VSD centrifugal chiller how it functions to control capacity

[nkhhh2003]

I am curious how the VSD (Veriable speed) centrifugal chiller able to control the capacity.
There is already a guide vane to control the capacity.
In the normal chiller (non VSD), the guide vane will open / close to match the required capacity.
With the addition of VSD that can control the speed of the rotation of the compressor, then which will be the priority?
Or the VSD only starts to kick in at very low loads?

 

[LittleInch]

You probably need to find and read the manual.

Guide vanes are usually only good for a certain range and VSD will extend that range.

A fairly vague question....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[moideen]

When reading the York white paper attached here, the VFD improves the system only during the part-load condition. with 25 to 30% energy efficiency compared to a constant speed inlet guide vane system. thanks

The problem with the world is that intelligent people are full of doubts, while stupid ones are full of confidence.
-Charles Bukowski-

 

[EnergyProfessional]

Unlike positive displacement compressors, a centrifugal compressor needs a minimum speed to achieve the required pressure. The pressure required depends on the temperatures in condenser and evaporator and therefore on the fluid temperatures (chilled and tower water). So based on that the manufacturer will employ vane and speed control. If it prioritizes the one or the other depends on how sophisticated they are and what pressures are required. Like if the tower water is warm, it may need more compressor speed. When tower water is colder, it may need less (less lift). Same if the chilled water setpoint is higher or lower. You can ask the manufacturer, but the exact details likely are proprietary. They may take into account more or fewer data points.

 

[nkhhh2003]

Apologize for the late reply, I have checked from here in the controls manual from Carrier 19DV centrifugal unit.
Link

It somehow mentioned (page 23, item 5.8) that the controls manual that during the startup, only guide vane will function, thereafter, VFD will kick in to modulate.

@Moideen, thanks for the link, but I can't seem to open the link.