HyperStat Split - 4Pipe Unit Ventilator Economizer

| Overview

A Unit Ventilator is a self-contained HVAC (Heating, Ventilation, and Air Conditioning) device typically installed along the exterior wall of a room, such as a classroom, office, or hotel room. Its main job is to provide heating, cooling, and ventilation for a single Space.

The 4-Pipe Unit Ventilator profile extends 75F's out-of-the-box smart control capabilities to legacy unit ventilators—making them more intelligent, improving comfort, and enhancing energy efficiency for customers.

Built on the Hyperstat Split architecture, the solution uses the Hyperlight for standalone algorithm execution, communicating over RF to the CCU and via a two-wire PR connection to the Connect Module, which then interfaces with the unit ventilator. The profiles offer flexible configuration options—such as fan speeds, damper control, heating stages, water valves, and universal inputs—including a mandatory supply-water-temperature input for mode determination. The profile is fully configurable based on whether control is through a face-and-bypass damper or a modulating valve.

| How It Works

• Indoor Air Recirculation: It draws in room air, conditions it (heats or cools), and circulates it back into the space.
• Outdoor Air Intake: It pulls in a controlled amount of fresh outdoor air to improve indoor air quality or to provide free cooling.
• Mixing Chamber: Indoor and outdoor air are mixed before being conditioned and distributed.
• Heating/Cooling Coil: Uses hot water, steam, or chilled water (or sometimes DX refrigerant) to adjust air temperature.

Bypass Damper:  Used to control airflow direction, allowing air to bypass the heating/cooling coil when temperature conditioning is not required. This improves energy efficiency and maintains desired ventilation rates.

| Usage

The Unit Ventilators are primarily used in classrooms in schools and colleges. It can also be an excellent HVAC option for:

• Hotels
• Dormitories
• Small offices

| Advantages

The unit ventilator comes with the following advantages

• Easy to install and maintain
• Provides both ventilation and conditioning
• Independent zone control
• Good for retrofitting older buildings
• Prevents cross-contamination between zones

| HS Split 4 Pipe Unit Ventilator Profile

The 75F HyperStat 4 Pipe Unit ventlator profile is a standalone profile that provides heating, cooling, and Economizer equipment controls for conditioning.

HyperStat split is a combination of Hyperlite and the Connect Module.

The Hyperlite module is mounted inside the room, providing the room Temperature, Humidity & IAQ sensing.

The Connect module is mounted on the Unit Ventilator to provide the necessary conditioning based on the temperature and IAQ sensed.

For more information on the HyperStat Split device and its mounting, refer to HyperStat Split Overview & Installation

It provides the flexibility to choose between fully modulating and staged equipment control. Possible equipment configurations include:

• Cooling Water Valve Control
• Heating Water Valve Control
• 3 Stages of Fan Speed Controls with additional Fan speed during ventilation.
• 2 Stage Auxiliary Heating Controls
• Fan Enable and Occupied Enable control
• Humidifier and Dehumidifier control
• Face & Bypass Damper Control
• DCV Damper Control
• Humidifier, Dehumidifier Control, Externally Mapped Control.
• 8 Digital/Analog/Thermistor-based Universal Inputs to accommodate varied forms of input, as provided below in the Configuration parameters section table.

| Wiring

The following is a sample wiring illustrated for a HyperStat Split.

The wiring for the communication and power to the HyperLite is connected to POR A, B of Connect Module to Normal A & B of Lite. 

The Table below provides more information on the wiring of the Hyperstat Split.

The Connect Module further features an additional OWI interface to connect 75F OWI-compatible sensors.

For more information on the jumper, refer to the HyperStat Split Overview & Installation.

| Setting Connect Module to HyperStat Split Mode

The Connect module can operate in three modes based on the profile and the usage for which it is being used.

• By default, the Connect module is configured to operate in split mode, supporting HyperStat Split-based profiles. The same can be visualized in the Communication Options screen of the Connect module UI as below.

| Configuration Steps

From the CCU floor layout screen.

• Click Pair Module.

The Select device type screen is displayed.

• Select the HyperStat Split device type.

The select module type screen is displayed.

• Select the Unit Ventilator: 4 Pipe with Economizer.

The pairing process steps screen is displayed.

• Click Pair to start the pairing process.

Setting HyperLite to Pairing Mode

From the Home screen.

