6. THERMOSTAT SELECTION
Any single stage heating and cooling thermostat can be used in zones 1 through 3. Zone 1 (only) has the option of using a single stage heat pump thermostat with an O terminal. Each thermostat must be capable of being turned off either through subbase or as a function of the thermostat.
Thermostat Requirements
Type: HEAT/COOL | THERMOSTAT TERMINALS: R (24V-hot), | RECOMMENDED THERMOSTATS: |
(Zones 1–3) | W (1st Stage Heat), Y (1st Stage Cool), G (Fan) | Aprilaire 8344, 8363, or 8570 |
| *See Note | |
Type: HEAT PUMP | THERMOSTAT TERMINALS: R (24V-hot), | RECOMMENDED THERMOSTATS: |
(Zone 1 Only) | O (Reversing Valve-cool), W (Auxiliary Heat), | Aprilaire 8346, 8365, or 8570 |
| Y (Compressor), G (Fan) | |
| *See Note | |
*Note: The C terminal (24V-common) in each zone of the control panel can be used for 24 volt powered thermostats. Terminal definitions (refer to thermostat manufacturer literature for matching terminals).
7. SEQUENCE OF OPERATION
Heat/Cool Thermostat Input Definitions: Heat = W, Cool =Y, Fan = G
Heat Pump Thermostat Input Definitions: Heat = Y, Cool = Y + O, Fan = G, Aux. Heat = Y + W, Emergency Heat = W
Fan Operation: A call for Fan from any zone will initiate the G equipment output terminal. The “NO” contact of the damper terminal for a zone not calling for Fan also energizes, while the “NC” contact de-energizes.
Heating Operation: When a zone makes a call for heat, the B, Y and G output terminal will energize. The “NO” contact of the damper terminal for any zone not calling for Heat also energizes, while the “NC” contact de-energizes. Following a 4-minute minimum on time, the Y terminal will de- energize when (1) all zones stop calling for heat, (2) the call has exceeded the heat/cool changeover time limit while a cooling call exists or (3) the call is interrupted by the high limit setting. Any energized damper terminals remain energized for a one-minute purge (if set to PURGE) or a
3.5minute purge (if set to NO PURGE). Should the same call exist for 20 minutes, the W terminal will also energize (if set to ELECTRIC) or the W terminal will energize immediately after the Y and G terminals de-energize (if set to GAS). Following a 2-minute minimum on time (if set to GAS) or immediately (if set to ELECTRIC), the W terminal will de-energize at the end of the heat call. When the W terminal is de-energized, it has a 4 minute minimum off time if set to GAS or no minimum off time if set to ELECTRIC. When the Y terminal is de-energized, a minimum off time delay of 4 minutes must elapse before it can energize again. The B terminal remains energized until there is a call for cooling.
Cooling Operation: When a zone makes a call for Cooling, the O, Y and G terminals will energize. The “NO” contact of the damper terminals in any zone not calling for Cooling also energizes, while the “NC” contact de-energizes. Following a 4-minute minimum on time, the Y terminal de- energizes when (1) all zones stop calling for cooling, (2) the call has exceeded the heat/cool changeover time limit while a heat call exists or (3) the call is interrupted by the low limit setting. The G terminal and any energized damper terminals remain energized for a one-minute purge delay if set to PURGE. If set to NO PURGE, the G terminal de-energizes immediately and any energized damper terminals remain energized for a 3.5- minute purge delay. When the Y terminal is de-energized, a minimum off time of 4 minutes must elapse before it can be energized again. The O terminal remains energized until there is a call for heat.
Emergency Heat Operation: Thermostat control of Emergency Heat only exists in Zone 1 when a Heat Pump thermostat is installed. In this case, the first call for Emergency Heat sets the system to the Emergency Heat mode of operation. All subsequent calls for heat by other zones are recognized as Emergency Heat calls until Zone 1 calls for normal heat or cooling.
If Zone 1 is configured as a heat/cool thermostat, Emergency heat can only be initiated by turning the E-HEAT switch on the zone control panel to the ON position. When the E-HEAT switch is in the ON position, all calls for normal heating will be recognized as Emergency Heat calls. The system will remain in Emergency Heat mode until the E-HEAT switch is moved to the OFF position, at which point calls for heat will once again be answered with normal heating.
When a call for Emergency Heat is recognized, the Y terminal will de-energize (if energized) after a 4 minute minimum on time, after which the B and W terminals (and G terminal if set to ELECTRIC) will energize. Following a 2-minute minimum on time (if set to GAS) or immediately (if set to ELECTRIC), the W terminal will de-energize when (1) all zones stop calling for heat, (2) the call has exceeded the heat/cool changeover time limit while a cooling call exists or (3) the call is interrupted by the high limit setting. Any energized damper terminals remain energized for a one- minute purge (if set to PURGE) or a 3.5 minute purge (if set to NO PURGE). When the W terminal is de-energized, it has a 4 minute minimum off time if set to GAS or no minimum off time if set to ELECTRIC.
Heat/Cool Changeover: When a call for heat/cool exists and an opposing call is made from another zone, a changeover time limit of 20 minutes begins at the time that the opposing call is made. If the original call is not satisfied within that 20-minute time period, the call will be interrupted, turning the equipment off and allowing for the normal fan purge cycle and minimum equipment off time. The opposing call will then be answered. After 20 minutes, if the original call still exists, the opposing call will be interrupted and the original call can once again be recognized.
High/Low Limit Temperature: The high/low limit temperature settings are designed to prevent the heat exchanger from overheating or the cooling coil from freezing. An 8052 Sensor mounted in the supply duct senses the delivered air temperature and interrupts the heating/cooling equipment (depending on the Heat and Cool temperatures set on the control panel) before overheating/freezing occurs. When a heating/cooling call is interrupted by the high/low temperature limit, the zone control panel turns the equipment off and energizes the G terminal (if not already energized). Once the temperature drops/rises 10°F, the equipment is turned back on if the call for conditioning still exists.
