FORM 150.68-EG1 (0212)
13
JOHNSON CONTROLS
Alarm Contacts
Each refrigerant system has a voltage-free normally open
contact that will close when control power is applied to
the panel, if no fault conditions are present. When a fault
occurs which locks a system out, or there is a power
failure the contact opens. To obtain a system alarm signal,
connect the alarm circuit to terminals 29 and 30 for No. 1
system and terminals 31 and 32 for No. 2 system.
Control Wiring - System Inputs
All wiring to the control terminal block (nominal 30 Vdc)
must be run in screened cable, with the screen earthed at
the panel end only. Run screened cable separately from
mains cable to avoid electrical noise pick-up.
The voltage free contacts must be suitable for 30 Vdc (gold
contacts recommended). If the voltage free contacts form
part of a relay or contactor, the coil of the device must be
suppressed using a standard RC suppressor. The above
precautions must be taken to avoid electrical noise that
could cause a malfunction or damage to the unit and its
controls.
Flow Switch
A chilled liquid flow switch of suitable type must be
connected to terminals 13 and 14 to provide adequate
protection against loss of liquid fl ow.
Remote Start/Stop
Connect a remote switch to terminals 13 and 51 to provide
remote start/stop control if required.
Remote Mode Selection
Remote mode selection can be accomplished by
connecting a contact between terminals 13 and 50. With
the contact open the unit is in the cooling mode, with the
contact closed the unit is in the heating mode.
Remote Reset of Chilled Liquid Setpoint
The PWM input (terminals 13 and 20) allows reset of
the chilled liquid setpoint by supplying a ‘timed’ contact
closure.
Remote Load Limiting
Load limiting prevents the unit from loading beyond a
desired value. The unit % load limit depends on the
number of compressors on the unit. The load limit inputs
to terminals 13 and 21 work in conjunction with the PWM
input to terminals 13 and 20.
Fan Full Speed Inhibit
To reduce unit noise the fans can be limited to run at a
maximum step of all fans in star (reduced speed) i.e. fan
full speed is inhibited. Connect a customer voltage free
contact to terminals 13 & 15.
EMS Analogue Input
Provides a means of resetting the leaving chilled or hot
liquid temperature from the BAS/EMS. Accepts 4 to 20
mA, 0 to 20 mA, 0 to 10 Vdc or 2-10 Vdc. Connect to
terminal A+ and A-.
Modbus, BACnet MS/TP and N2
Enable communications with building protocol systems
using Modbus, BACnet or N2 protocol. Connect through
standard RS485 port.
