Reznor ZQYRA Unit Installation Manual - Manual (Page 30)

Form I-ZQYRA P/N 260414R5, Page 30
o Once the OA temperature falls below the outside air changeover setpoint
( OaCngOvr = 65°F/18.3°C) by the difference of the outside air changeover
deadband ( OaCngOvrDb = 2°), the unit will maintain the leaving discharge
temperature heating setpoint low dewpoint ( DatHtgSpLoDp = 70°F/21°C).
Heat Pump Control Using Dewpoint with Heat/Cool Setpoints with Space Change-
over - Upon proof of the supply and exhaust air fans, the unit controller shall monitor
the wheel leaving air dewpoint.
•
If the dewpoint is above the Dewpoint Changeover Setpoint ( DpCngOvrLt =
59°F/15°C), the unit will enable the heat pump and modulate the system to
maintain a unit leaving discharge temperature high dewpoint setpoint ( DatSpHiDp
= 58°F/14°C).
•
If the dewpoint is below the Dewpoint Changeover Setpoint ( DpCngOvrLt =
59°F/15°C), the unit will enable the heat pump and modulate the system to
maintain a unit leaving discharge temperature low dewpoint heating and cooling
setpoint based on the space conditions.
o Once the zone temperature is above the zone changeover setpoint ( ZnCngOvr
= 70°F/21°C), the unit will maintain the leaving discharge temperature cooling
setpoint low dewpoint ( DatClgSpLoDp = 60°F/15.5°C).
o Once the zone temperature falls below the zone air changeover setpoint
( ZnCngOvr = 70°F/21°C) by the difference of the zone changeover deadband
( ZnCngOvrDb = 2°), the unit will maintain the leaving discharge temperature
heating setpoint low dewpoint ( DatHtgSpLoDp = 70°F/21°C).
Heat Pump Control Using Dewpoint with Outside Air Reset - Upon proof of the
supply and exhaust air fans, the unit controller shall monitor the wheel leaving air
dewpoint.
•
If the dewpoint is above the Dewpoint Changeover Setpoint ( DpCngOvrLt =
59°F/15°C), the unit will enable the heat pump and modulate the system to
maintain a unit leaving discharge temperature high dewpoint setpoint ( DatSpHiDp
= 58°F/14°C).
•
If the dewpoint is below the Dewpoint Changeover Setpoint ( DpCngOvrLt =
59°F/15°C), the unit will enable the heat pump and modulate the system to
maintain a unit leaving discharge temperature low dewpoint heating and cooling
setpoint based on the OA reset conditions.
o If the OA temperature is at or below the outside air low setpoint low dewpoint
( OaLoSpLoDp = 50°F/10°C), the unit will maintain the discharge air high
setpoint low dewpoint ( DaHiSpLoDp = 70°F/21°C).
o If the OA temperature is at or above the outside air high setpoint low dewpoint
( OaHiSpLoDp = 70°F/21°C), the unit will maintain the discharge air low
setpoint low dewpoint ( DaLoSpLoDp = 60°F/15.5°C).
o The discharge air setpoint is reset linearly from the discharge air high setpoint
low dewpoint to the discharge air low setpoint low dewpoint as the outside air
changes.
Reversing Valve Operation: Whenever the system calls for heating mode, the sys-
tem will energize (close relay and power valve) the reversing valve. This will reverse
the refrigerant flow and allow the system to provide heating. Whenever the system
calls for cooling mode the reversing valve is de-energized (no power at valve).
Optional PreHeat Control, Option PH1A (5kW) and PH2A (10kW)
The unit controller will monitor the outside air temperature, and if the temperature is
below the Preheat Enable Setpoint ( PreHtEnSP = 0°F/-17.7°C), the system will enable
the optional electric preheat coil(s). The optional preheat coil(s) will remain enabled
until the outside air temperature is above the outside air enable temperature by the
Preheat Enable Deadband ( PreHtEnDb = 5°F/3°C).
If Option PH1A or PH2A is not installed, the controller will hide all data associated with
the preheat coil.
8.3 Safeties, Alarms,
and Lockouts
8.2 Sequence of
Operation
(cont’d)
8.0 Controls
(cont’d)
Heat Pump Controls
(cont’d)
The system has two types of alarms built-in. The first type is all of the service alarms.
Service alarms are alarms that cause the system to react in a particular sequence as
described in Paragraph 8.3.1. Service alarms include alarms like fan failure, low limit
alarm, and heat pump failure.