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1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov HVAC Distribution Systems WEATHERIZATION ENERGY AUDITOR SINGLE.

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Presentation on theme: "1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov HVAC Distribution Systems WEATHERIZATION ENERGY AUDITOR SINGLE."— Presentation transcript:

1 1 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov HVAC Distribution Systems WEATHERIZATION ENERGY AUDITOR SINGLE FAMILY

2 2 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Learning Objectives By attending this session, participants will be able to: Name functions of the components of forced warm air, hot water, and steam distribution systems. Demonstrate common diagnostic and assessment methods for ducted distribution systems. Describe common problems for each distribution system type. Explain solutions to these common problems. HVAC DISTRIBUTION SYSTEMS

3 3 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Good Ducted System Design A well-designed duct system: Provides conditioned air to meet all room heating loads. Provides thermal comfort evenly in all conditioned rooms. Is properly sized so that static pressure is within manufacturer specifications. Is sealed to provide proper airflow and prevent air from entering the house or duct system from polluted zones. Has balanced supply and return airflows to maintain a neutral pressure in the house. Minimizes duct air temperature losses between the air handler and supply registers. HVAC DISTRIBUTION SYSTEMS

4 4 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Forced Air Distribution System The parts include: An air handler at the furnace. A heat exchanger where the heat from combustion is transferred to the distribution air. A supply air plenum to which the supply trunks are attached. Branches attached to the supply trunk. Supply registers through which conditioned air flows to the living space. Return grilles through which air flows back to the furnace. Return branches and trunks attached to the return plenum. HVAC DISTRIBUTION SYSTEMS

5 5 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Ducted Distribution System HVAC DISTRIBUTION SYSTEMS

6 6 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Ducted Distribution System, Contd HVAC DISTRIBUTION SYSTEMS

7 7 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Open Returns Photo Courtesy of PA Weatherization Training Center Open return Draft hood (open at bottom) HVAC DISTRIBUTION SYSTEMS

8 8 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Atmospheric Gas Furnace Distribution System Components Find the: 1. Circulating fan 2. Air filter 3. Cold air return 4. Heat exchanger 5. Warm air to house Source: Heating with Gas, Natural Resources Canada, HVAC DISTRIBUTION SYSTEMS

9 9 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Function of Heat Exchanger The furnace heat exchanger is where the heat from combustion gasesusually between 70% and 95% is transferred to the distribution air in the ductwork. The heat exchanger is an extremely important part of any furnace because it can have a significant impact on efficiency and health and safety. Combustion byproducts must not mix with distribution air. HVAC DISTRIBUTION SYSTEMS

10 10 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Heat Exchanger Leakage Testing Test methods: 1. Visual inspection 2. Inspection with small torch 3. CO reading 4. Wavering flame 5. Tracer gas Photo courtesy of New River Center for Energy Research and Training (NRCERT) Damaged area of heat exchanger HVAC DISTRIBUTION SYSTEMS

11 11 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Ductwork Efficiency Specify duct sealing where ducts are located in unconditioned spaces. Ducts in unconditioned spaces should be insulated to recommended levels. Seal all returns in spaces where atmospheric fossil fuel appliances are located. It is often necessary to remove duct insulation to properly seal ducts. Seal with mastic, then re-insulate. Photos courtesy of NRCERT HVAC DISTRIBUTION SYSTEMS

12 12 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Ductwork This sheet metal ductwork is located within the building envelope, so it does not need to be insulated. Photos courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

13 13 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Ducted System Controls The primary controls are: Thermostat. Fan and limit control. Balancing dampers. Motorized dampers (these are not common). HVAC DISTRIBUTION SYSTEMS

14 14 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Furnace Thermostat The thermostat activates the burner on a furnace. The fan and limit switch turns the air handler blower on and off. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

15 15 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Fan and Limit Control This control turns the air handler blower on and off at set temperatures. This is the fan control. It also shuts down the blower if the heat exchanger area gets too hot (usually at about 200 ). This is the limit control. Recent versions are electronic and cannot be adjusted in the field. Graphic source: Heating with Gas, Natural Resources Canada, Photo courtesy of Honeywell. HVAC DISTRIBUTION SYSTEMS

16 16 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Balancing damper Balancing Dampers Graphic source: Heating with Gas, Natural Resources Canada, Dampers help control airflow to rooms. Manual balancing dampers are not as common as they should be. Sometimes they need to be added. HVAC DISTRIBUTION SYSTEMS

