5
Controls
Features
and
Benefits
Lockout
Relay
50 VA Transformer
24 VAC Contactor
Compressor
Run Capacitor
2 Amp Fuse
(for use with
desuperheater
option)
Ground
10 Pole Terminal
Strip
Low Voltage
Thermostat
Low Voltage
High Voltage
Figure 3: Controls
24 Volt Controls
All electrical controls and safety de-
vices are factory wired, tested, and
mounted in the unit. The control
package includes:
q
Compressor contactor
q
24 Volt transformer
q
Lockout relay
q
Compressor run capacitor (1-
phase units only)
q
Reversing valve coil (For heat
pump only)
q
Fuse (for desuperheater)
A terminal strip with 1/4” fork con-
nections will be provided for field
thermostat control wiring. (See Fig-
ure 3).
Safety Devices
Each Trane water-to-water unit con-
tains safety devices to prevent com-
pressor damage. These include:
q
Low pressure switch
q
High pressure switch
q
Temperature sensor (freezestat)
q
Internal overload protection
Low Pressure Switch
The low pressure switch prevents
compressor operation under low
charge or in excessive loss of
charge situations. This device is set
to activate at refrigerant pressures
of 35 psig when a 35
F low temper-
ature detection thermostat is ap-
plied. An optional 7 psig pressure
switch is available when using a 20
F temperature low temperature de-
tection thermostat.
High Pressure Switch
For internal overload protection,
Trane provides a high pressure
switch. This de-energizes the com-
pressor when discharge pressure
become excessive.
Low Temperature
Detection Thermostat
The low water temperature detec-
tion thermostat is provided to pro-
tect the water-to-refrigerant heat
exchanger from freezing. This de-
vice prevents compressor opera-
tion if leaving water temperature is
below 35
F. An optional 20
F tem-
perature thermostat may be applied
for low water temperatures where
an appropriate antifreeze solution is
used.
Lockout Relay
When the safety controls are acti-
vated to prevent compressor short
cycling, the lockout relay (circuit)
can be reset at the thermostat, or by
cycling power to the unit.
Thermostat Hook-up
Low voltage and high voltage
knockouts are provided in the top
half of the unit. All control wiring to
the unit should be 24 Volt.
(See Figure 4 for termination
points).
24V Power
Compressor
Reversing Valve
(energized in clg)
Figure 4: Typical thermostat termination points