• Press the '+' and '-' navigation buttons together on the home screen.

The Inputs screen displays.

• Press the next navigation button to navigate to the installer option screen

• Press the down arrow    to navigate to the Pair with CCU option.

• Press the select button to set the Hyperlite to pairing mode.

The advertising screen broadcasts the Bluetooth address of the Hyperlite

• Click Pair

• Click the Bluetooth address of the Hyperlite

The window to enter the pairing pin from the device displays

• Locate the pin generated from the Hyperlite screen.

• Enter the PIN as displayed on the device.

• Click Pair to confirm

The pairing would take a few minutes and the configuration screen for the profile displays

Alternatively, to manually pair the hyperstat split, refer to Alternate or Manual Pairing of HyperStat Split

| Configuration Parameters

| Device Settings

The following are a few device settings that can be configured.

• Display in the device home screen provides the option to enable the sensor values to be displayed on the device home screen.
• PIN Lock provided the options to enable different PIN-based locks available on the device.
• Miscellaneous settings provide options to enable other settings.

| Configuration

• Configure the required parameters as shown below.

Sensor Bus Addresses

Relay-Based Controls

Analog-Based Output Controls & Universal Inputs

Analog Out Voltages at Fan Speeds & Different Dampers Controls

Outside Damoer Min positions and CO2 Damper opening Rate, IAQ Thresholds & Targets 

Device Settings

• Click Save to confirm the configuration.

| Post Configuration in CCU

Post configuration, the 4- pipe Unit Ventilator profile would reflect in CCU, as shown below.

| Post Configuration in Portals

Post configuration, the 4-pipe Unit Ventilator profile would reflect in portals, as shown below.

| OAO Controls and Operation

| Control System Object List

| Sequence of Operation

The sequence of operation is completely driven based on Occupancy mode,  Space Current Temperature, the set Cooling and Heating Desired Temperatures, Supply Water temperature, and Space CO2 levels.

Let us understand the Sequence of operations based on the occupancy modes, and how the other factors contribute to the sequence of operations during different types of occupancy modes.

| Occupancy Modes

The occupancy mode (Occupied or Unoccupied) shall be determined through a user-adjustable, graphical, seven-day schedule with a holiday schedule, alongside the configurable autoaway and forced occupied options (external schedule influencers) for optimized controls and enhanced energy savings.

Based on the above aspects factoring into the occupancy, the following can be the possible applicable occupancy modes:

• Pre- Conditioning
• Occupied
• Unoccupied
• Auto-Away
• Forced Occupied

| Sequence of Operation During Pre-Conditioning

Warm-up:

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning warm-up via HeatingLoopOutput / Auxillary Heating Stages, as below.
• The HeatingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on HeatingLoopOutput (FanLoopOutput= HeatingLoopOutput* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

If the heating load is not met, then:

• Then the Auxiliary heating stages are enabled.
  • Current temp= Heating Desired - auxHeating1Activate (3F) = AuxHeating1 enabled, where 3F is a tuner value
  • Current temp= Heating Desired -2F= AuxHeating1 off
  • Current temp= Heating Desired - auxHeating2Activate (4F)= AuxHeating2 enabled, where 4F is a tuner value
  • Current temp= Heating Desired -3F= AuxHeating2 off

• Fan stages ramp up based on the Auxiliary Heating stages.
• The dcvLoopOutput is disabled.
• OAO is disabled

Pre-cooling:

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning pre-cooling via CoolingLoopOutput, as below.
• The CoolingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on CoolingLoopOutput (FanLoopOutput= CoolingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.
• The  Auxiliary heating stages are disabled.
• The dcvLoopOutput is disabled.
• When OAO is favorable based on the conditions specified under the OAO operation section,  the OAOLoopOutput is enabled with the modulating between the analogOutxAtMinOAODamper  and analogOutxAtMaxOAODamper.

| Sequence of Operation During Occupied

At all occupied times: (based on a set schedule)

• The device maintains a space temperature within the Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

• A minimum fan speed is maintained, and the minimum fan analog voltages are set to 2V (customizable) for linear fans, and a recirculation fan speed voltage for staged fans.
• The DCV operation will be active during the deadband as well as the MAT safety check will be running. 

