Heat Strips Not Working?

Why Heat Strips Rarely Matter and Suddenly Do (Tampa Climate Context)

Tampa Bay winters are mild, which is exactly why heat strip failures sneak up on homeowners. Your electric heat strips only engage when outdoor temperatures drop below roughly 40°F, and Tampa sees that kind of weather for just 15 to 25 days a year. The rest of the winter, your heat pump handles heating duty on its own by pulling warmth from outdoor air, and the strips sit idle inside your air handler.

That rarity is the problem. A burnt-out heat strip element or dead sequencer can sit undiagnosed for 10 or 11 months out of the year without anyone noticing. Then a cold snap rolls in from the Midwest, temperatures dip into the upper 30s overnight, and homeowners wake up at 4 AM to a 58°F house. We get the bulk of our heat strip calls the week after Christmas and the first two weeks of January.

Emergency Heat vs Auto Mode: What Actually Happens

Your thermostat has two heat settings for a reason. In Auto mode, the system runs the heat pump first and only kicks in the strips when outdoor temps drop low enough that the heat pump alone cannot keep up. In Emergency Heat (Em Heat), the heat pump is completely bypassed and the electric strips run alone as your only heat source.

This matters for diagnosis. If you switch your thermostat to Em Heat and nothing warm comes out of the vents after 2 or 3 minutes, your strips are confirmed dead. The heat pump is out of the picture in that mode, so cold vent air in Em Heat points directly at the strips, the sequencer, or the contactor.

How to Test Before the Cold Snap Arrives

We recommend every Tampa homeowner run a 2-minute heat strip test in October each year. Flip the thermostat to Em Heat, set it 3 degrees above room temperature, and wait 2 minutes. Put your hand on a supply vent. Warm air means your strips are working. If something feels off, call us for a FREE diagnosis before December.

The 5 Causes of Heat Strip Failure in Tampa Homes

What a Tech Actually Measures

A single 5kW heat strip pulls roughly 20 to 22 amps at 240 volts. A 10kW strip pulls 40 to 45 amps. Most Tampa air handlers have a 10kW or 15kW total strip package, which means our clamp meter should read between 40 and 60 amps on the strip circuit when the thermostat calls for Em Heat. If we clamp the wire and see 0 amps with the thermostat calling, the fault is upstream in the sequencer, contactor, or control wire.

Is Running Emergency Heat All Day a Problem?

Yes, and your power bill will tell you so. Emergency Heat costs roughly three times more to run than normal heat pump operation because you have bypassed the efficient part of the system and are heating purely with electric resistance.

Let’s run the math on Tampa rates. TECO and Duke charge around $0.14 per kWh. A 10kW heat strip running at full capacity pulls 10 kWh per hour, which costs $1.40 per hour. During a cold snap, strips typically run 6 to 8 hours a day. That works out to $8.40 to $11.20 per day in strip usage alone. A 5-day cold snap adds $42 to $56 to your bill.

Signs Your Strips Are Running When They Should Not Be

• Heat pump reversing valve stuck, so the outdoor unit cannot switch to heat mode
• Defrost board failing, which can lock the system into a defrost loop
• Outdoor coil iced over in cold damp weather, blocking airflow
• Thermostat miscalibrated or set to Em Heat accidentally

If your heat pump is blowing cold air during a cold snap, the issue is usually in the outdoor unit, not the strips. See our heat pump blowing cold air guide.

60-Second DIY Self-Diagnostic Flowchart

1. Set your thermostat to Heat mode, temperature 5 degrees above current room temp. Wait 3 minutes.
2. Put your palm flat on a supply vent. If vent air feels warm, system is working. If cold, go to step 3.
3. Look outside at the condenser unit. Is it running and the fan spinning?
4. Outdoor unit NOT running + vent is cold = strips are the primary failure.
5. Outdoor unit IS running + vent is cold = heat pump problem, not strips.
6. Switch thermostat to Emergency Heat (Em Heat) mode. Wait 2 minutes.
7. Check vent again. Warm air in Em Heat mode = strips work, heat pump is the issue. Cold air in Em Heat = strips are dead.