Tag Archives: efficiency

Dual Fuel Heat Pumps: Comfort and Efficiency

Even though the worst part of winter is behind us in many parts of the country, we are still getting a lot of questions about dual fuel heat pumps. The main reason: our site focuses on how to buy a new AC and heating system, and all these components are often replaced at the same time. Now that the weather is warmer (and before the first wave of heat arrives) those who have waited to get their system replaced are now looking for ways to lower their utility bills or get tax a credit on higher efficiency HVAC equipment.

Let’s start with a definition: Dual Fuel Heat Pump

A dual fuel heat pump is a heating (A/C can also be combined…) system that relies on electricity and one other source of heat, such as natural gas or heating oil.

Before going further, we should include a bit of history

In the earlier days of heat pumps, they were often used in homes and buildings where a primary fuel such as natural gas, heating oil, or butane was not available. In that case, electricity was the only common option. Most heating was accomplished through the use of a compressor and working fluid (aka Freon or refrigerant). For easier understanding, heat pumps are often described as “an air conditioner or refrigerator in reverse”. That’s easy to understand if you have ever stood behind your refrigerator or outside AC unit. Anyway, in a heat pump the main work of creating heat is powered by electricity. Because they don’t “extract and move” heat very well when the outside temperature drops below a certain point, heat pumps require a secondary or “emergency” source of heat. Before dual -fuel models became available (and still today when electricity is the only energy source), the secondary heat source was resistance or “strip” heating. Nearly everyone has seen this type of heating in the orange glowing part of radiant heaters. The element in these gets hot quickly, but electrical resistance is generally not an efficient way to heat space –they use a lot of electricity for the amount of heat given off.

Because they require the use of a compressor and for other reasons, some might ask

In situations where gas or heating oil is available, why bother with the heat pump…why not just have a high efficiency furnace?

This is a good question, and it makes for lively debate. The quick answer is that, with a dual fuel heat pump, a sensor in the system chooses the mode (electricity powered heat pump OR gas/oil/etc. furnace) that is most efficient for the current temperature, outside conditions and thermostat setting. Here’s an example: in the daytime in cooler or cold season of the year, have you ever been inside your home or office feeling chilly, and walked outside to warmer feeling air? That’s a good example of when a heat pump would likely be more efficient choice than gas. Why burn fuel when you could “move” warmth from the outside with a lower energy equivalent of electricity.

While discussing ways a dual fuel heat pump can be installed, the following scenario was brought up:

Homeowner has a heating system in good condition and high enough efficiency, but their older or inefficient air conditioning unit goes out. If done properly, by a competent installer, a new combo air conditioner/heat pump can be installed and connected with the existing gas or oil furnace to create a dual-fuel option. In our experience, non-standard retrofits such as this require a higher level of skill than the normal installation of equipment that has been designed to work together.

If you want to read more about heat pumps, you can go to the about heat pumps page on this site.

Best Way To Compare New AC and Heating Systems Before Buying

This blog describes how to cut through the “clutter and noise”, and buy a new furnace and AC system wisely.   I first learned this way of thinking while working my way through college in a bicycle shop, and there are some useful, current parallels to the way HVAC equipment and systems are sold.

More Brands Than Factories
Working in the bike shop, I learned that there are a lot more bicycle brands than there are bicycle factories.  Same (or very similar) bicycles…different label, marketing and prices.  Bicycles have a frame onto which major and minor components, made by other manufacturers around the world, are added.  These are combined in a box at the bike frame factory, sold through distributors, and must be assembled by a trained mechanic at a shop to be warranted.

With air conditioners and furnaces, the frame is a box, usually made sheet metal. With a few exceptions, the main components, such as compressors, condensers, fans, coils, heat exchangers, come from factories around the world. As in the bicycle brand example, there are fewer AC and heating component factories than there are brands.  Parts do come in differing grades of quality and efficiency, and the cost (and sometimes the complexity) usually goes higher with the efficiency rating.

There are some generalities about HVAC equipment brands that may be worth knowing. However, before thinking about brand there are two more important aspects a buyer needs to focus on:

Needs Local Professional Assembly or Installation

For safety and efficiency, we mechanics often had to true the bike wheels, and adjust the gears & brakes.  Then we adjusted parts to the needs of the rider, and added accessories based on the conditions the rider would encounter.  If we goofed up, the bike would not ride efficiently or the rider could crash and get hurt.

With AC and heating equipment, the installation is a critical factor. Some types of mistakes are very difficult to correct.  First, the local company that installs your equipment should have helped you choose the size and efficiency specifications appropriate for your climate, envelope (the part of your house or building that interacts with the outside air), and budget. Next, the installers have to be skilled in plumbing, electrical, refrigeration and more to connect the wiring, piping and refrigerant to make the equipment run safely and efficiently. Also, if your existing ductwork is used, they must make sure it is in good condition and sealed.  Should the wrong size or type of equipment get installed into your home or building, it will be a major hassle making things right.

Assure Quality of Installation First, Then Compare Features For Cost
In summary, here are the action points to make a wise heating and AC system purchase. Each one has links for more details if you need them:

1- Choose a local service company with trained and experienced installers and technicians.  Go to this page to get more info on how to make a good choice.

