Furnaces

Forced air furnaces are the main equipment used to heat most of today's homes. Today's furnaces use natural gas, oil, propane, electric, coal, wood, pellets and other materials such as corn cobs. Many homeowners are confused between a boiler and a furnace. A furnace has a heat exchanger which in turn heats air. The heated air is then circulated throughout the house. Older furnaces used convection to circulate the air while today's furnaces use a blower. A boiler heats water and the hot water or steam circulates through radiators or tubing throughout the house to provide heat.  If you are interested in boilers please see our other article title Boilers and radiant heat or Click Here.

Electric furnaces are rated at 100% efficiency based on the premise that the electric heating elements produce 3.4 btus for every watt of electrical energy consumed. Electric furnaces can be used alone but generally are combined with a heat pump. Electric furnaces also come with an air conditioning coil for cooling purposes.

Hydronic furnaces have a hot water coil which use hot water, a pump and a blower to circulate the hot air. Hydronic air handlers use either a hot water boiler or are sometimes combined with a domestic hot water heater as the source for heat. As with electric furnaces a hydronic air handler is rated at 100% efficiency also. Hydronic furnaces usually come with an air conditioning coil for cooling purposes.

What has changed in the past years is the efficiency and size of furnaces. Today no manufacturer can produce a gas or oil fired furnace at less than 78% efficiency or rated as Annual Fuel Utilization Efficiency abbreviated as AFUE. Most furnaces 20 years or older that have a standing pilot have an AFUE of 70% or less. Many homeowners think that the efficiency of a furnace is determined solely by the amount of heat or btus input to the furnace versus the heat or output btus of the furnace. For example a furnace that has a rating of 100,000 btus input and 75,000 btus output is considered to be 75% efficient. This method only determines the firing efficiency of the furnace. What this does not take into consideration is the efficiency of the furnace blower motor and the amount for heat that is lost up the chimney during the off cycles. For this reason the total efficiency or AFUE was created which calculates the operating and off cycle losses together for a realistic efficiency. Older gas furnaces used cast iron or clam shell type heat exchangers. Today's high efficient furnaces use aluminized or stainless steel tubing which is more efficient. With no weld joints the tubing is less prone to weld and fatigue failures due to expansion and contraction and are more efficient with a larger surface area in a more compact space. For many years clam shell style heat exchangers were used which were two sheets of deep draw metal press formed under very high pressure and then welded around the lip of the heat exchanger. Although the clam shell type heat exchangers are still being used today by some manufacturers, they have become ancient technology and most furnaces are now using tubular heat exchangers.

In selecting a furnace you will want to have the most efficient furnace your budget permits. For oil furnaces the common efficiency is still around 80 to 86%. There are very few higher efficiency oil furnaces sold on the market today because of the high costs. Oil furnaces cost more than gas furnaces because the heat produced by oil burning is much hotter than gas. Generally the heat exchanger has to be thicker and more solid. Also oil furnaces have many more moving parts than a gas furnace which adds to the increased costs. Why are there not many high efficiency oil furnaces on the market? To produce a 90% or higher efficient oil furnace requires heavy gauge metals such as stainless steel to be able to sustain the high corrosiveness of oil combustion by products. One of the main components of oil byproducts condensing is sulfur and sulfuric acid which is extremely corrosive. Also the oil byproducts of carbon tend to be a very good insulator. So a high efficiency oil furnace must use thicker metals and be able to burn the fuel oil so as not to cause carbon build up along the walls of the heat exchangers. When the cost of a 90+ condensing oil furnace is compared to the energy savings of the standard 80-86% oil furnaces, the payback is generally too great to make the purchase appealing. As fuel prices continue to rise at their enormous increase, this will change in the near future and the additional costs for a high efficiency oil furnace will have a more attractive payback. Until then most homeowners will use the standard 80-86% efficient oil furnaces.

