1. GAS HEATING Planned Maintenance Produced by Joe Marchese

2. Personal Safety Good safety practices will prevent many injures
Safety must be first on your mind at all times
Always remove loose items when working around equipment with moving or rotating parts
Be cautious of sharp objects

3. Personal Safety Always lift with your legs and not with your back
Wear a back support belt when lifting heavy objects
When working with electrical equipment always verify that the power is off
Do not rely on a shut-off switch or disconnect being off -- always check yourself

4. Personal Safety Be cautious of hot surfaces or work areas
Be cautious of any gas or oil leaks
Always check for carbon monoxide
Always follow proper safety practices when working with ladders
Be cautious of confined spaces - provide proper ventilation when required

5. Personal Safety Equipment

6. Safety Shoes

7. Safety Goggles

8. Gloves

9. Pocket Voltage Detector

10. Back Support Belt

11. Oil Absorbent

12. Personal CO Detector

13. Why Perform Planned Maintenance?
To reduce equipment failures
To keep equipment operating in a safe manner
To keep equipment performing at peak efficiencies
To maintain good indoor air quality

14. What is the most important concern for a service technician while performing a preventive maintenance inspection?
SAFETY

15. Safety Carbon monoxide poisoning is a major concern
Natural gas leaks can create a serious hazard
Fire as a result of damaged or bypassed safety controls
Lack of heat from improperly operating furnaces

16. Keeping Equipment at Peak Efficiency
Poor electrical connections can cause the system to work harder
Improper gas combustion will decrease the efficiency of a gas-fired furnace
Dirty filters will reduce the airflow through a system which will decrease the system’s efficiencies

17. Indoor Air Quality
Humidifiers that are not operating properly can lead to poor indoor air quality
Filters not maintained can lead to poor indoor air quality
Carbon monoxide leaking into a structure is a serious indoor air quality issue

18. How Long Should a PM Inspection Take?
Depends on:
the type of equipment
the detail in which the inspection is performed
SHORT INSPECTION vs. LONG INSPECTION

19. What Are the Most Important Tools Used on a PM Inspection?
Your hands
Your eyes
Your ears
Your nose

20. First Steps Determine the type of furnace Barometric - standing pilot
Barometric - direct spark Ignition
Induced draft - DSI or hot surface ignition
High efficiency - sealed combustion

21. Maintenance Task Items
Always following the equipment manufacturer’s guidelines
Tasks can be grouped into four major categories:
Inspection
Cleaning
Lubrication
Operation checks

22. Maintenance Task Items
Check availability of combustion air (80% furnaces only)
Clean and inspect air system accessories such as humidifiers and electronic air cleaners
Check the condition of the electrical wiring and tightness of the terminals and connectors
Clean or replace air filters

23. Maintenance Task Items
Clean and inspect fan compartment
Clean and inspect the condensate drain system (90% furnaces only)
Clean and inspect the vent system
Clean and inspect burners and heat exchanger

24. Maintenance Task Items
Check thermostat and heat anticipator or cycle switch settings
Check sequence of operation
Check pilot/burner operation
Perform combustion tests
Check temperature rise
Check safety controls

25. Combustion Air
Different furnace designs will have different styles to bring combustion air into a furnace.
An 80% efficient furnace normally uses the air surrounding the furnace for its combustion air
A 90% plus furnace normally uses outside air for its combustion air

26. Combustion Air
When performing an inspection the location of the furnace should be examined to make sure it has a sufficient volume to provide enough combustion air
Make sure no other gas-fired appliances (such as a dryer or hot water heater) steal combustion air from the furnace

27. Combustion Air
Verify that the combustion air will not be contaminated by halogen compounds, such as fluoride, chloride, bromide and iodide vapor.
If installed in a laundry room, make sure the exhausted products vented by the dryer do not enter the furnace and are used for combustion air

28. Unconfined Space
An unconfined spaced has a volume of at least 50 cubic feet per 1000 Btus input total for all appliances located in the space
If the unconfined space is constructed unusually tight, the combustion air must come from outside air or from spaces freely communicating with the outdoors

