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Air Conditioning 2004
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Service AdvisorsGustave Larson A. Company
Plymouth Office: 800-827-9508
763-546-9508
Gale Patterson ext. 343Steve LeMay ext. 346
Pewaukee Office: 800-829-9609Steve Bukosky ext. 247
Tim Chamberlain ext. 285
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Air Conditioning 2004
Thermodynamics
InstallationAir Flow
R410 vs R22Service
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Air Flow
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Thermodynamics
Saturation Temperature
Density of Refrigerant VaporEnthalpy
Superheated Vapor
Sub-cooled Liquid
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Heat Transfer
Hot Object Cold Object
HEAT
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212
0
32
One pound of water being heated at one BTU per hour.
Temperature of the
water.
1310 total BTUs used.
16 144 180 966158 340 1306
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Basic Refrigeration
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Basic Refrigeration
Liquid LineLiquid Line MeteringDevice
Evaporator
Compressor
Condenser
Hi SideLow Side
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What is Saturation
Temperature?
Saturation temperature is the actual
temperature of the evaporator andcondenser coils.
In saturation conditions, both vapor
and liquid are present
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How do you find Saturation
Temperature?Refrigeration Gauges
The Only purpose of owning aset of gauges is to find therefrigerant saturationtemperature.
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Saturated Refrigerant
Liquid Line
Suction Line
Evaporator
Condenser
Discharge Line
Compressor
MeteringDevice
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Saturated Refrigerant
Liquid and Vapor inContact with EachOther in Equilibrium
Pressure andTemperature TiedTogether
P/T Chart is
Applicable
Saturated Refr igeration
Example: Conditions, R-22 - 287 PSIG
128F Temperature
P-T Chart at 287 PSIG R-22 = 128F
Line Temperature = 128F
Refrigerant is Saturated
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Pressure/Temperature Chart
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Thermodynamics/Condenser Coil
Purpose of condenser coil is to reject theheat load absorbed by evaporator coil, andto cool the refrigerant to a level that is
below the saturation temperature.-This is accomplished through (1) LatentHeat Transfer, and (2) Sensible Ht.Transfer.
-Proper sub-cooling prevents saturatedrefrigerant from leaving the condenser,thus optimizing metering deviceperformance.
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Sub-Cooled Liquid
Typical sub-cooling levels - 5 to 20 degrees-Not enough sub-cooling, or large pressure
losses in the liquid line create theformation of flash gas will affect theoperation of the metering device.-10 degrees overcomes 35PSIG of liquid
line pressure drop in R-22 systems.-10 degrees overcomes 50PSIG of liquidline pressure drop in R-410A systems.
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Sub-Cooled Liquid
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Sub-Cooling
Heat Removed fromthe Liquid Refrigerantthat Causes its
Temperature to DropBelow its SaturationTemperature
P/T Charts do not
Apply- TemperatureDrops without a Dropin Pressure
Sub-Cooling
Example: Conditions, R-22 - 280 PSIG
120F Line Temperature
P-T Chart at 280 PSIG = 125F
Line Temperature = 120F5F
Refrigerant Sub-cooled at 5F
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Sub-Cooled Liquid
Liquid Line
Suction Line
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Thermodynamics/Evaporator Coil
Purpose of evaporator coil is to absorb theheat load from the space being conditionedand to evaporate the liquid refrigerant to alevel above the saturated temperature.
This is accomplished through (1) LatentHeat Transfer, and (2) Sensible HeatTransfer.Proper superheating prevents liquid refrig
from leaving the evaporator, thusoptimizing the removal of heat from thespace and protecting the compressor fromdamage
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Superheat Principles
Superheat is the temperature of the refrigerantvapor above its saturation temperature.Superheating is done by the load. If the load islow, the superheat will be low. If the load is high,
the superheat will be high.Superheat is a Sensible Heat Transfer thatprovides very little useful cooling. This occursbecause there is no change in state; only change intemperature.Refrigerants should never leave the evaporatorcoil at saturation temperature, because liquid isstill present.
