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AMAZON multi-meters discounts AMAZON oscilloscope discounts OBJECTIVES: Knowledge-Based:
Skill-Based: Perform general maintenance procedures including:
+ Maintain and service condensate systems. + Replace through-the-wall air conditioners Some Terms: Carbon monoxide -- a poisonous, colorless, odorless, tasteless gas generated by incomplete combustion Carbon dioxide -- by-product of natural gas combustion that's harmful and can even cause death Introduction The primary function of heating, ventilation, and air-conditioning (HVAC) systems is to provide healthy and comfortable interior conditions for occupants. This chapter on HVAC will provide a practical description and overview of the various HVAC equipment and systems used in both residential and commercial buildings.
HVAC Safety As stated earlier, it's the responsibility of everyone to ensure that a worksite is safe. When working on a job site, one should behave in a safe and professional manner. Accidents on the job often result from carelessness. It is very important for workers to be aware of their surroundings at all times and to evaluate the immediate area for possible safety hazards. The following are a few of the safety rules that should be followed when working with or around HVAC: Never work on electric circuits while standing on a wet floor or when not wearing rubber-soled boots. Shocks received when standing in a wet location are quite often deadly as the current passes through the heart, causing it to stop pumping.
Water and electricity don't mix! Stay dry and stay safe. Should a wire come loose from inside an air-conditioning system and come in contact with the casing of the equipment, electric shock can result by simply touching the surface of the unit. Never leave tools or other materials on the top platform of the ladder. If the ladder is moved by another individual, the object can fall, causing injury. Never horseplay while at work. • Always be aware of your surroundings and potential hazards. • Dress properly for work wearing long pants, long sleeved shirts, and work boots. Remove metallic jewelry, as it's a good conductor of heat and electricity. • Use safety glasses, ear plugs, and gloves for additional protection from dangerous conditions on the job site. Power tools and equipment should be grounded to protect against electric shock. Electric shock occurs when the body becomes part of an electric circuit. • Always de-energize electric circuits before working on them. Ground wires and prongs should never be cut or disconnected. The GFI de-energizes a circuit when a current leak to ground is sensed. • Fire extinguishers are classified by the types of i res they are designed to be used on. • Fire extinguisher use: Pull, Aim, Squeeze, Sweep (PASS). • Always use tools for the tasks they are intended to perform. • Handle and use chemicals according to the manufacturer's directions. • Be prepared for injuries on the job and have a first aid kit handy. • OSHA, NFPA, and ANSI help ensure safety in the work place. Perform General Furnace Maintenance There are three common types of furnaces: gas, electric, and oil. Because each furnace manufacturer has a different set of specifications, the following are general guidelines for performing furnace maintenance. For more detailed instructions on maintaining a furnace, read the manufacturer's specifications or call a qualified repair person. Some common problems associated with gas furnaces are outlined in Table 1 shown below. = =Table 1: Common Problems with Gas Furnaces= = Problem: n Possible cause – n Solution Furnace won't run: 1. No power - 1. Check for blown fuses or tripped circuit breakers at main entrance panel, at separate entrance panel, at separate entrance panel, and on or in furnace; restore circuit. 2. Switch off - 2. Turn on separate power switch on or near furnace. 3. Motor overload - 3. Wait 30 minutes; press reset button. Repeat it if necessary. 4. Pilot light out - 4. Relight pilot. 5. No gas - 5. Make sure gas valve to furnace is fully open. Not enough heat: 1. Thermostat set too low. - 1. Raise thermostat setting 5º. 2. Filter dirty - 2. Clean or replace filter. 3. Blower clogged - 3. Clean blower assembly. 4. Registers closed or blocked. - 4. Make sure all registers are open; make sure they are not blocked by tugs, drapes, or furniture. 5. System out of balance. - 5. Balance system. 6. Blower belt loose or broken. - 6. Adjust or replace belt. Pilot won't light: 1. Pilot opening blocked. 1. Clean pilot opening. 2. No gas 2. Make sure pilot light button is fully depressed; make sure gas valve to furnace is fully open. Pilot won't stay lit: 1. Loose or faulty thermocouple. 1. Tighten thermocouple nut slightly, if no results, replace thermocouple. 2. Pilot flame set too low. 2. Adjust pilot so flame is about 2 inches long into thermocouple. Furnace turns on and off repeatedly: 1. Filter dirty 1. Clean or replace filter. Blower won't stop running: 1. Blower control set wrong. 1. Reset thermostat from ON to AUTO. 2. Limit switch set wrong. 2. Reset limit switch for stop-start cycling. Furnace noisy: 1. Access panels loose. 1. Mount and fasten access panels correctly. 2. Belts sticking, worn, or damaged. 2. Spray squeaking drive belts with belt dressing; replace worn or damaged belts. 