Emergency Heat Mode on a Heat Pump Clarified
When frigid winter air causes outdoor temperatures to plummet, heat pumps can struggle to extract enough heat to keep homes warm. During these cold spells, an emergency heat mode kicks in to prevent households from freezing over. But what exactly does this backup heating entail?
We'll cover when emergency heating activates, how it works, associated operating costs, usage best practices, and proactive maintenance tips. Equipped with this knowledge, you can better understand and optimize emergency heating for your home's heat pump system.
When Does a Heat Pump Activate Emergency Heat?
There are three main situations that automatically trigger a heat pump's emergency heat mode:
- Extremely cold outdoor air temperatures. Most heat pumps shut off below 35-40degF and shift to backup heat.
- Heat pump failure or malfunction. Faulty parts or ice/frost buildup can necessitate emergency heat.
- Defrost cycle initiation. Heat pumps use emergency heaters while reversing refrigerant flow to melt frost.
Frigid weather prevents heat pumps from transferring enough warmth, as refrigerants lose efficiency at low temperatures. Old or improperly maintained units also risk freezing up in cold weather if ice builds up on coils.
Switching to electric strips or a fossil fuel furnace provides necessary heating. Defrost cycles further reduce heat pump output, requiring supplemental emergency heat to maintain indoor temperatures.
Extreme Cold Temperatures
Why do heat pumps struggle in extreme cold? These machines absorb ambient heat by circulating refrigerant between indoor and outdoor coils. However, refrigerants lose heat-transfer capacity below 35-40degF. There eventually isn't enough warmth to extract, causing evaporator coils to freeze over.
Frozen coils prevent proper airflow, prompting automatic emergency heat activation to warm the home. The specific outdoor cut-off temperature depends on heat pump efficiency ratings and local climate norms.
Heat Pump Failure or Issues
Malfunctioning pumps lose the ability to properly move refrigerant and distribute heat. Common problems like failed sensors, electrical shorts, or leaks can all necessitate emergency heating. Preventative maintenance checks help minimize failure risks.
Outdoor unit icing also often activates backup heat. This buildup blocks airflow, lowering efficiency until coils completely freeze. Defrost cycles attempt to resolve ice dams, but emergency strips or furnaces provide heat in the interim.
Defrost Cycle EngagementTo combat wintertime evaporator icing, heat pumps periodically reverse refrigerant flow to melt frost. But this defrost process temporarily stops the distribution of warm air inside. Emergency heat activates to offset the loss of heating output while defrosting.
Defrost cycles typically last 5-15 minutes. The emergency heat then shuts off once the heat pump's normal operation resumes post-defrost. Checking your unit's outdoor coils daily helps catch winter icing issues early.
How Emergency Heaters Work on a Heat Pump
The emergency heat function sees separate electric heating strips or a fossil fuel system provide warmth when heat pumps fail. Let's compare how these two types of backup heating work:
Electric Heating Strips
Most modern pump systems rely on electric heating strips for emergency heat. These thin, wire-like heating elements pass current and rapidly warm up. Positioned above the indoor unit's fan, they circulate heated air when activated.
The simplicity and low maintenance of electric emergency suits most homes. But there are some disadvantages--namely higher energy consumption and thus electricity bills. We'll explore the operating costs later on.
Fossil Fuel Emergency Heat
Alternative systems leverage gas, propane, or oil furnaces for backup instead of electric strips. Integrated controls automatically switch from the heat pump to furnace when conditions call for it. These units then combust fuels to generate warmth.
Fossil fuel heating avoids increased electrical loads from emergency strips. But furnaces and fuel lines require extensive servicing and have significant breakdown risks. And unless you already have a furnace, installing this emergency equipment proves costly.
Let's now compare how heat pump emergency systems contrast standard heating operation.
Emergency Heat Without Compressor Activation
Standard heat pump heating sees refrigerant absorb and move warmth across indoor and outdoor coils called evaporators and condensers. An electric compressor circulates the refrigerant gas in this process.
But in emergency heat mode, backup strips or furnaces provide all the warmth directly. The heat pump compressor remains off, ceasing refrigerant circulation. Avoiding system overwork in cold conditions prevents potential damage.
In effect, emergency heat mode disables the unique heat transfer that defines heat pump efficiency. The backup sources then carry the full heating load alone--typically at greater energy expense.
Operating Costs of Emergency Heat Mode
Without its compressor running, emergency operation forfeits a heat pump's unique heating efficiency advantages. You pay a higher price both monetarily and through greater grid demand with each emergency heat activation. Let's examine associated running costs more closely.
Emergency Heat Uses More Electricity
Electric strip heaters offer a less complex emergency solution than whole furnaces. But these simple elements also consume immense amounts of energy activating frequently or for long runs.
Why does emergency heat use more electricity? Heat pumps move existing warmth, while strips must create heat from scratch. This requires up to 3 times more power than the pump's compressor.
Each emergency heat event thus spikes your home's electrical load and consumption. Be warned--just a few hours of heavy backup heating easily adds hundreds of dollars in seasonal costs!
Higher Energy Bills to Expect
Budgeting for increased seasonal bills helps ease emergency heat's pricing impact. On average, you may spend $200-500 more compared to relying solely on the heat pump.
But this varies widely depending on climate, pump quality, usage frequency, and electricity rates. Homes in extreme cold and occupants who keep settings excessively warm face steeper expenses.
While costly, emergency heating prevents potential pipe freezing damage far exceeding energy bills. But aim to minimize backup usage whenever possible to avoid budget shock!
Emergency Heat Vs. Dual Fuel Cost Comparisons
Homes having both heat pump and fossil fuel systems employ what's called dual fuel heating. Compared to electric strips, gas or propane backups reduce demand on the electrical grid.
But is dual fuel cheaper for emergency use? Generally, yes--but marginal savings depend on relative electric and fuel rates. Maintenance also proves more intensive than with straightforward strips.
Weigh your climate emergency heating needs against utility costs if debating between systems. Also factor long-term part replacement and potential service fees over decades of ownership.
Extending Emergency Heat Mode Runtime
Minimizing emergency heat usage saves energy year after year. While ambient conditions mandate its cold weather activation, certain steps help limit run times:
Adjust Thermostat to Conserve Power
Bumping down the temperature setting by just a few degrees while relying on emergency systems cuts their operating duration. Put on a sweater and save by letting the house cool marginally.
Also consider setting thermostats lower at night or when away from home. But take care to prevent pipes from freezing whenever reducing heat levels long-term.
Upgrade to a Cold Climate Heat Pump
Specially designed pumps better withstand sub-zero operation using advanced components and refrigerants. While pricier initially, the greatly reduced emergency heat events ultimately save cash.
Just make sure any contractor properly sizes replacement units for sufficient everyday heating needs. Overwork harms longevity over time.
Avoiding unit failure and coil icing minimizes emergency mode's necessity. Annual check-ups catch issues before they trigger problems needing backup heat.
Daily outdoor inspection for ice buildup also helps maintenance crews strategically run defrost cycles. And clearing snow around units improves winter efficiency and component longevity term.