Gas furnaces whether using natural or propane gas have come a long way even in the past couple years. From 80% to 93% efficiencies the new gas furnaces have more to offer than combustion efficiency. To many homeowners and contractors the 90+ furnaces are the best furnaces. But the technology has gone far beyond this arena. 90+ furnaces really aren't new technology. In fact condensing furnaces and their technology have been in mass production for over 25 years now. But let's take a look at the basic differences between 80% and 90+% furnaces. The 80% furnace is the oldest technology today and this type of furnace is really not much different than the 70% standing pilot furnaces of over 60 years ago except for the addition of electronic ignition and solid state timers which have replaced the fan limit switches. Other than those two improvements, the basic 80% furnace is not much of a change form yesteryear. To achieve 90+ efficiency the higher efficiency furnaces use a condensing coil which extracts most of the heat out of the gas allowing the furnace to be vented with regular plastic PVC pipe. When extracting this heat out of the burned gas the byproducts of combustion, there is primarily water and hydrochloric acid. This water condenses in the furnaces in a section called the condenser coil. So the condensing furnaces have a heat exchanger very similar to the 80% furnaces plus an additional heat exchanger called the condensing coil which looks very similar to an air conditioning coil. The condensing coils are generally made out of stainless steel to prevent corrosion attacking the metal. As stated previously one of the byproducts of condensing gas is water and hydrochloric acid. It is the hydrochloric acid which can cause destruction if the proper materials are not used in the condensing section of the furnace. All high efficiency 90+ condensing furnaces have drains to remove the acidic water. The advantage of a 90+ furnace over an 80% furnace is real energy savings, no chimney required and greater efficiency. However beyond that there is really no difference between the standard 80% furnace and the 90+ furnace. Here's why: Both furnaces use a standard multi speed blower motor. Now a multi speed blower motor allows the furnace to be preset at a desired fan speed. When the thermostat make a call for heat the gas valve comes on for approximately 30 seconds to allow the heat exchanger to warm up and then the blower comes on. The thermostat becomes satisfied and the gas valve turns off while the blower continues to operate for approximately another 30 seconds and extract the remaining heat from the heat exchanger. This isn't new technology. In fact this method of operation has been going on for furnaces for over 50 years. This method of operation is similar to taking your car and starting it up and pushing the throttle to the floor and when you reach your desired speed, you turn off the car and allow it to drift to a slower speed and then start the car back up again at full throttle to again achieve the desired speed.  This is a very crude way to operate a car and it is a very crude way to operate a furnace to try and achieve comfort. Not only is it crude and primitive but it also creates a lot of stress on the blower motor due to frequent starts and stops and to the heat exchanger for continued expansion and contraction. When you think about this method of operation it is amazing that a house with a standard operating furnace achieves any level of comfort. The furnace is sized according tot he coldest average days of the winter months. That means the furnace is essentially oversized for most of the heating season. Add to this problem contractors and homeowners who are obsessant about oversizing heating equipment and you have a real comfort nightmare. A furnace like a car needs at least 7 to 10 minutes of operating time to achieve operating efficiency. On moderate winter days with a furnace that is oversized the actual operating time will almost always be 5 minutes or less. This prevents the furnace form ever reaching operating efficiency plus the oversizing creates temperature over swing. The variance of temperature ion the house will deviate 5 degrees or more. The monster furnace comes on and by the time the thermostat is satisfied the furnace blowe4r continues to operate to remove the heat remaining form the heat exchanger and this causes over shooting of the desired temperature setting. In addition to the comfort problem, the furnace sends out hot blasts of air with a higher temperature than required resulting in drying of the air and further decreasing comfort levels. We've all felt this experience form over sized furnaces. The house warms up to the point of overheating and the monster furnace waits until the thermostat cools sufficiently to the point where you feel cold. Then the blast of hot air from the volcano erupts again to the point of overheating. We're here to tell you this isn't comfort and this isn't normal. This is a heating nightmare and it occurs so much that many people have come to accept this as a normal heating process. Overheating then cooling to the point of chills and then hot blasts of air that cause your sinuses to go out of control is not normal. With the standard operating furnaces which are in 90% of today's homes this problem doesn't have to be problem anymore.

There have been major advances in technology for today's gas furnaces that can create the perfect indoor environment. Instead of having 3 or 5 degree temperature swings from the thermostat setting, you can reasonably expect today's new high technology furnaces to provide 1/2 to 1 degree temperature swings and that is almost perfect. Up until the past couple years the only systems to achieve this type of accuracy in comfort levels were hospital operating rooms or large commercial and industrial systems that were very expensive. But now you can have that same level of comfort and efficiency as the large systems.  The new high technology furnaces such as the Goodman GMV9 furnaces or the Tappan furnaces have put a throttle in their furnaces. Instead of like the car described in the previous paragraph, the new furnaces have 2 stage gas valves and variable speed blower motors. In addition they have features like igniter monitor capabilities and Auto Comfort modes.