29. Confined Spaces
A confined space has a volume less than 50 cubic feet per foot per Btus of total input rating of all appliances installed in that space
There must be provisions for supplying combustion air; it can be ducted in from outdoors or from an unconfined space

30. Confined Spaces
The number of openings and the size of the openings will depend on whether the air comes from the outside or from adjoining unconfined space

31. Combustion Air Requirements
If combustion air is brought from within the structure there must be 2 openings
Each opening must have a minimum free area of not less than 1 square inch per 1000 Btu of total input rating for all gas appliances in the space (should not be less than 100 square inches)
If construction is unusually tight, outside air must be brought in

32. Combustion Air Requirements
If combustion air is brought from outside the structure there must also be 2 openings, however:
If two vertical ducts are used they must have at least 1 square inch of free area per 4000 Btus of total input for all gas appliances
If two horizontal ducts are used they must have at least 1 square inch of free area per 2000 Btus of total input for all gas appliances

33. Combustion Air Requirements
A single opening can be used if it has a free area of 1 square inch per 3000 Btus of total input for all gas appliances
Failure to comply with these guidelines may result in a furnace starved for combustion air which could lead to the formation of carbon monoxide

34. Cleaning and Inspecting Air System Accessories

35. Humidifiers Maintenance required: Replace media pad
Clean mineral deposits from:
water reservoir or drain pan
float, float valve orifice, and valve seat
water solenoid valve orifice and strainer

36. Humidifiers Maintenance required: Check for water overflow
On wheel-type humidifiers, an approved water treatment solvent can be applied to water reservoir
If a bypass humidifier is used, make sure the dampers are open for winter operation

37. Recommended Indoor Humidity Levels at Various Outdoor Temperatures

38. Electronic Air Cleaners
Maintenance required:
Turn voltage off to unit (9,000 to 11,000 VDC supplied by cleaner’s transformer)
Remove the pre-filters and air cleaner cells
Clean inside of cabinet
Clean pre-filters with a mild soap solution

39. Electronic Air Cleaners
Maintenance required:
Wash air cleaner cells with a solution of 3/4 cup of dishwasher detergent and hot water
Vinegar can also be used to clean cells
Soak cells in solution for 15 to 20 minutes
Rinse until all the solution is removed

40. Electronic Air Cleaners
Maintenance required:
Inspect cells for any damage and reinstall with pre-filters
Leave system’s blower on for 30 minutes with power off to air cleaner to dry the cells thoroughly

41. Heat Recovery Ventilators
Maintenance required:
Filters should be changed monthly and interior blower maintained on the same schedule as the furnace
Drain pans and interior of unit:
Clean interior surface and wipe the drain pans with a soft cloth and a mild cleaning solution
Check condensate drain

42. Heat Recovery Ventilators
Maintenance required:
Heat Recovery Cores:
Remove from unit
Use warm water and a mild soap
Soak recovery core in solution for about three hours
Allow to dry before reinstalling

43. Electrical Connections
Turn off voltage applied to the furnace
Make a visual inspection of all wire terminals and wires
Check for discoloration
Check for frayed or damaged insulation
Check for any loose connections and retighten all accessible screw terminals if needed
Check fuse holders for tightness, if applicable

44. Air Filters Maintenance required:
Can be either cleaned or replaced, depending on type
A clogged or dirty air filter will result in the system going off on its high temperature safety limit, resulting in poor heating of the conditioned space
Make sure to install air filters in the correct direction of airflow

45. Air Filters
Some owners may choose to replace their own filters or have their in-house maintenance personnel install the filters
There are many different types of filters available -- notify the customer of the various types so the best filter can be selected for the job

46. Fan Compartment
Check blower wheel for dirt build-up and clean when required
An important maintenance task
Dirt on blower wheel will reduce CFM delivered by fan
This may be a time-consuming task
May require removing entire drive assembly

47. Fan Compartment (Direct Driven Blowers)
Visually inspect fan motor for bearing wear by spinning fan wheel and notice how it slows down and stops
Check fan motor for excess end play
Some motors may have up to 1/8” end play
Check motor bearing for “oval shape”
There should be no vertical play with shaft
Lubricate motor, if required

