Chiller Selection

[haniyah]

If i have 600 ton load and i want to select a chiller, how should i proceed?

How many chillers will be ideal to cater this load??

 

[TwinScrew]

Comfort, or Process?

What type of building? Are you limited by space?

Water-Cooled, or Air-Cooled?

 

[haniyah]

Its an office building and i am going to select water cooled chiller. Assume i have no limitations of space then what should be my considerations? and if i have limited space then?

 

[marcoh]

You want 2 base load chillers at 267ton and a low load chiller at 66ton.

Suggest you contact your local York, Trane, Carrier representatives and get them to provide you various selections.

 

[KiwiMace]

You will likely be using water cooled centrifugals in this range as they will be very efficient, and have a good life.

Two 300ton chillers will probably be a better base option, and serve the full building load without needing the lower efficiency pony chiller mentioned above.

What you do from here entirely depends on the class of office building, low load and time spent at reduced load, which relates to climate and patterns of use:

* VFD's are becoming very affordable and almost de rigour(outside of the tropics, where you may not have sufficient wet bulb suppression to make them worthwhile).

* Long periods of low load operation may necessitate a smaller pony chiller, and the size of this will come from your load trends for the whole cooling season, otherwise you might get away with the turndown/Hot Gas Bypass on your base chillers.

* Some applications - occupant requirements or long cooling season for example - may make a third redundant 300ton chiller worthwhile.

 

[walkes]

You could also use modular chillers to handle your load. Multi-stack with MagLev compressors could work.

 

[RossABQ]

I would consider the water quality available too. An office system that size is not likely to get a lot of attention, so having cooling towers is a crap shoot. Air-cooled may be a better life cycle cost choice -- depends on cost of power, LEED, too.

I think this is not so simple a question as the OP believes. This is why engineers charge good money for a design.

 

[marcoh]

I would be hesitant to not provide a low load chiller, what happens if a single floor need to be conditioned on say a weekend or after hours. Low load issues seem to be a recurring issue on building without low load chillers.

600t may be the theoretical max load, but in real world operation the plant will run very rarely at full load.

 

[HVAC68]

If you want to do a good job - You need to have a load profile of the building - 24 hours x 365 days before deciding the ideal mix of chiller capacity and quantity.

Simple mathematics would tell you - use 2 x 300TR or 3 x 200TR !

HVAC68

 

[Waramanga]

How about some large chilled water storage instead of the low load chiller. If your low load isn't to frequent you could do 5000 litres or so of storage to get a reasonable minimum run time on a 50% or 33% chiller. The other thing to consider is redundancy, some clients will want any combination of chillers to meet say 75% of full load or something.

 

[cjw81]

Not such an easy question to throw out there.
HVAC68 is hitting the point when he(she) refers to load profile. I have found that spot cooling in a number of critical areas are more common and not so easily answered by a low load chiller. Areas like fire alarm system panels have batteries that tend to overheat if not properly cooled, pharmacies, conference rooms, telecom closets with router switches...you get the picture. All with different needs, different areas, ect. You really need to look at the load profile in the big picture.

 

[mauricestoker]

If it is a constant 600 TR load, then apply 600 TR cooling and consider maintenance. I would recommend three 300 TR chillers.

 

[walz]

I think this 600 Tons is the plant load and not the building load. if yes, then air cooled chiller is the best option for this small total tons. Put 2 x 300 Running, and if possible keep the third standby.

if this is the building load, then first determine the plant load, calculate the diversity on so on.

then do the same procedure