Danfoss VLT HVAC Drive Instruction Manual page 11

Danfoss FC Series VFD Reference Handling
This tutorial will explain how to interpret the reference parameters and achieve the desired
results.
The first step in the setup requires you to set up parameters in the P 3‐0* parameter group and
enter your desired minimum and maximum references, which can be entered in P 3‐02 & P 3‐03.
No matter which reference unit you will be working in, these are the lowest and highest allowable
values to be commanded to the VFD.
Next, for P 3‐04, there are two available choices, Sum or External / Preset.
When Sum is selected, any terminal programmed as a reference resource, including digital inputs,
analog inputs, preset references or serial bus references will be added together to produce the
total speed reference. Each of these different possible reference resources can be scaled to
produce a certain percentage of the P 3‐03 Maximum Reference.
When External / Preset has been selected, the drive will respond to either only preset references
OR the sum of all the external reference resources as described above. The drive will toggle
between the two using a digital input, as shown below.
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