Showing posts with label 3. Furnaces. Show all posts
Showing posts with label 3. Furnaces. Show all posts
Variable Speed = Health, Savings and Comfort
The best place to start may be "what is variable speed?"
"For any furnace, providing maximum comfort means achieving the proper amount of airflow. This is true for both heating and cooling operations. Unlike conventional single speed motors, a variable speed motor runs at a wide range of speeds. Using intelligent technology, it continually monitors incoming data from your heating and cooling system, and it automatically makes the adjustments necessary to meet your comfort needs. The motor varies the amount of air circulated, compensating for factors like dirty filters by increasing speed. Put simply, it delivers just the right amount of air necessary to provide the desired level of heating and cooling comfort." Danny Heineman
As you will see in the chart above, this feature enhances every part of your heating and cooling system. Both Comfort and Savings, even your Health, is affected by having a variable speed blower in your furnace or air handler. The easiest way to explain all this is going to be by taking these one at a time, so get ready.
We will start with the most important of the three, which may not be the one you would expect. It is your Health. There is an insane amount of data that will back up my claim, but all you need to know is that while you can see "dust" in the air and settled on surfaces, about 99% of the particles in the air are smaller than 1 micron (1 millionth of a meter). The human eye can only see particles bigger than 10 microns in size. So next time you are looking at all the dust in your air when the sun is shining in your window, think, "Wow, that is only 1%?!" and then call me.
How variable speed effects your health is really very simple. Tell me, what is your furnace doing when it is 68 degrees out side? That's right, nothing. What is your filter doing while your furnace is doing nothing? More nothing. That is where variable speed comes in; when the furnace is not heating or cooling and the fan in is constant operation, a Carrier or Coleman variable speed furnace will continue to slowly and inexpensively circulate air throughout your home. This allows your filters to capture more contaminants (because air is constantly passing through them), so you can breathe easier.
*Note: I have a Carrier Variable Speed Furnace with the Carrier Air Purifier, read my experience on the What's in My Home page.
From a Comfort stand point, variable is a god send. Literally, a gift to man sent from heaven. The hilarious thing is that it is just so simple. The element that it all boils down to is constant air flow, period. That is it. Most people do not turn on their fan 24/7 because they believe it will cost them a lot of money (on a standard blower they are correct) and more often than not, it is just too loud. What variable blowers do is ramp the blower down so you do not notice it running, nor does it cost you any more money than standard furnace operation.
Sorry, back to Comfort. Here is what variable speed will do by providing constant air flow. The greatest thing is the even heating and cooling you get. Instead of having the upstairs hot and downstairs cold, variable combines those two environments to create an equal and balanced air temperature. When I turn off my fan in my home the upstairs will generally be about 7-8 degrees warmer than my downstairs; once I turn it back on, the spread becomes 1 degree if not the same!
It also solves the age old issue of Cold Blow. This is the burst of cold air that comes from the ducts before the hot air gets to you, just like the cold water at your faucet. Well, just like plumbers have circulation pumps that keep hot water in the pipes at all times so when you turn on the faucet you just get hot water, we do the same thing with variable speed. When the furnace turns on, the ducts are already tempered with warm air flowing through them constantly, so you do not feel that blast of cold air in between heating cycles!
Next is Savings. Not only is the blower itself more efficient at about 8-10x that of a standard blower, but it makes everything it is attached to more efficient as well. You will consistently get better efficiency ratings on heat pumps and air conditioners that are attached to a variable speed system. Not only that, your furnace will operate better and your filters work harder for you.
Perhaps the most abstract, but exciting, feature that variable speed offers is the use of latent BTUs to evenly heat your home. When you touch a light bulb it is hot, your audio/video system is hot, your refrigerator pumps out heat like crazy, and you emit 400 BTUs per hour yourself, not to mention Solar heat gain! Just think if there was a way to take all that heat being generated and distribute it all throughout the house, creating less need for your heating system to turn on! Of course, you know the answer.
Get the service perspective; see what Bob says at Bob' Service Tips
The Five Furnace Types
Much like everything else, few people know anything about a particular piece of equipment until it breaks or needs replacing. For example, if you had all wood windows in your home, you would probably have little knowledge of what you wanted to replace them with until you started your research. I find that because most furnace decisions are made when a furnace dies, they are usually in a rush to get heat, etc. and do not have the proper info to upgrade or are afraid if they decide on a nicer furnace; they may be getting "sold" on something (see Mission Statement).
The purpose of this article is to give you a quick breakdown of the five furnace types that are now available and with them a listing of features. If anything, this will give you basic consumer knowledge and the ability to ask for what you feel fits your needs.