During Heating:

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning warm-up via HeatingLoopOutput / Auxillary Heating Stages, as below.
• The HeatingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on HeatingLoopOutput (FanLoopOutput= HeatingLoopOutput* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

If the heating load is not met, then:

• Then the Auxiliary heating stages are enabled.
  • Current temp= Heating Desired - auxHeating1Activate (3F) = AuxHeating1 enabled, where 3F is a tuner value
  • Current temp= Heating Desired -2F= AuxHeating1 off
  • Current temp= Heating Desired - auxHeating2Activate (4F)= AuxHeating2 enabled, where 4F is a tuner value
  • Current temp= Heating Desired -3F= AuxHeating2 off

• Fan stages ramp up based on the Auxiliary Heating stages.
• The dcvLoopOutput is disabled.
• OAO is disabled
• When the space CO2 level is above the CO2 threshold set, the dcvLoopOutput is enabled with the dcvCalculatedDamperPos = (sensorHyperStatCo2 - zoneCO2Threshold )/zoneCO2DamperOpeningRate, modulating between the analogOutxAtMinDCVModulationDamper and analogOutxAtMaxDCVModulationDamper
• OAO is disabled.

During Cooling:

• When the space current temperature is above the Cooling Desired Temperature,. the CoolingLoopOutput is enabled as below.
• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning pre-cooling via CoolingLoopOutput, as below.
• The CoolingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on CoolingLoopOutput (FanLoopOutput= CoolingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.
• The  Auxiliary heating stages are disabled.
• When the space CO2 level is above the CO2 threshold set, the dcvLoopOutput is enabled with the dcvCalculatedDamperPos = (sensorHyperStatCo2 - zoneCO2Threshold )/zoneCO2DamperOpeningRate, modulating between the analogOutxAtMinDCVModulationDamper and analogOutxAtMaxDCVModulationDamper
• When OAO is favorable based on the conditions specified under the OAO operation section,  the OAOLoopOutput is enabled with the modulating between the analogOutxAtMinOAODamper  and analogOutxAtMaxOAODamper.

| Sequence of Operation During AutoAway

• The range of Heating Desired Temperature and Cooling Desired Temperature drifts further away.
• The device maintains a space temperature within the newly set Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

• FanLoopOutput, HeatingLoopOutput, Auxiliary Heating Stages & CoolingLoopOutput, are disabled.

During Heating:

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning warm-up via HeatingLoopOutput / Auxillary Heating Stages, as below.
• The HeatingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on HeatingLoopOutput (FanLoopOutput= HeatingLoopOutput* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

If the heating load is not met, then:

• Then the Auxiliary heating stages are enabled.
  • Current temp= Heating Desired - auxHeating1Activate (3F) = AuxHeating1 enabled, where 3F is a tuner value
  • Current temp= Heating Desired -2F= AuxHeating1 off
  • Current temp= Heating Desired - auxHeating2Activate (4F)= AuxHeating2 enabled, where 4F is a tuner value
  • Current temp= Heating Desired -3F= AuxHeating2 off

• Fan stages ramp up based on the Auxiliary Heating stages.
• The dcvLoopOutput is disabled.
• OAO is disabled.

During Cooling:

When the space current temperature is above the Cooling Desired Temperature,. the CoolingLoopOutput is enabled as below.

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning pre-cooling via CoolingLoopOutput, as below.
• The CoolingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on CoolingLoopOutput (FanLoopOutput= CoolingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.
• The  Auxiliary heating stages are disabled.
• The dcvLoopOutput is disabled.
• When OAO is favorable based on the conditions specified under the OAO operation section,  the OAOLoopOutput is enabled with the modulating between the analogOutxAtMinOAODamper  and analogOutxAtMaxOAODamper.

| Sequence of Operation During Unoccupied

• The range of Heating Desired Temperature and Cooling Desired Temperature drifts further away.
• The device maintains a space temperature within the newly set Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

• FanLoopOutput, HeatingLoopOutput, Auxiliary Heating Stages & CoolingLoopOutput, are disabled.

