Enertech ZS., Руководство по установке и эксплуатации, Страница: 71 / 89

71 IOM, ZS/ZT Models Enertech Global
Water Flow Selection
Proper flow rate is crucial for reliable operation of geothermal heat
pumps. The performance data shows three flow rates for each entering
water temperature (EWT column). The general “rule of thumb” when
selecting flow rates is the following:
Top flow rate: Open loop systems (1.5 to 2.0 gpm per ton)
Middle flow rate: Minimum closed loop system flow rate
(2.25 to 2.50 gpm/ton)
Bottom flow rate: Nominal (optimum) closed loop system flow rate
(3.0 gpm/ton)
Although the industry standard is adequate in most areas of North
America, it is important to consider the application type before applying
this “rule of thumb.” Antifreeze is generally required for all closed loop
(geothermal) applications. Extreme Southern U.S. locations are the
only exception. Open loop (well water) systems cannot use antifreeze,
and must have enough flow rate in order to avoid freezing conditions at
the Leaving Source Water Temperature (LWT) connection.
Calculations must be made for all systems without antifreeze to
determine if the top flow rate is adequate to prevent LWT at or near
freezing conditions. The following steps should taken in making this
calculation:
Determine minimum EWT based upon your geographical area.
Go to the performance data table for the heat pump model selected and
look up the the Heat of Extraction (HE) at the “rule of thumb” water flow
rate (GPM) and at the design Entering Air Temperature (EAT).
Calculate the temperature difference (TD) based upon the HE and GPM
of the model.
TD = HE / (GPM x 500).
Calculate the LWT.
LWT = EWT - TD.
If the LWT is below 35-38°F, there is potential for freezing conditions if
the flow rate or water temperature is less than ideal conditions, and the
flow rate must be increased.
Example 1:
EWT = 50°F.
Model HT048, high capacity. Flow rate = 6 GPM.
Air Flow = 1650 CFM. HE = 35,600 Btuh.
TD = 36,600 / (6 x 500) = 11.9°F
LWT = 50 - 11.9 = 38.1°F
Since the water flow is leaving at approximately 38°F, the flow rate
is acceptable.
Example 2:
EWT = 40°F.
Model HT048, high capacity. Flow rate = 6 GPM.
Air Flow = 1650 CFM. HE = 30,600 Btuh.
TD = 30,600 / (6 x 500) = 10.2°F
LWT = 40 - 10.2 = 29.8°F
Water flow rate must be increased to avoid freezing.
Heating Cooling
LAT = EAT + HC
CFM x 1.08
LAT (DB) = EAT (DB) - SC
CFM x 1.08
LWT = EWT - HE
GPM x 500
LWT = EWT + HR
GPM x 500
LC = TC - SC
Heating & Cooling Calculations
Glossary of Terms
SECTION 11: EQUIPMENT START-UP PROCEDURES
ASC = Anti-Short Cycle HGT = Hot Gas Temperature
AFRZ = Anti-Freeze HP = High Pressure
CFM = Airflow, Cubic Feet/Minute HR = Total Heat Of Rejection, Btu/hr
CO = Condensate Overflow HWG = Hot Water Generator
COP = Coefficient of Performance = BTU Output / BTU input KW = Total Power Unit Input, Kilowatts
DGT = Hot Discharge Gas Temperature
LAT = Leaving Air Temperature, Fahrenheit
DH = Desuperheater Capacity, Btu/hr LC = Latent Cooling Capacity, Btu/hr
DLWT = Domestic Leaving Water Temperature LCT = Load Coil (Heat Exchanger) Temperature (Freeze)
EAT = Entering Air Temperature, Fahrenheit (Dry/Wet Bulb) LLT = Leaving Load Water Temperature, Fahrenheit
ECM = Electronically Commutated Motors LP = Low Pressure
EER = Energy Efficiency Ratio = BTU output/Watts input LWT = Leaving Source Water Temperature, Fahrenheit
ELT = Entering Load Water Temperature, Fahrenheit O/U = Over/Under
EWT = Entering Source Water Temperature, Fahrenheit ODD = On Demand Dehumidification
FS = Factory Setting SC = Sensible Cooling Capacity, Btu/hr
FSW Flow Switch SCT Source Coil (Heat Echanger) Temperature (Freeze)
GPM = Water Flow, Gallons Per Minute TC = Total Cooling Capacity, Btu/hr
HC = Total Heating Capacity, Btu/hr TEST = Test Mode
HE = Total Heat Of Extraction, Btu/hr WPD = Water Pressure Drop, PSI & Feet of Water