Why Your Heat Pump Blows Cold Air in Orange County
Almost every "my heat pump is blowing cold air" call we take in Orange County comes down to the same mechanism, and it is worth understanding because it changes what needs fixing.
First, the thing people are most often surprised by: a heat pump is your heating system and your air conditioning system — the same box does both. In summer it moves heat out of the house; in winter it runs the same cycle backwards and moves heat into it. There is no separate furnace. That is why a heat pump fault in December and a heat pump fault in July can have the identical root cause, and why the unit outside your house runs all year.
On a damp morning the outdoor coil picks up frost, and the system has to clear it — so it reverses itself again and briefly runs as an air conditioner, warming the outdoor coil and cooling the indoor one. That is the defrost cycle, and it is completely normal. What is supposed to happen at the same moment is that the electric heat strips in your air handler switch on, so the air arriving at the registers still feels warm.
When the strips are dead, defrost still runs. You just feel it. A few minutes of cold air, then it stops, then it comes back an hour later. People live with it for a whole winter assuming the heat pump is failing, when the outdoor unit is fine and the fault is a forty-dollar element or a stuck sequencer.
This is where Orange County differs from most of the country. In a cold climate the strips are there to carry the house when the heat pump runs out of capacity, and a failure shows up as a cold house. Here it almost never gets cold enough for that. So a failed strip presents as intermittent cold air, not as no heat — which is exactly why it gets misdiagnosed.
What We Actually Check
We measure. Every heat strip diagnosis starts with amp draw on each element and a look at what the control board is asking for, so we can tell you which part failed rather than which part we guessed at.
- The elements themselves. Strip heat is staged — a 10 kW kit is usually two 5 kW elements, not one. One burnt element means you get half the backup heat and a lukewarm defrost, which is harder to spot than a total failure. Amp draw on each stage finds it.
- The sequencer or relay. Elements are brought on in stages so the inrush does not slam the panel. A sequencer that has stopped closing leaves perfectly good elements sitting idle.
- The high-limit switch. A safety that opens if the plenum overheats — usually because airflow dropped. If a limit keeps tripping, the real problem is a filter, a blower or a duct restriction, and replacing the limit just hides it until it burns something.
- The circuit and breaker. Heat kits run on their own dedicated circuit. A tripped or undersized breaker, a loose lug, a corroded disconnect — all of these look exactly like a dead element from inside the house.
- Thermostat staging and wiring. If the thermostat was swapped and the auxiliary heat terminal was never wired, the strips will never come on no matter how healthy they are. We see this after DIY smart-thermostat installs constantly.
- Whether the heat pump is actually producing. If the strips are running far more than they should, the outdoor unit is usually the real fault and the strips are quietly covering for it — at resistance-heat prices.
Installation, Replacement & Sizing
Heat kits are not universal. Each air handler has an approved list, and fitting something off that list voids the listing and often the warranty. We size from the manufacturer's kit options and a load calculation — and in this climate that usually means a smaller kit than you would be sold elsewhere, because here the strips exist mainly to cover defrost rather than to heat the house.
The electrical side is where the real money is, and where most quotes go quiet:
| Heat kit | Approx. draw at 240V | Circuit it wants | Typical Orange County reality |
|---|---|---|---|
| 5 kW | ~21 A | 30 A | Fine on most existing services |
| 7.5 kW | ~31 A | 40 A | Usually fine |
| 10 kW | ~42 A | 60 A | Tight on a loaded 100 A panel |
| 15 kW | ~63 A | 80 A | Often needs a service upgrade |
| 20 kW | ~83 A | 110–125 A | Almost always needs 200 A service |
Figures are for single-phase 240 volt resistance elements and include the continuous-load allowance. Your actual circuit comes from the equipment nameplate and a load calculation, not from this table.
The Panel Question Most Quotes Skip
A large heat kit is one of the biggest electrical loads anyone will ever add to a house — bigger than a range, comparable to an EV charger. Plenty of Orange County homes from the fifties through the seventies are still on a 100 amp service that is already carrying an air conditioner, an electric range and, increasingly, a car.
There are only three honest answers to "will my panel take it", and they all require someone to actually run the numbers: the panel takes it as is, the panel takes it with a subpanel or some load management, or the service needs upgrading. A contractor who only holds a C-20 cannot give you any of those answers with authority — they have to bring in an electrician, usually after the heat kit is already sold.
