Furnace replacement: what to expect

A new furnace is an unusual delivery. It comes with a crew and a plan for getting the old one out. It is also a reason to move those boxes you’ve been meaning to sort.

The useful planning starts before the truck arrives. A clear quote tells you what the job includes. A plan helps you arrange your day. And a final walkthrough leaves you knowing how to use what you’ve bought.

This guide follows a crew replacing an old furnace, with examples for gas heat. A switch to a different type of heating needs its own plan. Already chosen your equipment and installer? Jump to getting your home ready or the final walkthrough.

Before you say yes, know what is being replaced

“New furnace” sounds like one thing to buy. The written quote should explain what happens around it, too.

Start with the scope of work, the list of what the contractor will do. It should name the new equipment, what stays and any work needed to connect it all. That includes the ducts, the passages that carry air through the house. You may be able to keep those ducts or the air conditioner. The installer needs to check whether they will work with the new furnace.

The choice of furnace should fit the house. Tell the contractor about the room that’s always colder than the others. Mention changes such as new windows or insulation, too. A load calculation works out how much heating the home needs. That gives the installer more to go on than the old unit’s size. Here, size means how much heat it can provide, not how big the box is.

Get the schedule, equipment details and included work in writing. Still weighing offers? Our guide to comparing heating and cooling quotes helps you line them up. If you need to borrow, our guide to paying for heating and cooling work explains the payment terms. Settle those choices before the crew arrives and everyone is answering three questions at once.

Plan the day around your home’s actual job

An arrival window tells you when the crew expects to turn up. It doesn’t tell you how long the heat will be off. It also doesn’t promise that every part of the job will be done that day.

Get those times, too. A job with hard-to-reach spaces, duct changes or other equipment can need more work. A useful question is: “What could make the work take longer in this house?”

That helps you plan work calls, school pickups and where everyone will spend the day. If the time without heat would leave your home too cold, discuss that before the crew starts. A calendar that says “furnace, Tuesday” is doing rather a lot of hopeful shorthand.

The job may need a permit, or approval from the local building office. Local rules may also call for an inspection of the work. Find out what applies, who arranges it, whether the fees are included and how you’ll know it is done. The crew may leave before the inspection is finished.

Make a path, then let the crew work

Before the visit, agree on which door the crew will use and which spaces they need to reach. A clear path for a person may not be wide enough for the equipment they carry.

Move loose items out of that path and the work area. That includes boxes, small furniture, rugs and things that could break. Leave the equipment and its connections to the installer. If a heavy item needs moving, arrange that with the crew before the day of the job.

For a furnace in an attic, closet or basement, talk through the path to that space. The crew may also need to reach the electrical panel and other connections. Let them tell you which areas they need. You do not need to guess how much room the work takes.

Pets need their own plan while doors are open and equipment is being carried through. A room away from the work can keep a curious dog from naming itself site manager. Let the crew know where the pets will be and which doors must stay closed.

Agree on how to reach you, too. If you’ll be away for part of the day, plan how the crew will get in and reach you with questions. Arrange to be there for the final walkthrough. Write a short note of what you want explained. “Show me the filter” is easier to remember when it isn’t competing with a phone call and a delivery.

What the crew will be doing

The steps depend on the home and equipment. In broad terms, the crew takes out the old unit, gets the space ready, puts in the new one and tests it.

The crew disconnects the old furnace and takes it out. They get the space ready and change any connections that need work. Then they place the new unit and connect it to the ducts, controls and the services it needs. For a gas furnace, that includes gas and exhaust connections. Leave these tasks to the crew; they are not jobs to tackle before the visit.

The quote should already say whether the crew will take away and get rid of the old unit. Settle that first, so it doesn’t become a surprise long-term member of the household.

If the crew finds work beyond the agreed job, get the details before it starts. Have the change, price and effect on the schedule explained and put in writing. Even a needed repair deserves a clear reason. “We found an issue” starts that talk; it doesn’t explain the whole job.

Once the unit is in place, the installer checks it and makes any needed adjustments. That final setup needs its own place in the walkthrough before the crew leaves.

The handover is part of the job

Leave time for this before everyone packs up. You can go over the equipment, the papers and the things you’ll do as its owner.

The installer may call the final setup commissioning. It means the measurements, tests and adjustments used to check and set up the new equipment. The word sounds like naming a ship. Here, it means getting the heating system ready for the house. Ask what was checked and get the records of that work. These setup checks serve a different purpose from a local building inspection.

Then move to the day-to-day details. Have the crew show you the thermostat, the control you use to set the heat or cooling. That beats finding a new menu at bedtime. Keeping the old thermostat? Have the installer explain how it works with the new unit and which settings you need to know.

Have the crew show you the filter, too. Find out how the owner is meant to reach and replace it, and which type the unit needs. Get the care instructions for your system. A general reminder may be meant for something else.

A warranty promises coverage if something goes wrong, under the rules it sets out. The terms should say which parts are covered and whether they cover labor, the repair person’s work. Look for any other charges or rules, too. The contractor may also offer a workmanship warranty, a separate promise about the work to put the unit in. Keep both sets of terms so they don’t blur into one comforting number of years.

Product registration means sending the equipment and install details to its maker to keep on record. Agree on who will do it, by what date, and how you’ll know it is done. The rules can differ by equipment and where you live. A deadline from someone else’s furnace may not apply to yours. Some installers do this for you. Agreeing who will do it beats finding out that everyone thought someone else had.

Keep this short checklist handy for the walkthrough:

• The equipment: model and serial numbers that name your unit, checked against the agreed job and final bill.
• The controls: how to use the thermostat, find and change the filter, and use the manuals.
• The setup: what was measured or tested, the records you get, and any work still to be done.
• The coverage: warranty terms, who sends the details to the maker and how you’ll know it is done.
• The follow-up: any required inspection still due, who arranges it, and whom to call with questions.

If something is still unfinished

If a paper is missing, a task is unfinished or a control needs explaining, go back to the written plan. Name what is missing so the installer can respond. For example: “The quote said you would take the old unit away. When will that happen?” That gives them more to work with than a general sense that the job isn’t done.

Write down any next steps, who will do them and the expected date. Keep that with the quote, final bill, manuals and coverage terms. One folder on your phone or in the paperwork drawer will do. Future you, trying to find a model number, will be glad it’s all in one place.

By the end of the walkthrough, you should know what was put in and how to use the controls. You should also know whom to call about the work. The heating and cooling hub brings together our other homeowner guides as they are published.