HVAC 136 - Heating Service Fundamentals
Examines the electrical schematics on most gas furnace manufacturers' equipment and perform live diagnostics using the multi meters wiring diagrams and shop furnaces. Tests for gas pressures, gas flow rates, and correct air flow measurement. Focuses on diagnostics involving the electrical circuits, airflow rates, gas pressures, gas flow rates and trouble-shooting the furnaces. Credit may be earned in either HVAC 136 or RHA 136 but not in both.
Prerequisite(s): HVAC 140 and HVAC 135
Lecture Hours: 35 Lab Hours: 10
Meets MTA Requirement: None
Outcomes and Objectives 1. Interpret the furnace operations and diagnose service problems from the wire diagram.
A. Develop mastery of wire diagram reading.
B. Interpret problems from the wire diagram.
C. Interpret correct operation of the furnace from the diagram.
D. Identify the correct stages of operation using a wire diagram.
E. Identify furnace components on the wire diagram and on the furnace.
F. Identify furnace problems from the diagram.
G. Identify the principles involved in flame rectification.
H. Identify from the diagram how to change blower motor time-on or time-off (when dipswitches are available).
I. Identify from the diagram how many motor speeds are available.
J. Identify the electrical components on the furnace.
K. Identify from the diagram how many speeds the motor has.
L. Identify from the diagram how to change blower motor speeds.
2. Use multi meters to test and diagnose electrical circuits in furnaces.
A. Develop a master in the use of multi meters when used as Ohmmeters, voltmeters, and amp meters.
B. Develop a master at using Ohms law and Kickoffs voltage laws in electrical circuits and diagrams.
C. Use multi-meters to measure current flow in amperes.
D. Use multi-meters to measure current flow in amperes.
E. Use multi-meters to measure resistance in Ohms.
F. Diagnose pressure switches, limit switches, relay switches, and other switching controls using an Ohmmeter.
G. Use an amp probe to test motor circuits and other electrical devices.
H. Use a milli-amp meter or micro-amp meter to test furnace holding and proving circuits.
I. Use a milli voltmeter to test furnace holding and proving circuits.
J. Diagnose motor problems using electrical diagrams and multi meters. (Note: Students will spend 12 weeks troubleshooting these types of
problems on gas furnaces.)
3. Service and repair the fuel system and gas burners.
A. Identify the types of gas fuels and their recommended fuel pressures at the meter, in the home fuel line, and at the gas valve on the
B. Identify the types of heat exchangers in a furnace-barrel type, serpentine type, tube type, sectional type, secondary fin, and tube type.
C. Identify types of gas burners-open atmospheric burners, sealed combustion burners, mono port burner, and ribbon type burners.
D. Identify combustions triangle and efficient burn for each gas fuel.
E. Identify pilot ignition systems.
F. Identify spark ignition systems
G. Identify HIS (Hot Ignition Surface) ignition systems.
H. Demonstrate knowledge of flame rectification operation and safety.
I. Identify how different gas valves work.
J. Identify how gas pressure regulators work.
K. Demonstrate the use of a gas pressure gauge or a liquid manometer for testing gas pressure.
L. Adjust the gas pressure at the pressure regulator properly.
M. Demonstrate ability to clock the gas flow rate using a gas meter.
N. Adjust primary air shudders properly.
O. Test for correct fuel efficiency.
P. Test for and repair gas leaks.
Q. Demonstrate knowledge of correct gas piping and sizing.
R. Demonstrate knowledge of gas furnace data plate and specifications.
S. Demonstrate knowledge of the BTU furnace specification.
T. Use the gas meter to clock the gas fuel consumption in BTUs/HR correctly.
4. Service the blower motor.
A. Remove the blower motor for service.
B. Locate and properly lubricate the blower motor for routine tune-up and cleaning.
C. Test the blower motor in the furnace using an amp probe.
D. Test for proper voltage to the motor using a voltmeter.
E. Test the motor windings using an Ohmmeter.
F. Remove, inspect, and replace the blower wheel from the blower housing.
G. Identify the type of blower wheel or fan that you have.
H. Identify the proper blower wheel rotation.
I. Use motor test sheet to blueprint all motor speeds and performance.
J. Identify how many speeds your motor has.
5. Demonstrate safety in the lab prior to work being done.
A. Demonstrate the proper use of gas fuels and gas piping.
B. Access a heating system properly while servicing.
C. Disable the electrical system or the fuel system on a gas furnace properly.
D. Use service tools properly.
E. Demonstrate proper servicing and ignition methods.
F. Demonstrate proper servicing and venting methods.
G. Demonstrate proper servicing and gas piping methods.
H. Demonstrate proper installation methods.
I. Test gas heating components safely.
J. Test electrical heating components safely.
K. Demonstrate knowledge of proper shut-off devices.
L. Demonstrate safe truck usage.
M. Demonstrate a knowledge of first aid for electrical shock and burns.
6. Demonstrate a knowledge of proper installation methods.
A. Identify proper installation methods.
B. Identify proper venting methods.
C. Identify correct furnace fuel efficiency ratings.
D. Identify proper gas piping methods.
E. Identify proper furnace spacing to walls, floor, and ceilings.
F. Identify proper furnace electrical connections.
G. Identify correct installation of furnace safety devices.
H. Identify correct methods for condensate drain piping and installation.
I. Measure for correct supply air flow.
J. Measure for correct gas pressure.
K. Measure for correct temperature rise.
7. Compose a written evaluation of your service procedure findings.
A. Describe the service problem accurately so that it is clearly and legally understood.
B. Identify the solution and/or repair procedure so that it is clearly and legally understood.
C. Identify the parts and costs required to repair the furnace on a work order.
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