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OD °F
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Refrigerant / System
SEER
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ID Return
Air °F (at coil)
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ID Supply
Air °F (at coil)
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ID Coil SEER
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DB
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WB
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DB
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WB
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High pressure
port used
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Discharge Line °F
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┌─────┐
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◄——
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Vapor Line °F
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╔
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═════╩═
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═════
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╡ │
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Suction Line °F
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╔═══╩═
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════════════════
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╗
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╚
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═══════════════
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╗
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│ ╞
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═══
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═══
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═╗║
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╔
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═══════════════
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╝
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╔
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═══Condenser════
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╝
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│ │
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┌ ║║─┐
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╚
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════Evaporator═══
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╗
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╚
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══
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══
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╗
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│ │
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│║ ║│
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╔
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══
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══
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╝
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╔
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═════
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═════
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╝
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│ │
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│╚═╝│
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╚
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═════
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═════
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╗
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╚
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═══
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-14~700psig
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═══
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╗
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┌──▬──┐
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└─▬─┘
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╔
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═══
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-14~500psig
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═══
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╝
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Manufacturers intended TXV subcooling
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╔
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Filter/dryer upstream
Metering device upstream
═══════════════
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╝
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Compressor
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Accumulator
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╚
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═══════════════
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╗
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║
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Liquid Line °F
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——►
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___
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║
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╚
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══════════════════════╩═
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═══════════════════
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═‖═
or ═ʘ═ ══════
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╝
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Metering device
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Evaporator Superheat
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Normal TXV superheat is 10 - 20°
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Evaporator TD
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Normal evaporator saturation temperature is 25 - 35° below return air DB for 13 seer & up
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Condenser Subcooling
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Normal TXV subcooling for 13 seer & up is 4 - 17°
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Condenser TD
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Normal condenser saturation temperature for 13 seer & up is 7 - 20° over OD temperature
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Compression Ratio
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Normal compression ratio for 13 seer & up is 1.7 to 3.1
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Indoor Air Delta T
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ID dry and wet bulb temperatures are needed to determine the target indoor air ΔT
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Legend:
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Adjustable Parameters
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٭
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Adjustable
parameters modified for temperatures
or humidity outside of typical design conditions
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Too low
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Normal
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Too High
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if less than
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if within
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if greater than
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TXV
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superheat
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-
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██
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No remedy suggested. Parameters are in
range
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subcooling
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4
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-
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17
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22
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Fixed Orifice subcooling
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17
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22
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██
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Somewhat
or a little out of range. Use caution
with systems that otherwise perform satisfactorily
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13 seer & up
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Evaporator Temperature Difference =
Evaporator − Return air
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██
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Remedy or repair action is recommended
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13 SEER & up
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-
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12 SEER or less
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-
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╩
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Pressure access port
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Δh
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Delta Enthalpy
(change in total heat content of air)
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Condenser Temperature Difference =
Condenser − Outdoor air
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ΔT
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Delta Temperature
(change in air temperature)
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13 SEER & up
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-
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CTD
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Condenser
Temperature Difference (from outdoor air)
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11 and 12 SEER
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-
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CR