During Heating:

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning warm-up via HeatingLoopOutput / Auxillary Heating Stages, as below.
• The HeatingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on HeatingLoopOutput (FanLoopOutput= HeatingLoopOutput* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

If the heating load is not met, then:

• Then the Auxiliary heating stages are enabled.
  • Current temp= Heating Desired - auxHeating1Activate (3F) = AuxHeating1 enabled, where 3F is a tuner value
  • Current temp= Heating Desired -2F= AuxHeating1 off
  • Current temp= Heating Desired - auxHeating2Activate (4F)= AuxHeating2 enabled, where 4F is a tuner value
  • Current temp= Heating Desired -3F= AuxHeating2 off

• Fan stages ramp up based on the Auxiliary Heating stages.
• The dcvLoopOutput is disabled.
• OAO is disabled.

During Cooling:

When the space current temperature is above the Cooling Desired Temperature,. the CoolingLoopOutput is enabled as below.

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning pre-cooling via CoolingLoopOutput, as below.
• The CoolingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on CoolingLoopOutput (FanLoopOutput= CoolingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.
• The  Auxiliary heating stages are disabled.
• The dcvLoopOutput is disabled.
• When OAO is favorable based on the conditions specified under the OAO operation section,  the OAOLoopOutput is enabled with the modulating between the analogOutxAtMinOAODamper  and analogOutxAtMaxOAODamper.

| Sequence of Operation During Forced Occupied

• The range of Heating Desired Temperature and Cooling Desired Temperature drifts further away.
• The device maintains a space temperature within the newly set Heating Desired Temperature and Cooling Desired Temperature Range.

During Deadband:

• FanLoopOutput, HeatingLoopOutput, Auxiliary Heating Stages & CoolingLoopOutput, are disabled.

During Heating:

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning warm-up via HeatingLoopOutput / Auxillary Heating Stages, as below.
• The HeatingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on HeatingLoopOutput (FanLoopOutput= HeatingLoopOutput* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.

If the heating load is not met, then:

• Then the Auxiliary heating stages are enabled.
  • Current temp= Heating Desired - auxHeating1Activate (3F) = AuxHeating1 enabled, where 3F is a tuner value
  • Current temp= Heating Desired -2F= AuxHeating1 off
  • Current temp= Heating Desired - auxHeating2Activate (4F)= AuxHeating2 enabled, where 4F is a tuner value
  • Current temp= Heating Desired -3F= AuxHeating2 off

• Fan stages ramp up based on the Auxiliary Heating stages.
• The dcvLoopOutput is disabled.
• OAO is disabled.

During Cooling:

When the space current temperature is above the Cooling Desired Temperature,. the CoolingLoopOutput is enabled as below.

• If the space temperature is below the occupied heating temperature setpoint, the pre-conditioning shall initiate the morning pre-cooling via CoolingLoopOutput, as below.
• The CoolingLoopOutput is mapped to the Water valve loop output
• The FanLoopOutput is enabled based on CoolingLoopOutput (FanLoopOutput= CoolingLoopOuptut* analogFanSpeedMultiplier(1)), which is mapped to the relay or analog-based fan speeds.
• The  Auxiliary heating stages are disabled.
• The dcvLoopOutput is disabled.
• When OAO is favorable based on the conditions specified under the OAO operation section,  the OAOLoopOutput is enabled with the modulating between the analogOutxAtMinOAODamper  and analogOutxAtMaxOAODamper.

| Sequence of Operation During Emergency Conditioning

when building limits are violated, and the recorded temperature is within the building limit plus leeway the conditioning will happen in the direction of zone load.

| Sequence of Operation During Temp Dead

And, When the Building temperature breaches the building limits, beyond the leeway limits all the following loops are disabled:

• CoolingLoopOutput
• HeatingLoopOutput
• Auxiliary Heating Stages
• FanLoopOutput
• dcvLoopOutput
• Outside Air Loop Output

| Humidifier Control

The humidifier is turned ON whenever the humidity level for the system drops below the targetMinInsideHumidty set. The humidifier will be turned OFF after being turned on when the humidity levels go humidityHysteresis above the targetMinInsideHumidty. Humidity control will not be maintained during UNOCCUPIED or VACATION modes.

| DeHumidifier Control

If the dehumidifier is selected, it turns ON whenever the humidity level for the system goes above the targetMaxInsideHumidty set. The dehumidifier will be turned OFF after being turned on when the humidity drops humidityHysteresis below the targetMaxInsideHumidty. Dehumidifier control will not be maintained during UNOCCUPIED or VACATION modes.

