PLC for HVAC System 2

[hossareh]

Dear friend

I had a mistake in my previuse question. My question was what is the PLC for HVAC system? What it has done for HVAC system but unfortunataly I have writen "what is in the PLC system" , So could you help me and let me know what PLC done for HVAC system.

 

[MintJulep]

Your question is still very vague. In very general terms the control system for an HVAC system turns things like fans, pumps and compressors on and off, and may control the speed at which they operate, or control unloaders. It may open or close dampers in the air stream, and control valves in the chilled water, steam, or refrigerant piping.

To do all of the above, the control system needs at least one input signal upon which to make decisions - preferably more than one.

The goal is to alter the state of the system devices such that the error between the input or inputs and their respective desired values is as close to zero as possible. Preferably this is also done with a method that results in the best system efficiency.

A PLC is not necessary for any of this, it can all be done quite nicely with much simpler technology. However, since PLCs are cheap and versitle, they are common.

 

[imok2]

hossareh, for a complete description of PLC go here

http://www.plcs.net/chapters/whatis1.htm