How to find total Kw Usage of an A/C Unit PLEASE HELP

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SUMMARY

The discussion focuses on calculating the total kilowatt (kW) usage of a 10-ton rooftop air conditioning unit, model TCD120C40AAB, with an EER of 9.2 and a system power of 12.83 kW. The user seeks to compare energy savings from switching to a "cool roof" with R-20 insulation versus a traditional black roof with R-6 insulation. It is clarified that total energy usage should be measured in kilowatt-hours (kWh) rather than kW, and that accurate projections require computer simulations rather than simple calculations. The primary savings from a white roof arise from reduced building heat absorption, leading to less frequent AC operation.

PREREQUISITES
  • Understanding of HVAC systems and their specifications, particularly EER and cooling capacity.
  • Knowledge of thermal insulation values, specifically R-values for roofing materials.
  • Familiarity with energy measurement units, specifically the difference between kW and kWh.
  • Experience with computer simulations for energy modeling in buildings.
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  • Research how to perform energy modeling using software like EnergyPlus or TRACE 700.
  • Learn about the impact of different roofing materials on building energy efficiency.
  • Investigate the relationship between ambient temperature and HVAC performance metrics.
  • Explore case studies on energy savings from cool roofs in commercial buildings.
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HVAC engineers, building energy analysts, architects, and facility managers interested in optimizing air conditioning efficiency and evaluating roofing options for energy savings.

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i am trying to find the total kw usage of a 10 ton rooftop unit. Its model # is TCD120C40AAB. Its EER value is 9.2. Nominal CFM is 4000. Gross Cooling Capacity is 125,000. System Power is 12.83 kw.

I am trying to figure out how much kw i will be saving by getting a "cool roof" instead of a typical black roof. The white roof will have R-20 insulation as the black roof only had R-6.

When i look at the Product Gross Cooling Capacity Performance Data Sheet, i can search what the MBH is going to be at different ambient temperatures. This way i can see what the kw usage is at 165 degree Fahrenheit and the kw usage at 115 degree Fahrenheit and determine how much i would save by implementing a white roof. I just cannot figure out how to calculate the kw usage of my unit at different temperatures as a projection.

PLEASE HELPP!
 
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Welcome to PF!

First, we need to discuss units. You asked for "total kW". The total kW of this unit is 13.83 kW. What you probably really meant was total energy usage. Energy is measured in kWh, not kW.

Now, the question you are asking can't be answered with a simple thumb rule or equation. It needs to be calculated with a computer simulation of the annual air conditioning required by the building.

Also, the temperature vs output data for the AC unit isn't critical here. Even if the AC unit is on the roof, it won't experience a condenser inlet temperature of 165F now and 115 later. But what will happen is the black roof will make the building heat up less than it does now, making the AC unit run less often, and that's where most of the savings comes from.
 
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So its better to have a black roof or white roof, and do you mean that the white roof will make the building heat up less?