If you are concerned about the high technology because of possible break downs, this technology is now over 15 years old and really isn't new technology. It's simply new to you. General Electric who is the sole manufacturer of the variable speed drive motors. The variable speed motors have been in production for over 15 years now making them a reliable proven product. The electronic control centers are built by Emerson Technologies. Emerson Technologies is also Copeland which is the manufacturer of the Copeland Scroll compressors which are known for their efficiency and reliability. Unfortunately many contractors don't promote the high technology for the new systems due to lack of familiarization and ability to install, troubleshoot or service the equipment. Also many contractors are also unfamiliar with the benefits of variable speed motors and the other technology features available today.

What do variable speed blower motors do? As we described previously the typical furnaces use mutli speed motors which have one preset speed. The standard multi speed blower motors are loud and create a whining noise and fast start of the blower motor. When they shut off they do immediately. Variable speed blower motors have a silent start. Variable speed motors start slowly and will accelerate to the required air speed. On shut down the variable speed motors will slowly decrease their speed until they shut off. A multi speed blower motor will consume up to 500 to 800 watts and over 2500 watts at start up. a variable speed motor will only consume 75 watts and  if there  are  install the equipment.

The new high technology furnaces also have 2 stage heating. Remember the standard furnaces regardless of efficiency fire at one capacity just like the car that uses full acceleration to maintain speed. Unfortunately most of the winter days are well above the outside temperature of what the furnace was designed for. Having two stages is like having two furnaces. One for the moderate days which is about 70% of the winter months and the other for the coldest days which is about 30% of the winter.

One of the most common failures of gas furnaces is the igniter failure. The igniter ignites the gas to produce combustion. Igniters glow at over 2000 degrees and for a preset amount of time. With the new smart technology the igniter is only in operation for the minimum amount of time extending igniter life 10 times more than with standard timing. 

Variable Speed Drive and Multi Speed

Standard versus Variable Speed Blower Systems

All furnaces have a blower and motor to circulate the air in the house. A standard furnace has a blower motor which when it comes on, immediately goes to full speed. This creates a tremendous amount of noise and is also very hard on the motor when this occurs frequently in the course of one day's operation. A similar example is having a car that has no throttle and when you turn the car on it immediately goes to full speed. When you reach the correct speed you would shut the car engine off to slow down and then restart the car again at full speed to again resume the desired speed. Imagine how hard this would be on your car if you operated the engine in this condition. That's exactly what happens when you operate a standard air handler. This is also how the blower motor operates in a standard furnace. Most of us have become accustomed to the click, bang and whoosh sound of an air handler or furnace starting and the loud noise the motor creates. Then the dead silence that occurs after the unit shuts off. 

What a variable speed motor does is give us a throttle. Instead of the fan motor coming on at full speed, the motor will start silently and then gradually and slowly within 30 seconds go to 50% of the air capacity and hold that position. This allows the duct system to become full of pressure so there are no shocks to the duct system or noise. After the duct system becomes pressurized then the blower motor will continue to increase slowly up to 100% of the full air speed. The net result of all this technology means you will not hear the blower motor come on and you won't hear the motor as it goes through the pressurization of the duct system and finally achieves full speed. All you'll hear is air movement if you hear anything. Add the variable speed blower motor to a premium duct system such as our fiberglass duct system, you will most likely never hear anything. On shut down of the air handler the blower motor will gradually decrease to 30% of the air speed and then after a short period of time will then shut off. Imagine an HVAC system that is totally quiet, energy efficient and performs so well with long life expectancy. That's what you can achieve with the variable speed blower system. Variable speed blower systems are available for our gas furnaces, heat pumps and air conditioning air handlers. Because of the variable speed design the blower will also take advantage of residual heat or cooling left on the indoor air conditioning coil removing every drop of energy used so as to eliminate waste. Variable speed blower systems also have a unique feature for air conditioning called the dehumidification cycle. Unfortunately many installing contractors who sell and install HVAC systems never tell the homeowner this feature exists on the variable speed drive motors or set it up for the homeowner to use. The dehumidification cycle does this: The air conditioner and the blower motor come on during their normal start up cycles but the blower motor only goes to 70% of the regular air speed and stays there allowing the air to move slowly across the coil to remove as much moisture as possible. When the coil becomes saturated with moisture or ice the blower motor senses this change and automatically increases the air speed so as to prevent damage tot he air conditioning compressor unit. This dehumidification cycle is perfect for those 80 degree high humidity days when the air conditioning system doesn't run long enough to properly dehumidify the air because there's not enough heat outside. When  running the system in the dehumidification cycle you can remove the moisture from he air without affecting the inside temperature as much as the normal cycle. This is a tremendous feature to the variable speed system when it's employed into operation. Unfortunately most contractors are unaware of this feature and never advise their customers so the homeowner never knows it exists. You can expect the high efficiency GMV9 furnace to operate for longer periods of time than a standard system. Not to worry though because this motor consumes the equivalent of a 75 watt light bulb in comparison to a standard blower motor which consumes as much as 7 or 8 large 100 watt light bulbs. All variable speed blower systems are manufactured by General Electric, a name which has become synonymous with quality, reliability and performance.