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Superheat Principles (cont)
Latent Heat Transfer gives us our greatest energy
transfer and results in massive cooling capacity.
The evaporator surface performance is based onthe amount of Latent to Sensible Heat Transfertaking place.
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Superheat
Heat Added to
Refrigerant Vapor that
Causes its Temperature
to Rise Above itsSaturation
Temperatures
P/T Charts Do Not
Apply - Temperature
Rises Without a Rise in
Pressure
Superheated Refrigerant
Example: Conditions, R-22 - 75.0 PSIG
Suction Line - 54F
Line Temperature = 54F
P-T Chart at 75.0 PSIG= 44F
10F
Coil Operating at 10F Superheat
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Superheated Refrigerant
Compressor
Suction Line
Liquid Line
Discharge Line
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What is R-410A?
R-410A is a blend of two refrigerants,near Azeotropic mixture of 50% HFC-32
and 50% HFC-125.Many of us have been using refrigerant
blends for awhile, R-502.
The Temp. Glide is negligible (< 0.3F).
There is no significant change incomposition due to system leaks.
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What is R-410A?
The Ozone depletion potential(ODP)for R-410A is 0.00 Vs 0.05 for R-22
(1.0 is R-12 which is the baselineestablished by EPA).The ASHRAE safety classification is
A1/A1, the same as R-22.Boiling point is -62.9F Vs -41.4F for
R-22.
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What is R-410A?
Flammability classified as non-
flammable.Combustibility can occur when
mixed with air under pressure
(same as R-22).Toxicity is classified as low.
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WHAT IS R-410A?
Thermal stability is similar to R-22.
Handling cautions are the same as R-22.
Remember 50 to 70% higher pressuresrequire the proper tools for
servicing.
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R-410A POE Oil
Non-contaminated POE oils willnot harm skin.
Non-contaminated POE oil has alight sweet odor.
POEs are classified as non-hazardous.
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R-410A POE Oil
POE oils from a severe acidsystem will smell like dirty
diapers.Severe burn outs create acids
and alcohol and moisture.
Waste oil may be disposedthrough waste recyclers.
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R-410A POE Oil
Synthetic oil will attack many roofingmaterials. When servicing equipment
mounted on a roof, the roof must beprotected from oil spray or spills. Usea plastic covering or tarp to protect
the work area.Wiping up a spill will notstop long
term damage to the roofing materials.
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R-410A POE Oil
Open containers can absorb
1500 to 2000 ppm/ water.
Keep containers sealed when not
in use.
Use reasonable refrigerationpractices.
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R-410A POE Oil
Vacuum pumps will not
completely remove moisture,
driers must be replaced everytime a refrigerant component is
replaced.
Not even a deep vacuum will
remove moisture from POE oils!
Oil M i t Ab ti R t
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Oil Moisture Absorption Rate(POE Oil)
Time Minutes
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Discus Compressors/Polyol Ester OilMoisture Content Versus Time
100
200
300
Sample Size: 13
237 PPM
129 PPM93 PPM
75 PPM
270 PPM
156 PPM
Filter Change at 60Days Operating
30 PPM
20 PPMExit Copeland Exit-Rack
Manufacturer
At Jobsite At Jobsite
30 Days 75 Days
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DRIERS
Suction line driers must only be usedon the low side of the system.Operating temperatures and
pressures may be exceeded if appliedon the high side.
High temperatures will cause theactivated alumina in suction linedriers to decompose, causing moreacid.
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LEAK DETECTION
Electronic leak detectors mustbe capable of detecting HFC
gases. Halide torches detectchlorine and will not work withHFC refrigerants.
Fluorescent dyes are notapproved for Trane equipment.
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Installation Considerations:
Airflow, Airflow, AirflowManual J
Refrigerant linesOutdoor unitsIndoor units Back-up heat Accessories Controls
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Installation Considerations:
Check unit Is it the right one???i.e., correct size, voltage, etc.
