AC 2004 presentation.PPT

8/10/2019 AC 2004 presentation.PPT

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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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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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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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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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High Side Change Outs: Capacity?

Efficiency? Line Set?

Condition of Evaporator Coil

Oil Logged? Clean?

Refrigeration Piping


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Why This Is Important: Oil Return

Suction Line Velocity Capacity Losses

Flash Gas Liquid Line

Flood Back - Compressor


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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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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



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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



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g y



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g y



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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


equals = Superheat



10

45


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Vapor

SaturatedVapor


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


equals =Superheat



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26


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Vapor

SaturatedVapor


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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Documents

AC 2004 presentation.PPT