lev-co 13-12, User Manual

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1.3.2 Model 13-13 – Type 2 – VFD System with Constant Duct Pressure
In this approach, the Type 1 system is extended to include a pressure sensor in the main duct down-
stream of the fan, which allows the VFD to actively control motor speed as a function of duct (negative)
pressure. This permits constant, effective exhaust at a target duct pressure no matter how many damp-
ers are open or (within limits) the state of the filters. The benefits of the Type 1 architecture also apply.
A MANUAL/OFF/AUTO switch permits the user to override pressure sensing and run the system at max-
imum speed. The same interlocks, indicators and options are available as for Type 1.
Figure 2 – Type 2 Architecture