User Guide

64
Design Guide - HZH/HZV Series
HZ Series 60Hz
Engineering Specications – Page 5
• Random start on power up mode.
• Low voltage protection.
• High voltage protection.
• Unit shutdown on high or low refrigerant pressures (loss of charge).
• Unit shutdown on low water temperature.
• Condensate overow electronic protection.
• Option to reset unit at thermostat or disconnect.
• Automatic intelligent reset. Unit shall automatically reset the unit 5 minutes after trip if the fault has cleared. If a fault
occurs 3 times sequentially without thermostat meeting temperature, then lockout requiring manual reset will occur.
• Ability to defeat time delays for servicing.
• Light emitting diode (LED) on circuit board to indicate high pressure, low pressure (loss of charge), low voltage, high
voltage, low water/air temperature cut-out, condensate overow, and control voltage status.
• The low-pressure (loss of charge) switch shall not be monitored for the rst 120 seconds after a compressor start
command to prevent nuisance safety trips.
• 24V output to cycle a motorized water valve or other device with compressor contactor.
• Unit Performance Sentinel (UPS). The UPS warns when the heat pump is running inefciently.
• Water coil low temperature sensing (selectable for water or antifreeze).
• Air coil low temperature sensing.
• Removable thermostat connector.
• Night setback control.
• Random start on return from night setback.
• Minimized reversing valve operation (Unit control logic shall only switch the reversing valve when cooling is demanded
for the rst time. The reversing valve shall be held in this position until the rst call for heating, ensuring quiet operation
and increased valve life.).
• Override temperature control with 2-hour timer for room occupant to override setback temperature at the thermostat.
• Dry contact night setback output for digital night setback thermostats.
• Ability to work with heat pump (Y, O) or heat/cool (Y, W) type thermostats.
• Ability to work with heat pump thermostats using O or B reversing valve control.
• Emergency shutdown contacts.
• Boilerless system heat control at low loop water temperature.
• Ability to allow up to 3 units to be controlled by one thermostat.
• Relay to operate an external damper.
• Ability to automatically change fan speed from multistage thermostat.
• Relay to start system pump.
• 75 VA control transformer. Control transformer shall have load side short circuit and overload protection via a built in
circuit breaker.
NOTE: Units not providing the 8 safety protections of anti-short cycle, low voltage, high voltage, high refrigerant
pressure, low pressure (loss of charge), air coil low temperature cut-out, water coil low temperature cut-out, and
condensate overow protections will not be accepted.
Note: To achieve full benet of the two-stage compressor and ECM fan, a 2 Heat/2 Cool thermostat (or a 3 Heat/2
Cool thermostat when electric backup heat is required) should be employed.
Digital Night Setback with Pump Restart
The unit will be provided with a Digital Night Setback feature using an accessory relay on the DXM2 controller and an
external, eld-provided time clock. The external time clock will initiate and terminate the night setback period. The
thermostat will have a night setback override feature with a programmable override time period.
An additional accessory relay on the unit DXM2 controller will energize the building loop pump control for the duration of
the override period. (Note: this feature requires additional low voltage wiring. Consult Application Drawings for details.)