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| Overview

The VVT-C Fully Modulating AHU is a profile that is used to control an AHU, which meet the HVAC demands of a space. The AHU supported is water a cooled AHU.

The profile supports up to three analog outputs for modulating cooling, heating and Fan speed equipment. Based on the preferences for the required conditioning, the controls required can be set and used.

| How it Works

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Once you select the VVT-C Fully Modulating AHU profile from the system selection, from all the relays, analog inputs and output that are available as a part of the CM board of the CCU, three analog outputs, a relay, and an auxiliary relay is made available in the profile screen to enable the conditioning required based on the preferences.

The Algorithm continuously track the average current temperature of the zones mapped as terminal profiles, under the VVT-C Fully Modulating AHU system profile, and looks for the change in the difference between the system level Desired Temperature and Average Current Temperatures and provides the required conditioning via modulating equipment.

When the Average Temperature increases above the set point or desired temperature and the zones demand cooling the cooling equipment ramps up based on the modulating output.

And when the Average Temperature decreases below the set point or desired temperature, and the zones demand heating equipment ramps up based on the modulating output.

Below the profile configuration is additional parameters for adjusting the analog output voltage to each piece of equipment.  You may program min/max output voltage for min/max system operation.

| Wiring

Below is a wiring schematic for the VVT-C Fully Modulating AHU, that show the connection from the CM board of the CCU to the RTU.

Note: The wiring schematic would differ for different staged control options set during the configuration.

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| Configuration

Below is the configuration screen for the VVT-C Fully Modulating AHU, The relays are enabled or disabled based on the preferences.

From the CCU

  • Click settings mceclip3.png icon
  • Select the DAD fully Modulating AHU for system profile.

The configuration screen displays as below.

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Analog-out1 - To enable the Cooling Equipment to perform or provide in a modulating range.

Analog-out2- To enable the Fan to perform or provide in a modulating range.

Analog-out3- To enable the Heating Equipment to perform or provide in a modulating range

Relay 3- To enable the Fan during the recirculation phase of the control.

Relay 7- To enable the humidifier or dehumidifier control.

Note: By default, the DCWB is disabled making the profile just a VVT-C fully Modulating AHU type, and below is information about usage and operation of the same.

And when the DCWB is enabled, the profile converts into a VVT-C Modulating AHU with DCWB, for more information on the usage and operation of profile refer to VVT-C Modulating AHU with DCWB

Below the profile configuration you can program the output voltage for the modulating equipment configured.

| Operations

Cooling

When the zones demand for cooling the algorithm calculates a loop output, which is based on the Proportional and Integral loop for control signals, called cooling loop output. This loop output which is in percentage is scaled to the different voltages of the modulating output that is set during the configuration.

  • Cooling loop output 0-100%, the Cooling Equipment ramps up from 0-10V of analog output

Heating

When the zones demand for heating the algorithm calculates a loop output, which is based on the Proportional and Integral loop for control signals, called Heating loop output. This loop output which is in percentage is scaled to the different voltages of the modulating output that is set during the configuration.

  • Heating loop output 0-100%, the Heating Equipment ramps up from 0-10V of analog output

Recirculate

When the zone demands recirculation along with cooling, the system will call for Fan speed which again uses the cooling loop output 0-100% to ramp up the speed from 0-10V of analog output.

Recirculate with VFD - When recirculating with a VFD, the default output voltage will be 4v. 

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