3. Blower belts too loose or too tight. 3. Adjust belt. 4. Motor and /or blower needs lubrication. 4. If motor and blower have oil ports, lubricate. = = Tightening Belts Loose belts on an air distribution system can cause the following: Insufficient airflow • Evaporator coil freezing • Inadequate cooling • If a belt is slipping, the inside surfaces of the pulleys will become polished to a near-mirror finish. If such is the case, the pulleys must be replaced. See the "Replacing Pulleys" section for more on this. If the pulleys are not polished, proceed to adjust the belts: 1. Make certain that the power to the blower is off and that the blower itself has come to a complete stop. 2. Open the blower access panel/service door on the furnace. Check manufacturer's specifications to locate the blower access panel/service door. 3. With a pencil, mark the position of the motor mounts on the furnace and the bolt positions on the motor base (Fgr. 1). 4. Using the proper size wrench, loosen the motor mount bolts so that the motor and the motor mount can move freely. Do not completely remove these bolts. Make certain to leave the motor secured to the motor mount itself (Fgr. 2). 5. Gently move the motor closer to the blower shaft and pulley to further loosen the belt. - - -
- - - - Fgr. 1: Mark position of motor mounts 6. Slide the belt off the pulleys. 7. Turn the belt inside out and inspect the underside for any cracks, missing pieces of the belt material, or other signs of excessive belt wear. 8. If the belt is worn, it needs to be replaced. Refer to the "Replacing Belts" section for more information on this. If the belt is in good condition, go to step 9. 9. With the belt removed, inspect the interior surfaces of the pulleys. The interior surfaces of the pulleys should look rough and should not be shiny. Shiny, polished surfaces on the pulleys are an indication that the belts have been slipping. Belt slippage will cause premature wear. Polished pulleys should be replaced. See the section on "Replacing Pulleys" for more on this (see Fgr. 6). 10. If both the belt and pulleys are in good condition, position the motor close to the blower pulley and replace the belt on the pulleys. 11. Gently push the motor away from the blower pulley to increase the belt tension. 12. When the motor mount is slightly past the pencil markings that were made earlier, begin to tighten the motor mounts to the chassis. Make certain that the new position of the motor mount on the chassis is parallel to the original markings to help ensure proper pulley alignment. 13. Check the belt tension by placing your thumb and fingers on the opposite sides of the belt and gently squeezing them together. Basically, you are trying to squeeze the two opposite sides of the belts together. There should be some play in the belts, but no more than one inch of deflection. 14. If the sides of the belts can be pushed in more than 1 inch, loosen the motor mounting bolts again and repeat steps 11 through 13. Fgr. 2: Loosen the motor mounts Fgr. 3: Adjust the motor to remove the belt Fgr. 4: Technician inspecting the belt Fgr. 5A: A good belt Fgr. 5B: This belt is cracked and needs to be replaced Fgr. 6: Comparison between normal and worn pulleys - - -
- - - Replacing Belts If the belt is broken, damaged, or worn, don't reinstall that belt on the system. Damaged and worn belts should be replaced immediately to help ensure the satisfactory, continued operation of the system. 1. Obtain the belt information from the old belt. If the information on the old belt can't be read, refer to the "Estimating Belt Sizes" section (Fgr. 9). 2. Obtain a new, exact replacement for the old belt. 3. If the belt has been removed from the pulleys and is damaged, proceed to step 6. If the belt simply broke, continue with step 4. 4. With a pencil, mark the position of the motor mounts on the furnace and the bolt positions on the motor base. 5. Using the proper size wrench, loosen the motor mount bolts so that the motor and the motor mount can move freely. Do not completely remove these bolts and make certain to leave the motor secured to the motor mount itself. 6. Position the motor close to the blower pulley and replace the belt on the pulleys. 7. Gently push the motor away from the blower pulley to increase the belt tension. 8. When the motor mount is slightly past the pencil markings that were made earlier, begin to tighten the motor mounts to the chassis. Make certain that the new position of the motor mount on the chassis is parallel to the original markings to help ensure proper pulley alignment. 9. Check the belt tension by placing your thumb and fingers on the opposite sides of the belt and gently squeezing them together. Basically, you are trying to squeeze the two opposite sides of the belts together. There should be some play in the belts, but no more than 1 inch of deflection. 