Variable speed drive blower motors increase your heating efficiency and increase air conditioning efficiency by usually one full Seer rating.  

Remember however that if your Heating or Air Conditioning system is oversized, you just threw away any and all energy savings.

What are the advantages and the differences?

General Electric is the manufacturer of all the variable speed electronically controlled blower motors for over 90% of all manufacturers.

Variable speed compared to a multi speed blower is the difference between day and night in performance, comfort, silent operation and technology.

A multi speed blower motor is a blower motor that simply has several speeds available. Those speeds are low, medium and high and sometimes more selections. Used in blower motors for furnaces and heat pumps the blower speed is selected during installation usually providing a lower speed for heating and a higher speed for cooling. The higher speed for cooling is because cold air is heavier than heated air and need more force to distribute the air throughout the duct system. The blower motor comes on when there’s a call for heating or cooling at full blast of the speed selected and simply shuts off when no longer needed. The motor also consumes high electrical usage and a high inrush of power when starting. You can almost always hear a multi speed blower start on a furnace and you also know the dead silence after the motor shuts off. There’s no high technology to the multi speed blower and they’ve been around forever. A furnace with a multi speed blower single stage is similar to having a car and starting it at full speed and when you’ve achieved the speed you want, you would simply turn the car off and wait for the car to coast to a lower speed and again restart the car at full speed and again attempt to reach the desired speed. Sounds fairly primitive doesn’t it? That’s why a standard furnace with a multi speed blower will have wide temperature variations. Just the same as the car would have wide speed variations.

Smart Igniter Technology

On many of the new high technology furnaces is a feature called smart igniter technology. On standard operating furnaces there is an igniter which heats up and becomes a bright orange color. This glow coil will stay lit for a predetermined amount of time up to 30 seconds or more. As with any high temperature item the longer the unit stays heated up the shorter the life span. The new smart technology will sense the amount of time the igniter tool to achieve flame ignition. Then every time the furnace restarts the smart board reduces the amount of time the igniter will glow. It will continue to shorten the period of time until the igniter actually fails to ignite the time. Then it will restart the furnace again but at a slightly longer period of time. By monitoring and reducing the amount of time the igniter is fired, the longer the life span of the igniter. All this shortening of time and adjusting of the igniter on time occurs without you even being aware of what is happening.

Auto Comfort Mode

This is an added feature to the new Goodman GMV9 furnaces which helps your air conditioning system achieve maximum dehumidification. On the control center there are four adjustments for the Auto Comfort mode. The first setting allows the variable speed blower to start up as it is described above under standard start up. But if you set up the control center to setting B, C or D you increase the amount of dehumidification the air conditioning will achieve especially for humid conditions such as in the South East areas of the country or those times when the outside air is not hot but is warm and humid. The Auto Comfort mode increases the amount of time to achieve full air speed allowing the air conditioning coil to achieve colder temperatures and providing maximum dehumidification. In the maximum setting of D on the Auto Comfort mode the blower will start slowly to 75% of the required air speed and hold that position for 7-1/2 minutes until it permits the blower to finally achieve 100% of the required air speed.

In setting A which is the equivalent standard setting an air conditioning system will take form 12 to 15 minutes to achieve a coil temperature to provide maximum dehumidification. On moderate summer days the air conditioning system will never operate long enough to achieve that temperature. So in setting D of the Auto Comfort mode the indoor coil will achieve maximum dehumidification in 2 to 3 minutes achieving proper dehumidification for shorter operating cycles.

With the new Goodman GMV9 high technology gas furnaces you will not only save energy but increase the comfort level of the heating and air conditioning systems. A 93% gas furnace with 2 stage heating and variable speed drive will save 10 to 15% more energy than a standard 93% furnace. The furnace also increases energy efficiency of the air conditioning system by one full Seer. The new technology furnaces are also more reliable than the standard furnaces with features such as smart igniter technology. So not only do you increase comfort, you save energy and you have amore reliable system. The high technology furnaces also have self diagnostics on he control centers to provide easier and quicker troubleshooting in the event of a system problem.

