How does electrical heating work?

$\begingroup$

I think that you have found that the question what exactly qualifies as work in thermodynamics? cannot easily be answered in one sentence. A way forward is perhaps to start by considering the terms in the first law of thermodynamics for a system which does not change in composition and to consider work as a process to do with energy transfer.

There is an internal energy term and then there is a heat transfer term which is energy transferred between a system and its surrounding because of a difference in temperature which importantly is a one way process in that the transfer is always from the higher temperature to the lower temperature.
In your diagram that would be the water (surroundings) having heat transferred from the tank (system) to the water.

You now look as the other ways of transferring of energy in and out of the system and call that work and this is where it becomes tricky but not for all examples.
Perhaps the simplest is the change in volume of a system by the application of external forces when mechanical work is done.
What is not so obvious is how to categorise the effect of the electric heater and to do that you need to decide as to whether the heater is part of the system or the surroundings.
If the electrical heater is part of the surroundings then the transfer between the heater and the system is via heat but doing that makes calculations difficult.
If the heater is part of the system then the transfer to the system would be characterised as work as per the falling weight definition with the falling weight doing work turning a generator which produces "electricity" which in turn increases the internal energy of the system.

I know that I have not told you which of the "one sentence" definitions of work I favour but I do suggest that you consider other examples eg temperature of the water in waterfall, infra-red radiation interacting with a system, etc and see if you can exclude heat transfer and then how it might be considered as work via the falling weight definition or the energy distribution definition that you have mentioned in your post or . . . . .

Did you know that nearly 45% of your utility bill goes directly to heating and cooling your home? When the temperature starts to dip it’s important to know where your money goes. In this video we’ll tell you everything you need to know about an electric furnace and how it works.

Hi, my name is Bryan with Fire & Ice. There are a number of ways to heat your home with a central air system. One of those ways is with an electric furnace by itself or paired with a heat pump. In this video we’ll cover what an electric furnace is, how it works, and the differences between gas and electric systems. By the end of this video, you’ll know if an electric furnace is right for you.

What’s an electric furnace?

Most homes in the United States rely on central air to heat and cool their home. A central air system uses a blower motor inside a furnace or air handler to take air from the house. The air is then heated or cooled depending on the season and pushed back throughout the house through the home’s ductwork and vents. In some homes, natural gas or propane is not available and an electric furnace or air handler is used to heat the home.

How does an electric furnace work?

Have you ever looked into the toaster when it’s toasting bread? Much like a toaster, an electric furnace works the same way to heat your home. An electric furnace consists of a cabinet with a blower motor and heating coils attached to it. The heating coils are also referred to as a heat package or heat strips.

When a call for heat comes from the thermostat, an electric current runs through the heating coils, making them extremely hot. As the blower motor inside the furnace pushes air over the heating coils, the air warms up and the temperature inside your home increases. Once the desired temperature is met, the thermostat tells the system to shut down until heat is needed again. 

How does an electric furnace compare to a gas furnace?

At a glance an electric furnace and gas furnace function the same because they both heat your home. However, the difference between them can be vast. For starters is their efficiency. An electric furnace is hyper-efficient being able to use 100% of the energy it uses. A gas furnace’s efficiency is measured by an AFUE rating and can convert 80-96% of its fuel towards heat resulting in waste. An 80% AFUE rating for example means that up to 80% of the fuel goes towards heating the home and the other 20% is exhausted as waste.

Next, is its application. If you live in warmer climates, you likely can get by with just an electric furnace to heat your home in the winter. However, if you live in cooler climates, like here in Central Ohio, electric furnaces can get expensive very quickly due to the high cost of electricity. In these cases, electric furnaces are often paired with a heat pump and are only used as auxiliary or “emergency heat.” High-efficiency heat pumps are capable of providing reliable heat even in freezing temperatures.

Lastly, is the maintenance of the equipment. Gas furnaces have several mechanical parts to function. Whereas an electric furnace has fewer internal parts, making maintenance easier.

Which furnace is right for me?

Now you might be wondering, which furnace is right for me? Electric or gas? The answer to that question depends on a number of factors, such as:

• Where do you live? If you live in the southern United States, chances are you don’t need a lot of heating in the winter. Therefore, an electric system or an electric furnace paired with a heat pump would make sense. However, if you live in an area where it gets cold for long periods you might want to consider a gas furnace and an air conditioner. That’s not to say you can’t heat your home with an electric system. It just will likely be more expensive since electricity has historically been more expensive than natural gas.

• Another determining factor is access to fuel sources. Some homes lack access to natural gas. In these cases an electric furnace and a heat pump would be worth considering.

• Next, are there any indoor comfort problems that you want to solve. Issues with humidity? Uneven temperatures? Hot and cold spots? The type of furnace you choose should address these concerns.

• Lastly is your budget and how long you plan on living in your home. If you plan on living in your home for the next 10-15 years you may want to consider the system with the greater investment. But if you plan on moving in the near future, upgrading your outdated system with a new, entry level furnace can add value to your home’s resale value.

How much does an electric furnace cost?

If you are looking to invest in a new electric furnace, expect to pay between $3,400 and $7,600 for the furnace alone. Keep in mind most electric furnaces are paired with a heat pump as well. A new heat pump can range between $5,500 and $13,000 depending on its type and features. At Fire & Ice all of our prices include the cost of equipment, installation, and any additional fees.

There are many factors that go into the cost of electric furnaces and heat pumps including the size of the unit, efficiency rating, add-ons, and any modifications that are needed during installation. There is no one size fits all solution when it comes to HVAC.

What can you do next?

Let’s talk about what to do next. If you are considering investing in a new electric furnace and/or heat pump we’re happy to help. If you live in the Central Ohio area and are in our service area, click the “Schedule Estimate” option on our website. One of our residential sales professionals would love to go over your options to find the best solution for your home. Thank you for watching and we look forward to making your day better.