17 17 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Motorized Dampers Motorized dampers are used for zoning a ducted distribution system, rather than for balancing. When a zone requires heat, the thermostat of that zone opens the zone damper and activates the furnace burner. Motorized dampers are uncommon. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

18 18 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Common Ductwork Problems Common problems include: Duct leakage to/from the outdoors. Restricted return side. System not balanced. Temperature too high or too low at heat exchanger. Static pressure out of range. Airflow of air handler fan not matched to system. People live within the distribution system. Closing a bedroom door or covering a register or grille can significantly alter airflow. HVAC DISTRIBUTION SYSTEMS

19 19 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Diagnostics for Ductwork Diagnostics include: Pressure pan (duct leakage). Duct blower (duct leakage). Static pressure. Temperature rise. Room-to-room pressure differences (door restrictions). Air handler blower CFM flow. HVAC DISTRIBUTION SYSTEMS

20 20 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Pressure Pan Test the duct system with a pressure pan and blower door to identify: Leakage to the outdoors when ducts are located outside the thermal boundary. Leakage pathways from duct-containing building cavities to the outdoors (e.g., floor-joist cavities adjacent to porch roofs, cantilevers). Photo courtesy of NRCERT Pressure pan testing of the duct system HVAC DISTRIBUTION SYSTEMS

21 21 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Depressurize house to 50 Pa with blower door. Test each register and grille. Document readings. Registers too large or oddly shaped may be covered with plastic and taped on edges. Seal duct leaks and retest. Goal = readings lower than 1 Pa Pressure Pan Procedure Summary Photo courtesy of NRCERT The handle allows for easy testing of hard-to-reach ducts. HVAC DISTRIBUTION SYSTEMS

22 22 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Pressure Pan Use Sample mobile home duct pattern Bedroom0.8 Pa Bedroom1.2 Pa Bath2.4 Pa Furnace Closet (living room)2.6 Pa Living Room2.6 Pa Kitchen1.2 Pa Kitchen0.5 Pa Total: 10.7 Pa 2.4 Pa at the bath register and 2.6 Pa at the living room register indicate a large leak between them, probably at the furnace plenum. Photo courtesy of NRCERT HVAC DISTRIBUTION SYSTEMS

23 23 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Duct Blower for Duct Leakage Use duct pressurization testing to quantify: Total duct leakage (to indoors and outdoors). Duct leakage to outdoors. Photo courtesy of The Energy Conservatory Manometer Duct blaster HVAC DISTRIBUTION SYSTEMS

24 24 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Duct Blower Procedure Summary #1 To test for total duct leakage: 1. Open a window or door to the outdoors. 2. Install duct blower to the air handler compartment. 3. Temporarily seal all supply registers and return grilles. 4. Insert manometer hose into a supply duct. 5. Open up rooms containing ducts. 6. Pressurize the ducts to 25 Pa and record the airflow. HVAC DISTRIBUTION SYSTEMS

25 25 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Duct Blower Procedure Summary #2 To test for duct leakage to outdoors: 1.Close all exterior windows and doors. 2.Set up blower door to pressurize the house. 3.Connect duct blower to air handler compartment and manometer hose to air handler compartment. 4.Temporarily seal all supply registers and return grilles. 5.Pressurize the ducts to 25 Pa. 6.Pressurize the house until the pressure difference of the house and the ductwork is 0 Pa. 7. Record the airflow at the duct blower. HVAC DISTRIBUTION SYSTEMS

26 26 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Room-to-Room Imbalances #1 Closed doors that prevent supply air from getting back to a return cause positive pressures in those rooms with supply vents... …which starves the return for air, causing negative pressure in the zone where the return is located. ReturnSupply Closed door HVAC DISTRIBUTION SYSTEMS

27 27 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Room-to-Room Imbalances #2 Master Bedroom Bath Utility Room Kitchen Living Room Whole-house return in hallway HVAC DISTRIBUTION SYSTEMS

28 28 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Room-to-Room Imbalances #3 Measure room-to-room pressure imbalances Room pressure imbalances over 3 Pa should be remedied by adding supply or return air. Then retest. Photo courtesy of PA Weatherization Training Center HVAC DISTRIBUTION SYSTEMS

