Chiller plant controller/ Chiller management system

[cikondu]

Hi, I am looking for a chiller plant controller that can control up to 6 chillers and accept any make of chiller. I have found on the market a few controllers but these usually control only their own make of chillers (e.g. Trane). Unfortunately, I have four different makes of chillers installed and would really like to install a good microprocessor-based chiller sequence controller that would provide a smooth energy-efficient operation of the chillers.
Thank you.

 

[krb]

Try Johnson Controls, they can help with your application.

 

[quark]

What do you want exactly? Do your chillers already have their own control systems and you want to communicate with all of them using a single controller or do you want to automize existing manually operated chillers(i.e only sequential operation based on load)?

The later can be easy with duplication of some I/Os where as former one requires more hardwork and more money you may not get permission from the OEMs.

 

[MintJulep]

The hardware is the easy part. Johnson Controlls, Honeywell, Allen-Bradley or any other recognizable name-brand will be able to accomodate the necessary ins and outs.

The hard part is the software. You will need to produce a detailed software requirement specification so that the supplier knows what to do, and so you can verify that you get what you asked for.

 

[cikondu]

Quark, to answer your question:
Each chiller has its own control system and is capable of loading and unloading the necessary compressors and stages to maintain the set point chilled water temperature -- usually 7C. The new chiller controller needs to have the capability to put on line the necessary number of chillers needed for the current load. When a chiller needs to be stopped the controller needs to have sufficient intelligence to unload its stages before stopping. Dedicating one chiller for 'feathering' purposes is another plus -- I have seen several other interesting features on some controllers which unfortunately do not accept chiller types other their own brand name.

 

[ClydeMule]

If each chiller has a digital input to turn the whole thing off and on, then it sounds like all you really need is a 4 stage controller.

At kele.com they have a controller that takes an analog input, say 0-10VDC from a JC A350 temp sensor. There is a potentiometer for each stage that allows you to chose the point in which each stage will come on. If divided evenly, you would set each pot to 2.5, 5.0, 7.5 and 10 VDC.

Or you could just use some kind of TStat with 1 analog in and 4 relay outs.

How sophistciated a controller you need depends on how fancy you want to be.

If you want to actaully control the individual stages of unloading then you need to somehow "cut-in" to the control circuit.

You could also mess around with setpoints. If each individual chiller will only run based on it own temperature control rountine, then to use the example I gave above, you would have to peg each individual tstat to its lowest level, so that each chiller would fire when the master controller asked for it. Then to get the "trim" chiller to unload, it's tstat would have to be set slightly higher than the lowest activiation point on the master.

Example, chillers 1-3 are set for 0C. Chiller 4 is set for 7C. For simplicity, I am igonring hysteresis for now. The master controller is set for 6C, with a band of say 2C and proportional control from 6C to 8C. While each chiller is idle, it thinks it needs to run based on the reading of its own temp sensors, but is locked out by the open remote stop/start contact. As the master controller sees cooling, it closes the start contact to each chiller and allows them to run. When it demands cooling for the 4th chiller, it will call for it to be on until the setpoint reaches 6C, but the chiller will unload to stay at 7C.

Obviously you will have to play around with it a bit. To rotate run time, you simply change the pots on the master controller, and then adjust the temperature setpoints of each chiller.

I hope this made sense.

I actually did something like this before and it work pretty well, but I did not use the kele controller I referenced. I programmed my own pco2.

Good Luck,

Clyde