Issue:
Can we setup a UC210, Symbio 210 or UC400 like a VariTrac box? Can we setup a UC210 or UC400 to do position control with no flow ring or pressure transducer?
Resolution:
Yes it is possible. The UC400, UC210 or Symbio 210 VAV will control the damper by position and not pressure. This is called pressure dependent mode operation.
There are two options:
1. Tracer TU V 10.4 or higher includes a factory configuration file for the UC210. The Symbio 210 config file was added in TU 11.4. See Help Center article below.
UC210 or Symbio 210 Varitrac replacement - Pressure dependent mode operation
- The factory configuration supports only auxiliary binary remote heat. Modulating reheat cannot be added. If modulating reheat is required, manually configure the UC or Symbio 210 per the instructions in this HUB document.
2. The UC400, UC210 or Symbio 210 VAV already does position control, like a VariTrac box, when it is in Pressure Dependent mode. It uses the airflow setpoint CFM divided by the nominal airflow of the box, to determine the % open the damper should be, based on the active airflow setpoint required for the current space temperature versus setpoint condition. It assumes that if the damper is open 100%, the airflow will be at the nominal flow for the box. For example, if the active airflow setpoint is 450 CFM, on a 900 CFM nominal flow box, the air valve will open to 50%. There are a few points that should be changed or put out of service, to eliminate diagnostics, and ensure full range operation, if the box will always be doing pressure dependent position control.
- Binary values 7, 9, 12 and 13, which are all diagnostic points related to airflow or the pressure transducer, should be put out of service, on the TU Binary Status page. This will eliminate flow sensor diagnostics. Cycle power with TU/USB cable disconnected to eliminate any existing alarms.
- The equivalent air valve position in % open should be calculated for each air flow setpoint. The airflow setpoints can be edited on the Equipment/Setup Parameters page, Flow Setpoints Setup group.
- The PD Mode Min Air Valve Position % should be edited to match the equivalent % of the minimum (or lowest value) airflow setpoint. The default PD Mode Min Position is 40%, which may be higher than the equivalent % open for the minimum flow setpoint. This setting can be accessed on the Equipment/Setup Parameters page, Air Valve Setup group.
- Analog value 20, Discharge Airflow may be reporting -2119 CFM. If you do not want -2119 displayed, put Analog Input 3 Pressure 1 Out of Service with a value of 0, then in Tracer TU go Utilities/Equipment /Commissioning, under Actions select Zero Air and Water Valve Position. This will calibrate the valve and when finished the Analog value 20, Discharge Airflow will show a value of 0.
- BV6 "Pressure Dependent Mode Reheat Enable" must be Enabled before Reheat will come on.
Notes:
Optional setting changes to align the reported flow setpoint with the reported damper position.
Navigate to Tracer TU Equipment/Setup Parameters
VAV Setup group
Box size = Generic box
Air Flow Nominal Status = 100 CFM (by setting the nominal flow to 100, all CFM setpoints are no in percent of box open, 65 CFM would result in 65 % open)
Unit Flow Gain = 0
Air Flow Measurement Offset = 0 %
Air Flow Gain = 0
Flow Setpoints Setup group
Air Flow Setpoint Minimum = 0 CFM (0% in PD mode)
Air Flow Setpoint Maximum = 100 CFM (100% in PD mode)
Standby Minimum Air Flow = 0 CFM (0% in PD mode)
Air Flow Setpoint Minimum Standby Heat = 0 CFM (0% in PD mode)
Air Flow Setpoint Minimum Heat = 0 CFM (0% in PD mode)
Air Flow Setpoint Maximum Heat = 100 CFM (100% in PD mode)
Air Flow Setpoint Minimum Local Heat = 0 CFM (0% in PD mode)
Air Valve Setup
PD Mode Min Air Valve Position = 0 %
Notes:
Link to original HUB doc-107461
Other Question/Problem/Cause Statements:
- Can we setup a UC400 as a VariTrac box?
- Can a UC400 VAV do position control of the air valve?
- Can we setup a UC210 as a VariTrac box?