10. If the sides of the belts can be pushed in more than 1 inch, loosen the motor mounting bolts again and repeat steps 7 through 9. Fgr. 8: Tension gauge Fgr. 9: Belt information = + = Ideally, technicians should use a belt tension gauge to ensure that the belt tension on the belts is correct (see Fgr. 8). Do not attempt to adjust the pitch on a variable-pitch pulley to tighten the belt tension. Doing so will change the rotation proportions of the drive assembly and change the speed at which the blower turns. Obtain spare belts and keep them on or near the equipment. In the event the belt breaks in the future, you'll have the system backup quickly. = + = Estimating Belt Sizes There will be times that you will not be able to read the information on an old belt. This can be due to excessive amounts of dirt, age, or simply the destruction of the belt itself. In order to determine important belt information, follow these steps. 1. Measure the center-to-center distance (in inches) between the motor shaft and the blower shaft (Fgr. 10). 2. Multiply the measurement in step 1 by 2. 3. Measure the diameters of the drive pulley and the driven pulley (Fgr. 11). 4. Add the two diameters in step 3 together. 5. Divide the result in step 4 by 2. 6. Multiply the result from step 5 by 3.14. 7. Add the result from step 6 to the result from step 2. This gives you the approximate length of the required belt. 8. Measure the width of the old belt. An "A" belt has a width of 17/32 inch, while a "B" belt has a width of 21/32" (Fgr. 12). 9. The results from steps 7 and 8 provide the type of belt and the approximate length of the required belt. Sample calculation: Estimate the length of a belt that's used to connect an 8-inch pulley to a 10-inch pulley that's installed on motor and blower shafts that are 16 inches apart. Here is the step-by-step solution, which corresponds to the steps in the original procedure: 1. The center-to-center distance between the motor shaft and the blower shaft is 16 inches. 2. 16 3 2 5 32 inches 3. Pulley diameters 5 8 inches and 10 inches 4. 8 inches 1 10 inches 5 18 inches 5. 18 inches 4 2 5 9 inches 6. 9 inches 3 3.14 5 28.26 inches 7. 28.26 inches 1 32 inches 5 60.26 inches 5 60 inches Fgr. 10: Measure center to center Fgr. 11: Measure pulley diameters Fgr. 12: A- and B-width belts A WIDTH BELT; B WIDTH BELT -- If the belt sits deep into one or both pulleys, determine the "effective" diameter of the pulley, which is the diameter of an equivalent pulley if the belt was resting at the outer edge of the pulley. --- Adjusting Pulleys Quite often, the cause for belt slippage, breakage, and premature wear is misaligned pulleys. To check pulley alignment: 1. Make certain that the system is off and all rotating equipment has come to a complete stop. Never attempt to stop rotating equipment by hand. Severe personal injury can result. 2. Remove the access panel on the blower compartment. Check the manufacturer's specifications to locate the blower access panel/service door. 3. Place a straightedge such as a wooden ruler against the faces of both the drive and the driven pulleys. 4. The straightedge should touch all four sides of the pulleys: a. outside edge of the drive pulley b. outside edge of the driven pulley c. inside edge of the drive pulley d. inside edge of the driven pulley 5. This will determine not only if the pulleys are lined up, but also if they are parallel to each other. 6. If the pulleys are not properly aligned but are parallel to each other, either the drive pulley or the driven pulley will have to be repositioned on the respective shaft. See the section on "Repositioning Pulleys." 7. If the pulleys are not parallel to each other, the mo tor mount or the blower mount must be adjusted to correct this situation. Fgr. 13: Pulleys must be aligned properly Fgr. 14: Spray the pulley hub and shaft Fgr. 15: Use Allen wrench to loosen set screw Replacing Pulleys If you have determined to replace one or more pulleys, the original pulley must be removed from the shaft. The shaft may be dirty and /or rusty, making this project potentially very time consuming. Here are some tips to accomplish this. 1. Clean the shaft completely. 2. Spray the shaft with a loosening agent (rust remover). 3. Allow the loosening agent to seep into the joint between the shaft and the hub of the pulley. 4. Completely remove the set screw that holds the pulley to the shaft. This may be a square set screw or an Allen key . 5. Be sure to place the set screw in a place where it will not be lost. 6. Spray loosening agent in the set screw hole and allow it to seep into the space between the pulley and the shaft. 7. If the above tips don't help in the pulley removal process, a pulley puller should be used. 8. Once the pulley has been removed, clean the shaft completely. 9. Obtain the new pulley and position the new pulley on the shaft so that it's perfectly aligned with the other pulley. Refer to the previous section on "Aligning Pulleys" for more on this. 10. Once the pulley has been properly positioned, tighten the pulley securely to the shaft. Repositioning Pulleys There are times when the pulley is in good shape, but needs to be repositioned on the shaft. Use the procedures, steps, and tips in the previous two sections to loosen, reposition, align, and retighten the pulley on the shaft. Fgr. 16: A pulley puller Replacing Filters on HVAC Units The most important thing you can do to keep your air conditioner operating efficiently is to routinely replace or clean its filter(s). Clogged, dirty filters restrict normal airflow, which can cause unfiltered air to carry dirt directly into the evaporator coil. Change air-conditioning filters monthly. 