Product Manual WHR-2 67
Series or Parallel Operation
Consider system pressure drop when designing the water piping. Parallel piped systems have half
of the total system flow going through the evaporator of each chiller, reducing the individual unit
and total system pressure drop.
Series piped evaporators require that the total system water flows through both evaporators. Not
only is the pressure drop through each evaporator increased but the pressure drops must be added
together to obtain the total evaporator pressure drop. Series piped evaporators normally require
larger circulating pumps for the chilled water system.
Electrical Connection
Every WHR chiller requires field installation of the main supply power plus flow switch and pump
starter relay. A control circuit transformer installed at the factory eliminates the need for field
installation of a separate 115V supply to the control circuit. A separate 115V field connection to the
control circuit can be substituted. A system time clock and remote on-off switch can also be field
installed.
See Figure 5, Field Wiring Diagram, on page 44 for field electrical hookups. The diagram shown
represent all WHR units; however, individual terminal numbers may vary between unit sizes. Each
unit is provided with its specific wiring diagram in the control panel. All wiring must be done
according to local and national codes.
Main Power Supply Disconnect Switch
Every WHR unit uses a single factory installed main power supply terminal block as standard. The
main power supply terminal block will accept single or parallel power supply wiring.
A field installed non-fused disconnect switch with an optional thru-the-door handle (required to
meet NEC Code for disconnects) is available as an option on WHR 040 and above with single point
power supply. The disconnect switch is properly sized for the model and voltage supplied.
A field supplied and installed remote disconnect switch can also be used.
Control Circuit
A control power transformer is standard equipment on WHR units. Terminals are provided in the
unit control center (terminals 1 and NB, typical field wiring diagram) for field connection to a remote
control circuit to a 115V power supply if desired.
Terminals are also provided for field connection of the chilled water flow switch, unit time clock,
ambient thermostat and/or remote on/off switch.
Compressor Time Lockout
A fixed 5-minute solid-state lockout time delays compressor restart after safety cutout or power
interruption, or under irregular cooling load demands.
Interlock Wiring
The condenser water pump should be interlocked to cycle with the compressor(s). This will
prevent the refrigerant pressure from being overly depressed during the off cycle and allows the
energy savings of pump shutdown. Interlock terminals are provided in the unit control panel.
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