Trane RT-PRC007-EN manual Selection Procedure, Supply Air Fan

Page 12

Selection Procedure

Selection ofTrane commercial air conditioners is divided into five basic areas:

1

Cooling capacity

2

Heating capacity

3

Air delivery

4

Unit electrical requirements

5

Unit designation

Factors Used In Unit Cooling Selection:

1

Summer design conditions — 95 DB/

76 WB, 95 F entering air to condenser.

2

Summer room design conditions — 76 DB/66WB.

3

Total peak cooling load — 321 MBh (27.75 tons).

4

Total peak supply cfm — 12,000 cfm.

5

External static pressure — 1.0 inches.

6

Return air temperatures — 80 DB/66WB.

7

Return air cfm — 4250 cfm.

8

Outside air ventilation cfm and load — 1200 cfm and 18.23 MBh (1.52 tons).

9

Unit accessories include:

a

Aluminized heat exchanger — high heat module.

b

2” Hi-efficiency throwaway filters.

c

Exhaust fan.

d

Economizer cycle.

Step 1 — A summation of the peak cooling load and the outside air ventilation load shows: 27.75 tons + 1.52 tons = 29.27 required unit capacity. From Table 18-2, 30-ton unit capacity at 80 DB/ 67 WB, 95 F entering the condenser and 12,000 total peak supply cfm, is 30.0 tons. Thus, a nominal 30-ton unit is selected.

Step 2 — Having selected a nominal 30- ton unit, the supply fan and exhaust fan motor bhp must be determined.

Supply Air Fan:

Determine unit static pressure at design supply cfm:

External static pressure

1.20 inches

Heat exchanger

.14 inches

(Table PD-14)

 

High efficiency filter 2”

.09 inches

(Table PD-14)

 

Economizer

.076 inches

(Table PD-14)

 

Unit total static pressure

1.50 inches

Using total cfm of 12,000 and total static pressure of 1.50 inches, enterTable PD-12.Table PD-12 shows 7.27 bhp with 652 rpm.

Step 3 — Determine evaporator coil entering air conditions. Mixed air dry bulb temperature determination.

Using the minimum percent of OA (1,200 cfm ÷ 12,000 cfm = 10 percent), determine the mixture dry bulb to the evaporator. RADB + %OA (OADB - RADB) = 80 + (0.10) (95 - 80) = 80 + 1.5 = 81.5F

Approximate wet bulb mixture temperature:

RAWB + OA (OAWB - RAWB) = 66 + (0.10) (76-66) = 68 + 1 = 67 F.

A psychrometric chart can be used to more accurately determine the mixture temperature to the evaporator coil.

Step 4 — Determine total required unit cooling capacity:

Required capacity = total peak load + O.A. load + supply air fan motor heat.

From Figure SP-1, the supply air fan motor heat for 7.27 bhp = 20.6 MBh.

Capacity = 321 + 18.23 + 20.6 = 359.8 MBh (30 tons)

Step 5 — Determine unit capacity:

FromTable PD-4 unit capacity at 81.5 DB. 67WB entering the evaporator, 12000 supply air cfm, 95 F entering the condenser is 361 MBh (30.1 tons) 279 sensible MBh.

Step 6 — Determine leaving air temperature:

Unit sensible heat capacity, corrected for supply air fan motor heat 279 - 20.6 = 258.4 MBh.

Supply air dry bulb temperature difference = 258.4 MBh ÷ (1.085 x 12,000 cfm) = 19.8 F.

Supply air dry bulb: 81.5 - 19.8 = 61.7.

Unit enthalpy difference = 361 ÷ (4.5 x 12,000) = 6.7

Btu/lb leaving enthalpy = h (ent WB) = 31.62

Leaving enthalpy = 31.62 Btu/lb - 6.7 Btu/lb = 24.9 Btu/lb.

FromTable PD-1, the leaving air wet bulb temperature corresponding to an enthalpy of 24.9 Btu/lb = 57.5.

