Preparing Your HVAC for a Texas Hard Freeze
How to prepare a Dallas-Fort Worth HVAC system for a hard freeze, why covering the outdoor unit backfires, and what to check first if the heat quits.
North Texas gets one or two genuinely hard freezes a year, and they arrive with about seventy-two hours of warning. February 2021 taught everyone here what happens when the grid and the housing stock meet a multi-day freeze at the same time — and the HVAC failures during an event like that are overwhelmingly preventable in the week before, not during.
What Should I Do Before a Texas Freeze?
- Run the heat now, for twenty minutes. If it fails, it fails on the first cold night, when every company in the metroplex is booked and parts houses are closed.
- Change the filter. A restricted filter overheats a furnace and trips the high-limit switch, which reads to a homeowner as “the heat stopped working” on the worst possible night.
- Test the CO detectors. Freeze events are when gas heat runs hardest and when people bring alternate heat sources indoors. This is not optional if you have a gas furnace.
- Clear the outdoor unit. Leaves and debris around a heat pump restrict the defrost cycle it depends on in cold weather.
- Find your water shutoff. Not HVAC, but the two failures arrive together, and looking for it in the dark with water running is a bad first attempt.
Should I Cover My Outdoor Unit in Winter?
Every winter someone wraps their condenser in a tarp. If you have a heat pump, that unit is your heat source — it must run all winter, and covering it will damage it. Even on a straight AC condenser, a sealed cover traps moisture and gives rodents somewhere warm to nest in your wiring.
A breathable top cover to keep debris out is fine. Full-body wrapping is not.
What Breaks on an HVAC System During a Freeze?
| Failure | Why It Happens |
|---|---|
| Heat pump runs constantly, house stays cool | Below freezing it leans on backup strips — often normal, not a fault |
| Furnace lights, then shuts down repeatedly | Dirty flame sensor or restricted airflow tripping the limit |
| No heat after a power blip | Control board lockout; a breaker cycle often clears it |
| Ice on the outdoor unit | Light frost is normal on a heat pump; a solid block is not |
| Frozen condensate line | High-efficiency furnace safety shuts the unit off |
What Should I Set the Thermostat To During a Freeze?
Set the thermostat and leave it. Dropping it overnight and asking for a ten-degree recovery in the morning forces a heat pump onto expensive resistance strips at the exact hour the grid is most strained. A steady setpoint costs less and holds better.
Open the cabinet doors under sinks on exterior walls, drip the faucets furthest from the water heater, and if the power goes out, close off unused rooms to shrink what you’re trying to keep warm.
And never use an oven, range, or outdoor grill as a heat source. Every freeze event in Texas produces carbon monoxide deaths from exactly this, and it is the most preventable harm on the whole list.
What Do I Do If the Heat Fails?
Check the simple things before calling, because on those nights everyone is calling: the breaker for the furnace and air handler, the furnace door panel seated properly, the filter, and the thermostat batteries. A surprising share of freeze-night no-heat calls end at one of those four.
If none of them apply, call early rather than waiting to see if it improves. Response times on the second day of a freeze are measured in days, not hours.
Before It Gets Cold
October and November are when a heating tune-up is a scheduled appointment. In January it’s a waiting list.
Call 214-900-2533, see our heating repair and maintenance services, or work through the fall HVAC checklist first.