48. Fan Compartment (Belt Driven Blowers)
Check belt tension for proper adjustment
3/8” to 1/2” depression with a 10 lb. force
If possible, use a belt tension gauge
Visually inspect belt, bearing and pulley for signs of wear
Visually inspect pulley and drive alignment
use straight edge or string

49. Fan Compartment (Belt Driven Blowers)
Check pulley and drive set screws for tightness
Record belt size
When possible leave an extra belt on the job
Mark belt size on unit
Lubricate motor and fan bearings, when possible
Some motors have sealed bearings and external lubrication is not needed

50. Clean and Inspect Condensate Drain System
Inspect condition of the condensate line
Clear lines with compressed gas, if necessary
Inspect condensate pump, remove and clean if required

51. Condensate Pumps Maintenance required: Remove pump from system
Remove reservoir from pump
Clean reservoir of any dirt or grime and check float
Reinstall
Add water to system to check pumping operation

52. Check Condition of the Vent System
Inspect pipes for any cracks or weak spots
Clean out chimney base if access door is provided
If no access door is provided, remove a section of pipe and examine for any clogs or restrictions
Verify the vent system is pitched toward the furnace 1/4” per foot

53. Draft Diverters If the system has a draft diverter:
Check for obstructions
Check for signs of corrosion
Lightly tap area to see if walls are rusted

54. Cleaning and Inspection of Gas Burners
Remove and clean burners, mainly multi-port burners only
Mono-port burners require little cleaning
Use a mild brush and shop vacuum
Do not damage or enlarge ports while cleaning
Cleaning of burners may not be needed on every inspection, but must be checked

55. Cleaning and Inspection of Gas Burners
Check burner alignment to ensure no flame impingement is occurring on the heat exchanger
Flame impingement will cause CO
Make sure the burners are secure
Check crossover tubes to ensure proper alignment

56. Heat Exchangers Check for cracks
Can be inspected for cracks in one of three ways:
Visual Method
Requires removing burners
The use of a good mirror and strong lamp
Difficult to perform
Air Flow Method
Test Gas Method

57. Standing Pilot Systems
Remove and clean pilot assembly, where required
Do not clean orifice with an object that may change the size of the orifice opening
Check and adjust pilot flame, if necessary

58. Pilot Assemblies
Pilot flame should impinge a height of 3/8” to 1/2” on the top of the thermocouple

59. Thermocouples Two dissimilar metals are welded together at one end
When one of the junctions is heated and the other end remains relatively cool, a low electric DC voltage is produced

60. Thermocouples
The voltage generated depends on the temperature difference between the hot and cold junctions

61. Output Voltages
Normal output voltage of an unloaded thermocouple is 26 to 32 milli-volts DC
The minimum acceptable output voltage is 18 milli-volts DC
Drop out time of the pilot solenoid should be within 2-1/2 minutes.

62. Direct Ignition (Hot Surface Igniter)
Hot surface igniter directly lights burners
Made of ceramic
Is very fragile
Uses flame rectification circuit

63. Direct Ignition (Hot Surface Igniter)
During preventive maintenance inspections, visually inspect for cracks or breaks
At room temperature the resistance should equal 45 to 90 ohms (if over 110 ohms, replace)

64. Thermostats On mechanical thermostats check:
That the thermostat is level
That the heating anticipator setting is properly set
That the temperature gauge on the thermostat is within 2°F of actual temperature of the living space
Electronic thermostats only require checking the accuracy of the temperature gauge

65. Heating Anticipators Wired in series with the controller contacts
Set to match the amperage draw of the heating controls
Too low of a setting will cause the on cycle to be too short
Too high of a setting will cause the on cycle to be too long

66. Sequence of Operation
A major part of a preventive maintenance inspection is checking the sequence of operation of a furnace
Necessary to verify the furnace is operating safely and efficiently
Different furnace types will have varying sequences of operation