Note: The humidity level for the system is either the average level reported by all the zones serviced by the RTU/AHU.

| Control Mode Summary

| Difference Between Fan Low & Fan Low Ventilation

• If fan low ventilation is mapped to one of the Relay, it would be ON whenever Fan Loop Output = 0 during the scheduled occupied period.
• And would be ON when Fan Loop Output > 0 during the unoccupied period.
• If Fan Medium and Fan High are mapped to other Digital Outs, then Fan Low Ventilation would be ON up to 33%+ relayActivationHysteresis/2 of the fan loop
• Fan Medium will be ON when Fan Loop Output > 33%+relayActivationHysteresis/2, and will turn OFF when Fan Loop Output <=33% - relayActivationHysteresis/2
• Fan High will be On when Fan Loop Output > 66% +relayActivationHysteresis/2  and  will turn OFF when Fan Loop Output <=66% - relayActivationHysteresis/2

Below is an illustration for the same:

Whereas 

• If fan low is mapped to one of the relays, it would be ON whenever Fan Loop Output = relay activation Hysterresis/2 during the scheduled occupied period.
• The other control stages activation and deactivation remain as its in the above section.

| Control Via Face and Bypass Damper Arrangement

Face and Bypass Damper is an arrangement that is part of the Unit Ventilator equipment, which iss used to regulate airflow and control the temperature of conditioned air without directly varying the heating or cooling coil water flow. Here’s how it works:

Face Damper

• Directs air through the heating or cooling coil.

• Used when active conditioning (heating or cooling) of air is required.

• Ensures the air passing through the coil is conditioned before being supplied to the space.

Bypass Damper

• Directs air around the coil instead of through it.

• Used when less heating/cooling is needed.

• Helps in fine control of supply air temperature by mixing bypassed (unconditioned) air with conditioned air.

How It Works Together

• The face and bypass dampers modulate inversely:

  • If the face damper opens more → more air goes through the coil.

  • If the bypass damper opens more → more air bypasses the coil.

• This modulation provides stable temperature control without frequent adjustments to coil water valves.

• Helps maintain comfort, improves efficiency, and reduces wear on coil control valves.

| Supply Air Temperature (SAT) Tempering Control Sequence

Unit ventilator profile provides the option to operate heat, if so equipped, to maintain a minimum supply air temperature during conditions where cold outdoor air causes the Supply Air Temperature to fall below the configured SA Tempering Setpoint. This occurs typically during periods when DCV is active, heating loop is 0 and increasing the amount of outdoor air to maintain min ventilation air for code compliance. Tuner called Supply Air Tempering Setpoint would be introduced for 4P Unit ventilator and the default value would be 70 F. SA Tempering will work when CO2 sensor value is less than CO2 threshold and DCV loop is 0. For SAT Tempering to work the following conditions should be true: 

• SAT should be mapped to either sensor bus or inputs
• SAT Tempering toggle should be turned on. When SA tempering toggle is turned on, validations would exist to ensure that the Heating water valve (either on analog or relay) is mapped along with Fan low ventilation speed, the Supply Air Temperature sensor and the OA damper is mapped. 
• SA Tempering Loop will be zero when the Supply Air Temperature sensor value is greater than SA Tempering Setpoint. 

SA Tempering Loop would be calculated based on a PI loop operated between SAT Sensor and SA Tempering Setpoint. MAT safety regulation is applicable , which is outlined in MAT safety regulation section.When SA tempering is active, the Face & Bypass Damper (relay or analog) needs to be operated based on SA tempering loop. F&B Damper if mapped to relay would be activated based on F&B damper relay activation hysteresis, and if mapped to analog, would be scaled between analog min and max based on SA tempering loop. 

| Test Signal

This is used for troubleshooting and testing the equipment if the configuration and the field setup are in sync, and the device is communicating properly with the controlled equipment. Also at any point, you can override the value of the output the algorithm decides. 

We can use the test signal for relays to turn them on or for analog out to ramp up and see if the equipment works according to commands from the device.

Test Signal Time Out

once enabled it will be active for an hour if the screen is not changed, after an hour of no interaction on the screen.  zone screen displays and the test signal will be OFF.

If the screen changes from the test signal configuration screen it will be timed out in one minute (time for the algorithm to run next).

Note: The test signal for modulating output is in deci volts, ranging from 0.0dV to 100.0dV.