PART 5: HVAC & DHW SYSTEMS

Transcription

1 PART 5: HVAC & DHW SYSTEMS Building Science Review

2 Building Science Review: HVAC & DHW Systems This document will help you: Correctly answer all parts of the HVAC Systems section in the Home Energy Score Tool Calculate equipment efficiency based on type and manufacture year Identify Heating Equipment 9 Types Identify Water Heating Equipment 5 Types Identify Cooling Equipment 3 Types Determine impact of multiple HVAC systems within a home Identify Duct Quality

3 HVAC Systems: Equipment Efficiency In practice, the actual energy efficiency of a piece of equipment is rarely known. Even if it is known, age and wear and tear tend to decrease the efficiency. To address this issue, the Dept. of Energy (DOE) has developed an efficiency calculator to help determine the efficiency. It is based upon the age of the equipment, whether it is routinely maintained and its initial efficiency. Link for the downloadable excel efficiency calculator. Link to find the age of equipment (more detail on next page): When using the Assessor Calculator, always use the current year when determining the equipment age. If you downloaded the Sim Calculator prior to January, 2016, it is out-of-date. Download the current Calculator.

4 HVAC Systems: Equipment Efficiency The Assessor Calculator is easy to use. Simply input the 4 data items: 1. System Type. Determine through visual inspection. 2. Is it well maintained? Determine through visual inspection and/or homeowner interview. If you don t know or can t tell, answer no. 3. System age. Determined from the equipment label & building center website. 4. Installed efficiency. Determined through the table found in the Assessor Calculator / given below:

5 HVAC Systems: Date of Manufacture If the date of manufacture is not clearly printed on the data plate, visit to learn how the manufacture year is coded into the to the serial number. Example of the manufacture date coded in the serial number on a Trane furnace. This unit was manufactured in (For Sim calculations, please disregard the month.) When using the Assessor Calculator always use the current year when determining the equipment age.

6 HVAC & DWH Systems: Types in the Scoring Tool Heating Equipment 9 Types: Central Gas Furnace Room (through-the-wall) Gas Furnace Propane (LPG) Furnace Oil Furnace Electric Furnace Electric Heat Pump Electric Baseboard Heater Gas Boiler Oil Boiler Water Heating Equipment 5 Types: Electric Storage Natural Gas Storage LPG Storage Oil Storage Electric Heat Pump Cooling Equipment 3 Types: Central Air Conditioner Room Air Conditioner Electric Heat Pump

7 Heating: 9 Equipment Types 1. Central Gas Furnace High Efficiency (Condensing) Mid-Level Efficiency (Induced Draft) Low Efficiency (Natural Draft) 2. Oil Furnace Condensing (High Efficiency) Flame-Retention Head Burner (Mid-Level Efficiency) Conventional Burner (Low Efficiency) 3. Room (through-the-wall) Gas Furnace 4. Propane (LPG) Furnace 5. Electric Furnace 6. Electric Heat Pump 7. Electric Baseboard Heater 8. Gas Boiler 9. Oil Boiler

8 Heating: Central Gas Furnaces Central Gas Furnaces 3 Types: Type Condensing HE Defining Features White PVC flue pipe connected to the outside, often paired with PVC intake pipe Starting Efficiency 0.90 AFUE Example Induced Draft Metal exhaust flue pipe, often connected to the chimney Inducer fan 0.82 AFUE Natural Draft Draft diverter or hood for air intake below the metal exhaust flue pipe 0.78 AFUE

9 Heating: Oil Furnaces Oil Furnace features: Barometric damper (except condensing), injection controller, oil tank. Type Condensing Flame-Retention Head Conventional PVC pipe exhaust venting Motor RPM 3450 Standard since mid 1980 s Natural draft exhaust venting Motor RPM 1725 Phased out in 1980 s Natural draft exhaust venting 0.90 AFUE 0.80 AFUE Defining Features Starting Efficiency Example photo missing? 0.72 AFUE