If they're built better and are more reliable then they should have a better warranty right??!! That's exactly right and the new Goodman GMV9 furnaces have the strongest warranty in the industry. First all the parts on the furnace are warranted for a full five years. In addition in the first ten years if the heat exchanger or the condenser coil fail as a result of defects in manufacturing, the entire furnace will be replaced, not just the parts. And even further the heat exchanger and condensing coil are warranted for as long as you own it. There's no better warranty anywhere. Goodman also produces a GMS9 furnace which is a standard 93% single stage furnace with a mutli speed blower motor. The GMS9 furnace is only $200 less than the incredible GMV9 furnace. Is it worth $200 more to have all this technology and a warranty that is the best in the industry? Our customers do and they have made the new GMV9 Goodman furnace the hottest selling furnace in the industry.

The Goodman GMV9 furnace is a two stage heating unit and requires a thermostat with high technology as well to properly utilize all the energy savings features of the furnace. Most thermostats are all single stage operation and will not properly operate the new GMV9 furnace. We provide the White Rodgers Ultimate 1F95 thermostat with every GMV9 furnace we sell to insure your new GMV9 will provide maximum energy savings and comfort. For complete details of the White Rodgers thermostat Click Here White Rodgers is also a division of Emerson Technologies, the leader in HVAC products including the Copeland Scroll Compressors.

Another important accessory for all 90+ condensing furnaces is a high media filter. Unlike the older furnaces which used a clam shell heat exchanger, the new condensing furnaces use a tubular heat exchanger with a condensing coil. As we described previously the condensing coil is very similar in appearance to an air conditioning coil. On the condensing furnaces if any dirt gets passed the blower and on the condensing coil, it will bake fast tot he condensing coil. Even standard fiberglass filters are very poor at prier air filtration and allow sufficient air to bypass these filters and then bake on to the condensing coil. In a very short time frame such as 2 or 3 years enough dirt will bake on to the coil and block air flow while destroying efficiency. This dirt once baked on to the coil can not be removed even with steam. This will result in a total furnace failure which is not covered under warranty. To protect your new furnace and keep it operating at full efficiency we require a high media filter with every condensing furnace. High media filters provide excellent filtration to remove the smallest of particles including mold spores, pollen and smoke. We want your new high efficient furnace to provide the maximum efficient trouble free operation for a lifetime and to do so we provide the best filtration system with every furnace. Proper air filtration is first and foremost to protect the HVAC equipment to keep it running efficiently and second to provide clean filtered air for the occupants.

To view the specifications of the Goodman GMV9 2 Stage Variable Speed Gas Furnace Click Here

To have your furnace sized and selected professionally and accurately Click Here

For more information on Factory Warranties Click Here

For more information on Heat Pumps Click Here

What components are necessary to make a complete heating and air conditioning system?

There are two basic types of heating and air conditioning systems, packaged units and split systems. A packaged unit is a system where the total system is in one wrapper. All that is necessary to hook up the packaged heat pump is the duct system, power and thermostat wiring. A packaged system is the easiest to install but does not provide such options such as variable speed or ultra efficiencies and requires long duct runs often resulting in insufficient air flow. A split system is a system where there is a furnace and an outdoor unit called the condensing unit.

Furnaces are mounted in three different positions. Some furnaces are capable of multi position mounting while other furnaces are only capable of one position. Be certain the furnace you require is for the proper mounting configuration.

UPFLOW

HORIZONTAL

DOWNFLOW

Split systems are the most common systems and provide versatility, variable speed drive, ultra efficiencies and maximum comfort control.

For a split system the components are as follows:

The furnace contains the heat exchanger(s) and blower: 

The indoor cased air conditioning coil:  This coil can be either vertical, horizontal or downflow depending on the furnace position and duct configuration.

The outdoor condensing unit:

The outdoor electrical disconnect for the condensing unit:

The outdoor electrical whip:

The White Rodgers Ultimate thermostat:  

Condenser pad base to place below the condensing unit:

Refrigeration lineset to connect from the outdoor unit to the indoor coil:  Available in 30 and 50 foot lengths.

House thimble for decorative outlet for the above lineset:

Thermostat wire to connect to the thermostat to the air handler and to the outdoor condensing unit:  

Humidifier for the air handler:

High Media filter for the air handler:

Auxiliary drain pan for the furnace in the horizontal position:

Condensate pump:

Vibration Isolator pads for the furnace to reduce noise transmission:

Duct materials to provide the air distribution system:

DESCO will select and assist you in the selection of all components to put together a complete heat pump system including the duct system. For more information visit us at http://www.descoenergy.com