Novar Controls (Sequence Of Operation); General; Cooling With An Economizer; Cooling Without An Economizer - Trane ReliaTel Diagnostic Manual

Novar Controls (Sequence of Operation)

Novar is a control system that is often interfaced with ReliaTel controls which allows others to take
control of our equipment. The Novar system includes, but is not limited to, a control module
EMT2024 or EMT3051, a relay panel and various sensors such as discharge and return.
The Novar system connects to our unit in the same manner as a conventional thermostat. Other
modifications are also made that allows the Novar system to take control of the economizer.
Novar Controls Sequence of Operation

General

Novar Control units use a hybrid Reliatel-Novar control scheme. The Reliatel system is controlled
using the RTRM thermostat inputs connected to a Novar Electronic Thermostat Controller that
serves as a master unit controller and BAS network communication device.
In addition to basic thermostat operation control, a Novar unit includes some additional relay
connections that provide master control of economizer operation.

Cooling with an Economizer

On a Novar-controlled system the master controller initiates control requests to the RTRM through
its Indoor Fan, Cool, and Heat command outputs and the RTRM thermostat inputs.
The economizer control actuator (ECA) is wired to a Damper relay and a Night mode Damper
relay as described in the Economizer Set-up section. To enter an economizer-cooling only mode,
the master controller will energize its Fan (G) output activating the supply fan and close the
contacts on the Damper relay allowing a valid signal from the mixed air sensor.
The unit will then modulate the outdoor air damper open if the mixed air sensor reading is high
compared to the mixed air setpoint of 53° F . If the Damper relay is not energized when the supply
fan is on the ECA will maintain the outdoor air damper at default minimum position.
When the Novar controller senses conditions that require additional cooling greater than that
provided from economizing, it will energize its Cool 1 (Y1) output calling for compressor
operation.
If additional cooling is required above that provided by the first stage of compressors the second
stage will be activated by energizing the Cool 2 (Y2) output.
Compressors will respond to these calls independent of the position or status of the economizer,
but they will continue to adhere to minimum on, off, and inter-stage timing.
Note: When compressors are activated and the indoor coil begins to cool down the temperature

Cooling without an Economizer

The Novar controller uses its zone temperature input and setpoint input to determine when to
initiate requests for compressors or heat. Calls for cooling are interpreted by the Reliatel controller
as thermostat requests. When the zone temperature is sufficiently greater than the setpoint, the
Novar will energize its Cool 1 (Y1) output to turn compressors on. It will also close the contacts
on its Fan (G) output to call for the Supply Fan to turn on.
The first compressor will energize after its minimum 3-minute off time has expired. If additional
cooling capacity is required above that provided by the first stage the second stage of compressors
will be activated by energizing the Cool 2 (Y2) output.
Once the zone temperature falls below the setpoint sufficiently the compressor and fan outputs on
the Novar controller will be deactivated and the RTRM will respond appropriately and deactivate
its respective outputs. As with normal thermostat control the Supply Fan will remain on for a period
of 60 seconds after the compressor output is de-energized for free cooling.
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of the mixed air sensor may drop below the mixed air setpoint causing the ECA to close the
outdoor air damper to minimum position.
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