DENVER GUIDE

Seasonal care before the swing and the first snow

The furnace has not run since spring, the condenser is full of cottonwood and alley dust, and the forecast is the first real snow. Shoulder seasons are when Denver equipment gets asked to change jobs. These notes are the checks that belong before that week, not a service contract in disguise.

By Mike Maziarz · Sources checked October 6, 2026 · How we write these guides

What the shoulder seasons ask

A warm afternoon and a cold night can share one date. The thermostat may call for cooling after lunch and heat after dark. That swing is ordinary along the Front Range. The equipment hates being surprised by it only if nobody has confirmed it still runs. Pick a mild day and call for heat until supply air warms, then, on a different mild day, call for cooling until the outdoor unit answers.

Do the heat test before you need heat. A failed igniter found on a Saturday in October is a repair appointment. The same failure on the first night that drops hard is a crowded board and a cold house. Use the National Weather Service to see the week, not as a dare to wait for the cliff.

Cooling deserves the same courtesy in late spring. Run it while you can still open windows if it fails. A condenser that sits silent in June, discovered on the first hot week, is how a simple part becomes a long wait. Write what you heard. Silence and a tripped breaker are enough of a note.

Filter, coil, and the air path

Find the filter before the season turns. Slide it out. If light will not pass and the media is collapsed, replace it with the size printed on the frame, not a guess from memory. A filter is one of the few parts of this system that is ordinary house care. The coil door behind it is not. Leave that door on.

Outdoor coils collect seed, dust, and grass. On a day the disconnect is off, rinse loose debris gently from the outside. Skip the pressure washer. Look at the pad. A condenser that has sunk or tilted may still run, and it is a note for a technician, not a pry-bar project. Keep shrubs off the fins. Shade from a bush is not worth a matted coil.

Indoor coils and blowers that need brushes, chemicals, or the panel off are a technician's season visit if you want one. Ask them to say what they cleaned and what they only looked at. A maintenance visit that becomes a replacement pitch should still hand you the filter size and the condition of the drain.

The first snow on the outdoor unit

Snow loads a condenser or a heat pump from the top and packs the fan. After the first storm, look from the ground. Brush loose snow off the top and away from the sides if you can do it without climbing and without bending fins. Do not chip ice off tubing. A heat pump buried to the fan cannot move air, and a cooling-only condenser does not need to run in a blizzard anyway.

Intake and exhaust pipes on a high-efficiency furnace can sit low on a side wall where a drift covers them. Walk that wall after a storm. If a pipe is buried, clear the snow back. If the pipe has separated, photograph it and leave the furnace off until someone reseats it properly. Tape is not a winter repair.

The heat pump questions cover defrost and backup heat, which you will meet on the first cold nights if that is your system. Seasonal care is the snow clearance and a test run. It is not a new theory of defrost. Confirm backup heat actually comes on once, while you are awake to hear it.

Combustion season and tight houses

The first real call for heat is when a vent problem stops being theoretical. Look at visible flue pipe for rust holes or a joint that has slipped, from a stance that does not put your face in the draft. Do not take the burner cover off to be thorough. If a carbon monoxide alarm is missing, expired, or chirping a fault, that is the priority over a filter. The carbon monoxide page is the one to read before heating season, not during an alarm.

Older brick and newer infill do not leak air the same way. A house that has been tightened holds heat and will also hold combustion products if a vent fails. That is a reason for working alarms and a clean vent path. It is not a reason to block a combustion-air louver because the basement felt drafty in November.

Ask a technician, when they are there for a seasonal look, whether the furnace or boiler is set up with elevation in mind. Denver sits about a mile up. The answer should be a sentence you can repeat. It should not be a drill size.

Smoke, dryness, and the drain

Some summers bring wildfire smoke to the Front Range. Before you rely on open windows, check AirNow. This page will not quote an index. On smoky days the filter works harder and the outdoor coil is not the thing that cleans the indoor air. Change a loaded filter. Do not tape the return shut.

Heating season dries indoor air that started dry outdoors. A humidifier, if the house has one, needs its own look: pad or media, drain, and whether it runs only when the blower runs. The indoor humidity notes stay with that topic and do not sell a model. Static and a scratchy nose in January are not a spring cooling failure arriving early.

Condensate drains matter twice: in cooling season, when the indoor coil makes water, and in winter, when a high-efficiency furnace makes water. A slime-filled trap or a pump that no longer pumps will shut equipment down or stain a ceiling. Pouring a labeled amount of vinegar or water is reasonable only if you already know that trap and the manual allows it. If you do not, leave the trap for the visit.

When seasonal work grows a permit

Cleaning a coil and changing a filter do not need a story about permits. Replacing a furnace, an outdoor unit, a coil, or a heat pump during a 'tune-up' does. In Denver, Community Planning and Development is the office that can say whether this scope needs a permit and an inspection. The permits and inspections guide keeps that line visible. Aurora, Lakewood, and Arvada are different counters if the house is not in Denver.

A seasonal visit is a good time to read the nameplate and photograph it. You will want that photo when a part fails later. You will want it if a quote names the wrong tonnage or the wrong fuel. This page does not tell you to decode the plate into a capacity figure.

Write a short log: date of the heat test, date of the cooling test, filter size, and anything the technician said about elevation, the drain, or the vent. The log is the maintenance. A magnet on the fridge with a company logo is not.