MODULATING ENERGY SAVING CONTROL — This provides for energy savings by reducing pump energy requirements. The control works the same way as modulating standard control with the following exceptions:

• Whenever the unit is not in the cooling mode, or is shut-off, both control valves are closed, preventing water flow through the unit.
• The valves are not proportional. When the economizer valve is active, the bypass valve is closed. If the economizer valve modulates, then water flow through the unit is modulated. If the water is cool enough for economizing but mechanical cooling is also required, the economizer valve is fully open, establishing full water flow through the condensers.

Whenever the water is too warm for economizing, and there is a call for cooling, then the economizer valve is fully closed and the bypass valve is fully open, establishing full water flow through the condensers. Refer to pages 7 through 12 for more information on application advantages.

Airside Economizer

The airside economizer option consists of two parts: the control section within the unit, which is factory installed, and the mixing box which is external to the unit and is field installed.

The filter mixing box actuator and linkage is a one piece assembly. Actuator and linkage are located on the left side of the mixing box (when viewed from the control panel side of unit). The mixing box must be mounted to the unit in the field via a transition piece that is also field installed on the unit.

The mixing box contains two sets of dampers, one for outside air, and one for return air, Configurations available include top and back, bottom and back, and top and bottom.

The airside economizer serves the same purpose as the waterside economizer except that it uses outside air instead of condenser water. An enthalpy control senses outdoor air conditions. When the outdoor conditions are suitable for cooling by economizer, the enthalpy control will permit the economizer to function as the first stage of cooling. The damper position is modulated in response to supply air temperature on VAV units and in response to the zone temperature sensor on Constant Volume units to maintain supply air setpoint or zone temperature setpoint respectively. If additional cooling is required, compressor operation is initiated.

When outdoor conditions are not suitable for cooling by the economizer, the enthalpy control will disable the economizer function and return the fresh air damper to the minimum position setting.

Refer to pages 7 through 12 for more information on application advantages.

Electric Heat

Electric heat is a factory installed option. A single kw rating is available for each unit size. (Refer to the data section of this catalog for sizes.) A single source power connection to the unit is all that is required, even with the electric heat option. All heaters are for 60 Hz, 3 phase power supply.

The heaters are of open coil construction and are located within the unit casing at the fan discharge.

The electric heat is controlled by the local HVAC system control, and can be used for night heat, morning

• Programmable night heat morning
• Night heat morning warmup
• ICS InterFace

Non-Fused Disconnect Switch

The unit disconnect switch consists of a non-automatic circuit breaker which is mounted inside the control panel. The switch is operable without opening any unit panels.

Condensing Pressure Control Valve

The condensing pressure control valve option is available only on units which do not have a waterside economizer. This electric valve  modulates water flow through the condenser in response to the unit control module to maintain refrigerant head pressure within an acceptable range.

Whenever the unit is not in the cooling mode, or is shut off, the condensing pressure control valve is closed, preventing water flow through the unit. This valve is factory installed in the unit. It will be extremely difficult to install in the field. If required, order this option prior to unit shipment.

Filters

Construction Throwaway — two inch flat face throw away fiberglass filters. After construction and startup is completed, these filters should be replaced with medium velocity throwaway or high velocity cleanable filters.

Medium Velocity Throwaway — two inch disposable medium efficiency pleated filters. These filters will need to be replaced periodically.

High Velocity Cleanable — two inch permanent metal type filters. These filters must be cleaned periodically.

Optional Evaporator Fan Motors

Both the VAV and constant volume units have open drip-proof T-frame motors as standard. The efficiency of these motors averages approximately 88%. Refer to the unit data section for available motors for each unit size. In addition to the standard motor, the following optional motors are available: warm-up heat, or daytime heat.

• Totally enclosed fan cooled (TEFC) Electric heat is available only on units motors are available for each unit in with the following system control the same sizes as the standard open options: drip-proof motors.
• High efficiency motors are available warmup in open drip-proof construction in the same sizes as standard motors. The efficiency of these motors is approximately 91% .

Vibration Isolators (Field installed)

Each unit ships with isolation pads constructed of molded neoprene to be set under the unit. This will provide sufficient isolation in most applications. Refer to the Applications Section, pages 7 through 12, for further information.