What You Should Know About Heat Pumps And Emergency Heat

What You Should Know About Heat Pumps and Emergency Heat

Anthony Barnes

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If you have a heat pump in your home or are interested in installing one, they can prove to be cost-effective.

By using a heating, ventilation, and air conditioning system, heat energy is pumped into your home from outside.

Like any system, occasionally something can go wrong and in this case, the emergency heat will be engaged.

Knowing what it is, why it comes on, and the implications of using it are important to know.

In this guide, we will look at what heat pumps are, what emergency heat is, and how emergency heat works with your heat pump.

We will also look at what are the few occasions when you should use emergency heat, why you should refrain from using it, why your emergency heat is not working, and when you should think about replacing your heating system. 

What Are Heat Pumps?

A heat pump is a method of heating a property that uses a heating, ventilation, and air conditioning (also abbreviated as HVAC) system.

The heat energy is effectively transferred from the heat source to a heat sink to ‘pump’ warmth from one place to the other.

This movement is in the opposite direction when compared to spontaneous heat flow as heat is absorbed from a cold space and then released into a warmer one. 

Heat pumps are primarily used in underfloor heating systems and warm air convectors though they can also be used to heat water.

The attractiveness of a heat pump (see also ‘Things To Check When Your Heat Pump’s Not Working Right‘) has a lot to do with its climate control capabilities and how it can be used as a conventional and reversed air conditioner. 

Heat is extracted, in this case from the soil or a water body outside your property, to move it inside.

This is similar to a familiar appliance in your home, only the refrigerator works by extracting heat out from the inside whereas a heat pump moves it into a space to be heated.

Heat pumps also work effectively in the cold winter months, even if the air temperature drops below 32°F (0°C). 

The heat pump works by transferring the heat energy from outside by activating the refrigeration coolant in the system.

The coolant in the HVAC system will circulate into your house and then enter a set of coils. The HVAC fan then circulates air into your house over the coil which will be heated and effectively warm your home.

If you wanted an energy-efficient means of warming up your home and lowering your carbon footprint by not combusting fossil fuels directly then consider installing heat pumps (see also ‘ Heat Pump Water Heater vs. Gas ‘).  

Heat pumps arguably date back to the 19th century when Lord Kelvin (he is also named for the unit of thermodynamic temperature), indicated their use for moving heat energy from a cold body to a warmer one. 

It was not until the 1940s that an appliance was formed when Robert Webber discovered that the freezing device condensor he used for his freezer was heating up substantially.

It was then that the world’s first direct exchange heat pump was built and well over a million units have been installed across the globe. 

What Is Emergency Heat?

You may have seen the emergency heat setting on your thermostat and been tempted to engage it. But do not, by doing so you could stress the system and ramp up your energy costs.

This is a true backup system that is only designed to keep your heat warm for a short period after your primary heating has failed, which should not be often if the heat pump is the right size and has been expertly installed.

Your primary heating is likely to be a heat pump though you may also have an oil, gas, electric, or hot water backup system too. 

What tends to happen when a heat pump fails as the primary setting is that the secondary heating, such as the oil, gas, electric, or hot water backup system, comes into effect.

This largely occurs when the temperature truly drops to below -37°C (-35°F) and the heat pump fails to work effectively to move the heat energy around. 

As you can imagine, when the temperature is that low, frost begins to collect on the coils of the heat pump and it should turn itself off automatically to defrost which is when the secondary heat source kicks in. 

When you do activate the emergency heat manually, the heat is drawn purely from that secondary heat source and your backup is the only source of heat that is severely less efficient. 

There may also be a light that shows up on your thermostat to indicate which setting is being used to heat your home.

How Emergency Heat Works With Your Heat Pump

The emergency heat setting may come on and it may be the heat pump that activates it.

Typically, the heat pump draws in heat from the outside though, on occasion, the emergency heat setting may be turned on when the outside temperature simply gets too cold. 

When this happens, the heating system shifts to the secondary system though this could indicate a problem for a qualified engineer to look at if it happens far too often without the temperature being that low.

When you manually activate the emergency heat setting, the system bypasses the main heat pump and is then forced into an auxiliary mode.

This puts sole reliance on the backup heat source to generate the heat for your home which could be an electric heat strip, hot water system, or backup gas furnace.

This will result in much higher energy costs than you may be prepared to face so it is far easier to simply get the heat pump fixed.

The Only Occasions You Should Use Emergency Heat

Emergency heat is named like that for a specific reason, it is only to be used in an emergency.

