Carrier WeatherMaker 48TC Series Product Data

Also see for 48TC series: Installation instructions User's information manual Installation instructions User's information manual Installation instructions

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33SELECTION PROCEDURE (WITH 48TC*A07 EXAMPLE)1I. Determine cooling and heating loads.Given:Mixed air dry bulb 80_F (27_C)Mixed air wet bulb 67_F (19_C)Ambient dry bulb 95_F (35_C)TCLoad 72.0 MBHSHCLoad 54.0 MBHVertical supply air 2100 CFMHeating load 85.0 MBHExternal static pressure 0.67 in. wgElectrical characteristics 230--3--60II. Make an initial guess at cooling tons.Refrig. tons = TCLoad / 12 MBH per tonRefrig. tons = 72.0 / 12 = 6.0 tonsIn this case, start by looking at the 48TC**07.III. Look up the rooftop’s TC and SHC.Table 19 shows that, at the application’s supply airCFM, mixed air and ambient temperatures, the48TC*A07 supplies:TC = 73.7 MBH2SHC = 54.4 MBH2IV. Calculate the building latent heat load.LCLoad = TCLoad -- SHCLoadLCLoad = 72.0 MBH -- 54.0 MBH = 18.0 MBHV. Calculate RTU latent heat capacity.LC = TC -- SHCLC = 73.7 MBH -- 54.4 MBH = 19.3 MBHVI. Compare RTU capacities to loads. 3Compare the rooftop’s SHC and LC to thebuilding’s sensible and latent heat loads.VII. Select factory options (FIOP)Local code requires an economizer for any unit withTC greater than 65.0 MBH.VIII. Calculate the total static pressure.External static pressure 0.67 in. wgSum of FIOP / Accessory static +0.13 in. wgTotal Static Pressure 0.80 in. wgIX. Look up the indoor fan RPM & BHP.Table 47 shows, at 2100 CFM & ESP= 0.8,RPM = 1358 & BHP = 1.52X. Convert BHP (Step VIII) into fan motor heat.Fan motor heat = 2.546* BHP/Motor Eff.4Fan motor heat = 4.9 MBHXI. Calculate RTU heating capacity.Building heating load 85.0 MBHFan motor heat --4.9 MBHRequired heating capacity 80.1 MBHXII. Select a gas heater.Table 3 shows the heating capacities of the48TCEA07 = 93.0 MBH. Select the 48TCEA07XIII. Determine electrical requirements.The MCA and MOCP tables show 48TC*A07(without convenience outlet) as:MCA = 30.5 amps & MOCP = 45.0 ampsMin. disconnect size: FLA = 30 & LRA = 157.LegendBHP — Brake horsepowerFLA — Full load ampsLC — Latent capacityLRA — Lock rotor ampMBH — (1,000) BTUHMCA — Min. circuit ampacityMOCP — Max. over--- current protectionRPM — Revolutions per minuteRTU — Rooftop unitSHC — Sensible heat capacityTC — Total capacityNOTES:1. Selection software by Carrier saves time by performing manyof the steps above. Contact your Carrier sales representativefor assistance.2. Unit ratings are gross capacities and do not include the effectof evaporator fan motor heat. See Step X. for determiningamount of evaporator fan motor heat to subtract from totaland sensible capacities to obtain net cooling and net sens-ible capacities.3. Selecting a unit with a SHC slightly lower than the SHC Load isoften better than oversizing. Slightly lower SHC’s will helpcontrol indoor humidity, and prevent temperature swings.4. Indoor fan motor efficiency is available in the Electrical Infor-mation. Use the decimal form in the equation, eg. 80% = .8.