VACH Slot Options

For years, personal comfort in a building was an unattainable ideal due to the prohibitive cost of individual zone controls. Typical zones include multiple offices or spaces that are controlled by one thermostat to reduce costs.

Occupant comfort is compromised due to this “one size fits all” approach. This situation is compounded in perimeter zones where linear slot diffusers are typically utilized. The VACH linear slot diffuser is specifically designed to solve this problem by offering a self-contained perimeter VAV zone in a single unit.

The VACH is unique in that it is full VAV in both the heating and cooling modes in addition to automatically changing between modes and optimizing discharge direction.


• Automatic change over knows when to adjust the flow from horizontal cooling to vertical heating.

• Existing systems are easily upgraded with the various diffusers available.


The VACH diffuser is similar to the LAD in that it automatically changes between the cooling and heating modes and also varies the direction of airflow for cooling and heating for optimal comfort. Where the VACH is unique is that it is also a VAV linear diffuser in both the cooling and heating modes.

A small amount of supply air is bypassed within the diffuser to serve two purposes. The supply air is passed over a thermostatic device to determine if the diffuser should be in the heating or in the cooling mode. The thermostatic device repositions the diffuser’s center blade to optimize the direction of discharge – horizontally along the ceiling in cooling and vertically downward in heating.

The second purpose of the bypass air within the diffuser is to induce a sample of room air over a second thermostatic control device. This device automatically varies the opening size from full open to full closed (in both heating and cooling modes) to modulate supply air as necessary to meet the zone setpoint. Optimal comfort is thus obtained in either case.

The zone setpoint and changeover temperatures are fully adjustable on the diffuser.


The VACH is a variable discharge opening diffuser. The room air temperature setting will vary the air supply volume. The operation of the VACH unit will provide room temperature control in the following configurations: vertical-VAV warm air flow; horizontal-VAV cooling air flow. All VAV-linear diffusers are factory calibrated to 72° room temperature plus or minus 2°. If room temperature adjustment is required, turning the room actuator located in the square opening on the face of the unit, clockwise rotation will lower room temperature; counter-clockwise rotation will raise the room temperature.

Cooling Cycle:
Supply air temperature range: approx. 68° or below. Room temperature range: greater than 73° /blade position will respond with appropriate horizontal volume discharge. Room temperature ranges: less than 73° /fully closed blade position.

Heating Cycle Change Over:
Supply temperature range: approximately 85° Room temperature range: less than 72° /blade position will respond with appropriate vertical volume discharge. Room temperature range: greater than 73° /full closed blade position.


Room air induction is created by a simple, but highly effective induction trough. A small amount of supply air is diverted out and through the induction trough at the top of the VACH plenum box. This causes room air to be induced into a small slot at the end of the VACH face. The sample of room air is drawn directly over the thermal actuator.


The coanda effect will be maintained and the throw will remain constant throughout a full-open to a minimum horizontal flow range.

All advantages of vertical heating are enhanced by the automatic discharge opening volume adjustment.