Demand Control Ventilation Setup operated by thermostat

Initial setup

• The unit must detect a working CO2 sensor at power-up to enable DCV. 
• You will need to simulate High CO2 by either breathing into the CO2 sensor or by connecting a 9-volt battery to the RTEM DCV Terminals.

Be sure to wire the CO2 sensor for a 0-10 VDC output, as shown below left, then you don’t have to worry about the Out2 Jumper position.

Notes

• A RTVM needs to be installed.
• An economizer on a Light Commercial Multi-Speed, Single-Zone VAV or 17 Plus must have a RTEM version 2.0 or higher.
• The Precedent RTOM J11 voltage depends on the position of the RTOM R136 Pot.
• Communicated BAS set points override any local potentiometer setting.

There are 2 different setups listed below

1. Precedent and Voyager Multi Speed and SZVAV units.

   • Precedent fan control signal from the RTOM J11 is 2.5 – 7.5 VDC
   • Voyager 2 fan control signal from the RTOM J11 is 0 – 10 VDC
   • There is no medium speed
   • No jumper plug on the RTOM J4-1 to 3

2. Precedent 17 Plus and WHC (High Efficiency Heat Pump) Units

   • Fan control signal from the RTOM J11 is approximately 9.5 – 17.6 VDC (Pulse Width Modulation)
   • These units have a jumper plug on the RTOM J4-1 to 3

For both types of units

• For damper position adjustment, the Lower Limit (LL) CO2 PPM adjustment potentiometer should be set to the lowest position (counterclockwise), and the Upper Limit (UL) CO2 PPM adjustment potentiometer should be set to approximately halfway. These can be adjusted later to the required CO2 levels.
• The DCV MIN OA Damper Pos controls the damper position when there is a low concentration of CO2 in the space.
• The Design MIN OA Damper Pos controls the damper position when there is a high concentration of CO2 in the space and ventilation is required.

For Precedent and Voyager Multi Speed and SZVAV units 

Note

• these units DO NOT have a jumper plug on the RTOM J4-1 to 3

Procedure

• Set both of the DCV MIN OA Damper Pos adjustment potentiometers (R41 on the RTVM) and DCV MIN POS on the RTEM to the minimum position (fully counterclockwise) as a starting position
• Set both of the Design MIN OA Damper Pos adjustment potentiometers (R130 on the RTVM), and DESIGN MIN POS on the RTEM to the maximum position (fully clockwise) as a starting position.

Set the LOW Fan Speed Positions (RTOM J11 output Voyager 0 VDC, Precedent 2.4 to 3.8 VDC)

• Enter into the test mode to the supply fan test step (1st step in test mode).
• Adjust the R41 pot on the RTVM to set the LOW fan speed DCV MIN OA Damper Pos. (for low CO2)
• Simulate a high concentration of CO2 to confirm the economizer damper responds to the call for ventilation.
• Adjust the R130 pot on the RTVM to set the LOW fan speed Design MIN OA Damper Pos. (for high CO2)

Set the HIGH Fan Speed Positions (RTOM J11 output Voyager 10 VDC, Precedent 3.4 to 7.5 VDC)

• Advance to the full compressor cooling in the test mode or any stage of heat. This forces the supply fan to the High fan speed.
• Adjust the DCV MIN POS pot on the RTEM to set the HIGH fan speed DCV MIN OA Damper Pos. (for low CO2)
• Simulate a high concentration of CO2 to confirm the economizer damper responds to the call for ventilation.
• Adjust the DESIGN MIN POS pot on the RTEM to set the HIGH fan speed Design MIN OA Damper Pos. (for high CO2)

After this procedure is finished, adjust the Lower Limit (LL) CO2 PPM and the Upper Limit (UL) CO2 PPM potentiometers on the RTEM to the required settings for the application. This is often determined by local codes.

For Precedent 17 Plus and WHC (High Efficiency Heat Pump) Units

Note 

• These units have a jumper plug on the RTOM J4-1 to 3

Procedure

• Set both of the DCV MIN OA Damper Pos adjustment potentiometers (R41 on the RTVM) and DCV MIN POS on the RTEM to the minimum position (fully counterclockwise) as a starting position.
• Set all three of the Design MIN OA Damper Pos adjustment potentiometers (R130 and R136 on the RTVM), and DESIGN MIN POS on the RTEM to the maximum position (fully clockwise) as a starting position.

Set the LOW Fan Speed Positions (RTOM J11 output 6.9 to 9.4 VDC)

• Enter the test mode for the supply fan test step (1st step in test mode).
• Adjust the R41 pot on the RTVM to set the LOW fan speed DCV MIN OA Damper Pos. (for low CO2)
• Simulate a high concentration of CO2 to confirm the economizer damper responds to the call for ventilation.
• Adjust the R130 pot on the RTVM to set the LOW fan speed Design MIN OA Damper Pos. (for high CO2)

Set the MEDIUM Fan Speed Position (RTOM J11 output 10.4 to 14.5 VDC)

• Advance to the 3^rd step in the test mode (1st stage compressor). This forces the supply fan to the MEDIUM fan speed.
• There is no DCV MIN OA Damper Pos setup for MEDIUM fan speed.
• The (low CO2) value from R41 from the previous step is retained for the MEDIUM fan speed.
• Simulate a high concentration of CO to confirm the economizer damper responds to the call for ventilation.
• Adjust the R136 pot on the RTVM to set the MEDIUM fan speed Design MIN OA Damper Pos. (for high CO2)

Set the HIGH Fan Speed Positions (RTOM J11 output 12.6 to 17.6 VDC)

• Advance to the full compressor cooling in the test mode (both compressors running) or any stage of heat. This forces the supply fan to the High fan speed.
• Adjust the DCV MIN POS pot on the RTEM to set the HIGH fan speed DCV MIN OA Damper Pos. (for low CO2)
• Simulate a high concentration of CO2 to confirm the economizer damper responds to the call for ventilation.
• Adjust the DESIGN MIN POS pot on the RTEM to set the HIGH fan speed Design MIN OA Damper Pos. (for high CO2)

After this procedure is finished, adjust the Lower Limit (LL) CO2 PPM and the Upper Limit (UL) CO2 PPM potentiometers on the RTEM to the required settings for the application. This is often determined by local codes.

WARNING:

Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.