Danfoss VLT HVAC Drive Instruction Manual page 29

In this lab you will simulate a Closed Loop HVAC application using the VLT HVAC drive. Closed loop
operation requires a small amount more programming and wiring. When a VFD is operating in
closed loop operation, it modulates the output in order to maintain a set‐point. The set‐point is
entered directly into the drive, and the feedback will come from a 2‐10 Vdc pressure transducer.
The drive will receive the start/stop signal by means of a BMS system. A relay output will indicate
when it is running at set‐point pressure (1.5 in WG). A normally closed over‐pressure switch is also
wired back to the drive that will shut it down in the event of a failure. For this lab, you will use the
switch box to simulate the BMS signals.

Understand the principal of closed loop control

Learn to wire a pressure transducer to the VLT HVAC Drive

Program the necessary drive parameters for closed loop control of an air handler

Gain an understanding of closed loop P.I.D. settings
VLT HVAC Drive Lab # 3
HVAC Closed Loop Fan Application
Introduction
Behavioural Objectives
28