1. Make certain that the system is off and all rotating equipment has come to a complete stop. Never attempt to stop rotating equipment by hand. Severe personal injury can result. 2. Remove existing filter(s) from the system. 3. Inspect the channel that holds the filters to be sure that the channels are in good shape and that the filter is supported on at least two sides. 4. Measure the filter channel. 5. Make certain that the replacement filter is the same size as the filter channel, not necessarily the size of the filter that came out of the unit. (Someone may have put the wrong size filter in the unit.) Fgr. 17: Remove the filter; Fgr. 18: Measure the filter rack 6. Obtain the correct size filter. 7. Locate the arrow on the edge of the filter. 8. Install the filter in the channel with the arrow on the filter pointing in the direction of airflow, which is toward the blower. 9. Mark the edge of the filter with the date and your initials. 10. Once the filter has been installed, inspect the filter and the channel to be certain that no air is able to bypass the filter. 11. Seal any and all air leaks to prevent/eliminate air bypass. 12. Make certain that any filter channel covers are replaced and secured. Fgr. 19: Directional arrow on the filter; Fgr. 20: Mark or initial the filter Maintaining the Heat Source on Gas-Fired Furnaces Servicing fossil fuel systems should be done by trained professionals, but there are a number of things that the maintenance technician can do to help ensure that the equipment remains in good working order. ********* Notes to keep in mind about filter replacement: • Air that bypasses the filter will cause dirt and dust to accumulate on the coils, blowers, air distribution system components, supply registers, and ultimately end up back in the occupied space. • Be sure to have an ample supply of filters on hand. • As an absolute minimum, change filters at the beginning of the heating and cooling seasons. It is recommended, however, to change them every month. • If the filters are metal permanent type filters, they can be cleaned. • If it has been determined that air filters are missing or too small, be sure to visually inspect the return side of the evaporator coil and ake certain it's free from dirt and dust. ***** 1. Typically, the fuel-burning portion of the system does not need to be adjusted each year. So, for best results, don't change any of the current settings on the system. 2. Perform a visual inspection of the burners, pipes, and manifold arrangement. Make certain that these components are free from dirt, dust, and rust. If it's found that there is excessive rust and rust-related damage, call for professional service immediately. 3. If excessive dirt or rust is present, the gas manifold may be carefully removed for cleaning. Follow these steps: a. Close the manual gas valve that feeds gas to the appliance. b. Disconnect the manifold, making certain to carefully disconnect any components that are attached to the piping. c. Blow out the manifold with pressurized air, making certain to wear the appropriate personal protection equipment to protect yourself from airborne particles. d. After the cleaning is complete, reassemble the manifold. e. Make certain that all piping connections are tight. f. Open the manual gas valve. g. Restart the system. 4. Observe the burners when they are lit. The flames should be bright blue with slightly orange tips. If the flames are yellow or are blue with yellow tips, carbon monoxide, a poisonous, colorless, odorless, tasteless gas generated by incomplete combustion is present. If yellow flames and /or tips are noticed, seek the assistance of a professional immediately (Fgr. 23A). 5. When burning, the flames should rest just above the burners. Flames that are too high above the burner indicate that there is too much air being introduced. Call for help (Fgr. 23B). 6. Flames should be uniform. Erratic flames may be an indication of a system in need of professional adjustment (Fgr. 23C). 7. Schedule a combustion test/analysis on an annual basis, before the beginning of the heating season. Fgr. 21: Disconnect the gas manifold Fgr. 22: Clean the manifold Fgr. 23: Proper and improper flames Fgr. 24: Combustion analysis kit Fgr. 25: Boiler being cleaned Fgr. 26: A gasket Fgr. 27: Changing the oil filter Perform General Maintenance of a Hot Water or Steam Boiler Only experienced contractors should work on boilers. If any of the following conditions are present, a professional should be called in to examine, troubleshoot, and remedy the situation: 1. Water accumulates on the floor around the boiler. 2. Water drips from the pressure relief valve. 3. Heat source fails to energize after one attempt to reset/restart the system has failed. 4. Boiler fails to operate after water has been added to the system. 5. Individual zones fail to heat after attempts to bleed air from the system have failed. 6. Individual zones fail to heat after attempts to troubleshoot zone valves have failed. Perform General Maintenance of an Oil Burner and Boiler Oil burners typically require regular service to ensure continued satisfactory system operation. Here is a list of items that must be addressed as well as some suggestions for keeping oil-i red heating systems in tip-top shape. 