Key Takeaways

• Aux heat lockout ≈ 35°F: Delays costly backup until needed.

• Compressor lockout ≈ 5°F: Heat pump runs except in deep cold.

• Rule: Aux lockout must stay above compressor lockout.

• Dual-fuel: Prevents furnace + heat pump from running together.

• Don’t trust defaults (~70°F): Too wasteful for U.S. climates.

why lockouts matter in a dual-fuel home

On cold mornings, your thermostat decides which heat source runs: the heat pump (efficient in mild cold) or the auxiliary backup (electric strips or gas furnace). If those hand-offs aren’t set right, the backup steps in too early, bills spike, and comfort can wobble. Lockouts are simple temperature rules that stop the wrong stage from running at the wrong time. In U.S. homes, tuning these points is one of the fastest ways to cut winter costs without sacrificing warmth or indoor air quality. In this guide, you’ll learn what balance point means, how to pick starting values, how to avoid common mistakes, and how to fine-tune settings over your first heating season. We’ll also point you to helpful gear and resources from The Furnace Outlet, including modern R-32 heat pump systems and support articles tailored for U.S. climates.

The common problem: wrong balance point and confused lockouts

A frequent issue is setting the aux lockout so high that the backup heat takes over on every chilly day. Another is letting the heat pump and furnace run together, which burns money without adding comfort. The result: rapid cycling, rooms that feel uneven, and high utility bills. A clear rule helps: backup heat should help, not lead. Start by identifying your home’s balance point—the outdoor temperature where the heat pump can no longer hold the indoor setpoint by itself. Then align lockouts so the heat pump does most of the work above that point, and the furnace (or strips) take over below it. Keep the wiring and control logic clean, enable dual-fuel mode, and verify an outdoor sensor or trusted weather feed is present. These basics prevent 90% of winter headaches and create steadier, quieter comfort.

Terms made simple: balance point, aux lockout, compressor lockout

• Balance point: The outdoor temperature where heat from the pump equals your home’s heat loss. Above it, the pump keeps up alone; below it, it needs help.

• Auxiliary heat lockout: The outdoor temperature above which backup heat is not allowed to run. This protects your wallet by delaying strips or the furnace.

• Compressor lockout: The outdoor temperature below which the heat pump is not allowed to run. In very deep cold, letting the furnace take over can be smarter.

Golden rules

1. Never set aux lockout below compressor lockout. That creates a conflict.

2. Avoid simultaneous operation. Turn on dual-fuel so only one heat source runs at a time.

3. Don’t rely on default factory settings. They’re usually over-safe for U.S. homes and wasteful.

4. Use an outdoor sensor or Wi-Fi weather. Many thermostats require it to enforce lockouts accurately.

Expert starting points you can trust (then fine-tune)

Most manufacturers provide a safe launch pad: set auxiliary heat lockout to ~35°F and compressor lockout to ~5°F. These numbers strike a balance: the heat pump carries most of the season, and backup heat is reserved for when it truly helps. From there, watch and adjust during your first real cold spell:

• If rooms are stable and recovery is timely, lower aux lockout a few degrees to save more.

• If recovery lags after long setbacks or windy nights, raise aux lockout slightly.

• Keep compressor lockout low unless your unit struggles or gets noisy in deep cold.

Pro tip: Review your thermostat’s run-time reports weekly in January. A quick look at aux runtime vs. outdoor temperature tells you whether to nudge settings. Keep notes—you’ll dial in a “set-and-forget” combo quickly.

How to find your real balance point (simple field method)

You don’t need lab gear just a notebook or spreadsheet.

1. Pick a stable indoor setpoint (e.g., 70°F).

2. For a week with varying weather, record outdoor temp hourly (your stat often logs this) and note when the heat pump alone holds setpoint.

3. When you see indoor temperature drift down or aux engages at a certain outdoor temperature, you’re near the balance point.

4. Cross-check with comfort (are bedrooms steady?) and noise (furnace short-cycling is a red flag).

5. Set aux lockout a few degrees above that balance point. Keep compressor lockout low unless noise, icing, or poor capacity says otherwise.

This method respects your actual home—insulation, windows, duct design, and wind exposure—rather than a guess. If you want a second opinion, use a Manual-J load estimate and the heat pump’s performance table, then compare to your notes.

Thermostat setup that avoids conflicts (dual-fuel & sensors)

Lockouts only work if the thermostat enforces them cleanly. Enable “Dual-Fuel” mode so the heat pump and furnace never run together. Confirm wiring is correct and that the outdoor sensor (wired or Wi-Fi) is present and reading accurately—many lockout features won’t work without it. Don’t use factory defaults; on many stats the aux lockout default can be around 70°F, which is far too high for most U.S. homes. Double-check these guardrails:

• Aux lockout > compressor lockout (always).

• Recoveries: If your stat allows staged or rate-based control, give the compressor time before calling aux.

• Defrost behavior: Brief steam outdoors is normal; don’t let it trigger manual “Emergency Heat.”

If your stat offers reports, monitor stage usage and outdoor temperature—that’s your feedback loop for small, smarter tweaks.

U.S. climate & fuel cost tweaks (how to localize settings)

America’s climates vary widely, so fine-tune by region and rates:

• Mild South/Coastal (many days >35°F): Keep aux lockout lower (30–35°F) to let the heat pump carry more hours.

• Cold Midwest/Northeast: Start around 35–40°F for aux lockout; keep compressor lockout low unless you see comfort issues below 0–10°F.

• High electric rates / low gas rates: Let the furnace take over a bit earlier for cost control.

• Low electric rates / solar homes: Push aux lockout lower so the heat pump earns more of the load.

Always think comfort first in bedrooms and basements. Small building upgrades (air sealing, filter changes, duct sealing) often lower the balance point, which means the heat pump can do more. Explore equipment options and upgrades at Furnaces, R-32 dual-fuel packaged units, 

Quick troubleshooting: when aux or furnace runs too often

If the furnace or strips seem to run constantly, check these in order:

1. Outdoor sensor present and accurate? Replace batteries or fix wiring if needed.

2. Lockouts reversed? Aux above compressor, never the other way.

3. Dual-fuel mode on? Disable any setting that allows simultaneous operation.

4. Setpoint jumps or long setbacks? Big morning recoveries can force aux; try smaller setbacks.

5. Airflow: Dirty filters or duct issues make the heat pump look weak.

Frequently Asked Questions

What is a good starting aux lockout for most U.S. homes?
About 35°F is a practical starting point; adjust up for faster recovery or down for more savings.

When would I raise the compressor lockout above 5°F?
If your heat pump gets noisy, struggles to defrost, or can’t hold setpoint in deep cold, inch it up a few degrees.

Why can’t my heat pump and furnace run at the same time?
Running both wastes energy and can confuse airflow and staging. Dual-fuel mode keeps operation clean.

Do I need an outdoor sensor?
Yes. Many thermostats won’t enforce lockouts without a wired sensor or a reliable weather feed.

Are factory defaults okay?
Usually not. Defaults (like a ~70°F aux lockout) are too conservative for many U.S. homes.

How do I know I hit the right balance point?
Your home holds setpoint smoothly, aux runtime is low, and you don’t notice long, cold recoveries.

Can better filters or duct sealing change my settings?
 Yes. Improved airflow and tighter ducts lower the effective balance point, letting the heat pump do more..