should the air curtain create an airflow barrier? Second: when should that airflow also be heated? Treating both functions as one permanent ON/OFF command can lead to unnecessary heating or poor seasonal operation.

The control strategy therefore uses door status to identify entrance activity and temperature conditions to determine whether heating is required. Fan and heating functions are coordinated, but they are not assumed to have identical operating logic.

Customer Challenges

· The entrance door opens frequently and the operating pattern changes throughout the day.

· Continuous air-curtain operation can add unnecessary fan runtime during periods with little or no door traffic.

· Heating the discharge air whenever the fan runs is not appropriate in every season or indoor condition.

· A simple manual switch depends on staff behavior and does not respond automatically to door status.

· The controller must match the electrical/control interface of the actual air curtain rather than assume one universal power arrangement.

The control problem is therefore more specific than 'turn the air curtain on when the door opens.' The designer needs a sequence that reflects the unit type, entrance traffic, heating source and required run-on behavior.

HVAC Control Solution

A door contact provides the controller with a clear indication that the entrance is open. The controller uses that signal as part of the fan operating sequence, allowing the air curtain to respond to real door activity instead of relying only on a fixed manual schedule.

Where the air curtain includes a heating function, temperature control is handled separately from the door signal. Heating is enabled only when the project conditions call for it and when the equipment interface allows it. This prevents the door contact from becoming an unconditional heating command.

A short fan run-on period can also be useful in some applications so the air barrier does not disappear the instant the door closes, particularly where people pass through in quick succession. The required delay should be set around the entrance pattern rather than chosen simply because a timer is available.

Control Sequence in Practice

During a quiet period with the door closed, the air curtain can remain off or follow the project's standby strategy. When the door opens, the controller activates the required fan operation. If heating demand is also present, the heating output is enabled according to the configured sequence.

When the door closes, the fan may stop immediately or continue for a defined run-on period. Heating can be disabled according to the selected control logic rather than remaining active solely because the fan is still running.

This separation is useful in shoulder seasons as well as winter. The building may still benefit from an airflow barrier during door opening even when additional heat is unnecessary.

System Architecture

External Door
    |
    `--> Door Contact -----------
                                  
Temperature Condition -----------> Air Curtain Controller
                                      |
                                      |--> Fan Control ----> Air Curtain Fan
                                      |
                                      `--> Heating Output -> Heating Stage / Interface*

* Final connection depends on the air curtain's electrical and heating-control design.

The controller sits between the entrance conditions and the air curtain control inputs. It should not be shown as directly switching loads that exceed its rated output or bypassing the air curtain manufacturer's required contactors, relays or internal controls.

Installation & Commissioning

Before wiring begins, the installer confirms how the air curtain expects to be controlled. Fan stages, heating enable, supply voltage, relay/contact requirements and any internal control terminals are checked against the equipment documentation.

The door contact is then verified for the correct open/closed logic. Its physical position matters: a poorly aligned contact can make the controller believe the door is open when it is not, creating intermittent or continuous operation that looks like a controls fault.

Commissioning is carried out through real entrance events. The team checks door opening, fan response, heating enable conditions, door closing and any configured run-on period. Several quick consecutive openings should also be tested because that is often closer to real retail or lobby traffic than a single open-close cycle.

Finally, the discharge direction and air curtain installation itself are checked. A correct control sequence cannot compensate for a unit that is mounted too high, poorly aimed or undersized for the opening.

Project Results

The entrance air curtain now responds to the condition that creates the problem: door activity. Fan operation no longer has to depend entirely on staff remembering a switch, while the heating function can follow its own temperature requirement rather than being tied permanently to fan operation.

For the building operator, this creates a clearer operating sequence and reduces unnecessary runtime opportunities. For the installer, the controller provides a defined relationship between door contact, temperature condition and equipment outputs that can be tested during commissioning.

The control strategy does not guarantee a fixed energy-saving percentage. Actual performance depends on climate, door traffic, air-curtain sizing, installation height, heating source and the wider HVAC system. Its practical value is better matching operation to entrance demand.

Key Benefits

· Door status becomes an automatic input to air-curtain operation rather than relying only on manual switching.

· Fan demand and heating demand can be treated as separate control decisions.

· Run-on timing can be adapted to entrances with repeated short door-opening events.

· The control sequence is easier for installers to verify because each input and output has a defined role.

· Unnecessary operation can be reduced during periods when the entrance is inactive or additional heating is not required.

· The same control concept can be adapted to different commercial entrance types once the actual air-curtain interface is confirmed.

Where This Solution Fits Best

This approach is relevant to retail stores, supermarkets, showrooms, office lobbies, restaurants and public-facing commercial buildings where external doors open frequently and an air curtain is used to reduce the impact on the indoor environment.

For entrances that remain open continuously, use revolving doors or have a different vestibule strategy, the control sequence may need to be designed differently. The value of door-contact control is highest where door status is a meaningful indicator of when the air barrier is required.

Designing Air Curtain Control for a Commercial Entrance?

CosyClimate provides dedicated air curtain control solutions for commercial entrance applications, including door-related control and coordinated fan/heating operation.

Contact CosyClimate to share air‑curtain electrical interface, fan stages, heating type, door‑contact requirement and operating sequence; we match controller logic to site equipment.