Operations
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CAT 258 • REBEL APPLIED ROOFTOP
Operations
These are example operations of typical system applications.
The MicroTech 4 controller provides flexbility beyond these
sequences. Contact your local sales rep to discuss specific
application sequences.
General
The MicroTech 4 controller provides users with full control
over unit operation, occupancy, optimal start functionality,
and scheduling. Advanced functionality like discharge air
temperature reset, smoke controls, refrigeration and filter load
monitoring and others are also available.
The MicroTech 4 can be configured to interact with up to (3)
Analog or Network Space Sensors and up to (2) Humidity
Sensors. These sensors can be set to operate the unit based
on the highest, lowest or average reading across the sensors.
Single Zone Variable Air Volume
Single Zone VAV control operates the unit as a single VAV
box. The cooling is controlled to maintain a discharge air
temperature setpoint and the supply fan is modulated to
maintain a space temperature setpoint, the occupied cooling
and occupied heating setpoint.
Variable Air Volume
Variable Air Volume control operates the supply fans to
maintain a duct pressure setpoint. The duct pressure varies as
the VAV boxes throughout the served spaces modulate based
on load. The cooling is controlled to maintain a discharge
air temperature setpoint and the supply fan is modulated to
maintain a space temperature setpoint, the occupied cooling
and occupied heating setpoint.
100% Outside Air Application
100% Outside Air Systems can be configured to supply neutral
temperature, dehumidified air or to provide cooling to the
space. The cooling is controlled to maintain a discharge air
temperature setpoint and the supply fan is configured to deliver
the correct ventilation volume using airflow measuring, CO
2
,
building pressure and more. Dehumidificiation is controlled
using outdoor and/or space humidity sensors and free
reheat is used to control the supply air temperature during
dehumidification operation.
Building Pressure Control
Units equiped with return or exhaust fans can be configured
to control building pressure directly or via several indirect
methods like, fan tracking, flow differential control, duct
pressure control, or airflow control.
Outdoor Air Control
Units may be configured with a 100% outdoor air (OA) damper,
a 0-100% OA Economizer, or a 0-30% OA damper. During
occupied, normal operation, units with a 0-30% OA or 0-100%
OA economizer damper control to a minimum outdoor air
position which is determined from a number of control factors,
including fans speed, CO
2
or other reset methods. During
economizer operation, dampers will open beyond the minimum
outdoor air control to provide free cooling.
If a unit is equipped with a 0-100% Outside Air Economizer,
and the outdoor air is suitable for free cooling, the unit
attempts to satisfy the cooling load by using the outdoor air
before using mechanical cooling. If the control temperature is
above the Occupied Cooling Setpoint by half the deadband
and the outdoor air is suitable for free cooling, the unit will
enter the Econo State. Outdoor air suitability for free cooling
is determined based on the type of economizer selected.
Economizer can be selected based on Comparative Drybulb,
or Comparative Energy/Enthalpy control. Economizer fault
diagnostics are available to provide a warning alarm indication
of over economizing, under economizing, stuck dampers and
excess outdoor air.
Energy Recovery
Energy Recovery is provided by drawing outside air across half
of an energy recovery wheel and drawing exhaust air across
the other half. Latent and sensible heat is transferred from
the hotter, moister air stream to the colder dryer air stream. In
summer operation the direction of transfer is from the outdoor
air to the exhaust air. In winter operation, the direction of
transfer is from the warm exhaust air to the cold dry outdoor
air. Control of the wheel consists of start and stopping the
wheel, and modulating the speed. The outdoor air dampers
and supply and exhaust fans are controlled normally during
wheel operation. Frost prevention is controlled using a VFD or
an electric preheater coil on the energy recovery device.
Summary of Contents for DPSA
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