Leaving air temperatures = 61.7 DB/57.5WB

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RT-PRC007-EN

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Contents Packaged Rooftop Air Conditioners Introduction American Standard IncContents Features and Benefits Standard FeaturesOptional Features Proven DesignThroughTesting and Research Trane 3-DScroll CompressorSimple Design with 70% Fewer Parts LowTorque VariationFeatures Benefits Quality and ReliabilityMicro Controls MicroRigorousTesting Ease of InstallationSingle Point Power FC Fans with Inlet GuideVanesEasy to Service ValueVariTrac Application Recommendations Power Exhaust Fan Exhaust Air OptionsBarometric Relief Dampers Altitude CorrectionsAcoustical Considerations Clearance RequirementsDuct Design Selection Procedure Supply Air FanAir Delivery Procedure Electric Heating SystemNatural Gas Heating System Unit Electrical RequirementsModel Number Description General Data Table GD-1 General Data 27 1/2 30 TonsTable GD-2- General Data 35-40Ton Table GD-3- General Data 50Ton Performance Adjustment Factors Table PD-1- Enthalpy of Saturated AIRTable PD-3 Gas Heating Capacity Altitude Correction Factors Performance Data Table PD-4 27 1/2 Ton Gross Cooling Capacities MBhTable PD-5- 30Ton Gross Cooling Capacities Mbh Table PD-6 35Ton Gross Cooling Capacities Mbh Table PD-7 40Ton Gross Cooling Capacities MbhTable PD-8 50Ton Gross Cooling Capacities MBh Table PD-9 Electric Heat AirTemperature Rise Table PD-10 Available Electric Heat KW RangesTable PD-11 Natural Gas Heating Capacities Table PD-12 Supply Fan Performance 27½ 35Ton Static Pressure in. wg1Table PD-13 Supply Fan Performance 40 and 50Ton Table PD-14 Component Static Pressure Drops in.W.G.1 Heating System Filters2 NominalGas Heat Electric Heat3 ID Coil Table PD-15 Supply Air Fan Drive Selections 20 HPNominal Drive Table PD-16- Power Exhaust Fan Performance Controls VAV Units OnlyCV Units Only Unoccupied ZoneTemperature Control Cooling and Heating Supply AirTemperingAuto Changeover ConventionalThermostat InterfaceOccupied/Unoccupied Switching Fan Failure SwitchCoil Freeze Protection Frostat Night Setback SensorsElectrical Service Sizing Electrical DataSet 2. Rooftop units with Electric Heat Table ED-2 27½-50Ton Electrical Service Sizing Data1 Dimensional Data Figure DD-1 27 1/2 35Tons TC,TE,YC Low HeatDimensional Data Figure DD-3 40-50Tons TC,TE,YC Low & High Heat Dimensional Field Installed SensorsConstant CV and VAV Integrated Comfort System SensorsWeights TableW-2 Point Loading AverageWeight1TableW-3 ComponentWeights TableW-4 Minimum Operating Clearances for Unit InstallationMechanical Specifications Unit Options Accessories LP Conversion Kit 20-60Ton Literature Order Number File Number PL-RT-TC/TE/YC-27½ 50-TONS-PRC0007-EN-10-2001

RT-PRC007-EN specifications

The Trane RT-PRC007-EN is a part of Trane’s highly regarded line of air-cooled chillers, designed to provide exceptional performance and efficiency for a variety of commercial applications. This model is known for its robust engineering and cutting-edge technologies, making it a favored choice among facility managers and HVAC professionals.

One of the key features of the RT-PRC007-EN is its energy efficiency. Its advanced compressor design, alongside innovative heat exchanger technology, allows it to achieve significant energy savings, meeting or exceeding standards set by the Department of Energy. This efficiency not only results in lower operational costs but also contributes to a smaller carbon footprint, making it an environmentally friendly choice.

The chiller is equipped with variable speed compressors which adjust their output in relation to the cooling demand. This feature ensures optimal performance at all times, reducing energy consumption during partial load operations. Additionally, the RT-PRC007-EN incorporates Trane's unique Adaptive Control technology. This intelligent control system continuously monitors system parameters and environmental conditions, optimizing performance in real-time to ensure reliable operation.

Another standout characteristic of the RT-PRC007-EN is its quiet operation. The inclusion of sound-dampening technology and strategically placed acoustic insulation allows this chiller to operate with minimal noise, making it suitable for installations in noise-sensitive environments like hospitals or schools.

Durability is another hallmark of the RT-PRC007-EN. Built with high-quality materials, it is designed to withstand harsh operating conditions. Its corrosion-resistant components ensure longevity and reduce the need for extensive maintenance, making it a reliable choice for operators.

Lastly, the RT-PRC007-EN comes with a variety of customization options, including different refrigerant types, control systems, and capacity configurations. This flexibility allows it to adapt to the specific needs of different applications and building designs.

In summary, the Trane RT-PRC007-EN represents a fusion of efficiency, reliability, and advanced technology, making it an excellent option for those seeking a cutting-edge air-cooled chiller for their commercial HVAC needs.
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