Connected Craftsman LLC
The useful thing about this list is the timing, not the list. Everything here is easier, cheaper and less stressful to sort out on a warm afternoon in September than at nine o'clock on the first genuinely cold night, when everyone who fixes heating is already booked.
1. Turn the heat on now, for ten minutes.
That's the whole tip. Set it to something the house isn't currently at, listen for the burner to light, and let it run until you feel warm air at a register upstairs and downstairs. If something is wrong, you have found it on a warm day with time to deal with it. It will also smell of burnt dust for a few minutes, which is normal and much less alarming in daylight.
2. Change the filter, and find out which way it goes.
There is an arrow printed on the frame and it points the way the air travels — toward the furnace, away from the return duct. Backwards filters bow and let air past the edges. Write the date on the edge of the new one in marker; it settles the argument next time.
3. Look at the flue and the intake from outside.
A high-efficiency furnace vents through a white plastic pipe out of the side of the house, usually low down, sometimes two pipes side by side. They need to be clear — of mulch, of a shrub that had a good summer, of a bird's nest, and later of drifted snow. An older system vents up a metal flue, and what you want there is nothing obviously loose or rusted through at the joints.
4. Test the carbon monoxide alarm, properly.
Not the little chirp when you press the button — that only tests the speaker and the battery. Look at the date printed on the back of the unit. CO sensors expire, typically between seven and ten years from manufacture, and an expired one keeps chirping cheerfully while doing nothing. If the date is past, it isn't a battery job, it's a new unit. There should be one on each floor and one near the sleeping rooms.
5. Find the emergency switch and the shut-off before you need them.
There is a switch that looks like a light switch, usually at the top of the basement stairs or on the wall near the furnace, and it kills the furnace. Everyone in the house should know where it is, and nobody should discover it by flipping it looking for the basement light. Label it. While you are there, find the gas shut-off and the water shut-off too.
If you have radiators, add one more: bleed them once the system has run. Cold at the top and warm at the bottom means trapped air, and the key costs a couple of dollars.
If you're thinking about a smart thermostat this year, check the wiring before you order. Pull the thermostat face off the wall plate and look for a wire actually landed in the terminal marked C — that is the one that gives a smart thermostat continuous power. A labelled terminal with nothing in it does not count. It takes five minutes. If your heat comes from a heat pump, look for the wire in O or B as well. It tells the system which way round to run, it gets set in the thermostat's own setup menu rather than on the wall plate, and getting it wrong is how you end up asking for cooling on the first warm day and getting heat. That check decides which thermostat you should be buying, and whether it is a job worth doing yourself.
None of this is a service call. It is a Saturday morning, and it is the difference between an inconvenience in September and an emergency in November.