HPR4282: Backup Power for my Gas Furnace

Hacker Public Radio

Hello, again. This is Trey. Before I begin, please note: In the show notes, I include links to several informative videos, and to specific products which might be used for a project like this. I do not endorse, nor support any of the products or influencers linked. I do not profit from anything on or associated with any of the links. They are provided merely for additional information or for reference. I live in the eastern part of the state of Tennessee in the southeast United States. Our summers are fairly hot and humid, but our winters are generally mild. Last winter, we experienced an ice storm, with temperatures dropping into the single digits (Fahrenheit) or below -12 degrees Celsius. This was not a problem until tree limbs heavy with ice began to break off and fall, on occasion taking power lines with them. As a direct result, we lost power at my home. The icy road conditions made it difficult for service vehicles to reach impacted areas, and also made it impossible for us to leave our home. My house is heated by a natural gas forced air furnace. However, the fan which blows hot air throughout the house, and the electronics which control everything from telling the furnace to turn on to igniting the gas, all require electricity. For anyone unfamiliar with how a forced air furnace works, I am including a link to a helpful YouTube video by The DIY HVAC Guy Link So, with the loss of electrical power, came a loss of heat. We experienced a full day of being huddled under blankets and drinking warm beverages. These I could heat up on my gas stove, when I used a match or lighter to ignite the burner. Thankfully, the next day our power was restored, and our home warmed up again. But that got me thinking, and searching for solutions. I needed to provide an alternative electrical power option for my gas furnace so that it would continue to work when the electricity was interrupted. I found a really interesting video, also by The DIY HVAC Guy ( Link ), explaining an option for retrofitting the electrical connections to the furnace, but I never got around to doing it. That changed, a couple months ago, when I found a real deal on a brand new portable solar generator. It is effectively a large lithium iron phosphate (LiFePO4) battery, an inverter, and a charging system, all bundled together in an easy to carry case. It provides over 1,000 watt hours of power. It can be charged using portable solar panels (which I purchased at the same time), or supported using external power sources from 12v to 48v DC. The retrofit of the of the electrical feed line into my furnace was easily accomplished by doing something very similar to what was done in the video linked above. I turned off the circuit breaker for the furnace in the house's main electrical panel, and then located the switch box mounted on the side of my furnace. I removed the switch plate cover and tested the wires inside using a non-contact voltage tester, which would light up and scream at me if there was still any power to any of the wires. No screaming. No power. Good. Next, I removed the switch from the box, disconnected the black power source "hot" wire from the switch. This would carry 120v AC directly to the switch and allow a user to turn the furnace on and off. Th