The CFM not Pos Output setting can determine whether the Vo output represents the valve or VAV box. The CFM is determined by the UVM, and the valve position is determined by the UVM.
The feedback sensor signal is obtained from the output Vo in the non-VAV case, or obtained from the flow pressure sensor in the VAV case.
In the checked state, the feedback signal converts to a position and translates through the CFM curve to a CFM value for the non-VAV box case.
With the VAV, the pressure signal converts to velocity with the K sqrt(P) math and applied to the box area to get flow. This scaled value is based on the CFM/Press at 10 V range and output on Vo. If not checked, the signal from the feedback sensor converts to the previous position of 0% to 100%. However, the value scales from 0% to 100% = 0 V to 10 V. IS then applies to the Vo output. The position valve is not applicable to the VAV box case.
The CFM not Pos Input setting can determine what the 0 V to 10V signal on the IN input represents. With an unchecked check box, the voltage on the IN connection represents a 0% to 100% positional percentage setpoint for the 0 V to 10 V signal. For example, if 5 V is the applied signal, the valve actuator moves to the 50% position.
A checked box interprets the input voltage as a CFM request. The CFM/Press at 10 V setting defines the scale of this interpretation.
For example, if the setting is 1500 CFM, 0 V is 0 CFM and 10 V is 1500 CFM. The UVM moves the actuator to 1500 CFM. The CFM setting is not relevant when the UVM operates in the VAV mode. Ensure this setting box is unchecked for VAV mode use.
The Reverse Acting 2 setting enables the normal or reverse mode of operation of the UVM. For a checked box in UVM revisions before 0.7x, there is an inverted Io signal to the actuator. For a checked box in UVM revisions after 0.7x, there is an inverted SP input signal on IN and an inverted actuator output signal on Io.
For example, the IN signal takes 0 V to 10 V to be xxx CFM to 0 CFM. For exhaust and hood valves, use reverse acting. Ensure the IN-signal box is unchecked for VAV box use. See the image below for more information on wiring and normal or reverse setting recommendations.
For normal and reverse modes of operation switch and state settings, see Figure 33 below.