1. Schedule a combustion analysis before the start of the heating season. If the oil-i red equipment is used to supply domestic hot water year round, this should be done more frequently. As shown in Fgr. 24, the combustion analysis test should include: a. Smoke test b. Carbon monoxide level c. Carbon dioxide (a by-product of natural gas combustion that's harmful and can even cause death) level d. Stack temperature e. Draft test 2. Keep the oil tank as full as possible. The more oil there is in the tank, the less likely that condensation will form and accumulate in the oil. Water mixed with the oil can result in combustion and operational problems. 3. Clean the heat exchanger on the equipment. To do this, follow the manufacturer's recommendations. The steps involve: a. Disconnect the flue pipe connection. b. Use a boiler brush and vacuum to clean the spaces between the boiler sections. c. Wear a protective dust mask (Fgr. 25). 4. Replace the oil filter. a. Make certain that the oil valve line is in the closed position. b. Unscrew the existing oil filter. c. Replace the filter, making certain that the filter canister gasket is in place (Fgr. 26). d. Make certain that the new filter is tight. e. Dispose of the oil filter as you would any other hazardous material (Fgr. 27). 5. Check and clean the flue pipe. a. Be sure to wear a protective dust mask. b. Make certain that a high-quality (filtering) vacuum is used (Fgr. 28). c. Be sure to reassemble the flue pipe when finished. d. Make certain that the flue pipe is sloped upward toward the chimney. e. Inspect the chimney if possible and remove any obstructions or debris from the chimney. Fgr. 28: Cleaning the flue 6. Check the oil tank for water accumulation. 7. Inspect the area around the unit for traces of oil. 8. Visually inspect the oil lines for damage. 9. Make certain that fill pipe and vent caps are in place. 10. Check for oil leaks in the tank area. 11. Check for unusual oil odors. 12. Inspect the sight glass (steam boilers only). a. If the water level is low, add water to the system via the feed valve. b. If the system is losing water at a very fast rate, call for service. 13. Remove the burner from the unit. a. Place a drop cloth or other barrier between the boiler and the floor. b. Make certain that the main oil line is closed. c. Disconnect the oil line to the burner, making certain that you have rags on hand for any oil drop lets (Fgr. 30). d. Disconnect power to the boiler. e. Disconnect the wiring connections to the burner, making certain to discharge any capacitors (Fgr. 31). f. Place the burner on the floor or work bench. 14. Inspect the combustion chamber. a. Look for cracks in the refractory. b. Look for and clean up any soot build-up (Fgr. 32). Fgr. 29: Sight glass on a steam boiler Fgr. 30: Disconnect the oil line from the burner Fgr. 31: Disconnect the power supply Fgr. 32: Inside of a combustion chamber 15. Replace the nozzle and check the firing assembly. You will need to access the manufacturer's guidelines for this, as each manufacturer and each oil burner model has different procedures for accessing/removing the firing assembly. a. Make certain that the new nozzle is an exact replacement for the existing part. Be sure to have plenty of spares on hand. b. Be careful to not damage the electrode porcelains. c. Inspect porcelains for damage. 16. Clean the cad cell (on systems that are equipped with them). a. Open the top of the oil burner. b. Locate the cad cell. c. Wipe the cell down to remove accumulated dirt. 17. Clean the transformer springs. a. Double check to make certain there is no power being supplied to the unit. b. Open the top of the oil burner. c. Clean the transformer springs. Fgr. 33: Replacing the nozzle on the oil heating system Fgr. 34: Opening the oil burner Fgr. 35: Cleaning the cad cell Fgr. 36: Cleaning the springs Repair and Replace Electrical Devices, Zone Valves, and Circulator Pumps Here are some general suggestions and tips for replacing electrical devices on heating and air-conditioning equipment. 1. Make certain that all electrical power sources are de-energized. Keep in mind that some heating and air-conditioning systems are powered by more than one power source so, even if one source is off, there may still be power to some system components. 2. Make certain that all system capacitors are discharged to avoid receiving an unexpected electric shock. 3. Make certain that an exact replacement, whenever possible, for the component being replaced has been obtained. 4. In the event an exact replacement component is not available, make certain that the replacement component ratings match those of the original as closely as possible. 5. When replacing components that are directly connected to a water-carrying piping arrangement, make certain that the water from the system has been completely drained to avoid an unexpected flood. a. If a zone valve motor is being replaced, there is no need to drain the water system, as the valve mechanism will remain intact. b. If the entire zone valve is being replaced, however, the water system must be drained, as the water circuit will be accessed. c. If the motor on a circulator pump is being replaced and the linkage/impeller assembly is remaining in the system, the water does not need to be drained. d. If the entire circulator is being replaced, the system must be drained. 