We hold both classifications under CSLB #1108650 — C-20 for heating and air conditioning, C-10 for electrical. So the load calculation happens before the quote, the panel work and the heat kit are one job with one permit, and if the answer is "your service cannot carry 20 kW", you hear it while you can still choose a smaller kit instead of after the equipment is on your driveway.
Verify it before you book: search licence #1108650 at cslb.ca.gov and you will see both classifications, the bond and the workers' compensation. Do the same with every other quote you get — more on that on our certified technician page.
Heat Strip Questions We Get Asked
My heat pump is blowing cold air. Is the heat strip broken?
Possibly, but that is the second thing we check, not the first. Every heat pump periodically reverses itself to melt frost off the outdoor coil — the defrost cycle — and while it does that it is running your air conditioner in reverse. The heat strips are supposed to switch on during defrost so the air coming out of the registers stays warm. When a strip element, sequencer or limit switch has failed, defrost still happens but nothing warms the air, so you get a few minutes of genuinely cold air and then it passes. In Orange County that is the classic presentation. We measure amp draw on each element rather than guessing, because a burnt element and a failed sequencer feel identical from the thermostat.
What is the difference between heat strips, auxiliary heat and emergency heat?
They are the same hardware used three ways. Heat strips are electric resistance elements sitting in the air handler. "Auxiliary heat" is the thermostat bringing them on to help the heat pump — during defrost, or on the rare Orange County morning cold enough that the heat pump alone cannot keep up. "Emergency heat" is you telling the thermostat to ignore the heat pump entirely and run on strips alone, which is what you do if the outdoor unit has failed. Emergency heat is expensive to run, so if you have been leaving it on because it is the only thing that works, the outdoor unit needs looking at.
How many kilowatts of heat strip do I need?
It depends on the air handler, the house and what the strips are actually for. Most Orange County homes are fine with 5 to 10 kW, because here the strips exist mainly to cover defrost rather than to heat the house outright. Bigger is not better: an oversized heat kit costs more to install, wants a much larger circuit, and on a mild climate's electricity rates it is genuinely expensive to run. We size from the air handler's approved kit list and a load calculation, not from a rule of thumb.
Will my electrical panel handle a heat kit?
This is the question most quotes skip, and it is the one that decides the real price. A 10 kW heat strip pulls roughly 42 amps at 240 volts, and because it is a continuous load the code wants the circuit sized about 25 percent above that — so a 60 amp breaker. A 20 kW kit lands near 83 amps and wants something in the 110 to 125 amp range. A lot of Orange County houses are still on a 100 amp service that is already carrying an AC condenser, a range and maybe an EV charger. We run the load calculation before quoting, and if the panel cannot take it we tell you at estimate time rather than on installation day.
Can you do the panel upgrade too, or do I need an electrician?
We do both. Aerosphere holds a C-20 for HVAC and a C-10 for electrical under the same licence, CSLB #1108650. On a heat strip job that matters more than it sounds, because the work genuinely spans both trades: the kit and the sequencer are HVAC, the dedicated circuit and any service upgrade are electrical. One company, one quote, one permit, one inspection. You are not coordinating two contractors who each think the other is handling the part that went wrong.
Do heat strips need a permit in Orange County?
Adding or replacing a heat kit means new or resized electrical circuits, so yes — it is permitted work, and depending on the city it may pull a mechanical and an electrical permit. California Title 24 also applies to the air handler side. We pull permits under our own licence, meet the inspector and hand you the signed card. Unpermitted electrical work of this size is the kind that surfaces during escrow and stalls a sale.
Is strip heat expensive to run in Orange County?
Run constantly, yes — electric resistance heat is the least efficient way to make heat, and it is why we size conservatively rather than selling you the biggest kit on the shelf. But that is not how it is used here. In this climate the strips typically run for a few minutes during defrost and on a handful of genuinely cold mornings a year. If yours are running far more than that, something else is wrong — usually the heat pump is not producing and the system is leaning on the strips to cover for it. That is worth diagnosing, because you are paying resistance-heat prices for a problem that may be a cheap repair.
Related Heating Services
Heat strips are one part of a heating system. We also handle the rest of it: heat pump repair and installation · furnace & heating repair · electrical panel upgrades · Orange County HVAC · all services.
We service heating, cooling, ventilation and electrical only — we do not service water heaters or tankless water heaters of any brand.