Heating and Air Conditioning Spartan Chassis Air Conditioning & - - PowerPoint PPT Presentation

Gary May

Heating and Air Conditioning

Spartan Chassis Air Conditioning & Maintenance

Principles of HVAC Basic Components and their functions EPA requirements of safe handling Diagnoses of HVAC systems pressure readings. Service tips

Course Outline

The Basic Principles of Air Conditioning The Basic Principles of Air Conditioning

In a solid, molecules are locked together in position. In a liquid, molecules move and share a loose relationship with each other. Molecules in a gas, share no relationship with each other because they move very fast. Heat, commonly described in degrees of temperature, such as Fahrenheit (o F) or Celsius (o C), describes the random motion or “vibration” of molecules. When a substance becomes hotter, its molecules move faster. How fast these molecules move determines whether the substance is a solid, a liquid, or a gas.

Principles of HVAC

Principles of HVAC

When a fast, hot molecule collides with a slower, colder molecule, like a fast car colliding with a slower car…. The slower molecules speeds up (it becomes hotter) like the car, but never as fast as the car that hit it, and it “cools” the faster car, too. Heat always goes from hot to cold because a slower molecule cannot make a faster molecule go faster! Have you ever heard of a car going 15 MPH catching up to and hitting a car going 30 MPH?

Principles of HVAC

Removing heat is simple. Since heat always goes toward a colder

• bject, all we have to do is give heat a cold thing to flow into. A good

example of this is a iced drink. To cool the drink down, we put in ice

• cubes. Since ice cubes are colder than the worm liquid, the heat will

flow into the ice cubes. The ice cubes absorb the heat and melt, removing the heat from the liquid. Now the drink is much more enjoyable.

How A/C Works

Principles of HVAC

Heat always goes to cool

Principles of HVAC

Hi Side Out Put need to increase temperature about 21/2 times over ambient Low pressure

gas

Hi pressure gas

Remember that raising the refrigerant pressure is necessary to begin the process of rejecting heat into the outside air. On it down stroke the compressor piston collects the expanded refrigerant inside the

• compressor. On its up-stroke the piston forces the refrigerant

molecules closer together. The refrigerant vapor is raised in pressure, temperature and boiling point before being forced out of valve plate assembly. The temperature of the vapor is normally two and a half time higher than the temperature of the outside air. Since heat always flows hot to cold, the refrigerant must be much hotter than the outside air to be able to move heat out of the system.

Compression Heating

Looking at this in a different way a truck cooling system would boil at 212 Deg. when a 16 lb. radiator cap is installed coolant will boil at 252 Deg. The pressure of the system at 16 lb. raises the boiling point because it compresses the molecules and limits there ability to move this raises the boiling point of the coolant.

Compression Heating

The hot, high pressure vapor makes its next stop at the condensing

• coil. The condenser is just like the evaporator-it is a heat exchanger.

It looks a little different from a evaporator because it is more flat and a little larger Inside the condenser coil, the gas starts it way from the top to the bottom, cooling down a little with each pass. By the time the refrigerant reaches the lower third of the coil, it cools down enough to change back into liquid, it continues to cool 15-30

• deg. F. below its boiling point in a process called “sub cooling” Sub

cooling is an important concept to understand because it will tell what is wrong with the high side of the system.

Sub Cooling

Principles of HVAC

180 deg. to 240 deg. 135 deg. to 180 deg. gas Liquefied gas Liquid

Principles of HVAC

Install in correct direction

The expansion device creates a pressure drop by restricting the flow

• f refrigerant around the system. Slowing down the flow of

refrigerant caused the compressor to partially evacuate one side of the system. This low pressure void is called the “Suction side” or the “Low side” of the system. Side the low side has a very low pressure, the refrigerant can begin to boil off into a gas. When the refrigerant changes from liquid to gas it gathers heat from the cab air. The pressure difference is created by an expansion device.