Single-Stage Furnace (more info)
- Available in both 80% and 92% efficiency
- Starts up at 100% btu capacity
- Has one fan speed
- Basically, your standard on/off furnace
- Available in both 80% and 92+% efficiency
- Starts at 60% btu capacity and moves to 100% capacity if needed
- Has two fan speeds
- Not more efficient, but provides higher comfort
- A little bit quieter than single stage furnace
- Available in both 80% and 95+% efficiency
- Starts at 60% btu capacity and moves to 100% capacity if needed
- Has variable fan speed motor
- Blower motor is 10x more efficient than single and two-stage furnaces
- Much quieter than single and two-stage furnaces
- Recommended for matching with air cleaners for maximum indoor air quality
- Recommended for matching with heat pump
- Recommended for 2+ story homes
- Required with 2-Stage Heat Pump
- Available in 95% efficiency
- Starts at 40% btu capacity and moves to 60% 0r 100% capacity if needed
- 3rd stage means increased comfort beyond 2-stage furnaces
- Has variable fan speed motor
- Blower motor is 10x more efficient than single and two-stage furnaces
- Even quieter than two-stage variable speed furnace
- Recommended for matching with air cleaners for maximum indoor air quality
- Recommended for matching with heat pump
- Recommended for 2+ story homes
- Required with 2-Stage Heat Pump
- Available in 95% efficiency (80% coming soon)
- Gas valve can stage anywhere from 35% btu capacity to 100% (65 stages)
- Multiple stages means increased comfort beyond 2 and 3 stage furnaces
- Closest we can get, with a furnace, to matching the heat loss of your home
- Has variable fan speed motor
- Blower motor is 10x more efficient than single and two-stage furnaces
- Similar sound volume of 3 stage
- Recommended for matching with air cleaners for maximum indoor air quality
- Recommended for matching with heat pump
- Recommended for 2+ story homes
- Required with 2-Stage Heat Pump
Gas Furnace Terms and Definitions
Annual Fuel Utilization Efficiency (AFUE): The Annual Fuel Utilization Efficiency (AFUE) rating, indicates how well a furnace converts energy into usable heat. The rating is expressed as a percentage of the annual output of heat (output rating in Btus -- British thermal units, a measure of energy) to the annual energy input to the furnace (input rating in Btus). Ratings can be categorized in the following way: Ratings between 84 and 89 percent are not common. Acidic condensate, harmful to the furnace, forms at these percentages. Public Law No. 100-12, passed in1987, requires that all gas furnaces manufactured after January 1, 1992, have aminimum AFUE of 78 percent. Atmospheric Vent Combustion: If a chimney is available, furnaces with this system are the least expensive to install. Atmospheric vent furnaces have AFUEs of 60-65 percent when equipped with standing pilots, and AFUEs of 63-70 percent when equipped with electronic ignition systems.With special vent dampers, atmospheric vent units can achieve AFUEs of 78-80 percent. Condensing (or Recuperative Units): These units are super efficient with some designs reaching AFUEs of up to 97 percent. Unlike conventional forced air furnaces, condensing units capture most of the water vapor and heat contained in hot flue gases that would normally escape up the chimney. The escaping gases then pass through a second heat exchanger and condensate is expelled. The heat exchangers are made of corrosion resistant stainless steel, and many have lifetime warranties. Exhaust is cooler than that of conventional furnaces and can be vented with PVC piping. Downflow or Counterflow Furnace: These units have a blower at the top to draw air into the furnace. Heated air is blown out at the bottom. This type of furnace isused to supply floor duct systems. Electronic Ignition: An electronic ignition eliminates the need for an energy-wasting standing pilot. Fuel is used only when needed. The pilot is ignited with an electric spark. Heat Exchanger: The heat exchanger is a metal chamber in the furnace that houses a gas burner. The flame produced by the burner heats the chamber. When the outside of the chamber becomes hot, the air surrounding it is warmed and used to heat the house. Improved designs enhance efficiency and provide quieter operation. Horizontal Flow Furnace: Air travels horizontally from one side of the heater, across the heat exchanger, and hot air is blown out the other side. This type of furnace is installed in areas with limited head room, such as attics or crawl spaces. They can also be installed below floors or suspended below ceilings. Nonweatherproof: These units are designed to be installed indoors. Power Combustion: In this system, combustion is produced by a blower. The blower pushes the combustion gases through the vent, and regulates the amount of combustion air. Power combustion furnaces do not require a draft hood. This reduces off-cycle losses and improves efficiency. Many power combustion furnaces operate at 78-80 percent AFUE. When equipped with an additional heat exchanger, they can operate at AFUEs of 90-96 percent. Pulse Combustion: (These models are listed under condensing furnaces.) Pulse combustion is produced by self-perpetuated "pulses." This unique system mixes air and fuel in a sealed combustion chamber. A spark ignites the mixture, and the resulting increase in pressure closes the gas/air inlet valve. The combustion products are forced through an exhaust pipe and the pressure in the combustion chamber drops, re-opening the inlet valve. The next combustion cycle is ignited by the heat remaining from the previous cycle. This process repeats itself about 60 times per second. Furnaces with this combustion system have AFUEs from 91-97 percent. Exhaust gases, at 100-200 degrees Fahrenheit, are cool enough to vent through PVC piping. Sealed Combustion: Sealed combustion systems draw in all the air used for combustion from the outside, and exhaust gases are direct vented to the outside. Since cold outside air is not mixed with the warm indoor air during combustion, efficiency is enhanced. Furnaces with this type of combustion system have an AFUE range of 70-80 percent. Upflow Furnace: These units have blowers at bottom that draw air into the furnace. Heated air is blown out at the top. These heaters can be installed in utility rooms, closets or basements. Vent Damper: The vent damper is a "flapper" device installed in the flue. When the heat demand has been met, the damper closes, trapping residual heat for circulation in the home. When heat is needed, the damper opens before the burners are ignited to allow combustion fumes to escape. The damper remains open only as long as the burners are on. Burners cannot ignite if the damper is closed. Weatherproof: These units are designed to be installed outdoors.