29 29 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Room-to-Room Imbalances #4 Graphic source: Air Distribution System Design, DOE, Solutions 1.Undercut door. 2.Add jumper duct. 3.Add door grille. 4.Add wall grille. 5.Add transfer grille. 6.Install return in affected room. Find the size of the free vent area of your solution by opening the door while the air handler is running. When the manometer reading falls below 3 Pa, measure the in 2 of door opening. This is the in 2 of free opening for your solution. HVAC DISTRIBUTION SYSTEMS

30 30 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Point the tip into the air stream Measuring Static Pressure #1 Static pressure tip Photo courtesy of Rob deKieffer Magnet Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

31 31 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Measuring External Static Pressure Check nameplate for External Static Pressure (ESP). Measure both return and supply sides of the air handler as the unit was shipped. o Measure at inlet and outlet of blower. o Have a clean filter in place (suggested). o Dont measure beyond the A/C coil unless it shipped with unit. Add return and supply pressures together, IGNORING the negative sign. Measuring Static Pressure #2 HVAC DISTRIBUTION SYSTEMS

32 32 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov External Static Pressure IWC (Pa) Air Handler Fan Flow Cubic Feet per Minute 0.69 (173)1, (155)1, (138)1, (118)1, (98)1, (78)1,600 If the static pressure is too high, the fan flow will drop. General External Static Pressure and Fan Relationship Measuring Static Pressure #3 HVAC DISTRIBUTION SYSTEMS

33 33 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Measuring External Static Pressure If ESP is too high, the airflow might be blocked or the ductwork might be too small or restricted. If ESP is too low, the ductwork might be very leaky or the fan might be dirty or damaged. Typical ESP totals are around 0.5 IWC or 125 Pa with an air conditioning coil and filter. Typical ESP totals are around 0.25 IWC or 62 Pa without an air conditioning coil and filter. It is preferred to have the return and supply sides of similar magnitudes, for example, a return of -34 Pa and supply of +31 Pa. Measuring Static Pressure #4 HVAC DISTRIBUTION SYSTEMS

34 34 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Place thermometer in supply side as close to furnace as possible but out of sight of the heat exchanger. o Use manufacturers recommended measurement method, or o Use the four-corner method (measure at each corner or supply plenum and average readings). Place thermometer in return side. Fire furnace. When the supply-side temperature reaches steady state, subtract return-side from supply-side temperature to get temperature rise. Check specified temperature rise on furnace name plate. Actual should be in the middle of the nameplate range. Temperature Rise Test #1 HVAC DISTRIBUTION SYSTEMS

35 35 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Measuring Temperature Rise & Calculating CFM Temperature Rise Test #2 The temperature rise for this example is 70 : 145 supply side -75 return side 70 temperature rise HVAC DISTRIBUTION SYSTEMS

36 36 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Excessive temperature rise can result from: Low fan output. o Wrong fan speed, bad motor bearings, low voltage to motor, dirty blower wheel, wrong motor rotation, slipping blower belt. Low airflow from restrictions in system. o Undersized or restricted ducts, dirty filter, dirty cooling coil. Overfired burner (gas pressure or oil nozzle). Temperature Rise Test #3 HVAC DISTRIBUTION SYSTEMS

37 37 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Low temperature rise can result from: Excessive fan speed. Excessive duct leakage. Underfired burner. o Low gas pressure. o Oil nozzle not matched with airflow rate. Temperature Rise Test #4 HVAC DISTRIBUTION SYSTEMS

38 38 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Temperature rise that is too high can: Damage the heat exchanger. Cause rocking on the high limit. Temperature rise that is too low can: Lead to condensation. Cause excessive soot buildup. Lead to occupant discomfort. Temperature Rise Test #5 HVAC DISTRIBUTION SYSTEMS

39 39 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov TrueFlow ® Air Handler Flow Meter Measures airflow in residential air handlers #20 #14 Measuring Air Flow at Air Handler #1 Photos courtesy of The Energy Conservatory HVAC DISTRIBUTION SYSTEMS

40 40 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Airflow in CFMFurnace BTUH Input 500Less than 60, ,000 to 79, ,000 to 99,999 1,200More than 100,000 Measuring Air Flow at Air Handler #2 General Minimum Airflow Values HVAC DISTRIBUTION SYSTEMS

41 41 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Analysis of Existing Ductwork - 1 Interview occupants about the thermal comfort of the existing system. Ask about: Uncomfortable rooms. Excessive noise. Frequent cycling of furnace. Assessing Ductwork #1 Plumbing through return duct! Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

