DENVER GUIDE

What you can do yourself, and what needs a technician

The filter is overdue, the condenser is full of cottonwood, and a forum thread is telling you to jumper a switch. Some heating and cooling tasks are ordinary house care. Others can start a fire, a gas release, or a refrigerant leak. The line is the panel you do not open and the chemical you do not add.

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

Work that stays in the house-care column

Replace a filter that slides out, with the size printed on the old one. Set the thermostat to heat or cool on purpose, and change batteries if the model uses them. Brush loose snow off an outdoor unit from the ground. Rinse loose debris from the outside of a condenser only with the disconnect off, without a pressure washer and without soaking the electrical compartment. Those are fair tasks.

Clear a return grille that a rug has covered. Open supply registers you closed last winter and forgot. Write down the sounds after a setpoint change. Photograph the nameplate without removing a live cover. The overview of the equipment helps you name what you are looking at so the note is a furnace, a boiler, or a heat pump, not 'the big box.'

If a task needs a screwdriver on a burner door, a meter, or a gauge set, it has already left this column. Curiosity is not a credential. The closet in an older brick house is tight enough that a dropped screw and a forced panel are how a simple look becomes a damaged wire.

Gas and combustion are not practice

Do not adjust a gas valve, do not open a gas union, and do not soap-test a joint you just loosened. If you smell gas, leave the building, do not flip switches, and from outside call the emergency number on the gas bill. Xcel Energy is the utility many bills name. The rest of this list is void until the utility says the building is clear.

Do not tune a burner for elevation with a drill bit and a chart you found online. Denver sits about a mile up, and the setup question is for a technician who will explain this furnace or boiler after looking at it. You will not improve combustion with a guess. You can make carbon monoxide.

The carbon monoxide page is the exit if an alarm sounds or if people feel sick and then better outdoors. Do not 'confirm' a vent problem by blocking the flue, running a car in the garage, or holding a probe you do not know how to read in the burner glow. Alarms get tested with their own button.

Safety switches stay in the circuit

Do not jump out a rollout switch, a limit, a condensate float, or a pressure switch. Do not tape one down so the furnace will keep calling. Those switches are why a dangerous condition stops the burner. Defeating them is not a temporary heat strategy. It is a way to run equipment that was trying to shut off.

A door switch that kills power when the blower door opens is there because the compartment is not a viewing gallery. If the door is off and you are looking at a spinning blower or an open board, put the door back. One reset of a tripped breaker is a note. A second trip means the breaker stays off and the experiment is over.

Thermostat wiring mistakes belong here too. Do not jumper terminals to force the outdoor unit. Do not add a wire from a place you have not identified. If a previous owner left a jumper, photograph it, stop calling for heat, and hand that photo to a technician. Do not improve it.

Refrigerant is not a top-off

Do not add refrigerant. A can with a hose is not a measurement, and the port is not a tire valve you should learn on a Saturday. Low charge usually means a leak. Adding more, then running the system, is how the rest of the charge leaves and how you can damage a compressor. Stop at the ice, the warm register, or the short runtime, and write those down.

The refrigerant basics page is the longer version: what the chemical is doing between the indoor coil and the outdoor unit, why recovery matters, and what a technician should explain. Federal rules apply to people who handle it. They are not a homeowner hobby with a gloves recommendation from a video.

Do not unbolt a line set, do not cut out a filter-drier, and do not 'empty the system' by loosening a fitting. Venting refrigerant on purpose is not a repair step you get to invent. If a line is already damaged and hissing, leave the area ventilated, kill the call for cooling or heating at the thermostat, and get a technician. Do not put your face over the oil mist.

A failed attempt becomes a larger job

The cost factors on a later visit include whatever the first attempt disturbed. A bent fin from a pressure washer, a stripped gas fitting, a breaker that was oversized with the wrong fuse, or a board damaged by a jumper are new problems. The cost factors page lists access, parts, and after-hours work without prices. Add 'undiagnosed tampering' to the list you are honest about. Tell the technician what you touched.

Honesty shortens the next diagnosis. Hiding a jumper or a can of refrigerant wastes the hour you are paying for and can keep a safety device out of the circuit. You will not be the first person who tried. You will be harder to help if you pretend the panel was never off.

Some jobs look small and are still professional because of where they sit. A condensate pump in a finished ceiling, a flue that passes a bedroom, a heat pump on a roof slope: the part may be simple and the access may not. If you cannot stand in a safe place and see the whole task, it is not house care.

A plain test before you start

Ask three questions. Can I finish this without opening a burner, a blower compartment, or a refrigerant port? If I stop halfway, is the house safer than when I started? If I am wrong, is the failure mode a dirty filter or gas, shock, or carbon monoxide? House care passes the first and fails toward the mild end of the third. Everything else waits.

Use that test on the tempting ones. Vinegar in a condensate trap you already understand and the manual allows can pass. Vinegar poured into a mystery hole does not. A thermostat schedule change passes. A board swap does not. Snow brushed from a pad passes. Ice chipped off a coil does not.

When the test fails, hire with notes, not with shame. Say what the house did, what you already did, and what you refused to do. That refusal is competence. The technician's job starts at the panel you left on.