Principles of Expansion

Principles of HVAC

The 5 basic components of a/c Compressor Condenser Expansion device Receiver dryer Evaporator

Diagnostics Of A/C Systems

How A/C Works

180 psi to 240 psi 140 psi. to 180 psi 18 psi to 26 psi

Cold referent absorbs heat from cab air while the reorient circulates inside the evaporator coil. Heat from the cad air passes through the metal of the evaporator and causes the reorient to expand by boiling off into a

• vapor. This boiling is possible because referent used in AC

systems have a boiling point of about one pound per square inch per 1deg. F. For example, the boiling point of refrigerant is approximately 20 deg. F. at 20 psi. As the refrigerant expands by boiling into a vapor, it takes massive amounts of heat with it.

Low-Side Operation

Expansion Valve Operation

Principles of A/C

Air Conditioning Basics: Major Components Air Conditioning Basics: Major Components

Replaced Fuse Plug (melt bolt)

Pressure Relief Valve

Compressor

10 P Type Compressor

Clutch on Spartan has 5.5 amp draw

Compressor Oil / Pag 100

Condenser

Condenser

Condenser Fans

Fan draw 8.5 amp each

Dual Pressure Binary Switch / Opens 392 psi high 29 psi low

Pressure switch is installed on the liquid tube between the receiver drier and expansion valve. If abnormally high pressures (or low pressures) are detected, the contacts open. This interrupts the ground to the magnetic clutch relay. Clutch is disengaged.

The O-rings of the piping connectors that are used in CFC-12 air conditioning systems and those that are used in HFC-134a systems ARE NOT INTERCHANGEABLE. O-rings for CFC-12 systems used in HFC- 134a systems will foam and swell, resulting in leakage of refrigerant.

O-Rings

Receiver Drier

Caution Install in correct direction

Major Components

Liquid Solenoid Valve Front & rear Thermostats Heater control valve Evacuation Pump 3 Amp fuse

Picture of bilge pump fuse location

Bilge pump fuse location

Breaker replace with max fuses

Condenser breakers

Evaporator Condenser Pump

The evacuation pump works independent of A/C. Power is supplied by IGNITION. Pump runs any time ignition is on. Internal timer will run pump as long as there is water present then shut off. Then restart about every 2 minutes.

Tools: Refrigerant Recovery/Recharging Machine Leak Detector Tools: Refrigerant Recovery/Recharging Machine Leak Detector

Refrigerant Recovery/Recharging Machine

Service Precautions: Refrigerant Handling Environmental Regulations Service Precautions: Refrigerant Handling Environmental Regulations

R134A cylinder is Light Green (Teal) High side hose is Red with Black stripe. Low side hose is Blue with Black stripe. Service hose is Yellow with Black Stripe All A/C hoses must have manual shut off with in 6” of the service port end.

Environmental Regulations

Environmental Regulations

Refrigerant Handling

When tightening connecting parts: Apply a few drops of compressor oil to O-ring fittings for easy

• f tightening and to prevent leaks.

Use a backup wrench to avoid twisting the tube.

Refrigerant Handling

• Tighten

connections to specified torque

Refrigerant Handling

An undercharged system will provide inadequate lubrication to the compressor. Charge a system that is operating through the low-pressure side only. Refrigerant charged to an operating system must be in gas form only. An overcharged system can cause inadequate cooling, poor fuel economy and engine

• verheating.

On-Vehicle Inspection: Troubleshooting Evacuation & Charging Performance Test On-Vehicle Inspection: Troubleshooting Evacuation & Charging Performance Test

All Spartan fire truck systems have die installed at the factory Use a black light and yellow glasses to detect leaking. Look for spray patterns not finger prints from installation.

Leak Detector Use Black Light

V-Mux Diagnostics

Spartan Chassis needs the following first in order to best direct you to Spartan or OEM for assistance. SO# _______ Mileage _________ Verify customers complaint. Check for proper voltage to compressor. Record ambient air temperature at time of diagnosis. .

Fire Truck A/C Diagnoses

Check static pressures and record both hi and low gauge reading the same Check running high and low pressure at idle and record. Check high and low pressure at hi idle and record.