Check Product Data Sheets,Installation Guide, and/or ServiceFacts
FCCV/TXV?Air Flow
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Installation Considerations:
Air, moisture, and dirt WILL cause afailure or problemsooner or later
Replace liquid line drier anytime thesystem is opened after initial install
Use oxy-acetylene for brazing
Rap valves, etc with wet rag toprotect
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Installation Considerations:
Purge with Nitrogen when brazing
Remove valve core
Evacuate to 500 microns(MICRON GAUGE)
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Micron Gage
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(430-535F)
(1190-1465F)
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Installation Considerations:
High Side Change Outs: Capacity?
Efficiency? Line Set?
Condition of Evaporator Coil
Oil Logged? Clean?
Refrigeration Piping
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Refrigeration Piping
Why This Is Important: Oil Return
Suction Line Velocity Capacity Losses
Flash Gas Liquid Line
Flood Back - Compressor
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Refrigeration Piping
Points To Remember: OK up to 50 Ft
Elbows add EQUIVALENT length >10 Ft rise CALL
>50 Ft EQUIVALENT - CALL
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When You Call
What is the actual length?
What size tubing or pipe
How many elbows are expected?
Long sweep or short?
Is condenser above or belowevaporator?
Air Flow
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Air Flow
Ai Fl
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Air Flow
Air is Invisible
Everyone assumes adequate airflow
Reality is Airflow is frequently 30-50% LOW
Duct leakage or high static pressure
Air properties MUST BE MEASURED
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Ai Fl
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Air Flow
The Equipment or the System???
Cannot get proper performance from
equipment with CORRECT AIRFLOWCannot accurately charge a fixedorifice system without CORRECT
AIRFLOWSo.What do we do?
Ai Fl B i
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Air Flow Basics
Total Air Volume Cubic Feet Per Minute(CFM)
Velocity Feet Per Minute (FPM)
Static Pressure
Velocity Pressure
Total Pressure
Converting Static Pressure into VelocityAir Movement
Static Pressure
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Velocity Pressure
Total Pressure
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Duct Losses
30% not uncommon!
Fix duct losses and get more capacity!
Return lossBottom pan
Supply loss
Leaking humidifier bypass damper
Duct Leaks
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Duct Leaks
Leaks can cause dirty, unconditionedair to enter a residence.Leaks also contribute to loss inefficiency and capacity: 1% in totalairflow = 1% loss in capacity2.5 ton 30,000 BTUH 1000 CFM
-3,000 BTUH -100 CFM*
27,000 BTUH 900 CFM*10% loss in air and capacity
Air Movement System
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Air Movement System
If any part of the distributionprocess is oversized or undersized,closed off or restricted, the entiresystem can be disrupted. This cancause: Comp. Flooding; Drafty rooms;Humidity problems; Mold/Mildew;Sweating ductwork; Motor wear;
Noisy systems; Dust; Hear Exchangerfailure; Electrical problems; Positiveor Negative house pressure
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Air Flow Measurements
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Air Flow Measurements
Total Static Pressure
CFM Measurements:-Temperature Rise
-Evaporator Pressure Drop
-Air Velocity
-Temperature Drop*
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Static Pressure Measurement
The key to system airflow diagnostics
A companion to airflow measurement
It takes less than 5 minutes tomeasure
Similar to blood pressure diagnostics
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Total Static Pressure
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Total External Static
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Total External Static
Pressure
+.65 (Supply side reading)
-.45 (Return side reading)1.10 Total External Static Pressure
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Air Flow Measurement-
Temperature Rise Methodto determine CFM
Airflow Measurement
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rf ow M asur m nt(Temperature Rise Method)
(Red Book, Pg. 33)
CFM By Temperature Rise
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CFM By Temperature Rise
BTUH OUTPUT
T X 1.08*=CFM
*1.08 = constant number for std air. Its acombination of a number of values that are in thecomplete equation. Std air is 70F, sea level
CFM By Temperature Rise
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CFM By Temperature Rise
55,200 BTU output
60 X 1.08=850 CFM
64.8
CFM Per Room?
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CFM Per Room?
-7,500 BTUH Heat Loss
-Room temperature = 72 F
-Supply air = 125F
-How many CFMs required?
CFM Per Room?
