Trane 120 GEH, Model 180 GEV, Model 012 GEH manual Direct Digital Controls

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Features and Benefits

ZN510 & ZN524 Controls

Direct Digital Controls

When the ZN510 or ZN524 controller is linked directly to the Tracer Summit, each Tracer Summit building automa- tion system can connect a maximum of 120 Tracer ZN510 or ZN524 controllers. See Figure 27 for the Tracer ZN524 board.

Figure 27: Tracer ZN524 board.

Tracer ZN510 and ZN524 functions include:

Compressor Operation

The compressor is cycled on and off to meet heating or cooling zone demands. Single and dual compressor units use the unit capacity and pulse width mod- ulation (PWM) logic along with mini- mum on/off timers to determine the compressor’s operation. The compres- sor is controlled ON for longer periods as capacity increases and shorter peri- ods as capacity decreases.

Random Start

To prevent all of the units in a building from energizing major loads at the same time, the controller observes a random start from 0 to 25 seconds. This timer halts the controller until the ran- dom start time expires.

Reversing Valve Operation

For cooling, the reversing valve output is energized simultaneously with the compressor. It will remain energized until the controller turns on the com- pressor for heating. At this time, the reversing valve moves to a de-ener-

gized state. In the event of a power fail- ure or controller OFF situation, the reversing valve output will default to the heating (de-energized) state.

Fan Operation

The supply air fan operates at the facto- ry wired speed in the occupied or occu- pied standby mode. When switch is set to AUTO, the fan is configured for cycling ON with heating or cooling. In heat mode, the fan will run for 30 sec- onds beyond compressor shutdown in both occupied and unoccupied mode.

Fan Run Timer

The controller’s filter status is based on the unit fan’s cumulative run hours. The controller compares the fan run time against an adjustable fan run hours limit and recommends unit mainte- nance as required.

Data Sharing

The Tracer ZN510/ZN524 controller is capable of sending or receiving data (setpoints, fan request, or space tem- perature) to and from other controllers on the communication link. This allows multiple units to share a common space temperature sensor in both stand-alone and building automation applications.

Night Setback

The four operations of the Tracer ZN510/ZN524 controller include occu- pied, occupied standby, occupied bypass and unoccupied.

In an occupied situation, the controller uses occupied heating and cooling set- points to provide heating and cooling to the building. This occupied operation is normally used during the daytime hours when the building is at the high- est occupancy level.

In an occupied standby situation, the controllers heating and cooling set- points are usually wider than the occu- pied setpoints. This operation is used

during daytime hours of temporary low occupancy. To determine the space occupancy, an occupancy sensor is applied.

In an unoccupied situation, the con- troller assumes the building is vacant, normally during evening hours. In the unoccupied mode, the controller uses the default unoccupied heating and cooling setpoints stored in the con- troller. When the building is in unoccu- pied mode, individual units may be manually placed into timed override of the unoccupied mode at the units wall sensor. During timed override, the con- troller interprets the request and initi- ates the occupied setpoint operation, then reports the effective occupancy mode as occupied bypass.

In the occupied bypass mode, the con- troller applies the occupied heating and cooling setpoint for a 120 minute time limit.

High/Low Pressure Safety Controls The Tracer ZN510/ZN524 controller detects the state of the high pressure or low pressure switches. When a fault is sensed, the corresponding message is sent to the controller to be logged into the fault log. When the circuit returns to normal, the high pressure control and low pressure control automatically reset. If a second fault is detected with- in a thirty-minute time span, the unit must be manually reset.

Condensate Overflow

When condensate reaches the trip point, a condensate overflow signal generates a diagnostic which disables the fan, unit water valves (if present), and compressor. The unit remains in a halted state until the condensation returns to a normal level. The switch in the drain pan will then automatically reset. The controller’s condensate over- flow diagnostic must be manually reset to clear the diagnostic and restart the unit.

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