Air Conditioning

1
Air Conditioning Charging Procedures Review
2
Basic Refrigeration
3
Basic Refrigeration
Liquid Line
Liquid Line
Metering Device
Condenser
Low Side
Hi Side
Evaporator
Compressor
4
Saturation Temperature
5
What is Saturation Temperature?

• Saturation temperature is the actual temperature
  of the evaporator and condenser coils.
• In saturation conditions, both vapor and liquid
  are present

6
How do you find Saturation Temperature?

• Refrigeration Gauges
• The Only purpose of owning a set of gauges is to
  find the refrigerant saturation temperature.

7
Saturated Refrigerant
Liquid Line
Metering Device
Condenser
Evaporator
Discharge Line
Suction Line
Compressor
8
System Charging
9
First things first

• You must verify that you have proper airflow!and
  you must have the proper tools to do the job.

10
Air Flow
11
Air Flow is Critical
12
Air Flow Measurements

• Total Static Pressure
• CFM Measurements
• -Temperature Rise
• -Evaporator Pressure Drop
• -Air Velocity
• -Temperature Drop

13
Static Pressure Measurement

• The key to system airflow diagnostics
• A companion to airflow measurement
• It takes less than 5 minutes to measure
• Similar to blood pressure diagnostics

14
(No Transcript)
15
Total Static Pressure
16
Air Flow Measurement-Temperature Rise Methodto
determine CFM
17
Airflow Measurement(Temperature Rise Method)
(Red Book, Pg. 33)
18
CFM By Temperature Rise

• BTUH OUTPUT
• ?T X 1.08

CFM
1.08 constant number for std air. Its a
combination of a number of values that are in the
complete equation. Std air is 70F, sea level
19
CFM By Temperature Rise

• 55,200 BTU output
• 60 X 1.08

850 CFM
64.8
20
CFM By Evaporator Pressure Drop
21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
Velocity

• Velocity FPM
• CFM FPM X Area in Square Feet
• Free Area

26
Humid Air
Dry Air
27
Fan Speed Taps

• Check Service Facts for proper air speed tap to
  use
• Match tap to size (BTUH) of unit

28
(No Transcript)
29
Blower should always be on high speed?

• 2 TON 800 CFM

30
(No Transcript)
31
System Charging
32
The Right Stuff

• Basic Tools
• Refrigerant Gauges
• Digital Thermometer (one with Wet Bulb
  capabilities)

33
SYSTEM CHARGING

• The sub-cooling method is required when charging
  TXV systems.
• The super-heat method is required when charging
  fixed orifice systems.
• Charging charts are included in the Service Facts
  document that come with the outdoor equipment.
• Remember to allow sufficient time for the system
  to stabilize before adjusting the refrigerant
  charge.

34
Beer Can Cold and Sweaty
35
SYSTEM CHARGING(SC) Using the Charging Chart-TXV

• Measure temperature and pressure at liquid line.
• Use line length lift to choose which curve to
  use.
• Plot the intersection of temp. pressure.
• If above the curve, remove refrigerant.
• If below, add refrigerant
• Wait 20 minutes to stabilize.

36
Sub-Cooling Calculation

• Low Sub-Cooling indicates LOW charge
• High Sub-Cooling indicates OVER charge ( or
  possible liquid line restriction)
• Rule of thumb 10 - 15 degrees of sub-cooling
  Manufactures usually design to 10 degrees

37
(No Transcript)
38
(390 PSIG 115º F)
39
SYSTEM CHARGING(SH) Using the Charging
Chart-Fixed Orifice

• Measure indoor dry bulb (R/A)
• Measure outdoor dry bulb (at unit)
• Measure suction pressure
• Measure suction temperature, before suction
  service valve
• Use chart to determine SH
• Above 5 F above, add. If 5 F below, remove.
• If below 5 F limit line, DO NOT ADD.
• If RH gt70 or lt20, use ID wet-bulb

40
Superheat Calculation

• Superheat indicates that complete vaporization of
  liquid refrigerant in the evaporator coil has
  taken place
• Low Superheat means liquid refrigerant is present
  at or near the outlet of the evaporator -
  compressor damage is immanent
• High Superheat means liquid is boiling off too
  soon and could mean evaporator is starved

41
(No Transcript)
42
Customer Complaint

• System does not cool like it before when it was
  new
• What do you do?

Check the Enthalpy of the Evaporator Coil
to verify system capacity
43
Use the Formula

• Total Heat Removed
• CFM X 4.5 X Change in Enthalpy (Heat Content)

44
Enthalpy

• Same as TOTAL HEAT
• The sum of sensible heat and latent heat

Wheres the 4.5 come from? Its how many BTUs
are in one pound of DRY air (0Rh)
45
(No Transcript)
46
Total Heat CFM X 4.5 X Enthalpy Change
69 WB33.25 60 WB26.46 Difference 6.79 800 X
4.5 X 6.79 24,444 BTUH !

47
(No Transcript)
48
(No Transcript)
49
(No Transcript)
50
(No Transcript)
51
(No Transcript)
52
(No Transcript)