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CFM Per Room?
-Use formula: CFM= BTUH
T X 1.08
-CFM = 7500 BTUH
(125-72F) X 1.08
-CFM = 131
BTUH Per Room?
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BTUH Per Room?
-Air delivered to room = 131 CFM
-Room temperature = 72F
-Supply air = 125F
-How many BTUs delivered?
BTUH Per Room?
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BTUH Per Room?
-Use formula:
BTUH = CFM X T X 1.08
-BTUH = 131 CFM X (125-72F) X
1.08
-BTUH = 131 X 53 X 1.08
-BTUH = 7,498
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CFMBy EvaporatorPressure Drop
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Velocity
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Velocity
Velocity = FPM
CFM= FPM X Area in Square Feet
Free Area
Measuring Air Velocity
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M asur ng r V oc ty
Measuring Air Velocity
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g y
Measuring Air Velocity
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g y
Measuring Air Velocity
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Measuring Air Velocity
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g y
CFM By Temperature Drop*
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CFM By Temperature Drop
It can vary depending on outsidetemperature and indoor wet-bulb
What if the system is undercharged,overcharged or dirty condenser?
What if its too cold outside?
Have you ever seen a manufacturerswritten specification for it?
Humid Air
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Dry Air
Fan Speed Taps
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Fan Speed Taps
Check Service Facts for proper air
speed tap to use
Match tap to size (BTUH) of unit
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Blower should always be on high speed?
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y g p
2 TON800 CFM
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Break-timeBe
Back in 10minutes
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Time Remaining
10 Minutes
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Time Remaining
9 Minutes
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Time Remaining
7 Minutes
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Time Remaining
4 Minutes
Time Remaining
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3 Minutes
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Time Remaining2 Minutes
Time Remaining
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1 Minute
Time Remaining
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15 Seconds
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OK, Times Up!
Let get the show on the road!!!
Basic Tasks-Spring Tune-Up
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Wash Condenser Check for clean filters and evaporator
Service blower
Check drainage
Check controls
Check refrigerant charge
Check overall Performance
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System Charge Airflow!
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System Charge Airflow!
Correct starting point for ANYrefrigeration system diagnostics
Validate proper airflowGauge pressure reads low, but is lowcharge the real problem?
Dont automatically add gas.
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Beer Can Cold andSweaty
How do I know what I have?
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How do I know what I have?
What kind of metering device?
Remember, TXVs may be built with
evaporator and not apparent.
Bl k d s i t is h d
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Block condenser air to raise head
pressure Piston/cap tube - gage pressures
will rise at a fairly even rate TXV will tend to keep suction
pressure stable as head pressure
increases
SYSTEM CHARGING(SC)Using the Charging Chart TXV
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Using the Charging Chart-TXV
Measure temperature and pressure atliquid line.
Use line length & lift to choose which curveto use.Plot the intersection of temp. & pressure.
If above the curve, remove refrigerant.
If below, add refrigerantWait 20 minutes to stabilize.
Sub-Cooling Calculation
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g
Low Sub-Cooling indicates LOWchargeHigh Sub-Cooling indicates OVERcharge ( or possible liquid linerestriction)Rule of thumb = 10 - 15 degrees of
sub-cooling Manufactures usuallydesign to 10 degrees
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(390 PSIG & 115 F)
SYSTEM CHARGING(SH)Using the Charging Chart-Fixed Orifice
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Using the Charging Chart Fixed Orifice
Measure indoor dry bulb* (R/A)Measure outdoor dry bulb (at unit)Measure suction pressure
Measure suction temperature, beforesuction service valveUse chart to determine SHAbove 5 F above, add. If 5 F below,
remove.If below 5 F limit line, DO NOT ADD.*If RH >70% or
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Superheatindicates that completevaporization of liquid refrigerant in theevaporator coil has taken place
Low Superheatmeans liquid refrigerant is
present at or near the outlet of theevaporator - compressor damage isimmanent
High Superheatmeans liquid is boiling off
too soon and could mean evaporator isstarved
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As Little As...
As Much As...
