Chapter 21 Exercises

Exercise 1: Thermostat Wire Audit

Materials needed: Screwdriver, smartphone camera

Remove the cover from your current thermostat and photograph the wiring before touching anything. For each wire connected, record: (a) the terminal label it's connected to, (b) the wire color, and (c) what that terminal controls based on the label guide in Section 21.3. Is there a C wire? If not, identify whether a C wire conductor exists in the cable bundle but isn't connected. Document your findings and determine whether your current wiring configuration is compatible with a smart thermostat of your choice.

Exercise 2: Schedule Savings Calculation

Using your last 12 months of utility bills, calculate your average monthly heating or cooling cost. Then estimate your current heating/cooling schedule: how many hours per day is the home unoccupied or everyone asleep? Design a setback schedule (note: setback temperatures, times, and days of week). Using the 10–15% savings estimate from Section 21.2, calculate your estimated annual savings. What is the payback period for a $200 smart thermostat under this estimate?

Exercise 3: Thermostat Placement Evaluation

Walk through your home and evaluate your thermostat's current location using the criteria in Section 21.1. Check for: (a) nearby heat sources (lamps, vents, appliances), (b) exterior wall mounting, (c) proximity to doors or windows, (d) direct sunlight at any time of day, (e) whether the location represents the temperature of rooms you actually use. Write a brief assessment: is your thermostat well-placed? If not, where would a better location be, and what would relocation require?

Exercise 4: System Cycling Observation

Set your thermostat to call for heating or cooling, then time the system's operation. Record: (a) how long the system ran before shutting off, (b) how much the temperature changed during that run, (c) how long before the system cycled on again, and (d) how many times it cycled in a 30-minute period. Compare to the normal range of 2–4 cycles per hour. Is your system short-cycling, running long cycles, or operating normally?

Exercise 5: C-Wire Investigation

Even if you don't plan to install a smart thermostat now, trace the thermostat wire from your thermostat to the furnace or air handler. At the furnace end, identify which conductors in the cable are connected to which terminals on the control board. Are there any unused conductors? Is the C terminal on the control board populated? Document what you find and determine what wire additions, if any, would be needed to support a smart thermostat.

Exercise 6: Comfort Zone Mapping

Create a rough floor plan of your home. For two days, record the temperature in each major room at the same time in the morning, afternoon, and evening (a cheap digital thermometer makes this easy — $10–$15). Map the temperature variation. Are there rooms consistently warmer or cooler than others? Note the time of day when differences are greatest. Based on Section 21.4, assess whether the temperature variation is consistent with a duct issue, an insulation/envelope issue, or a genuine zoning opportunity.

Exercise 7: Heat Pump Identification

If your home has a heat pump, find the outdoor unit and look for the manufacturer's data plate. Record: (a) manufacturer and model number, (b) rated heating capacity, (c) SEER2 or SEER rating, (d) HSPF2 or HSPF rating. Check the thermostat wiring and identify whether the O or B terminal is used (meaning: is the reversing valve energized for cooling or heating?). Look up your model's specification sheet online to confirm whether O or B is the correct configuration.

Exercise 8: Smart Thermostat Feature Audit

Research two smart thermostats — one in the $150–$200 range (e.g., Ecobee SmartThermostat, Google Nest 3rd Gen) and one in the $80–$120 range (e.g., Honeywell Home T6 Pro, Emerson Sensi). For each, document: (a) whether a C wire is required, (b) whether it supports heat pump O/B wiring, (c) what scheduling features it offers, (d) whether it supports room sensors, and (e) whether it qualifies for any utility rebates in your area. Based on your home's current wiring and your priorities, which would you choose and why?

Exercise 9: Zoning Cost-Benefit Analysis

For a home you know (yours or a family member's), identify at least two areas that have different occupancy or temperature preferences during the day. Research the installed cost of a two-zone damper system from a local HVAC contractor (request a quote or use the ranges in Section 21.4). Using an assumed 12–18% energy savings from zone setback, calculate the annual dollar savings and the simple payback period. Does zoning make economic sense for this home? What non-economic factors would you weigh?

Exercise 10: Geofencing Setup and Evaluation

If you have or install a smart thermostat with geofencing capability, enable the feature and observe its behavior for two weeks. Document: (a) how accurately the system detected when you left and returned, (b) whether it ever adjusted incorrectly (assumed away when you were home, or home when you were away), (c) how the temperature behaved during transitions, and (d) whether the geofencing reduced or increased your energy use compared to the two weeks prior. Write a 200-word assessment of whether geofencing is a net benefit for your household's schedule.

Exercise 11: Thermostat Diagnostic Practice

Simulate a thermostat diagnostic scenario. With your system off and the thermostat set well above room temperature (calling for heat), use a multimeter set to AC voltage to check: (a) voltage between R and C terminals at the thermostat (should read ~24V), (b) voltage between R and W terminals when the thermostat calls for heat (should read ~24V when calling, 0V when not). If you don't have a multimeter, research and price the tool ($20–$40 for a basic unit) and understand why electrical testing is a fundamental homeowner diagnostic skill. Write up what you found or what you would do.

Exercise 12: Smart Home Integration Research

Choose one smart home platform (Amazon Alexa, Google Home, or Apple HomeKit). Research which smart thermostats are fully compatible with your chosen platform. Identify one practical automation routine that would genuinely improve your comfort or energy use — not just something that sounds clever. (Example: "When I lock the front door at night, set the thermostat to 65°F.") Document the routine, the hardware needed, and an honest assessment of whether the complexity is worth the benefit.