Home Heating Efficiency Improvement

1. Home Heating Efficiency Improvement Trevor Thompson Senior Project II Vermont Technical College Spring 2011

2. Problem Statement Inefficient heat distribution from the living room woodstove to other rooms in the house resulting in ~7deg delta in temperature between the living room and the nursery (room 1). Room 2 ~63 deg Room 3 Room 1 Room 5 Room 4 Living Room ~70 deg House Layout

3. Solution Statement • Design a heat distribution system that takes heat provided from the living room wood stove and distributes it to other rooms when called for. • If the temperatures are not being met the controller will trigger the furnace to turn on and compensate. room 5 V(T) Room 3 Room 2 Room 1 V(T) V(T) V(T) Furnace Actuator Controller Damper Damper Actuator Damper Actuator Outside Temp Intake Temp Damper Room 4 Damper Actuator Room 5 Living Room V(T)

4. Project Plan

5. Mechanical Design

6. Step #1: Calculate Required Btu/hr Formula: BTU/hr Required = Volume of Room (ft3) X Insulation Rating + (# of Windows X 1000) Length (ft) X Width (ft) X Height (ft) * All Formula’s Obtained at www.engineeringtoolbox.com

7. Step #2: Determine Required Air Flow Formula Air Flow (cfm) = [(6.76kW)(3.42)] / [(1.08)(30deg F)] = 713 cfm 1 kW (kJ/s) = 859.9 kcal/h = 3,413 Btu/h (23,000 Btu/hr) X (1kW/3413Btu/hr) = 6.76kW 23000 Btu/hr ~700 cfm Required

8. Step #3: Choosing Duct Size Formula • Air velocities in ducts should not exceed certain limits to avoid high pressure losses and unacceptable noise generation. Step 1: Determine Desired Air Velocity Step 2: Calculate Duct Diameter Branch Duct Calculation v = 400ft/min q = 78cfm Duct X-Sectional Area = 144 X (78cfm / 400ft/min) = 28in2 Area = pi X r2 so; r = sqareroot (Area / pi) r = square root(28in2 / pi) = 3 inches Duct Diameter = 6 inches Main Branch Duct Calculation v = 900ft/min q = 700cfm *This will be used in the next step Duct X-Sectional Area = 144 X (700cfm / 900ft/min) = 112in2 Area = pi X r2 so; r = sqareroot (Area / pi) r = square root(112in2 / pi) = 5.97 inches Duct Diameter = 12inches

9. Step #4: Determining Friction Loss in the Duct Formula 700 cfm Friction Loss = [0.109136 X (700cfm)1.9 ] / (12in)5.02 Friction Loss = 0.1 inch H2O

10. Step #5: Choosing Fan

11. Step #6: Verifying Duct Equivalence Confirmation that the existing duct can carry the same air volume as the new 12” round.

12. Step #7: Choosing Return Locations What Do We Know? • Each room has a fixed volume. • As hot air is forced into the room existing cool air needs to be pulled out. • Want air flow in each room to envelope the room with hot air to reduce cold air from penetrating the exterior walls. • Since hot air rises I choose a low location for the return vent so the air that was force out was the cold air that resided in the room.

13. Solidworks Flow Simulation Initial Hot Air Vent Location Final Hot Air Vent Location

14. SolidWorksModeling

15. 90deg Elbow 45deg Elbow Transition Box Actuator Duct Intake Centrifugal Fan Dampers 6 in Branches Main Existing Trunk 12 inch Main Trunk SolidWorks Modeling

16. Controllable Damper Assembly Actuator Damper Damper Assembly Controllable Damper Assembly Damper Duct

17. Complete SolidWorks Assembly Existing Duct Assembly New Duct Assembly Combined Duct Assembly

19. Hot Air Control Vent System Level Diagram Room 1 Temperature Plate Room 2 Temperature Plate Room 3 Temperature Plate Room 4 Temperature Plate Room 5 Temperature Plate 10K Type 3 Ethernet Port 24VAC Furnace Centrifugal Fan Outside Temp 24VAC Computer Intake Temp 0-10V Signal Room 5 Relay Room 1 Actuator Room 4 Actuator Room 3 Actuator Room 2 Actuator Room 4 Damper Room 5 Damper Room 1 Damper Room 2 Damper Room 3 Damper

20. Electrical Wiring Diagram • Four wire to each actuator. • Two wire to; • Temperature Plates • Fan Control • Outside Temperature • Intake Temperature • Furnace • Power to Fan. • Power to Transformer. • Tie into Controller Furnace OA Temp Intake Temp

21. Controller Layout • 8 Universal Inputs • Temperature Plates (4) • Outside Air Temp Probe (1) • Intake Temp Probe (1) • 4 Analog Outputs • Actuators (4) • 4 Digital Relay Outputs • Furnace • Centrifugal Fan • 15 VDC Out • Ethernet Ports • Battery Backup Pack

24. Fabrication / Installation Process

25. Installation Process • Cut in zone control dampers and attach actuators • Install clearance extension • Install 90deg elbow • Install fan • Install 45deg tie-in elbow • Install back draft damper • Install 12” round duct pipe • Install Temperature Plates • Install Outside & Intake Temp Probes

26. Designing Intake Area of 12” Round Duct = (pi)r2 = pi x 62 = 113.1 in2 Area Intake = Length X Width Length = 113.1 in2 / 4in = 28.3 in ~29 inches • Cross sectional area of intake must equal or exceed that of the 12’ round duct. • Clearance behind woodstove limits width to 4 inches. • Intake must travel from duct in basement through floor to rear of woodstove. • Design must include a removable filter to remove dust/ash/smoke before going through system.

27. Initial Design Verification • Find location of woodstove in the basement • Review basement layout for any obstructions • Determine where to tie into existing duct

28. Initial Sketch of Intake

29. Controller Wiring Mount Controller Run Trunk Line / Install Mounting Board Connect Wires to Terminals

30. List of Materials / BOM

31. Demo Questions