6. Disconnect the electrical splices one at a time, making certain to label or tag the wires so that you will be able to identify the wires when it comes to reconnecting them. 7. Carefully remove the defective component, making certain to place any screws and other small parts in a container such as a cup to prevent them from getting lost . 8. Mount the new component in place before making the electrical connections. 9. Once the device has been securely mounted, begin connecting the wires one at a time, making certain that the new wiring corresponds to the wiring of the original device. Be sure to use wire nuts or other mechanical connectors (Fgr. 39). 10. Once completed, make certain that the electrical connections are tight and that no bare wire is extending from the underside of the wire nuts (Fgr. 40). 11. Make certain that no bare current-carrying conductors are making contact with the frame or casing of the device. 12. Make certain that all ground wires are properly connected (Fgr. 41). Fgr. 39: Types of wire connectors Fgr. 40: Side-by-side nut connections done correctly and incorrectly Fgr. 37: Tag the wires Fgr. 38: Place screws and small parts in a plastic cup Fgr. 41: Ground wire connected to the metal box Lighting a Standing Pilot When you perform any procedure on a piece of equipment, it's always recommended that the manufacturer's recommendations and procedures be used before general procedures and suggestions. Here are the steps used to light or relight a standing pilot. 1. If the gas valve is in the ON position, close the valve by turning the knob to the OFF position and allow 15 minutes for any unburned fuel to rise through the appliance. 2. Set the gas valve knob to the PILOT position and push the knob into the valve (Fgr. 42). 3. At the same time, light the pilot by using a large barbeque-type match to avoid coming in close contact with the pilot light (Fgr. 43). 4. Once the pilot light is lit, continue to depress the gas valve knob for about 1 minute. 5. After 1 minute, release the knob. 6. The knob should pop up and the pilot should remain lit. If the pilot light goes out, repeat steps 2 through 5. 7. Turn the gas valve knob to the ON position. Fgr. 42: Standing gas valve Fgr. 43: Light the pilot Perform General Maintenance of a Chilled Water System Since chilled water systems contain refrigerants, only qualified air-conditioning technicians should access the refrigeration circuits. The EPA requires that all technicians who work on the refrigeration circuits of air-conditioning and refrigeration system be certified under Section 608 of the Clean Air Act. However, a number of items can be checked by uncertified maintenance personnel. 1. Inspect the piping circuits for signs of leakage, oil, and damage. 2. Inspect the water pumps. a. Measure the amperage of the pumps and verify that the amperage is within an acceptable range. b. Listen to the pumps and make note of any unusual or abnormal noises and vibrations. 3. Check the system thermometers. a. Water being supplied to the chilled water coil should be in the range of 45°F. b. Water returning from the chilled water coil should be in the range of 55°F. 4. Measure the temperature difference between the return air temperature and the supply air temperature. This difference should be between 16°F and 20°F. 5. Make certain that all air filters on the air distribution system are clean. 6. Make certain that the blower/motor assembly is operational. a. Check pulley alignment. b. Check belts for cracks and damage. c. Check motor amperage. Fgr. 44: Turn gas valve to ON Clean Coils If air filters are properly installed and air is not permitted to bypass the filters, there should be very little, if any, dirt accumulation on the return air side of the evaporator coil. On occasion, though, system air filters are removed or not properly installed and air is permitted to bypass. To determine that the evaporator coil is actually clean, visually inspect the coil. This may be a difficult task given the configuration of the system and the installation practices employed. Examining the coil may be as easy as removing the access panel on the air handler or may involve having to cut an access door into the duct system if the coil is mounted on top of a furnace. In any event, once the coil has been inspected and it's determined that the coil is indeed in need of a cleaning, here are some tips and suggestions for doing so. 1. Make certain that the system has been turned off and that all rotating machinery has stopped. 2. Make certain that the area is well ventilated as some cleaning agents give off fumes that may irritate the skin or eyes. 3. Wear proper personal protection equipment such as safety glasses and gloves. 4. Using a brush, remove as much of the dirt as possible. 5. Avoid using a rigid wire brush, as the bristles may cause damage to the coil. 6. Avoid flattening the fins on the coil, as this will have a negative effect on the airflow through the coil. 7. Avoid getting cut on the evaporator coil fins. They are sharp and cuts received from them are very painful. 8. Mix the coil cleaner as directed on the product label (Fgr. 46). 9. Apply the water/cleaner mixture to the coil with a high-pressure sprayer and allow it to sit, allowing the chemicals to break up the accumulated dirt on the coil surface. Make certain that the strength of the high-pressure sprayer is weak enough to prevent the bending of the coil fins (Fgr. 47). 