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GAS HEATING Planned Maintenance Produced by Joe Marchese.

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Presentation on theme: "GAS HEATING Planned Maintenance Produced by Joe Marchese."— Presentation transcript:

1 GAS HEATING Planned Maintenance Produced by Joe Marchese

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

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

4 Personal Safety n Be cautious of hot surfaces or work areas n Be cautious of any gas or oil leaks n Always check for carbon monoxide n Always follow proper safety practices when working with ladders n 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? n To reduce equipment failures n To keep equipment operating in a safe manner n To keep equipment performing at peak efficiencies n 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 n Carbon monoxide poisoning is a major concern n Natural gas leaks can create a serious hazard n Fire as a result of damaged or bypassed safety controls n Lack of heat from improperly operating furnaces

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

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

18 How Long Should a PM Inspection Take? n 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 n 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 n Always following the equipment manufacturer’s guidelines n Tasks can be grouped into four major categories: –Inspection –Cleaning –Lubrication –Operation checks

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

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

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

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

26 Combustion Air n 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 n Make sure no other gas-fired appliances (such as a dryer or hot water heater) steal combustion air from the furnace

27 Combustion Air n Verify that the combustion air will not be contaminated by halogen compounds, such as fluoride, chloride, bromide and iodide vapor. n 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 n An unconfined spaced has a volume of at least 50 cubic feet per 1000 Btus input total for all appliances located in the space n 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 n A confined space has a volume less than 50 cubic feet per foot per 1000 Btus of total input rating of all appliances installed in that space n 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 n 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) n If construction is unusually tight, outside air must be brought in

32 n 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 Combustion Air Requirements

33 n 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 n Failure to comply with these guidelines may result in a furnace starved for combustion air which could lead to the formation of carbon monoxide Combustion Air Requirements

34 Cleaning and Inspecting Air System Accessories

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

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

37 Recommended Indoor Humidity Levels at Various Outdoor Temperatures

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

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

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

41 Heat Recovery Ventilators n Filters should be changed monthly and interior blower maintained on the same schedule as the furnace n 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 Maintenance required:

42 Heat Recovery Ventilators n 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 Maintenance required:

43 Electrical Connections n Turn off voltage applied to the furnace n 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 n Can be either cleaned or replaced, depending on type n 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 n Make sure to install air filters in the correct direction of airflow Maintenance required:

45 Air Filters n Some owners may choose to replace their own filters or have their in-house maintenance personnel install the filters n 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 n 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) n Visually inspect fan motor for bearing wear by spinning fan wheel and notice how it slows down and stops n Check fan motor for excess end play –Some motors may have up to 1/8” end play n Check motor bearing for “oval shape” –There should be no vertical play with shaft n Lubricate motor, if required

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

49 Fan Compartment (Belt Driven Blowers) n Check pulley and drive set screws for tightness n Record belt size –When possible leave an extra belt on the job –Mark belt size on unit n 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 n Inspect condition of the condensate line n Clear lines with compressed gas, if necessary n Inspect condensate pump, remove and clean if required

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

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

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

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

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

56 Heat Exchangers n Check for cracks n 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 n Remove and clean pilot assembly, where required n Do not clean orifice with an object that may change the size of the orifice opening n 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 n Normal output voltage of an unloaded thermocouple is 26 to 32 milli-volts DC n The minimum acceptable output voltage is 18 milli-volts DC n Drop out time of the pilot solenoid should be within 2-1/2 minutes.

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

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

64 Thermostats n 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 n Electronic thermostats only require checking the accuracy of the temperature gauge

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

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

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

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

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

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

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

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

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

74 Flame Conditions

75

76

77 Combustion Testing

78 Combustion Efficiency n Measuring the CO 2 and flue gas temperature is a means of determining the combustion efficiency n Steady state efficiency is the point at which combustion gas content reaches equilibrium and the stack temperatures stabilize

79 Combustion Tests n Measure ambient temperature and the stack temperature to obtain the net stack temperature n Measure draft pressure n Measure the carbon dioxide(CO 2 ) level n Measure the oxygen (O 2 )level n 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 n Tested by measuring the temperature rise across the heat exchanger n Generally low-efficiency furnaces will have a temperature rise of 75°F to 100°F n Generally high-efficiency furnaces will have a temperature rise of 40°F to 70°F n Always look on the data plate of the furnace for the correct range

85 Temperature Rise n 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 n Before checking the temperature rise of a furnace, make sure the filter is clean and the airflow is not being restricted

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

87 Temperature Rise n A temperature rise that is higher than the range stated on the furnace indicates a shortage of airflow across the heat exchanger n 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 n 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 n 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 n Verify the operation of the high temperature switch n Block return airflow completely and observe the gas valve shutting down n 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


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