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# How to calculate the energy saving for chiller

## How to calculate the energy saving for chiller

(OP)
A below chiller was serving for a building. In order to achieve energy saving, one fan coil unit was switched off.
Cooling Capacity of Chiller (Kw): 347
Electricity Consumption of Chiller (KWH): 117.485
Operating Current of Chiller (A): 210
COP of chiller: 2.95
Cooling Capacity of Fan coil unit (KW): 6.8
I would like to seek someone help for assessing the below calculation for energy saving.

(347-6.8)/2.95 = 115.322KWH
Saving for Electricity Consumption of chiller = 117-115.322 = 2.163KWH

### RE: How to calculate the energy saving for chiller

Use a nominal rate for electric supply cost, estimate run hours with all coils in service versus run hours with one coil turned off and do the simple math.

### RE: How to calculate the energy saving for chiller

If things would be so simple, HVAC engineers wouldn't be needed at all, secondary school children would solve HVAC problems.

### RE: How to calculate the energy saving for chiller

COP is not a constant, it changes with lift, ambient temps etc.
If switching FC off saves energy, why not switch everything off and save all the cooling energy?

### RE: How to calculate the energy saving for chiller

(OP)
I would like to know how a simple method to calculate the amount of electrical saving for a chiller if one or two air conditioners were switched off in the building. Many Thanks

### RE: How to calculate the energy saving for chiller

Without knowing the layout of your building, switching a fan coil off does not mean that the heat it was rejecting disappears. It is either going to be rejected by other fan coil units (which will only save you fan power) or if you are lucky, be exhausted/radiated out of the building by other means.
You need to look at your system an analyse it. Build an excel model, use bin data.

### RE: How to calculate the energy saving for chiller

Tell whomever asked you this question that it does not have a simple answer.

### RE: How to calculate the energy saving for chiller

You can calculate the enegy consumption for a chiller but energy saving can be calculated if you want to compare two chiller systems with different part load efficiencies.
Chiller efficiency depends on two external factors
1. Head– Ambient Conditions for Air Cooled Chillers or Condensing water
temperatures for Water Cooled Chillers
• Higher Ambient, Lower Efficiency (Air Cooled Chiller)
• Higher ECWT, Lower efficiency (Water Cooled Chiller)
2. Load – Evaporator water flow rate, entering / leaving chilled water conditions,
fouling.
Lower LWT, Lower Efficiency
kW/Ton , EER and COP measure efficiency at one point only.
Air Conditioning Equipment do not operate at one point throughout their annual
operation.
As discussed by other professional here, we need realistic load profiles, chiller unloading data, ambient relief etc.If you know the NPLV for the chiller, you can calculate the annual energy consumption for the chiller as follows.
Annual Energy = NPLV x Avg chiller load x Operating hours
Example: Annual energy = 0.7978 kw/ton x 200 tons x 8760 hrs = 1397745 kwhr
If cost of electricity is 0.08 $/kwhr then annual energy cost of chiller = 1397745 x 0.08 =$ 111819

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