This is largely because this is the second stage of your heating system which should only be used when the temperature drops so low that the heat pump is not physically able to remove any heat from outside, usually below -37°C (-35°F). 

At that point, the emergency heat setting becomes an option though it should not be used as the only energy source for your home.

The heat pump may be broken or frozen so you may use the emergency heat while you wait for a qualified engineer to take a look and, hopefully, fix it.

Why You Should Refrain From Using Emergency Heat As A Primary Heat Source

Several reasons should be used to dissuade you from using emergency heat but there are two overarching ones.

Stressing The System

Once you engage the emergency heat setting, you effectively force the system to bypass the heat pump.

This shift puts huge stress on the backup element and secondary heating source that is only to be used in drastic situations.

What You Should Know About Heat Pumps and Emergency Heat

Unless your heat pump (thermostat) has completely failed you should never turn on the emergency heat manually though you should look to get the heat pump fixed by a qualified engineer. 

High Cost

Let’s not forget that emergency heat will also ramp up your energy bills. Simply by switching the setting from the heat pump to the electric heat strip, backup gas furnace, or hot water system, you are choosing a far more expensive and less effective means of heating your home.

There will be far more economical choices that you can make before turning to the emergency heat.

Why Your Emergency Heat May Not Be Working

There may even be cases where your emergency heat may not be working too, in which case you need to contact a qualified engineer.

The likely cause is due to an electrical fault such as a faulty heating element or a tripped circuit breaker which may require further investigation.

The circuit breakers should be flipped and working as you expect them to, so you can move onto the fuses and check whether enough volts are getting to the unit by using an electric current checker and then verifying what the voltage should be. 

If these are not identified as the problems then you can open up the unit and check that the sequencer is working as it should.

This is the tiny electrical circuit that controls the energy flow for the heat pump and shuts itself off and on with varying switches that shift depending on the electrical settings. 

It works by ‘sequencing’ the different heating elements in the right order.

To check the sequencer, you can use an electrical test meter though you have to ensure that the power is off.

You can always contact a qualified engineer if you are in any doubt about doing it yourself. 

Even the heat pump unit may be faulty and warrant replacement. This should be an option if the problem persists and you struggle to heat your home as efficiently as possible.

When You Should Replace The Heating System

Replacing the entire heating system is an expensive and time-consuming process. Firstly, you have to investigate your current unit and ensure that it does not simply require an easy fix.

If it is missing a part or is simply experiencing a fault then calling out a qualified engineer is far easier than getting a brand new heating system. 

The emergency heat strips can suffer burnout, the sequencer may need replacing and the heat pump can simply lose its performance gradually.

However, over time a unit can simply deteriorate and this can get worse if it is not serviced regularly.

Look towards replacing specific parts of your heating system and then scheduling servicing as keeping the same heating system in place is far more cost-effective than replacing the entire system. 

Frequently Asked Questions

Why Have My Energy Bills Gone Up So Much After A Long Cold Spell?

One reason why this may have occurred if you have a heat pump is if the temperature was below -37°C (-35°F) for a long period of time.

At this low temperature, the heat pump will effectively rely on the emergency heat system as it cannot pump the heat energy as well as it should be able to, typically down to a buildup of frost. 

However, in these circumstances, you will be putting stress and strain on your system and you will be expected to pay a higher cost for it so you are better off getting the heat pump working or using another source of heating. 

My Thermostat Does Not Have An Emergency Setting, Why Not?

If you are living in a moderate climate that very rarely sees the temperature go down to even close to -37°C (-35°F) then your HVAC system may have been installed without an emergency setting.

That could be in places such as along the Gulf Coast, Arizona, Texas, California, and Florida.

Put bluntly, the climate is so good there that the option of emergency heat is an unnecessary one as it simply does not get cold enough to warrant it being included.

Final Thoughts

If you happen to live in a moderate climate, you can benefit from a heat pump (see also ‘How Big Is A Heating Pump And What Size Do I Need?‘) to keep your home warm when the temperature begins to dip, particularly in the winter months.

Heat pumps use emergency heat for those situations when you may need it due to damaged equipment or when the outside temperature drops to -37°C (-35°F).

The emergency heat should be used only when you truly need it as you can expect some high energy bills and it should not be your primary heat source.

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By Anthony Barnes

Anthony Barnes is the founder of Water Heater Hub and a second-generation plumber by profession. Before developing Water Heater Hub, Anthony Barnes was a full-time plumber, and he has undertaken a wide variety of projects over the decades. As a second-generation plumber, it was easy for Anthony to get used to the technicalities of all from a tender age