furnace emergency power project
furnace emergency power project:
This mod started as my mulling ideas on how to restore power to my furnace as I watched the temperature drop
in the house after some idiot took out a major distribution circuit a mile away after losing control on snowy
roads and knocking down a power pole. I was just about to go downstairs and start tinkering when power came
back, but that got a bug in my hear on how to switch over quickly and safely.
Fast forward a few years and I randomly ran into a youtube video on modifying your furnace with an emergency
power bypass switch. I don't have a generator and that looked like overkill, but it got me thinking. How
about just turning my furnace into a plug-in appliance like my microwave, and then when power goes out I can
just unplug it from the dead outlet and plug it into a sine inverter? I'd have to tell my furnace to switch to
"emergency heat" so it ran only on gas and not on the heat pump, but an inverter would have NO problem running
the main board, blower, and gas ignition system.
I just finished the mod today. Most furnaces have a "light switch" on them to make it easy for the HVAC tech to
turn off power to the furnace before opening it up. So I replaced the single switch with a switch/outlet combo
and wired the switch to power the outlet. (instead of the furnace) I then ran a regular heavy gauge power cord
out a knockout on the bottom of the switch box, and just plug it into the switched outlet. The cord provides
power to my furnace.
So now when the tech shows up he can just switch off the furnace like normal to work on it. (and now there's
an indicator light on the switch, so it's an upgrade for him) And when power goes out I can just turn on the
inverter and run a drop cord over to the furnace. Unplug it from the (dead) outlet and into the inverter.
And now I'll have heat. It's all planned out, easy, fast, and safe.
Pictured below is the wiring schematic and a few pictures of the modification before I closed it up. The switch
I used is designed to be an always-on outlet as well as a switched source of hot to run to something like a
light fixture, so it took a little reconfiguring. I removed the break-away connector that provides the outlet
with hot all the time, and connected a jumper from the switch output to the outlet hot.
Reassembled pictures show it put back together and turned on. I had to turn off the work light for the camera
to be able to see the "power light" on the switched outlet. The original switch didn't have an indicator on
it so this is actually an improvement even if you ignore the emergency power option now easily available.
