TEMPMASTER
50
FORM TPM3-EG1 (518)
Powered Variable Volume Exhaust - Discharge Damper Controlled
This optional variable volume powered exhaust system consists of a fixed speed fan con-
figured with a proportionally controlled discharge damper. The unit controller monitors the
pressure inside the building and controls the exhaust damper and the exhaust fan. If the
building pressure rises, the exhaust damper is proportionally controlled open and the ex-
haust fan is controlled ON. If the building pressure falls, the exhaust damper is proportion-
ally controlled closed and the exhaust fan is controlled OFF. The position of the exhaust
damper in which the exhaust fan is controlled ON and OFF as well as the building pressure
setpoint are user selectable from the user interface.
Powered Variable Volume Exhaust - VFD Controlled
This optional variable volume powered exhaust system consists of an exhaust fan driven
by a variable frequency drive (VFD), which is controlled by the unit controller. The unit
controller monitors the pressure within the building. As the pressure rises, the VFD is
controlled to increase exhaust fan speed. As the pressure falls, the VFD is controlled to
decrease exhaust fan speed. The building pressure setpoint is user selectable from the
user interface. ON/OFF control is maintained the same as exhaust-discharge damper
control stated above.
Return Fan Controlled
This optional variable volume powered return fan system consists of two return fans con-
trolled by one VFD that is controlled by the unit controller. The VFD is controlled to maintain
a slightly positive pressure over the mixing box section to prevent reverse flow. As the return
and/or exhaust air dampers open, the return plenum pressure drops and the fan will speed
up to maintain pressure. When the return and/or exhaust air dampers close, the return ple-
num pressure increases causing the VFD to slow the fan speed down.
LOW AMBIENT/HEAD PRESSURE CONTROL OPERATION
The unit controller continuously monitors the OAT to determine if mechanical cooling
should be allowed. As a safety, if the OAT falls to or below the low ambient lockout tem-
perature, mechanical cooling is prevented from operating. For units with economizers,
the low ambient lockout temperature is typically low enough that mechanical cooling will
rarely be required. However, for some applications mechanical cooling is required when
the OAT is lower than the low ambient lockout temperature.
For these applications, the unit must be equipped with optional low ambient controls.
For optional low ambient operation, the unit controller monitors the refrigeration system
discharge pressure and takes measures to limit the flow of air across the condenser coil.
With the optional low ambient controls, mechanical cooling is allowed down to an OAT of
0.0°F.
SMOKE PURGE SEQUENCES
General
The controls of the TempMaster OmniElite are designed as standard with a ventilation
override sequence to remove, exhaust, or ventilate smoke, fumes, or other airborne con-
taminates from the occupied space. This feature offers three selectable operations: purge,
pressurization, and evacuation. The sequence is activated via one of three binary inputs.
A few typical contact closures include smoke detectors, fire alarms, and manual switches.
Controls (Cont'd)
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