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RB SERIES ENGINEERING GUIDE
Reference Calculations
Legend and Notes
ABBREVIATIONS AND DEFINITIONS:
cfm = airflow, cubic feet/minute
EWT = entering water temperature, Fahrenheit
gpm = water flow in gallons/minute
WPD = water pressure drop, psi and feet of water
EAT = entering air temperature, Fahrenheit
(dry bulb/wet bulb)
HC = air heating capacity, MBtu/h
TC = total cooling capacity, MBtu/h
SC = sensible cooling capacity, MBtu/h
kW = total power unit input, kilowatts
HR = total heat of rejection, MBtu/h
HE = total heat of extraction, MBtu/h
HWC = hot water generator capacity, MBtu/h
EER = Energy Efficient Ratio
= BTU output/Watt input
COP = Coefficient of Performance
= Btu output/Btu input
LWT = leaving water temperature, °F
LAT = leaving air temperature, °F
TH = total heating capacity, MBtu/h
LC = latent cooling capacity, MBtu/h
S/T = sensible to total cooling ratio
Notes (Refer to Performance Data tables)
• Performance ratings are based on 80°F DB / 67°F WB EAT for cooling and 70°F DB EAT for heating.
• Three flow rates are shown for each unit. The lowest flow rate shown is used for geothermal open loop/well water systems with a
minimum of 50°F EWT. The middle flow rate shown is the minimum geothermal closed loop flow rate. The highest flow rate shown is
optimum for geothermal closed loop systems and the suggested flow rate for boiler/tower applications.
• Entering water temperatures below 40°F assumes 15% antifreeze solution.
• For non-standard EAT conditions, apply the appropriate correction factors on (Refer to Correction Factor Tables).
• Interpolation between EWT, gpm, and cfm data is permissible.
Heating Calculations:
Cooling Calculations:
LWT = EWT +
LAT(DB) = EAT(DB) -
LC = TC - SC
S/T =
HR
gpm x 500
SC
cfm x 1.08
SC
TC
HE
gpm x 500
LWT = EWT -
LAT = EAT +
TH = HC + HWC
HC
cfm x 1.08
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