Unit installation

38 OMRCPMICRO
Start-up (THRs operated in heating mode)
If none of the "off" conditions are true, the MicroTech controller will initiate a start sequence. The chilled
water pump output relay is energized any time the Templifier is enabled, the Templifier will remain in the
Waiting For Flow mode until the field installed flow switch indicates the presence of chilled water flow. If flow
is not proven within 30 seconds, the alarm " LossofWaterFIow" will be activated and the Templifier will
continue to wait for proof of chilled water flow. Once flow is established, the alarm will automatically be
cleared and the unit will go into the Wait For Load mode.
Once flow is established, the controller will sample the condenser water temperature and compare it against the
Leaving Condenser Water Set Point ("Lvg Cond"), the Control Band and the Load Delay which have been
programmed into the controller's memory. If the leaving condenser water temperature is below the Leaving
Condenser Water Set Point minus 1/2 Control Band minus the Start-up Delta-T, the controller will select the
refrigerant circuit with the fewest number of starts as the lead circuit and enter the first stage of the Cool
Staging mode. The controller will open the liquid line solenoid valve of the lead refrigerant circuit (SV1 or SV2)
allowing refrigerant to flow through the expansion valve and into the evaporator. When the evaporator
refrigerant pressure rises above the LPCutIn Set Point, the controller will start the first compressor and the
condenser pump (if wired into MicroTech). If additional capacity is required, the controller will de-energize an
unloader. If the load is still not satisfied, the controller will start the lag refrigerant circuit in the same manner.
The compressors and unloaders will automatically be staged up or down as required to meet the heating needs
of the system. Once the heat pump has started, a stage up in capacity occurs when the leaving condenser
water temperature falls below the Leaving Condenser Water Set Point ("Lvg Cond") minus 1/2 the Control
Band. The delay between the current heating stage and the next stage up request is controlled by the user-
adjustable Inter Stage Timer ("InterStg", Menu 16). A stage down occurs when the water temperature rises
above the Leaving Condenser Water Set Point plus 1/2 the Control Band. The stage down request time delay
is a fixed 1/3 ratio of the stage up delay.
If the Templifier is operating at minimum capacity (Stage 1) and the leaving condenser water temperature rises
above the Leaving Condenser Set Point plus 1/2 the Control Band plus the Shut Down Delta-T, the controller
will shut off the last operating compressor, enter the Waiting For Load mode, and monitor the leaving
condenser water temperature.
Condenser control
The first condenser fan stage will be started in conjunction with the first compressor to provide initial head
pressure control. The MicroTech controller continuously monitors the lift pressure referenced to several head
pressure control set points and will adjust the number of operating condenser fans as required to maintain
proper head pressure. For WHR and THR water-cooled units, the condenser pump will be started in
conjunction with the first compressor to provide head pressure control.
Low ambient start
If the saturated condenser pressure is less than 102 psi (60°F) at the time of circuit start-up, the low ambient
start logic will cause the following changes in the normal start-up sequence.
The first compressor will start when the solenoid valve is opened regardless of whether the evaporator
pressure has risen above the LPCutIn set point. The refrigerant freeze protect set point will be ignored for 180
seconds to allow time for the refrigerant pressure to build. If at the conclusion of the 180 second timer the
evaporator pressure is still below the freezestat set point, the circuit will shutdown and the alarm output "Lo
Evap Pressure" be activated.
The chilled water freeze alarm set point is enforced during low ambient starts and will shut down the chiller if a
water freeze condition is detected.
If at any time during low ambient start the evaporator pressure drops to 2 psi for more than 20 seconds, the
chiller will shut off and a "Lo Evap Pressure" alarm will be generated.
This safety protects the compressor from operating in a vacuum during compressor start-up.