2- Verify that you are getting the correct type and size of equipment for your climate, structure, and circumstances. More info here

3- Use our free cost comparison grid to compare the most important features.

4- After you have done this, you can see how brand fits into the picture.

If you find this useful, please comment so others can learn. If not, send a suggested topic and we’ll consider it.

Product Category Overview: Ductless Air-Conditioning, A/C and Heating Units

Ductless units go by a number of names, most of them referring to the lack of ductwork necessary for distribution of the warmed or cooled air. A few of the other names commonly used  are mini-split, mini-splits, and split-ductless.

Where Ductless A/C and Heating Can Be A Solution

These units typically work best in situations such as: room additions, garage enclosures, basement renovations, sunroom additions, workshops and garage apartments.  Primarily they are used in retrofits or replacement of small non-ducted indoor cooling and heating.  For smaller homes ductless can be a good choice for replacing space heaters and window units.  These can also be a solution where duct installation is either physically not possible, or not cost effective.  Finally, there are some indoor environments where ductwork needs to be avoided for health considerations, such as severe asthma cases or in hospitals.

A Brief History of Ductless HVAC Units
These clever units were developed in Japan, where the dense population and high energy costs called for features that window units or ducted systems did not provide.

Features and benefits

  • As the name indicates, there no duct work.  Since there is no ductwork, there is no loss of heating or cooling due to leaks in ductwork, or ducts being located in unconditioned space.  With these units,very high efficiency is available, up to 26 SEER.
  • The units tend to be quiet, because the compressor sits outside instead of closer to you, as in window units or other package units do.  Certain ductless models will qualify for 30% federal tax credit, up to $1,500, for 2009 and 2010 on parts and labor costs.   Be sure to get the qualifications of your unit in writing before purchasing.
  • Some models have up to four indoor air handling units connected to one outdoor unit. This means the one outdoor unit can handle up to four rooms or zones. This depends on how much heating or cooling the structure or each zone needs.  As is always the case in HVAC , the amount of insulation, the climate, and other conditions of the envelope (structure) affects the heating or cooling capacity required.
  • Since each zone gets a separate thermostat, this gives more flexibility on comfort and ways to save energy.
  • Some models offer features for added humidity control and air filtration.

Considering Buying A Ductless Unit Online?
On their website for the Mr. Slim ductless Mitsubishi states that they do not authorize or provide warranty for the online retail selling of its Mr. Slim air-conditioning and heat pumps. The company gives a number of reasons, with the upshot being you are much more likely to be satisfied with the performance if the unit is sized and installed by a professional HVAC technician.  This is consistent with all our research and feedback.  Unlike the older window units or portable models, although they have no ducts, they still require the running of lines for coolant, drainage, etc., and they have to be charged with refrigerant. While reading the latest on this topic, we did notice some Mistubushi mini-splits being sold online. If you are considering buying a unit online and having it installed for you by a licensed technician, you should ask for a copy of the warranty to be sent to you before purchasing. From what we have consistently read and heard, you will be better off going through a local HVAC service company you trust for everything.

Brands Of Ductless AC and Heating Units

If you want to compare features, below are some of the leading manufacturers and brands.
AmcorAire®
Comfort-Aire
Sanyo
Fredreich
Fujitsu
LG
Mitsubishi

Intital Cost vs. Lifetime Operating Costs

According to the U.S. Department of Energy, ductless equipment costs more per unit of cooling: 30% more than a central split system and 50% more than a window unit.  Of course, the absence of ductwork and future costs related to it (periodic checking for leaks, cleaning, and eventual replacement) must be factored in. Also, ductless units are available in some of the highest efficiency ratings that can be purchased.  The savings in energy costs will offset the higher initial cost.  To determine the extent of that offset, ask your professional installer for an estimate of the monthly and total cost of ownership over the projected life of the unit.

If you have an experience or other info to share regarding ductless units, send it to us and we will post it, so that all our readers can benefit.

Tax Credits to Make Homes and Buildings More Energy Efficient for Heating and A-C

Listening to National Public Radio yesterday, I heard a report that discussed the use of tax dollars to renovate schools to make them more energy efficient. Of course, this sounds like a good idea. A follow up search on Google delivered the Schools for Energy Efficiency website. According to this source, one-third of the energy currently being consumed in schools is not used efficiently, and annual energy usage for heating and air conditioning costs up to $250 per student. This means that schools spend more on energy for heating and A-C than on books and supplies!

A similar situation exists with home air conditioning and heating. The condition of the envelope of the home (windows, doors, insulation, vents and the parts of the home that interface with the outside environment) has a lot to do with how well any heating or A-C equipment will heat or cool inside. The federal government still has programs in place to help homeowners make energy efficiency improvements, and a good place to start reading about them is on the Energy Star website. There, we found the following statement:

Tax credits for these residential products, which had expired at the end of 2007, will now be available for improvements made during 2009. However, improvements made during 2008 are not eligible for a tax credit.

To learn more about these programs you should ask your tax advisor and a local heating and A-C contractor. They should know which federal, state or local programs are available in your area to offset some of the costs of home improvements for energy efficiency.

If you know of a good case history or other example of home or building renovations to save energy in your area, please tell us about them in a comment or email them to us.