Backup Heat: What Heat Strips Are Supposed to Do
Heat strips are the backup singers of your heating system — essential in their role, but never meant to carry the whole show. In your Mitsubishi Electric heat pump system, the compressor does the efficient work of moving heat from the outdoor air into your Nokomis home. The electric heat strips, mounted in the air handler, exist for three specific jobs: supplementing the heat pump when demand exceeds its capacity, providing heat during defrost cycles, and serving as emergency heat if the outdoor unit cannot run.
Problems start when the strips take on a bigger role than designed. A failed sequencer, a welded relay, or a control fault can leave the elements energized far longer than they should be — or even running while the system is trying to cool. Because resistance heat is the most expensive heat your home can produce, the first symptom of a heat strip failure is usually financial: an electric bill that jumps with no other explanation.
Hyper-Heating and Why Strips Still Matter
Mitsubishi Electric systems equipped with Hyper-Heating INVERTER technology are designed to keep producing efficient heat at outdoor temperatures where conventional heat pumps give up. That capability means the strips are needed less often than in older equipment — which makes a strip failure more surprising when it happens, and also more costly, because the system was engineered around the assumption that backup heat would be rare.
This is exactly why heat strip problems on advanced systems deserve a specialist’s diagnosis. The interaction between the inverter-driven compressor, the system’s control logic, and the staging of the backup elements is specific to Mitsubishi Electric engineering. A generalist who treats the air handler like generic equipment can miss the control fault that is actually driving the failure — and replace elements that were never the problem.
Staging Controls: The Brains Behind the Elements
Heat strips do not simply switch on and off. They are staged: sequencers bring the Nichrome elements online one bank at a time and shut them down in reverse order. This staging protects your electrical panel from sudden load spikes and gives the system fine control over how much supplemental heat it adds.
Most heat strip failures are actually staging failures. A sequencer that sticks in the closed position keeps its element bank energized indefinitely. A relay with welded contacts does the same. A thermostat or control board fault can call for strip heat when none is needed. During diagnosis, we test the complete staging sequence — elements energizing in order, de-energizing cleanly, and staying off when the heat pump is carrying the load alone. Replacing elements without verifying the controls is how the same failure returns within weeks.
How We Diagnose a Heat Strip Failure
Diagnosis starts with the simplest instrument: a clamp meter on the strip circuits. If the elements are drawing current when the thermostat is not calling for auxiliary heat, we have confirmed the core problem in minutes. From there, we work backward through the control chain — sequencer, relays, low-voltage wiring, thermostat signals — to find which component is holding the strips on.
We also verify the heat pump side of the equation. Sometimes the strips are running excessively because the compressor is underperforming — low refrigerant charge, a failing reversing valve, or a control issue that keeps the outdoor unit from doing its share. In that case the strips are compensating for a different failure, and the honest repair addresses the root cause rather than the symptom. You deserve a diagnosis that distinguishes the two.
Replacement With Genuine Mitsubishi Electric Parts
When replacement is the right call, the details matter. The new strip assembly must match your air handler’s voltage, amperage rating, and staging configuration exactly, and on Mitsubishi Electric equipment it should be a genuine part so it integrates with the system’s controls and safety limits. Aftermarket elements that do not match the staging design can create new control faults or trip safety devices.
The replacement itself is electrical work, not refrigerant work, so it is completed faster than most heat pump repairs — typically in a single visit. Our vans carry the strip assemblies, sequencers, and electrical components most commonly needed, along with the instruments to verify the full staging sequence before we leave. And because the work is performed by qualified specialists with genuine parts, your manufacturer warranty stays intact.
Scheduling Heat Strip Service in Nokomis
A malfunctioning heat strip assembly will not fix itself, and every billing cycle it runs unchecked is money lost. We provide 24/7 emergency service with same-day dispatch across Nokomis, so a spiking electric bill or a heating system stuck on expensive backup heat gets attention fast. If your bills have climbed, your system runs strips when it should not, or your breaker keeps tripping on the air handler circuit, call now — we will find the fault in the control chain and restore your system to the efficient operation it was designed for.
Why did my electric bill spike if my heat pump is efficient?
Because the heat strips — the least efficient part of the system — may be running far more than designed. A stuck sequencer or failed relay can keep resistance heat energized continuously, and that shows up directly on your bill.
How long does a heat strip replacement take?
Usually one to two hours on site, including full testing of the staging sequence. Since it is electrical work rather than refrigerant work, most replacements finish in a single visit.
What is the difference between auxiliary heat and emergency heat?
Auxiliary heat is the thermostat automatically adding strip heat to supplement the heat pump. Emergency heat locks out the outdoor unit and runs the strips alone — useful as a temporary measure, but much more expensive to operate.
Can heat strips be repaired instead of replaced?
Sometimes the elements themselves are fine and only the sequencer or relay has failed — in that case we replace the failed control component. If the Nichrome elements are burned out or shorted, the assembly is replaced.
Will this repair void my Mitsubishi Electric warranty?
Not when performed by qualified specialists with genuine Mitsubishi Electric parts. Warranties are voided by unqualified electrical work or non-genuine components that do not integrate with the system’s controls and safety limits.