42 42 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Analysis of Existing Ductwork - 2 Inspect air handler and ductwork for such things as: Disconnected ducts. Duct leakage. Restricted returns. Panned floor joists. Ducts in unconditioned spaces. Balancing dampers. Assessing Ductwork #2 Disconnected duct! Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

43 43 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Do technical testing and appraisal of the duct system and equipment. Duct leakage o Pressure pan testing o Duct blower testing Room-to-room pressure imbalances Static pressure Temperature rise Blower CFM Assessing Ductwork #3 Very dirty blower vanes! Photo courtesy of NRCERT HVAC DISTRIBUTION SYSTEMS

44 44 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Analysis of Existing Ductwork - 5 Determine strategies for duct repair: Write down possible problems. Determine required alterations to furnace and ductwork. Decide on consumer education strategies. Assessing Ductwork #4 HVAC DISTRIBUTION SYSTEMS

45 45 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Good Hot Water Distribution Design Good design: Provides conditioning to meet all room heating loads. Provides thermal comfort evenly in all conditioned rooms. Heats the dwelling quietly. Hot water or steam distribution is often referred to as hydronic. HVAC DISTRIBUTION SYSTEMS

46 46 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Hot Water Distribution System The parts include: Thermostat(s) that activate the circulator pump. Circulator pump(s). Might include zone valves rather than two or more circulator pumps. Aquastat control. A heat exchanger where the heat from combustion is transferred to the distribution water. Supply and return piping at boiler. The expansion tank. Hot water baseboard units (convector) where the thermal energy is transferred to the conditioned rooms. HVAC DISTRIBUTION SYSTEMS

47 47 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Series Loop Hot Water System Based on graphic from the International Association of Certified Home Inspectors, Inc. A series loop hot water distribution system is probably the most common system layout because it is the least expensive. HVAC DISTRIBUTION SYSTEMS

48 48 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Series Loop Hot Water Baseboard Typical hot water baseboard distribution Photos courtesy of Slant/Fin Damper fin HVAC DISTRIBUTION SYSTEMS

49 49 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Expansion Tanks Old-style tanks (above) and newer tanks (right) allow for expansion of heated water and contraction of cool distribution water. Photos courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

50 50 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Hot Water Distribution Controls Thermostat Circulator pump(s) Zone valves Aquastat HVAC DISTRIBUTION SYSTEMS Basic controls include:

51 51 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Boiler Thermostat The thermostat activates the boiler circulator or zone valve and circulator. The aquastat controls the burner. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

52 52 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Boiler Aquastat An aquastat: 1.Maintains boiler water temperature. 2.Provides high-limit temperature protection. 3.Will not allow circulator to operate if boiler water temperature is too low. Also assists with DHW temperature control if the water heater is tankless or indirect-fired. Normally, the aquastat control is covered. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

53 53 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Zone Valves Zone valves are controlled by thermostats in each zone. This house has 3 zones with one thermostat for each. The 4th zone valve is for domestic hot water from the boiler. Zone valves take the place of circulators. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

54 54 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Potential Problems with Hot Water #1 Poor maintenance: If a hot water distribution system is maintained properly, there is little that can go wrong. o Oil-fired boilers should be cleaned and tuned every year. o Gas-fired boilers should be cleaned and tuned once every three years. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

55 55 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Potential Problems with Hot Water #2 Older tanks (above) should be drained and refilled annually. Newer expansion tanks (right) require very little maintenance. Poor expansion tank maintenance Photos courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

56 56 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Potential Problems with Hot Water #3 If the air bleeder valve malfunctions, air will not be purged from the distribution system. This air (oxygen) will create sludge and make the system noisy as the air is pumped with the water. Air bleeder vent Expansion tank Air in the distribution system HVAC DISTRIBUTION SYSTEMS

57 57 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Good Steam Distribution Design A good design: Provides conditioning to meet all room heating loads. Provides thermal comfort evenly in all conditioned rooms. HVAC DISTRIBUTION SYSTEMS

58 58 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Steam Distribution System The parts include: A thermostat(s) that activates the circulator pump. Pressure control (Pressuretrol). A heat exchanger where the heat from combustion is transferred to the distribution water/vapor. Supply and return piping at boiler. o For one-pipe distribution, the supply and return pipes are the same. o For two-pipe distribution, there are separate supply and return pipes. Steam radiators that transfer thermal energy to the conditioned rooms. HVAC DISTRIBUTION SYSTEMS

