24 Volt Controls
All electrical controls and safety de- vices are factory wired, tested, and mounted in the unit. The control package includes:
θCompressor contactor
θ24 Volt transformer
θLockout relay
θCompressor run capacitor (1- phase units only)
θReversing valve coil (For heat pump only)
θFuse (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
Features | Controls | |
and |
| |
Benefits |
| |
Lockout | 50 VA Transformer | |
24 VAC Contactor | ||
Relay | ||
| Ground |
Compressor
Run Capacitor
Low Voltage
High Voltage
2 Amp Fuse
(for use with 10 Pole Terminal
desuperheater Strip option)
Low Voltage | Thermostat |
| Figure 3: Controls |
θLow pressure switch
θHigh pressure switch
θTemperature sensor (freezestat)
θInternal 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
Ftemperature low temperature de- tection thermostat.
High Pressure Switch
Low Temperature Detection Thermostat
The low water temperature detec- tion thermostat is provided to pro- tect the
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).
For internal overload protection, Trane provides a high pressure switch. This
24V Power
Compressor Reversing Valve
(energized in clg)
Figure 4: Typical thermostat termination points
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