Operation
Sequence of Operation
Automatic 3-minute
Compressor Lockout
After the compressor cycles off, it will not restart for three minutes. This feature prevents the compressor from short cycling and extends the overall life.
Automatic 2nd Stage Electric Heat (PTHE only)
If the room temperature falls to 2.5°F below the setpoint temperature or the unit compressor fails, the reverse cycle heat is shut off and the electric heat is turned on.
Indoor Room Freeze
Protection
When the unit senses room temperatures of 40°F or below, the unit activates the indoor fan motor and either the electric resistance heater or the hydronic heater to help prevent pipes or fixtures from freezing.
This also overrides the Energy Management System input for unit mounted or wall mounted display modules
Random Restart Function
This function allows random restart of the PTAC units in the event of a power outage. The restart delay reduces the initial inrush current from the building to help prevent a second power outage caused by too much current draw.
The random restart function will occur after every power up cycle by delaying the operation of the unit for 0 to 90 seconds. Compressor minimum off time is enforced after the random restart function has completed.
Door Switch Occupancy Sensor
The PTAC can accommodate a field- installed door switch and occupancy sensor to operate the energy management feature.
Remote Thermostat Control
Each unit can be operated from any standard 4 or
Setpoint Limiting
The setpoint limiting feature reduces energy costs by controlling the maximum setpoint in heating and the minimum setpoint in cooling.
Active Defrost (PTHEs only)
PTACs have an active defrost system that removes ice
Remote Thermostat
Operation
The GL, GH, O, W, Y, R, and C terminals provide control inputs for a remote
The terminals listed control the operation of the unit when no display module is used. A display module will take precedence over any of these inputs.
Mode Button Operation
OFF - cooling and heating functions stop.
HEAT - room temperature is maintained by cycling in heat pump mode or electric heat. The model PTHE switches from heat pump mode to electric heat when the outdoor air temperature is below 20°F (approximately), or when the heat pump cannot keep up with the heating load when using a
COOL - room temperature is maintained by cycling the air conditioner.
FAN - the fan runs at the user selected speed or runs as otherwise configured.
Fan Mode
Figure 17. Digital display module
Fan Operation
The fan speed may be user selected as either high or low. Fan cycling versus continuous is operation configurable. See section on configuration for details.
Front Desk Control (FD1, FD2 Inputs)
The energy management input is used to move the setpoint up in the case of cooling and down in the case of heating. This conserves energy by reducing the demand in the space.
The energy management input is a dry contact closure; typically this is driven from either a occupancy sensor or a front desk control system.
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