67. Intermittent Pilot Furnaces
Sequence of operation:
Thermostat calls for heat
Spark is generated to light pilot
Once pilot flame is proven, the gas valve opens and flame is produced
After a delay the indoor blower is turned on

68. Standing Pilot Natural Draft
Sequence of operation:
Thermostat calls for heat
Gas valve opens
Burners are lit
After a delay, based on air temperature the indoor blower motor will come on

69. Standing Pilot Induced Draft
Sequence of operation:
Thermostat calls for heat
Induced draft blower comes on
Once draft has been proven, the gas valve opens and flame is produced and the flame is proved
Indoor blower is turned on after a delay

70. Direct Ignition Condensing Furnace
Sequence of operation:
Thermostat calls for heat
Induced draft blower comes on
Once the induced draft blower builds a negative pressure in the blower housing, the differential pressure switch closes
Hot surface igniter is energized

71. Direct Ignition Condensing Furnace
Sequence of operation (cont.):
After a delay the gas valve opens and flame is produced
Once the flame is proved, the gas valve will remain energized
Indoor blower is turned on after a delay

72. Check & Record Manifold Gas Pressure
Compare with manufacturer’s specifications
Normally natural gas is 3.5” w.c. at the outlet of the gas valve
Normally LP is 11” at the outlet of the gas valve

73. Flame Color
The flame should be a well-defined blue with slightly orange tips 
If yellow tips are observed, it is a sign of incomplete combustion and the cause should be found and rectified 
A yellow-tipped flame is producing CO which is not a desired result of combustion

74. Flame Conditions

75. Flame Conditions

76. Flame Conditions

77. Combustion Testing

78. Combustion Efficiency
Measuring the CO2 and flue gas temperature is a means of determining the combustion efficiency
Steady state efficiency is the point at which combustion gas content reaches equilibrium and the stack temperatures stabilize

79. Combustion Tests
Measure ambient temperature and the stack temperature to obtain the net stack temperature
Measure draft pressure
Measure the carbon dioxide(CO2) level
Measure the oxygen (O2)level
Measure the carbon monoxide (CO) level

80. Category I Appliance

81. Fan Assisted Furnaces

82. Category I Appliance Test Points

83. Category IV Appliances

84. Checking Airflow
Tested by measuring the temperature rise across the heat exchanger
Generally low-efficiency furnaces will have a temperature rise of 75°F to 100°F
Generally high-efficiency furnaces will have a temperature rise of 40°F to 70°F
Always look on the data plate of the furnace for the correct range

85. Temperature Rise
Always check the supply air temperature out of the line of sight of the heat exchanger, and the return air temperature as close as possible to the heat exchanger
Before checking the temperature rise of a furnace, make sure the filter is clean and the airflow is not being restricted

86. Temperature Rise All registers and dampers must be open
The system should be operating for at least 15 minutes
Use the same type thermometer for measuring the supply and return temperatures
Before checking the temperature rise, compare the accuracy of thermometers

87. Temperature Rise
A temperature rise that is higher than the range stated on the furnace indicates a shortage of airflow across the heat exchanger
A temperature rise that is lower than the range stated on the furnace indicates too much airflow across the heat exchanger

88. Adjusting the Fan Speed
A direct drive blower’s fan speeds can usually be changed by selecting the appropriate speed tap
Common Color Coding:
White = common
Black = high speed
Yellow = medium high speed
Blue = medium low speed
Red = low speed

89. Adjusting the Fan Speed
Belt-driven blowers can usually be adjusted by changing the flange on the motor pulley
Adjusting the pulley flange towards the fixed flange will increase the speed of the blower
Sometimes the pulley will need to be changed, using the formula:
Diameter(drive) = Diameter(driven) X (rpm(fan)/rpm(motor))

90. On belt driven fans always check the amperage draw of the motor after making any adjust to the fan speed

91. Safety Controls Checks
Verify the operation of the high temperature switch
Block return airflow completely and observe the gas valve shutting down
On induced draft furnaces, remove one end of the rubber hose from the air pressure switch and observe the gas valve shutting down

92. THE END