• Contactor M4 controls outdoor fans ODFAN3 & 4.
If the initial call for cooling requires both stages (Y1 and Y2), the UCB will delay the second stage by 30 seconds to avoid an excessive power inrush.
When the call for cooling (Y2) is satisfied, the UCB disables the signal to RY2 and M2 as long as the specified minimum run time (ASCD) has elapsed.
When the call for cooling (Y1) is satisfied, the UCB disables the signal to RY1 and M1 as long as the specified minimum run time (ASCD) has elapsed.
Low Ambient Cooling
These units are factory equipped with low ambient switches that work through the Simplicity control board to operate the compressors and condenser fans normally to 40ºF ambient temperature. The Electronic Low Ambient Controller 2LA04703000 Accessory is designed to assure safe operation through condenser head pressure regulation down to 0ºF ambient temperature.
Low Ambient Control Operation
•A call for cooling closes contactor M3 which energizes all condenser fans. The Low Ambient Control starts all fans at full speed then adjusts according to the liquid line temperature.
Refer to the appropriate 2LA low ambient kit instructions for additional detail on the factory or field installed low ambient kit and its operation.
Heating Sequence of Operation
General
Heat pump models are to be matched with air handlers of equivalent tonnage ratings. Twinning of heat pumps and air handlers is not recommended.
A two stage thermostat is required to operate the heat pump in heating mode.
All reversing valves are
The heat pump operates all compressors during a first stage call for heating unless locked out by the Unit Control Board (UCB).
First Stage Heating Operation
When the thermostat calls for first stage heating (W1):
•The Simplicity control board (UCB) goes into a five minute ASCD timer delay.
•When the ASCD time delay is satisfied, the UCB closes its internal compressor relay contact, thus energizing the contacts of relay RY1 and contactor M1.
•Relay RY1 has two functions: 1) control the operation of crankcase heater CCH1, and 2) control the 24V output signal to S1 on terminal block TB2.
•Contactor M1 controls compressor COMPR1.
•Relay RY3 (RY2 for PC090 model) toggles the 24V signal from the "O" terminal of DC to the "Y" terminal assuring the reversing valve cannot be energized except during defrost.
•Concurrently, a 24V signal is sent to one of the "CFAN" terminals of DC. The output signal from the remaining "CFAN" terminal closes the coil of contactor M3.
•Contactor M3 controls outdoor fans ODFAN1 & 2 (all models) and ODFAN3 & 4
(PC120-240; PD180-240 models)
•After a two second delay, the UCB energizes the contacts of relay RY2 and contactor M2.
•Relay RY2 has two functions: 1) control the operation of crankcase heater CCH2, and 2) control the 24V output signal to S2 on terminal block TB2.
•Contactor M2 controls compressor COMPR2.
(PD180-240 models only)
•Concurrently, a 24V signal is sent to one of the "CFAN" terminals of defrost control board DC2. The output signal from the remaining "CFAN" terminal closes the coil of contactor M4.
• Contactor M4 controls outdoor fans ODFAN3 & 4.
Second Stage Heating Operation
When the thermostat calls for second stage heating (W2):
•A 24V signal passes through UCB sending an input signal to the "W" terminal of DC. This signal passes through DC as an output signal to the "66" terminal of TB2 to be used as a control signal for first stage electric heat.
Emergency Heating Operation
When the thermostat calls for emergency heating (EMER):
•The UCB
•A 24V signal passes through UCB sending an input signal to the "W" terminal of DC. This signal passes through DC as an output signal to the "66" terminal of TB2 to be used as a control signal for first stage electric heat.
•The normally closed contacts of
20 | Johnson Controls Unitary Products |
