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BCI-R™ / BCI2-R™ RTU - Outdoor Air Control; Economizer & Ventilation

Updated

BCI-R / BCI2-R RTU - Outdoor Air Control; Economizer & Ventilation

Summary:

Outdoor Air Control refers to the management of outdoor air flow into a building or enclosed space. This is achieved through the use of and economizer and proper ventilation. If your RTU is equipped with an Economizer, you have a few options for standalone or BAS control related to all things outdoor air - Economizing aka Free Cooling and Ventilation. 

 

The points below are "controllable" points related to economizing/ventilation/outdoor air control that will be present on BCI-R RTUs equipped with economizers.

  1. Economizer Minimum Position Enable Command (BO/7)
  2. Economizer Airside Enable BAS (MO/1)
  3. Economizer Minimum Position Setpoint BAS (AO/1)
  4. Outdoor Air Temperature BAS (AO/14)
    1. all units
  5. Outdoor Air Humidity BAS (AO/15)
    1. all units
  6. Outdoor Air Minimum Flow Setpoint BAS (AO/16)
    1. when equipped with TRAQ & RTRM>v8 (Voyager III)
  7. Space CO2 Concentration BAS (AO/18)
    1. all units?
  8. Exhaust or Return Fan Configuration (AO/33)
  9. Power Exhaust Enable Setpoint BAS (AO/34)
  10. Economizing Temperature Enable Setpoint (AO/41)
  11. Economizing Enthalpy Enable Setpoint (AO/42)
    1. Enthalpy setpoint below which economizing can be enabled
    2. Valid range (F*), 19.0 - 28.0 Btu per lb.

Supporting Literature:

ReliaTel Sequence of Operation

See attached literature excerpts for Economizer, Ventilation 

 

To use Outdoor Air Minimum Flow Setpoint BAS (AO/16), AO/1 and BO/7 must be set to Out of Service.  AO/16 must be in service.

 

To use Economizer Minimum Position Setpoint BAS (AO/1), use the following setpoints.

 

Step BACnet Point Type / Instance BACnet Point Name

1. Service

("Out of Service" BACnet Property)

2. Present Value

(BACnet Property)

 

Choose the most appropriate for your application, when

 Notes
  BO/7 Economizer Minimum Position Enable Command In Service

ACTIVE ("Enabled") - use economizer min position

INACTIVE ("Disabled") - disable economizing

- If ACTIVE, will use AO/1 as min position setpoint

- If INACTIVE, min position setpoint determined by local sensors / HI / RTOM setting (often used for Demand Control Ventillation aka DCV)
  AO/1 Economizer Minimum Position Setpoint BAS IN SERVICE 10% (typical; range 0 to 50%)

Value used for econ min position if BO/7 is ACTIVE

If standalone DCV required, Out Of Service may need to be ACTIVE
  MO/1 Economizer Airside Enable BAS IN SERVICE

1 = Disabled

2 = Enabled

3 = Auto (Typical)

1 = Disabled - Unit will never economize

2 = Enabled - Unit will use economizer as first stage of cooling, regardless of actual OA conditions (should rarely be used)

3 = Auto - Rooftop makes economizer decision

 

 

 

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.

 

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