Fire Truck A/C Diagnoses

The LED of thermostat 35-0734 has four status: 1, Light always ON: normal operation. 2, Blink 1 time per second: De-icing sensor has problem. 3, Blink 2 times per second: Clutch open/short circuit, or

• ver current output

4, Blink 3 times per second: Clutch circuit short to battery.

Electronic Thermostat Switches

Spartan fire truck use PAG 100 refrigerant oil. Normal operation pressure on 80 deg. day are 18 to 22 psi low side and 180 to 240 psi high side pressure. Static pressure on 80 deg. day should be 86 psi.

Diagnoses Of A/C Systems Fire Truck Chassis

To check for failed clutch control switch turn A/C on front blower fan on. Tilt cab and turn the ignition on. If A/C clutch fails to engage check for voltage at A/C clutch plugged in with system turned on. Then check voltage with A/C clutch un plugged. If voltage reading is higher then with clutch plugged in the clutch cycling switch has failed.

Diagnostics Of A/C Systems

Condenser fans must be running for A/C to run. If condenser fans are not running check for load shed by load manager. Rear A/C will not cool if front A/C is not working.

Diagnoses Of A/C Systems

Temperature PSIG F ( C ) 40 (4.4) 35 psi 45 (7.2) 40 psi 50 (10 ) 45 psi 55 (12 ) 51 psi 60 (15 ) 57 psi

R134A Pressure to Temperature

Temperature PSIG F ( C ) 65 (18 ) 64 psi 70 ( 21) 71 psi 75 ( 23) 78 psi 80 ( 26) 86 psi 85 ( 29) 95 psi

R134A Pressure to Temperature

Temperature PSIG F ( C ) 90 (32 ) 104 psi 95 (35 ) 113 psi 100 (37 ) 124 psi 105 (40 ) 134 psi 110 (43 ) 146 psi

R134A Pressure to Temperature

If pressure is higher then reading for the temperature then system is over charged. If pressure is lower than on chart then add Freon to correct pressure. Reclaim or add Freon until both gauges read the correct pressure run a/c and check for performance. Then reclaim system evacuate system and recharge to correct amount.

Diagnostics Of A/C Systems

Static Pressure on 80 Deg. Day

86 psi Low side 86 psi High side

Fire Truck

Normal Readings on 80 Deg. Day

18 to 22 psi Low side 160 to 240 psi High side

Diagnostics Of A/C Systems

Diagnostics Of A/C Systems

Diagnostics Of AC Systems

Air Entered in the Cycle

Diagnostics Of AC Systems

Expansion Valve Trouble (opens too much) OR Improper Installation of Heat Sensitizing Tube

Troubleshooting

Refrigerant Fails to Circulate

Diagnostics Of AC Systems

Faulty Compression of Compressor

Diagnostics Of A/C Systems

Tips to Make Repairs Easier

Tips to Make Repairs Easier

Tips to Make Repairs Easier

Tips to Make Repairs Easier

Routing of hoses Gladiator

Routing of hoses Gladiator

Routing of hoses Gladiator

Routing of hoses Gladiator

Routing of hoses Gladiator

Routing of hoses Gladiator

Routing of hoses Gladiator

The drop out and voltages for checking the ATM (automatic temp control) are located at the back of the right side (officers side) of over head unit. (5 pin connector) The voltage readings and wire numbers are on the 0152- GG9-027 drawing.

Checking the ATM Automatic Temp Control

AT Right rear of A/C unit there are drop out to check voltage to ATM if wire # 11C has 5 volts then ATM should be at full heat at 0 volts ATM is fully closed or max A/C. If voltage is changing from 0 to 5 volts the V-mux is sending the correct signal.

Checking the ATM Automatic Temp Control

Then check wire 30C if the voltage is 0.9 valve is fully closed at 9.0 volts the valve is fully open. If both voltages are correct the motorized heater valve need to be changed.

Checking the ATM Automatic Temp Control

The venture pump uses air from the truck air supply system to create vacuum and remove water from the drain pan. Pump is located behind driver seat. When checking for air leaks A/C must be turned off. Venture pump is on any time A/C compressor is on.

Venture Pump Operation