Trane OABE OADE OAKE OANE (Water Source Heat Pump) Katalog
20
OAU-PRC003A-EN
Application Considerations
Many dedicated outdoor air systems supply reheated air directly to terminal units or to spaces that
have terminal units performing local sensible cooling. This results in the local terminal units re-
cooling the previously re-heated outdoor air. Resetting the supply air dry-bulb temperature of the
Outdoor Air Unit offers the opportunity to minimize the amount of time re-cooling occurs. Refer to
have terminal units performing local sensible cooling. This results in the local terminal units re-
cooling the previously re-heated outdoor air. Resetting the supply air dry-bulb temperature of the
Outdoor Air Unit offers the opportunity to minimize the amount of time re-cooling occurs. Refer to
for more information.
Cooling Setpoint
Because the Trane OAU dehumidifies the outdoor air by cooling it, this cool outdoor air can reduce
the sensible cooling load on the local terminal unit. At low space sensible loads, the cool outdoor
air may sub-cool the space, causing the local terminal unit to add heat (new energy heat).
Therefore, reset occupied Space Cooling Setpoint (SPCS—Space Control Sequence) or Evaporator
Cooling Setpoint (ECS—Outdoor Air Control Sequence) of the OAU to minimize space sensible re-
cooling so the terminal unit with the lowest sensible load is almost at zero cooling capacity (within
the limit of the dew point setpoint). To take full advantage of space demand based dry-bulb reset,
you may need to size some of the local terminal units based on neutral outdoor air temperature.
This strategy will more effectively manage occupant comfort during seasonal changeover for two-
pipe terminal unit systems. Because the OAU is not connected to the chiller or boiler plant,
accomplish this by resetting the Outdoor Air Unit SPCS or ECS to keep the critical zone at zero
heating capacity when the boiler is off and zero cooling capacity when the chiller is off. A Trane
Integrated Comfort™ system can provide this control capability.
the sensible cooling load on the local terminal unit. At low space sensible loads, the cool outdoor
air may sub-cool the space, causing the local terminal unit to add heat (new energy heat).
Therefore, reset occupied Space Cooling Setpoint (SPCS—Space Control Sequence) or Evaporator
Cooling Setpoint (ECS—Outdoor Air Control Sequence) of the OAU to minimize space sensible re-
cooling so the terminal unit with the lowest sensible load is almost at zero cooling capacity (within
the limit of the dew point setpoint). To take full advantage of space demand based dry-bulb reset,
you may need to size some of the local terminal units based on neutral outdoor air temperature.
This strategy will more effectively manage occupant comfort during seasonal changeover for two-
pipe terminal unit systems. Because the OAU is not connected to the chiller or boiler plant,
accomplish this by resetting the Outdoor Air Unit SPCS or ECS to keep the critical zone at zero
heating capacity when the boiler is off and zero cooling capacity when the chiller is off. A Trane
Integrated Comfort™ system can provide this control capability.
Unoccupied Space Humidity Control
The Horizon™ OAU provides conditioned outdoor air for the ventilation and/or make-up air needs
of a building during occupied hours. It can also limit building relative humidity during unoccupied
hours. To do this, provide a return air path to the OAU and place a relative humidity sensor in the
space served by the OAU or in a common relief air path (like a return corridor) if the OAU serves
multiple spaces. The unit will cycle as required to limit the space humidity to the unoccupied
Dewpoint Setpoint (NSDS) setpoint. Reheat and return air damper options are required for this
operation. For dedicated outdoor air systems ducted to terminal units, these units must cycle with
the operation of the Horizon OAU. A Trane Integrated Comfort™ system can provide this control
capability.
of a building during occupied hours. It can also limit building relative humidity during unoccupied
hours. To do this, provide a return air path to the OAU and place a relative humidity sensor in the
space served by the OAU or in a common relief air path (like a return corridor) if the OAU serves
multiple spaces. The unit will cycle as required to limit the space humidity to the unoccupied
Dewpoint Setpoint (NSDS) setpoint. Reheat and return air damper options are required for this
operation. For dedicated outdoor air systems ducted to terminal units, these units must cycle with
the operation of the Horizon OAU. A Trane Integrated Comfort™ system can provide this control
capability.
Space Control
For single space applications, the Horizon OAU can control space temperature and limit space
relative humidity. To do this, size the airflow to meet whichever is the highest: the space loads and
ventilation and/or make-up air needs of the application. Install a temperature sensor in the space
to provide temperature control and reset the supply air temperature. If reset of the supply air dew
point is desired, install a space relative humidity sensor in the space to provide relative humidity
limit control.
relative humidity. To do this, size the airflow to meet whichever is the highest: the space loads and
ventilation and/or make-up air needs of the application. Install a temperature sensor in the space
to provide temperature control and reset the supply air temperature. If reset of the supply air dew
point is desired, install a space relative humidity sensor in the space to provide relative humidity
limit control.
Outdoor Airflow Balancing
Establish final unit airflow through a field air balancing procedure. Change the fan speed through
replacement or fan sheave adjustment (belt drive indoor fan motor) or VFD Setpoint via the UC600
controller (direct drive fan motor).
replacement or fan sheave adjustment (belt drive indoor fan motor) or VFD Setpoint via the UC600
controller (direct drive fan motor).
Air to Air Energy Recovery
Energy recovery can significantly reduce HVAC system first-cost and operating energy costs.
You can use recovered energy for two purposes:
You can use recovered energy for two purposes:
1.
to temper or reheat supply air for independent control of sensible and latent capacity, or
2. to precondition outdoor air as it enters the building for ventilation.
The Horizon™ OAU offers refrigerant heat recovery for reheating the supply air. To precondition