10. After the manufacturer's suggested time period, rinse the coil with high pressure water. 11. Do not use a water hose connected to the building's water supply, as this can damage the coil fins and saturate the duct system. Fgr. 45: Brush the evaporator coil Fgr. 46: Directions on product label 12. Depending on the amount of dirt on the coil, it may be necessary to repeat Steps 9 and 10 to ensure that the coil is as clean as possible. 13. Once the coil has been cleaned, reseal the duct if it was necessary to cut in an access door. If such is the case, be sure to avoid damaging or piercing the refrigerant lines with screws (Fgr. 48). Fgr. 47: Spray the coil cleaner on the coil Fgr. 48: Comparison of clean and dirty coil Fgr. 49: Remove oil plugs from motor Fgr. 50: Insert oil spout into the oil port Lubricate Motors Periodic motor lubrication is often required to keep the motors in good working order. Permanently lubricated motors don't need to be lubricated, but all others do. Unless otherwise specified, use a medium (20-weight) oil. 1. Remove the oil port plugs from the oil ports on the motor. Typically, there are two oil ports on a motor, so be sure to remove them both (Fgr. 49). 2. Place the oil plugs in a safe place to avoid losing them. Not replacing the oil plugs can allow dirt and dust into the motor, affecting the operation of the component. 3. Insert the oil port on the oil container into the oiling tubes (Fgr. 50). 4. Depending on the motor, you should add between three and six drops of motor oil into each port. 5. Make certain to replace the oil port plugs. 6. Do not over-lubricate motors. 7. If the motor is equipped with grease fittings, the lubrication process is different: a. Loosen and remove the relief screw on the motor. The relief screw is located on the opposite side of the motor as the grease fitting (Fgr. 51). b. Using a grease gun, pump grease into the motor until grease leaves through the relief screw. c. Replace the relief screw. d. Repeat this for both sides of the motor. Fgr. 51: Grease fitting Follow Systematic Diagnostic and Troubleshooting Practices When you attempt to diagnose a system problem, using a systematic approach is best. Consider these tips when you encounter a problem. 1. If the system appears to be OFF when it's turned on and operation is desired, check the main power supply to the piece of equipment. Very often, a circuit breaker or switch may have been inadvertently turned off. 2. Check for proper airflow through the air distribution system (furnace and air conditioning applications). a. Reduced airflow can be responsible for a multitude of problems. b. Check air filters. c. Check belts and pulleys. 3. Check the operational controls on the system. a. If a zone valve is not opening, make certain that the thermostat for that zone is calling for heat. b. If a boiler is not operating and the water pipes are hot, the water temperature may have reached the desired temperature. c. If an air-conditioning system is not operating, make certain that the thermo stat is set for cooling before calling for service. d. Check for low voltage by switching the fan switch to the ON position (furnace and cooling applications). e. If a boiler fails to operate, check safety devices such as high-limit controls, pressure controls, and /or low water cutoff switches. 4. Check for safety or trouble lights. a. Many newer controls have trouble and /or diagnostic lights. b. Keep all manufacturers' literature on hand. This paperwork contains valuable information regarding steps you can take to keep equipment up and running. c. Manufacturers' literature contains the trouble codes that often appear on the control's display. 5. Check system operating temperatures and /or pressures. a. Determine which parameters are within acceptable ranges. b. Determine which parameters are not acceptable. 6. Write down your findings. a. Keep logs of your findings. b. This may help evaluate future system problems. c. Keep records of what was done and when. d. This will also help service technicians who do the job. 7. Narrow your search. a. Eliminate items that are definitely operating properly. b. Make a list of possible system problems and examine/eliminate them as needed. 8. Ask yourself why? a. Be sure to i x the cause, not the effect. b. Fixing the effect does not fix the underlying problem. Fgr. 52: Damaged condensate pan Fgr. 54: Condensate pump Fgr. 55: Through-the-wall air conditioner Fgr. 56: Wall sleeve for air conditioner Replace Through-the-Wall Air Conditioners If you have determined to replace a through-the-wall air conditioner, perform the following steps to replace it (Fgr. 55). 1. Remove the existing unit from the sleeve (Fgr. 56). Service note: Be sure to place a drop cloth or other protective barrier on the floor below the unit to protect the floor from any sharp edges on the unit. 2. Obtain all information from the unit, including the make, model, serial number, voltage rating, amperage rating, and plug type from the unit. 3. Take all unit measurements as well as the internal (daylight opening) measurements of the existing sleeve. 4. Slide the existing unit back into the sleeve. 