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Compression Ratio
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9 and 10 SEER
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-
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CSH
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Compressor
Superheat (entering compressor)
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8 SEER or less
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-
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CST
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Condenser
Saturation Temperature
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DST
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Discharge Saturation Temperature
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Compression ratio = (high + ambient) ÷
(low + ambient)
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DB
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Dry Bulb temperature
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13 SEER & up
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-
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ETD
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Evaporator Temperature Difference (from return air)
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11 and 12 SEER
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-
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ESH
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Evaporator SuperHeat (at insulated vapor line)
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9 and 10 SEER
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-
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EST
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Evaporator Saturation Temperature
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8 SEER or less
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-
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FO
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Fixed Orifice
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ID
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Indoor
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Tolerance for thermometer/pressure
gauge calibration
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OD
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Outdoor Air Temperature (entering condenser)
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Tolerance for fixed orifice target
superheat temperature
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RA
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Return Air temperature (entering evaporator)
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Tolerance for target evaporator air
delta temperature
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SA
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Supply Air temperature (leaving evaporator)
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Tolerance for target or manufactures
TXV subcooling
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SC
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Subcooling
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Tolerance for nominal CFM calculated
from Δh
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sCFM
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Standard Air Cubic Feet per Minute
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Estimated temperature drop for
filter/dryer
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SH
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Superheat
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Estimated temperature drop for metering
device
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SHR
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Sensible Heat Ratio
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Minimum temperature for a fully charged
evaporator
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TD
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Temperature Difference (of refrigerant and air)
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Maximum refrigerant temperature entering compressor
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TSA
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Target Supply Air (temperature from ΔT chart)
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Min. temp. difference between max. TXV
SC and CTD
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TXV
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Thermal expansion Valve
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R-22 estimated normal condenser
pressure drop
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%
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WB
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Wet Bulb temperature
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R-410a estimated normal condenser
pressure drop
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%
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Maximum suction line temperature above
vapor line
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Notes:
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FALSE
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0.00
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(all temperatures Fahrenheit)
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This analyzer incorporates a flexible range
for evaporator and condenser temperature differences and system compression
ratios. This enables it to analyze a wide range of indoor and outdoor
conditions. It has the ability to diagnose over forty different issues
including a combination of issues. It will provide a list of possible causes
and recommendations.
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This analyzer can be customized to a
manufacturers model lineup and/or specific system. Send inquires to
waynependergast at the domain name comcast with a dot, and the word net.
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Temperature
Difference is between two substances (air vs refrigerant). Delta Temperature
is change in single substance (air in vs out)
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spacer
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Run system on high stage and long enough for liquid refrigerant
to un-migrate from crankcase, vapor line, coils and accumulator.
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spacer
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Return air wet bulb temperature is essential for diagnosis,
humidity greatly affects the indoor coil which affects the entire system.
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spacer
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Record traversed average temperature of
moving air shaded from radiant heat, (sun, body, heat exchanger, heater coil
etc.) Use clamp style probes for taking pipe temperatures.
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Discharge line temperature should be 225°F or less, 6" from
compressor, if higher, check the manufacturer’s maximum.
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When liquid refrigerant is present, its
saturation temperature dictates the pressure. This saturation temperature is
affected by heat absorption or rejection (airflow), the compressors ability
to pump, and the metering devices ability to allow or restrict flow.
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spacer
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When adding refrigerant, it's best to open
the charging valve to a pressure at, or just above, the desired EST. Letting
the low side of the system "see" a high tank pressure can extend
the time it takes for the refrigerant to stabilize.
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spacer
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If a steady state condition is not
achievable, an inverted trap may be missing from the top of the vapor line
riser, liquid traps may be in the horizontal vapor line, non-condensables may
be in the system, or an oversized (hunting) TXV may be the cause.
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For A/C units, every 1º of added subcooling
without raising condensing pressure, produces an average increase of .5%
system efficiency. Increasing both subcooling and condensing pressure (more
than necessary to feed the metering device) reduces efficiency. For heat
pumps, use the manufacturers recommended subcooling value (correct charge in
cooling assures correct charge in heating).
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Compressor amperage depends on both the
rate of refrigerant flow and the difference in pressure. Without a
significant change in flow, the compressor amperage will follow the
compression ratio, when the CR is high the amperage will be high and
vice-versa.
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spacer
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Change of State in a liquid line sight
glass while subcooling is measured indicates non-condensables, impure
refrigerant, or calibration error. A single bubble can be due to expansion in
the sight glass.
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Calculations
assume a pure refrigerant but can indicate the presence of non-condensables
or impure mixtures.
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Psychrometric calculations made using .075 ft³/lb density and
the perfect gas relationship for dry and moist air. Ideal Gas Law: pV=nRT
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This calculator is a useful tool for
assisting a technician with diagnostics and repairs, but it is the
technicians responsibility to verify the validity of the analysis made by
this application.
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efficientcomfort.net. All Rights Reserved.
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