We are going to
be looking at how to calculate the efficiency of a chiller now why we might
want to know this well chillers are actually pretty expensive to run. So you
want to make sure that the chiller is running in its optimal performance. The
way to check that is to do some calculations on the chiller efficiency.

A very low
efficiency means you're getting very little output for your money and a very
high efficiency means that you're getting a lot of value for your money so it's
a good calculation to perform on your chiller at different loads and also if
you have multiple chillers test them all at different those to see which one is
the most efficient and run that as the main one at that peak.

So chiller
efficiency is measured in COP, the COP stands for coefficient of performanceÂ Â Â Â Â and really the

COP = Ratio of
how much refrigeration you get per unit of electricity that you put into the
compressor

Now the formula
for this one is very simple

Â **COP = Kw of Refrigeration (Output) / Kw of Electricity (Input)**

So, we're going
to do the calculations on this we need is the electricity in and that's
measured in kilowatts now that's very easy to get, you just put on a clamp meter
on supply lines to get it or maybe from your BMS or on the head end of the control
panel.

You should be
able to read them from so many of the electricity in will depend upon the power
consumption by this unit will vary by the amount of load that is pressed onto
the compressor.

Now the second part you need in this equation is the refrigeration effect so how much cooling are you getting out of this chiller now we want the units in kilowatts.Â If you don't know how to calculate this, then I highly recommend you read our other article just before this which is how to calculate the chiller cooling capacity.

Also Read: How to Calculate Cooling Capacity of a Chiller in HVAC

So back to the
calculation we're just
going to drop in the number. We'll put refrigeration effect that at the top of the
division and then we'll also put the amount of electricity going into the machine
as well.

Â **COP =Â Kw of Refrigeration (Output)Â /Â Kw of Electricity (Input)**

**COP = 2500 Kw / 450 Kw**

**COP = 5.5**

If you want to
calculate in imperial units then follow this calculation;

**1 Kw =Â ****3412.142 Btu/h**

So

**8,533,364 Btu/hÂ ****Ã·Â ****3412.142 =Â ****2500 Kw**

**COP =Â 2500 KwÂ /Â 450 Kw**

**COP = 5.5****Â **

You'll see that
these COP comes out of five point five that's very good that's really very good
so what this means is that for every one kilowatt of electricity that you put
in you will get five point four kilowatts of cooling out so there you go you
get five times yourÂ Â Â Â Â money's worth of
electricity out in cooling.

So like I said
the COP of a chiller will actually vary throughout the amount of low that's
placed on the compressor throughout the year throughout the day as well unless
you've got a constant load then COP will be also be approximately constant.

There is a
difference in the COP compared to a constant speed chiller or a variable speed
chiller. Variable speed chillers others are more efficient usually because in normal
buildings it's actually quite rare that a chiller would operate at certainly 100%.

Most of the time
is operating at part load so it's only going to be few days per year when the
chiller will actually be operating full load. The majority of the time it's going
beÂ Â Â Â Â somewhere between 40% - 60%. So
if you have a variable speed chiller then it's going to be much more efficient.

But you can see in
the graph at 90% - 100% load it reaches its peak performance but on normal load during the normal time
of the year it's probably going to be a COP of 6 at 40% to 60% part load.
Whereas at the same time variable speed chiller will give you a COP of 8 or
maybe 9.

so thatâ€™s how you calculate the coefficient of performance and how efficient your chillers are do remember that you can upgrade your chillers and if you have a normal building like an office type building and you are in certainly the northern hemisphere then you really consider installing a variable speed drive on the compressor and speak to your manufacturer or service provider for that.

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