When Frozen Nights Make for Frozen Thermostats

No one likes waking up to a cold home after a night of freezing temps — but unfortunately, it can sometimes happen with a high-efficiency furnace. Because they have a condensate line (also known as the drain line) that exits the house, the liquid can freeze, and the furnace can’t remove condensation as designed. With nowhere for the water to go, the system protects itself by shutting down. 

The result? A blank thermostat and a chilly home. 

Once you’ve ruled out a thermostat issue (such as a bad battery or a system setting) and checked the breaker switch, try this tip, which often resolves the problem before you hire someone to come out and repair it.

The quick fix: safely thawing the line

This built-in shutdown is intentional and prevents a much more expensive problem, but you can safely nudge it back to work by thawing any frozen ice. 

Using an extension cord and hair dryer, follow these four easy steps to safely thaw the condensate line and get your system operating:

1. Go outside to the point where the condensate pipe exits the home.
2. Use the hair dryer on low or medium heat.
3. Gently warm the pipe and surrounding area until the ice melts.
4. Once the water can drain freely again, the furnace should reset and restart on its own within a few minutes.

NOTE: A hair dryer is the safest option. Never use an open flame or anything too hot. PVC pipes can melt or crack.

Preventing frozen condensate lines

With a few small actions, you can also reduce the chances of this happening again. The most effective way is to weatherproof the line so our technicians recommend homeowners:

• Add heat tape (installed by a professional).
• Insulate the portion of the pipe that’s exposed outdoors. 
• Use Ice Melt on the underside of the condensate line’s exit point before it gets cold, or keep snow and ice from piling up around the exit point.

Your thermostat should start back up if the line was frozen, but if you find your furnace still isn’t working, reach out to our team by sending a message or calling 800-398-4663.