5. With the acquired information, obtain a replacement unit, making certain that all measurements and specifications match those of the existing unit. 6. Uncrate and inspect the new unit. Fgr. 53: Pour water into condensate drain pan 7. Check to make certain that the sizes are correct, the voltage and amperage ratings are the same as the old unit, and the plug is the same. 8. Remove the old unit from the sleeve. 9. Clean and vacuum out the existing sleeve. 10. Slide the new unit into the existing sleeve and secure it according to the manufacturer's installation literature. 11. Make certain that all shipping materials have been removed from the unit and that the air filter is in place before putting the unit into operation. Maintain and Service Condensate Systems An integral part of the operation of an air-conditioning system is the ability to remove condensate from the structure. Quite often, condensate pumps are used to accomplish this. Depending on the location of the system, condensate pump failure can result in water damage to the structure. Even if there is no condensate pump being used, a gravity-type condensate removal system can cause damage in the event that that line becomes clogged. Here are some tips and suggestions for maintaining condensate removal systems. 1. Inspect the condensate pan under the evaporator for: a. signs of rust b. signs of damage c. dirt, dust, and debris accumulation Repair and clean as needed. 2. Test condensate lines by pouring a significant amount of water into the drain pan located under the evaporator coil. a. Observe the rate of water drainage. b. Stop pouring water into the line if water does not drain. c. Inspect the area around the condensate drain pan for signs of water. 3. Inspect the termination point of the line. a. If the line terminates outdoors, observe the end of the line before introducing water to the line and again afterward. b. Make certain that the water is actually leaving the structure. c. If the line terminates in a condensate pump, make certain that the water is indeed ending up in the pump. 4. If the line is not draining, use pressurized air to blow out the line. Repeat Steps 2 and 3 to ensure that the line is now draining. 5. On systems with condensate pumps, make certain to check the operation of the pump. 6. Make certain that the pump remains plugged in or, better yet, have the pump hard-wired to ensure that there is constant power to the pump. 7. Test the pump operation by adding water to the pump and inspecting the end of the discharge pipe connected to the outlet of the pump, as in Step 3. 8. Inspect the area around the condensate pump for signs of water. QUIZ and PRACTICE SHEETS: List three common types of furnaces used in residential and commercial environments. List three symptoms of a loose belt on an air distribution system. List the steps for tightening the belt on an air distribution system. List the steps for replacing a belt on an air distribution system. Estimate the length of a belt used to connect a 6-inch pulley to a 12-inch pulley that's installed on motor and blower shafts that are 14 inches apart. Show your work. How often should an air filter be replaced on a HVAC system? List the steps for lubricating a motor. List the steps for replacing a through-the-wall air conditioner. HVAC Perform General Inspection on a Furnace: Upon completion of this job sheet, you should be able to perform a general inspection on a furnace system. Type of furnace: ________ Model: _____________ Last maintenance date: ___________ Maintained by: _______________ B Describe the general running condition of the furnace. C List four possible fan motor mechanical problems. D Arrange the following troubleshooting steps in the correct order.
E. List the three key indicators that pulleys are aligned properly on the blowers. Instructor's Response: HVAC Replacing Belts Upon completion of this job sheet, you should be able to replace belts on a furnace motor. Type of furnace: ___________ Model: __________ Last maintenance date: ________ Maintained by: _____________ Check off the following tasks as they are completed: Task: ___ B Obtain belt information from the old belt. ___ C Obtain a new, exact replacement for the old belt. ___ D With a pencil, mark the position of the motor mounts on the furnace and the bolt position on the motor base. ___ E Loosen the motor mounts so the motor and motor mounts can move freely. ___ F Replace the belt on the pulleys. ___ G Position the motor, based on the marks in Step 3, to increase belt tension and tighten the motor mounts. ___ H Check the belt tension. Task Completed? HVAC Lighting a Standing Pilot Upon completion of this job sheet, you should be able to light a pilot light on a gas furnace. Type of furnace: ________ Model: _____________ Last maintenance date: __________ Maintained by: ___________________ Check off the following tasks as they are completed: Task: __ B Take the access cover off the furnace and look for the gas control knob. __ C Turn the knob to OFF and allow 15 minutes to allow unburned fuel to rise through the furnace. __ D Turn the knob until the arrow is pointing to the word "Pilot." __ E Push the knob to start the flow of gas. __ F Hold a long match or large barbeque-type match up to the pilot to light the pilot. __ G Once the pilot light is lit, continue to depress the gas valve knob for about 1 minute, then release it. __ H Turn the knob to the ON position. Prev: |