When a furnace is past repairing

The finding that ends it

A cracked heat exchanger means the furnace gets shut down that day. Any technician who finds one should show it to you and turn the furnace off, and you shouldn't let anyone restart it until it's been replaced.

Is it worth replacing a 30 year old furnace?

In most houses, yes. A 30 year old furnace is well past the fifteen year mark where we start pricing a replacement next to every repair, and it has more against it than age.

• A furnace that old was built to a minimum efficiency of about 78 percent, so roughly a fifth of the gas went up the flue even when it was new. A condensing furnace turns more than 90 percent of the gas into heat.
• Its heat exchanger has been through thirty winters of heating up and cooling down, and a crack in it is a carbon monoxide risk.
• Ignitors, control boards and motors for furnaces that old are harder to find and slower to arrive, often in the coldest week of the year.

If it lights every time, the heat exchanger checks out and the house stays warm, it can wait. Have it inspected before the season and plan the replacement for a mild month.

Failures that don't end it

Ignitors, flame sensors, pressure switches, inducer motors and control boards are all ordinary repairs. On a furnace under fifteen that's otherwise in good shape, they're worth doing. What moves the furnace repair cost is covered in the repair cost guide.

Age and the repeat repair

Two expensive repairs in back to back seasons on a furnace past fifteen is the pattern that says replace. So is a system that has never held the house at the setting on a cold night.

While the system is open

Replacing a furnace is the cheapest time to fix the venting, the combustion air and undersized returns, because the old equipment is out and everything is easy to reach. Doing it later means paying to get in there twice.