## chiller efficiency

## chiller efficiency

(OP)

I'm looking for a good paper out there that outlines clearly the relationship between variable chiller flow and its direct effect on efficiency (i.e. kw/ton). The machine in question is a centrifugal 415 ton chiller with manufacturer's stated efficiency of 0.65 kW/ton. Thanks in advance!

## RE: chiller efficiency

MattSh(visitor)I assume you are asking about a variable speed centrifugal chiller and the relationship between refrigerant flow capacity and chiller efficiency in kw/ton?

The .65 kw/ton you mentioned is a fairly efficient chiller and is right there with the newest machines which have ratings in the .58 & .59 kw/ton range. You must realize, that the specified kw/ton indicated in the manufacturers literature is that specific chiller, under a specified load, and at pure design conditions (chilled temp/flow - condenser temp/flow), and furthermore with specific electrical characteristics.

Generally, if you do the electrical math calculating rated tons vs actual voltage/amps/power factor or kw, you'll find out that the math usually doesn't add up. This is caused by the actual electrical characteritics and power factor being different from the ones tested or used by the manufacturer.

What this is summarizing, is that all parameters have to be at the precise and exact optimum characteristics for the specified kw/ton to actually exist on the job site. The real truth is, that your chiller efficiency would have been calculated the same as how all manufacturers do, and you just have to compare this efficiency from one to another.

If your question is just asking at what percent load and chilled/condenser conditions can I operate to obtain the maximum efficiency, this information can be determined in many ways - info from manufacturers data or calculating actual chiller gpm and delta t to obtain actual tonage at different percentages of load and measuring amperage at each of those load conditions as well. This will give you actual job site efficiency at each of the percentages of load where the readings were taken. In order to do this however, you must have fairly accurate tools to measure the chiller/cooler pressure drop to obtain gpm, an accurate thermometer to measure delta temperature across chiller/cooler, then calculate actual tons. to measure the amperage, either use the chiller display if its micro proccessor based or a good amp meter. from these readings, you can calcualte where the best efficiency is being achieved. The condenser flow should be at design gpm (somewhere around 1200 to 1250 gpm) and the condenser water inlet temp should be at 85 degrees. It is important that you have 85 degree condenser water for the testing because in the summer months, 85 degree condenser is at or around the best achievable temperature. Of course, this condition changes with your geological location.

Chiller efficiency increases with decrease in condenser water temperature. The condenser water temperature can be manipulated to increase chiller efficiency. You have to be a little carefull however that you dont run the temperature too cold to cause chiller problems (when you can get it there depending on ambient conditions), or definately not to the point where you waste cooling tower fan horse power trying to get the condenser water down to an unachievable temperature. There are controls on the market or can be built that look at ambient wet and dry bulb conditions to deterimine the achievable condenser water temperature. From this determination, a condenser fan set point is developed and controlled for, without wasting fan power, and getting the best out of your tower and efficincy out of your chiller.

I hope this can be of help to you,

Steve

## RE: chiller efficiency

## RE: chiller efficiency

the answers you want have been debated in papers

on the trane.com and york.com website, where trane

is proposing 2usgpm/ton for condenser water flow,

and york is refuting it.

also note that at ari conditions of 44degF and

85degF, the latest trane centrifugal chillers

are inching towards 0.48kw/ton. we were already

using 0.54kw/ton units from york in the mid 1980s.

rgds

leelock

## RE: chiller efficiency

MattSh(visitor)## RE: chiller efficiency

re the 2 x 700tr yorks, at standard ari

conditions at this size range york can

get to 0.53kw/ton or thereabouts.

trane could get to about 0.48kw/ton.

however depending on the wet bulb in

your region it might make sense to have

inverters fitted for the compressors, in

which case i think york has the edge in

annual efficiency.

rgds

leelock

## RE: chiller efficiency

Sir/madam,

Im looking for some answer to the problem i got right now. Im replacing old chiller with motor rating l/p kw= 375kw ton=402..=Ikw/ton =0.7

New chiller motor rating l/p kw=206kw, ton=350..=Ikw/ton 0.59.

can someone help me to find out how much i save in dollar term & KWH and how do you work it out? .

Thank you.(needed help very fast).

## RE: chiller efficiency

## RE: chiller efficiency

Sorry i make a booboo on my last question i posted.

I should have put down 280/402=0.7kw.The 375 was the motor Horse power. Can you please help me on this again.

Thank you so much for your help.

## RE: chiller efficiency

I need someone to tell me if there's any problem with the RH in the room if i increase the delta T by 1 degeed.At the moment the chiller is operating on delta T (4) which i think it's abit low, with ambeint tempt at 31c.Is the flow too fast or what? the leaving tempt from chiller is 5.9c and the entering is 9.7c, the condenser is 34c rtn, 28.7c supply.Any idea i can use? flowrate is 69.5 l/s

2.AHU (1) entering 8c, leaving 9c what can happen here? do we have choked coil or flow too fast?

Thank you