| Options (cont.) 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. |