59 59 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Steam Distribution Controls and Gauges Basic controls include: Thermostat Pressure control (Pressuretrol) Sight or gauge glass Low-water cutoff HVAC DISTRIBUTION SYSTEMS

60 60 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Steam Boiler Thermostat The thermostat activates the steam boiler burner. The Pressuretrol turns the burner off when the set pressure is reached. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

61 61 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Steam Boiler Pressuretrol (pressure control) Pressuretrol (pressure control) Sight glass Low-water cutoff Oil burner Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

62 62 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Steam Distribution Controls Sight (gauge) glass Low-water cutoff The low-water cutoff will shut off the burner if the water falls to an unsafe level. This is required by code. The sight or gauge glass provides an easy way to determine the water level in a steam boiler. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

63 63 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Pressure Control for Steam Photo courtesy of Honeywell Controls This device determines the operating range of the boiler during the heating cycle. When the thermostat calls for heat, the burner will cycle up to the cut- out pressure setting of the Pressuretrol. The burner will then shut off. HVAC DISTRIBUTION SYSTEMS

64 64 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov One-Pipe Steam Distribution Graphic based on Basic Steam Heating Systems, Hoffman Specialty, ITT Industries, 1999, p. 2, One-Pipe Steam Distribution Both steam and condensate use the same pipe. Steam travels to each radiator, condenses (giving off heat), and flows back to the boiler through the same pipe as condensed water. HVAC DISTRIBUTION SYSTEMS

65 65 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Two-Pipe Steam Distribution Steam moves to the radiators in one pipe and the condensate flows back to the boiler through the other pipe. These pipes are usually a smaller diameter than one-pipe systems. Graphic based on Basic Steam Heating Systems, Hoffman Specialty, ITT Industries, 1999, p. 2, HVAC DISTRIBUTION SYSTEMS

66 66 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Potential Problems with Steam #1 Steam distribution pipes are sometimes covered with asbestos insulation. If this material is friable, be careful; it might be best to avoid blower door testing. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

67 67 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Potential Problems with Steam #2 Air valve Supply valve If one- or two-pipe radiators dont heat up, the supply valve may be closed or the air valve may be blocked. Two-pipe radiator Photo source: The Open Fire Centre Ltd., Yorkshire St., Oldham, Lancashire, UK. HVAC DISTRIBUTION SYSTEMS

68 68 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Potential Problems with Steam #3 Steam pressure is often set too high. This can cause distribution problems and wastes energy. For most residential low-pressure, one- pipe systems, 2 psi cut-out pressure or less will work fine and maximize efficiency. High pressure can cause distribution problems and waste energy. Photo courtesy of Bill Van der Meer HVAC DISTRIBUTION SYSTEMS

69 69 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Potential Problems with Steam #4 When replacing a steam boiler, the new unit must be sized to match the installed radiation, rather than the heat load of the house. Photo courtesy of R. Karg HVAC DISTRIBUTION SYSTEMS

70 70 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Summary #1 The function of all distribution systems is to provide even thermal comfort in all rooms of the home. Major components of forced air distribution systems include an air handler, heat exchanger, supply air plenum, supply and return registers, grilles, branches, and ducts. Forced air system diagnostic procedures include duct leakage testing, measuring static pressure, temperature rise, room-to- room pressure imbalances, and airflow across the heat exchanger. Common problems associated with ducted systems include room pressure imbalances, improper temperature rise, and energy wasted through duct leakage to the outdoors. HVAC DISTRIBUTION SYSTEMS

71 71 | WEATHERIZATION ASSISTANCE PROGRAM STANDARDIZED CURRICULUM – December 2012eere.energy.gov Summary #2 Major components of hot water distribution systems include the thermostat, circulator pump, aquastat control, heat exchanger, supply and return piping, expansion tank, and hot water baseboard units. Major components of steam distribution systems include the thermostat, pressure control (Pressuretrol), heat exchanger, supply and return piping at the boiler, steam radiators, sight glass or gauge glass, and low-water cutoff. Some common problems associated with hot water or steam distribution include expansion tank degradation, low water levels (steam), or improper sizing once the home is weatherized. Compared with ductwork, hot water and steam distribution are relatively trouble-free, and diagnostic procedures are easy. We merely ask the occupants if there are problems with the thermal comfort of the home and conduct a simple inspection of the distribution components. HVAC DISTRIBUTION SYSTEMS


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