What this winter check can explain
Seeing AUX heat, frost, or a home that will not warm up? The check starts with what you can already observe. It explains possible meanings, keeps unknown answers visible, and helps you prepare an optional service inquiry. It cannot diagnose equipment, confirm safety, select a repair, or predict heating performance.
Safety comes first. If a CO alarm sounds, you suspect CO exposure or a gas leak, or you see smoke or fire, leave the affected area and contact emergency help from safety. For suspected gas leaks, do not operate switches or devices in the affected area or investigate the source. This tool and the website form are not emergency reporting channels. If unsure about an immediate hazard, this tool cannot establish safety; follow emergency instructions for suspected hazards.
- Observe: report the visible thermostat label, comfort trend and what you already noticed from an accessible, safe location. “Not sure” is useful.
- Understand: read a conditional explanation and its limits. A reported hazard pauses ordinary guidance.
- Choose: read the guide or deliberately include a summary with the existing service request. Review or remove it before submitting.
AUX heat and emergency heat mean different things
AUX identifies supplemental heat that controls may call during heating or recovery. Backup may use electric resistance elements or another fuel. The label does not identify the source, its power or energized hours. A raised thermostat setting is context, not proof of the cause.
EM or emergency heat is a separate mode that can rely on backup instead of the heat pump. This check does not tell you to select it, turn AUX off or change installer settings. Consult your system instructions and ask about an unexpected display. There is no universal AUX activation temperature. Carrier explains auxiliary heat, backup types and emergency heat.
Brief defrost changes and ice that keeps growing
An air-source heat pump can collect frost on its outdoor coil during heating and enter defrost. Temporary changes, including a cloud of water vapor, can accompany that process. An observation alone cannot establish that a cloud is harmless steam rather than smoke, or confirm correct operation.
Ice that persists or grows, repeated concerns, or lost warmth calls for assessment. Do not chip ice, pour hot water on equipment, touch lines or remove covers. There is no universal defrost timer or temperature threshold here. Outdoor-coil explanations apply to air-source equipment; do not transfer them to geothermal, furnace or unidentified systems. Trane describes defrost changes and ongoing-icing concerns.
When the home does not reach the setting
Report whether the home reaches its setting, is warming without reaching it, or is unchanged or cooling. Note whether the concern cleared, recurs or continues. Weather, building heat loss, controls, airflow and equipment condition can matter; this check measures none of them or assigns a fault from a temperature difference.
For continuing loss of warmth or a persistent concern, use the published phone contact for service and explain the pattern. A website request does not confirm an appointment or dispatch. See heat pump service and installation; commercial property questions have a separate commercial HVAC service route.
Useful observations without opening equipment
- Read the visible thermostat mode and display. Note a recent setpoint change if known.
- Report an accessible filter's condition only if already known or visible without unsafe access. “Not checked” is acceptable.
- Notice obstructed accessible supply and return air paths. Follow equipment instructions for routine care.
- Describe frost or ice only if visible from a safe location. Do not go outside, climb, remove panels or approach damaged equipment to answer.
- For winter preparation, know the thermostat modes, find the system manual and keep the published service contact available. Discuss professional HVAC maintenance options.
Do not reset breakers repeatedly or perform electrical or refrigerant work. This checklist does not authorize operating suspect equipment. Unknown observations stay unknown.
What staff receive if you choose to share
Guidance needs no contact details. Choosing “Include” prepares an unsent, homeowner-reported summary for the existing form: concern, system, display, comfort trend, timing, safe observations and uncertainties. Review it, edit the check or remove it. Cost details travel only through the separate illustration inclusion choice.
Completing the tool sends nothing. Submit the standard form to request follow-up. Your summary helps staff understand the observations; it does not replace equipment records, measurements or an on-site assessment.
Example: a homeowner reports a ducted heat pump, AUX displayed, a warming home and a recent raised setting. AUX can assist recovery; those observations do not confirm correct operation. Continuing loss of warmth or a persistent concern needs service guidance instead of reassurance.
What the backup-electricity illustration measures
Enter known or deliberately hypothetical resistance input in kW, energized-equivalent hours over your stated period, and variable electricity rate in dollars per kWh. Energy = kW × hours; illustrated energy cost = kWh × rate. The DOE-hosted energy education module explains this arithmetic; its historical rates are not defaults.
Made-up example — not your equipment or utility rate: 5 kW × 2 hours = 10 kWh; 10 kWh × $0.15/kWh = $1.50 for the entered period. Zero energized hours gives zero illustrated energy and energy cost. These examples establish arithmetic only.
AUX does not establish electric strips, their power or full-stage runtime. For staged elements, hours must correspond to the specified stage/input; otherwise keep the illustration hypothetical. Unknown inputs can be left unused. Do not open equipment to obtain them.
The result excludes fixed service charges, other system electricity and other bill items. Taxes, tiers, cycling and changing rates can alter the bill; whole-bill cost divided by kWh is not automatically the applicable variable rate. This is not a whole-system, monthly or seasonal bill, savings estimate, COP calculation or geothermal comparison. Supported bounds are illustration limits, not likely household values.
Assessment, equipment selection and geothermal
A professional assessment investigates the pattern using the actual equipment, controls, airflow and property conditions. Ask what measurements support the findings and what remains uncertain. This helper does not size equipment, compute a home's load or balance point, or establish code compliance.
ACCA Manual J addresses residential heating and cooling loads. Manual S addresses equipment selection using loads and manufacturer performance data. Completing this check performs neither and makes no staff-certification claim.
Geothermal systems exchange heat with the ground rather than using an outdoor air coil. Air-source defrost observations and a resistance-use illustration cannot assess ground loops, site suitability or geothermal savings. Explore the geothermal heat pump assessment guide and heat pump and central AC assessment questions with a professional.
Common winter questions
Does AUX prove something is wrong?
A display label alone proves neither a fault nor correct operation. Record the context and whether warmth returns; continuing concerns deserve assessment. Do not turn supplemental heat off on this tool's advice.
Can this identify a cloud as steam?
No. It cannot identify a substance or establish safety. Smoke, fire, suspected CO or gas needs emergency help from safety, not an ordinary inquiry.
What if I do not know my system or cost inputs?
Choose “Not sure.” The uncertainty stays visible and you receive general guidance. The cost panel is optional; it supplies no default tariff, equipment power or inferred runtime.
Sources and limits of this guide
Published by Coastal Breeze Air as general educational information. Follow equipment instructions and qualified advice for your property. Manufacturer explanations describe possibilities, not universal operating rules.
- Carrier: auxiliary and emergency heat.
- Trane: heat pump defrost.
- ACCA: Manual J and Manual S.
- DOE-hosted energy and cost arithmetic (PDF; historical teaching material).
- CPSC: carbon monoxide questions and answers.
- Peoples Gas: suspected gas leak safety.