** Condensers**

As I mentioned in the previous
newsletter, different industrial refrigeration compressors have similar energy
efficiencies at identical suction pressure and discharge
pressure.

It is a different story for evaporative
condensers. These condensers come in frame size. Several models have the same
frame, but different heat rejection efficiency (MBH/HP). This is because for
higher capacity unit, additional heat rejection is being added primarily with
additional airflow or additional condenser energy. Therefore, heat rejection
efficiency of different condensers with the same fan type (axial or centrifugal)
can very **up to 50 %**.

Another important factor is that
centrifugal fan units usually require **50% to 100%** more fan power than axial
fan units. As shown above, one condenser can use significantly more energy than
another one of identical capacity.

Condenser energy efficiency is a major
factor in determination of condenser sequence.

*Example*. We have refrigeration plant with 6
condensers. First one in condenser sequence operates 12 months (**8760 Hrs**). Last one operates just 1
month (**744 Hrs**) during the period of
hottest ambient conditions. First condenser is using **50 HP**. Last one is using **30 HP**. Capacity of these two condensers
are identical. If we switch these condensers in

condenser sequence, we will save **50 - 30 = 20 HP** for a period of 11 months (**8016 Hrs**).

At energy rate 0.1$/KWh,
total energy savings would be

**(20 x 0.75 = 15
KW) 15 x 0.1 x 8016 =
$12,024**.

New condenser sequence will save us
$12,000 without any capital investment.

Recently, I visited one production facility inOntario. They have a
refrigeration plant and the condenser power of this plant is around **400 HP**. I suggested to them a new
optimum condenser sequence that immediately saved 120 HP of condenser power. Estimated annual energy
savings of this action would be around **$30,000**. This company was planning to
get similar energy savings by buying compressor VFD for **$100,000**. Assume that payment for a new
optimum condenser sequence would be **$5,000**. This company will get a return
on investment in condenser sequence 20 times ( **2,000 % **) better than investment in
compressor VFD. It looks like too
good to be true, but these are the real life numbers.

Probably, not everybody agreed with
my statement (March 2006 newsletter) that operating savings are significantly
more cost effective than designing energy savings. However, the example
mentioned above is proving that small investment in optimization of
refrigeration plant operation will give you much better return than investment
in energy saving equipment.