Understanding Efficiency Ratings of Furnaces
A central furnace or boiler's efficiency is measured by annual fuel utilization efficiency (AFUE). The Federal Trade Commission requires new furnaces or boilers to display their AFUE so consumers can compare heating efficiencies of various models. AFUE is a measure of how efficient the appliance is in the energy in its fuel over the course of a typical year.
Specifically, AFUE is the ratio of heat output of the furnace or boiler compared to the total energy consumed by a furnace or boiler. An AFUE of 90% means that 90% of the energy in the fuel becomes heat for the home and the other 10% escapes up the chimney and elsewhere. AFUE doesn't include the heat losses of the duct system or piping, which can be as much as 35% of the energy for output of the furnace when ducts are located in the attic.
An all-electric furnace or boiler has no flue loss through a chimney. The AFUE rating for an all-electric furnace or boiler is between 95% and 100%. The lower values are for units installed outdoors because they have greater jacket heat loss. However, despite their high efficiency, the higher cost of electricity in most parts of the country makes all-electric furnaces or boilers an uneconomic choice. If you are interested in electric heating, consider installing a heat pump system.
The minimum allowed AFUE rating for a non-condensing fossil-fueled, warm-air furnace is 78%; the minimum rating for a fossil-fueled boiler is 80%; and the minimum rating for a gas-fueled steam boiler is 75%. A condensing furnace or boiler condenses the water vapor produced in the combustion process and uses the heat from this condensation. The AFUE rating for a condensing unit can be much higher (by more than 10 percentage points) than a non-condensing furnace. Although condensing units cost more than non-condensing units, the condensing unit can save you money in fuel costs over the 15- to 20-year life of the unit, and is a particularly wise investment in cold climates.
You can identify and compare a system's efficiency by not only its AFUE but also by its equipment features, listed below.
Old, low-efficiency heating systems:
- Natural draft that creates a flow of combustion gases
- Continuous pilot light
- Heavy heat exchanger
- 68%–72% AFUE
Mid-efficiency heating systems:
- Exhaust fan controls the flow of combustion air and combustion gases more precisely
- Electronic ignition (no pilot light)
- Compact size and lighter weight to reduce cycling losses
- Small-diameter flue pipe
- 80%–83% AFUE
High-efficiency heating systems:
- Condensing flue gases in a second heat exchanger for extra efficiency
- Sealed combustion
- 90%–97% AFUE
80% vs. 92% Furnaces: Where and Why
One of the most recognized and least understood differences in furnaces is efficiencies. I believe that there is a place for both the 80% and the 92% furnace, but as you will see below, we can make a pretty good case to never put in another stand alone 80% furnace again. Also, while I do sell this stuff for a living and stand by the Built Green philosophy, I am also a realist. I understand that it just may not be everyones cup of tea or in everyones budget.
The best thing is that we know our options, so, in this article I want to break down the different types of furnace efficiencies and what the mean to you, the contractor, and the homeowner.
Click on the 80% or 90% title to go furnace literature.
(for every $1.00 spent on fuel $.20 is wasted)
Warning: The one place that an 80% furnace does not belong is in the Propane application. If you are building a custom project and the homeowner decides to use an 80% furnace, always get a quote in writing from your heating contractor that let’s them know what the upgrade to a 92% furnace would cost. When they start screaming about the energy costs in their new home, you can show them that they were given the choice to upgrade. If they had the option and did not choose it, you are off the hook.
The only thing left is to educate them on the differences and since studies show that they will hold your opinion higher over even their best friends’ when it comes to their new home, right here seems like a good place to start.
(for every $1.00 spent on fuel $.08 is wasted)
Here are some of the differences between the 80 and the 92. By upgrading to a 92% furnace on a 2,200 square foot home; the homeowner will save approx. $350 per year on Natural Gas or $500 per year on Propane*. These types of savings are equivalent to not driving 104,000 miles or planting 500 trees. With the cost of upgrading at around $500-$600, it kind of makes you go hmmmmm. Cascade Natural Gas also rebates $150 for the installation of a 90%+ furnace.
*All savings estimates are in no way exact or binding figures.
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