10 Heating: Other Furnaces Type Defining Features Starting Efficiency Through-the-Wall Gas furnace No ductwork Temperate regions 0.78 AFUE Example Propane / LPG Identical to natural gas furnace in house Also has propane tank sometimes buried in yard Typically found in rural areas Boiler plate on equipment will indicate type of fuel Same as natural gas

11 Heating: Boilers Gas and Oil Boilers are used to heat homes with hot water or steam pumped through radiators. Type Defining Features Starting Efficiency Gas Boiler Open draft diverter Large pipes attached to the system Lack of ducts AFUE Example Oil Boiler Barometric damper (top circle) Outside oil injection controller (bottom circle) Flue AFUE Tankless Coil A tankless coil has an additional controller on the outside. no DHW heater or storage tank present AFUE

12 Heating: Electric Type Defining Features Efficiency Electric Baseboard Wiring No pipes No Combustion 0.99 AFUE Example Electric Heat Pump Thermostat has Emer Heat setting / light Turn up thermostat on heat mode until system comes on. If outside unit is running, then it is a heat pump HSPF Electric Furnace Large electric breaker in front Heavy wiring No flue 0.99 AFUE

13 Cooling Equipment: Distinguishing Types Cooling Equipment 3 Types: Type Defining Features Starting Efficiency Central Air Conditioner Outdoor compressor unit Two copper pipes, one insulated Evaporator coil 9-20 SEER Example Room Air Conditioner window mounted or through-the-wall No central / outdoor unit 8-12 EER Electric Heat Pump Thermostat has Emer Heat setting / light Looks and functions like central A/C compressor 9-20 SEER

14 HVAC Systems: Multiple Furnaces The Home Energy Score Tool is able to account for 2 heating or cooling systems within a home. If there are more than two systems, then the two largest system characteristics should be entered.

15 HVAC Systems: Ducts The Scoring Tool requires data on the ducts. If the ducts are in more than one floor/location you must estimate the % in each location. In this diagram, 50% of the ducts are in unconditioned attic and 50% are in an unconditioned basement and unvented crawlspace. (Note: the basement is unconditioned as per the Home Energy Score definition of conditioned areas, because there are no supply registers located there.

16 Ducts: Schematic Determining duct locations in a multi-story home: If supply vents on the top floor are in the floor, you can assume the vents are in a conditioned area - the floor joist space of the living space. If they are in the ceiling of the top floor the ducts are in the attic. Use the floor area ratios as an approximation for duct % in these difficult cases.

17 Ducts: Exterior Insulation Duct insulation is usually indicated on the exterior of the ducts with a foil or plastic covering. Rigid insulated ducts will often have the insulation R-value printed on the outside.

18 Ducts: Interior Insulation Interior duct insulation can usually be determined by knocking on the ducts. A hollow sound indicates no insulation. You should be able to see the insulation through the duct register. There is a material called duct board that is pressed fiberglass with a reinforced foil-like covering. It will give if you poke it, unlike metal ducts, but not as much as exterior insulation.

19 Ducts: Sealing A common duct sealant is mastic, shown in these photos. If the duct joints are sealed with duct tape, this is not considered sealed as the tape tends to deteriorate quickly. Look for presence of sealing at the return of the furnace/ac unit and/or at joints in the duct work.

20 Domestic Hot Water: Distinguishing Types Water Heating Equipment 5 Types: Type Defining Features Starting Efficiency Natural Gas Storage Open draft diverter Large pipes attached to the system, no ducts 0.55 EF Example LPG Storage Looks like natural gas but with storage tank outside. Boiler plate says LPG EF Oil Storage Barometric damper Oil injection controller Flue 0.53 EF Electric Storage Heavy wiring No exhaust flue 0.87 EF Electric Heat Pump Storage Compressor attached to top of water heater Heavy wiring No exhaust flue Assume 2.5 EF