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Knowledge
EMS Energy Maintenace Service
How to improve A/C efficiency
 2.1 What is kW/ton
nkW/ton means electrical energy that total plant consumes to produce 1 cooling ton for 1 hour.
( 1 Cooling ton = 12,000 Btu)
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 What is kW/ton
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Useful information about kW/ton
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 kW/ton of split-type A/C is ~ 1.4
kW/ton of package A/C is ~ 1.2
kW/ton of water chiller A/C is ~ 1.0
If we can improve kW/ton from 1.0 to 0.9, we will save money 10% in every ton cooling.
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Where is kW from ?
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nkW plant is total power consumption of chiller plant
= kW Chillers +
kW Chilled water pumps +
kW Condenser water pumps +
kW Cooling towers
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Where is Ton from ?
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nTon is total cooling production from chiller plant
= (Tch return – Tch supply)x Flow /24 when
T ch return is chiller water return temperature (F)
T ch supply is chiller water supply temperature (F)
Flow is chiller water flow rate (USGPM)
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Nature of kW/ton
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2.2 Variable Speed Drive
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Affinity law
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Why VSD can save energy ?
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Sample: Traditional condenser pump plant
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New condenser pump with VSD
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Saving Energy from VSD
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2.3 How to improve kW/ton
We have 2 ways to reduce kW/ton
1. Increase Cooling ton output or..
2. Decrease kW consume of the plant
To increase cooling ton has limits.
Most of plant is fully capacity
Output capacity must depend on machine’s performance
Chiller has internal control to adjust output capacity automatic. To force them to work more than capacity is not possible.
It’s possible to increase “flow” in some situation to increase “ton” without start more chiller but you have to know a way.
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Sample: Increase cooling capacity by vary primary flow
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kW/ton comparison
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