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Sub-cooling andSuperheat
SL Temperature
SL Pres. To Saturation
equals =S h t
minus -Sub-cooling & Superheat
Calculation Explained55
10
45
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Indoor Coil Outdoor Coil
High Pressure,High Temperature
Vapor
SaturatedVapor
High Pressure,Sub-cooled Liquid
Low Pres.Liquid
Saturated
Vapor
Superheated
Vapor
minus -
LL Pres. to Saturation
LL Temperature
equals =Sub-cooling
Basic Refrigeration CircuitProperly Charged Unit
equalsSuperheat
Sensible
Latent
Sensible
Sensible
Latent
10
76#
98
10
220#
108
What Happen If ?
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What Happen If?
Over-Charged System
versusUnder-Charged System
Over-Charged System
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High Sub-Coolingreading indicates excessiveamount of refrigerant in the condenser coil Head pressure reading will be high Saturation temperature will be high
Liquid line temperature at or near ambient Unit will use excessive wattage to do the same
amount of work
If TXV is working properly, work at indoor coil willbe basically the same as properly charged systemand Superheatwill be normal
SL Temperature
SL Pres. To Saturation
equals = Superheat
minus -Sub-cooling & Superheat
Calculation Explained55
10
45
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Indoor Coil Outdoor Coil
High Pressure,High Temperature
Vapor
SaturatedVapor
High Pressure,Sub-cooled Liquid
Low Pres.Liquid
Saturated
Vapor
Superheated
Vapor
minus -
LL Press. to Saturation
LL Temperature
equals =Sub-cooling
Basic Refrigeration CircuitOver Charged Unit
q Superheat
Sensible
Latent
Sensible
Sensible
Latent
10
76#
118
17
316#
135
Under-Charged System
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-Low Sub-Coolingreading indicates lack ofrefrigerant in the condenser coil.-Head pressure reading will be low-Saturation temperature will be low
-Liquid line temperature will be high-Unit will use excessive wattage due to doextended run times to do the same work
-TXV will not work properly, due to lack of liquidseal resulting in capacity loss
-Superheatwill be high - coil starved.
SL Temperature
SL Pres. To Saturation
equals =Superheat
minus -Sub-cooling & Superheat
Calculation Explained68
42
26
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Indoor Coil Outdoor Coil
High Pressure,High Temperature
Vapor
SaturatedVapor
High Pressure,Sub-cooled Liquid
Low Pres.Liquid
Saturated
Vapor
Superheated
Vapor
minus-
LL Press. to Saturation
LL Temperature
equals =Sub-cooling
Basic Refrigeration CircuitUnder Charged Unit
Superheat
Sensible
Latent
Sensible
Sensible
Latent
42
50#
95
0
182#
95
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Mechanicalversus
Air Flow
Troubleshooting
Proper Tools
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-Gauges
-Amp Probe
-Digital Thermometer-Sling Psychrometer
-V-O-M
-Magnehelic
-Paperwork
Troubleshooting.
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Verify AIR FLOW is proper
Identify problem
Observe and record operation ofequipment BEFORE adding gas!
When in doubt call for assistance
75 IDB
63 IWB
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Slightly
Or Normal
95 OAT
75#
237#
5 DEG SH
8-13 SUB
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Base Line Data
Customer Complaint:
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System does not cool like it beforewhen it was new
What do you do?
+ Check the Enthalpy of the EvaporatorCoil to verify system capacity
Use the Formula:
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Total Heat Removed =CFM X4.5 X Change inEnthalpy (Heat
Content)
Enthalpy
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Same as TOTAL HEATThe sum of sensible heat and latentheat
Wheres the 4.5 come from?
Its how many BTUs are in onepound of DRY air (0%Rh)
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Total Heat =CFM X4.5 XEnthalpy Change
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69 WB=33.25
60 WB=26.46
Difference = 6.79
800 X 4.5 X 6.79
= 24,444 BTUH !
The 10% Rule
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It is difficult to duplicate theaccuracy of factory laboratories
But, field results within 10% aregenerally adequate.
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Wall of Shame
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