Daily Archives: April 26, 2014

Common Approaches to Heating Your Home: Part III

This is Part III of a 3 part Series.  Part 1 is here; Part 2 is here.

Hybrid Heat Pump

This choice is sometimes referred to as a Dual Fuel Heat Pump. It utilized both gas and electricity to heat your home. The efficiency of a heat pump is because at most heating temperatures, it moves heat from outside to inside.

Think about your refrigerator. When the inside warms up to 40•, the food risks going bad, so the fridge finds the heat and pumps in out.  Your food stays refrigerated. At 40• outside, a heat pump can find heat and efficiently bring it inside. This costs less than consuming natural gas, propane or electricity to produce heat in a furnace.

At much lower temperatures, a heat pump will need a boost to maintain the heat. This is an electric resistance strip heater. It is used in emergency and back up situations.

A hybrid heat pump uses a conventional furnace for emergency and back up. This is less expensive than electric resistance heat.

Your Choice

In our climate zone; I believe the rank of these approaches should be:

  1. Geothermal
  2. Hybrid Heat Pump
  3. Traditional Furnace / AC
  4. Air Source Heat Pump

This ranking is based primarily on Efficiency Issues with overall comfort issues second.  This rank considers only long term operating costs. It does not consider capital costs (installation).

There are two primary considerations for all of the installation and ultimately comfort issues.

  • The home must be ready for an efficient heating/ac equipment installation.  This means the thermal envelope must be sealed and well insulated. Your thermal envelope is defined as the basement walls, or crawl space walls, the wall above ground, the ceiling.
  • The calculations for equipment size, and selection must be done professionally. The use of a recognized computer program authorized by the ACCA (Air Conditioning Contractors of America); showing the Manual J calculations of the improved home for determining heat loads; and the Manual S calculations to select the equipment. You may wish to have your ductwork reviewed and perhaps resized.  This would call for calculations with ACCA Manual D.

The choice to go with Geothermal or ASHP would mean very little gas usage, only the hot water heater. That could be converted to electric with the ASHP. With a Geothermal Unit, you could utilize a system of hot water that is known as ‘de-superheating’.  It uses otherwise wasted heat from the Heat Pump unit to heat water.

The capital costs of these units in the Wichita area are estimated at:

  • Geothermal:               15-25,000+ (open or closed loop)
  • ASHP:                           7 -12,000
  • Hybrid Heat Pump:    7 – 12,000
  • Furnace/AC                 7 -12,000

The Geothermal unit is considered to be a renewable energy source and carries a 30% tax credit, with no limit.  It is available through 2016. Before giving much thought to a geothermal system, a homeowner should discuss the location with a driller to determine the depth of wells and the quality of the water. Do not install an open loop (also known as pump and dump) without a water quality test in your possession. Consider a closed loop system, if there are any concerns about water quality or the amount of water needed. Drought is a reality in Kansas. A well designed and installed geothermal system will last many years.  I have audited homes with systems that are 30+ years old. I have audited homes with failed systems, of 10 years or less, that were not well planned.

Comfort Note: Conventional Furnaces blow heated air into the duct work at temperatures from 105 – 150; depending and the design factors of the furnace.  If you have come in from the cold and stood neat the supply register of a forced air furnace, you feel the heat.  A heat pump type of heating does not create heat to be blown into the duct work at these high temperatures, a heat pump typically blows air into the ducts at 85 – 95 degrees.  This change can cause people to not like a heat pump; air source or ground source. A hybrid heat pump would provide the same range as a furnace with lower outside temperatures.

Please post your questions below as comments!

Common Approaches to Heating and Cooling Your Home: Part II

The Traditional Furnace and Air Conditioner Approach

Part I of this article can be found here.

The traditional furnace burns fossil fuel, either electricity or gas to create heat. The air conditioner is a one way heat pump. Air conditioners are almost exclusively powered by electricity today. It has not been that long since there were many gas powered air conditioners and refrigerators. Burning fossil fuel; either coal or natural gas is the primary source of electricity in Kansas. Less than 10% of our power is nuclear or wind generated, as of 2010.

The efficiency loss of a gas furnace can be as much as 50 percent of the heat literally going up the chimney. The most efficient gas furnaces are sealed combustion types. They utilize a condensing flue to achieve an extremely high efficiency. These units usually do not have a chimney through the roof. They exhaust out the wall near the ground. The temperatures are low enough, to allow plastic flue piping.

Their efficiency rates from 92 – 95 percent. In 2011, the Federal Income Tax Credit allowed home owners that purchase a 95 AFUE condensing furnace. An added feature of these furnaces is the sealed combustion chamber. They require no make up air from inside the home, and they cannot back draft deadly flue gasses into the home.

Electric furnaces are generally considered to be 100% efficient in the home. The electrical transmission system, does see a loss that amounts to about 35%. The generator burning fossil fuel also has less than 100% efficiency.

Air conditioners, available at this time, at a minimum are rated at 13 SEER. Most existing units vary from 6 – 11 SEER. You can purchase units with a rating of 18 – 20 SEER. A rating 15 SEER is the most common available High Efficiency Unit. Some manufacturers have a 14.5 SEER that is certified to use less power than a 16 SEER unit.

CompressorWhat is that trick? It is not a trick, but is part of the tool kit available for selling heating and ac units. An air conditioner consists of two parts. The outside unit, referred to as the compressor or the condenser, and the inside unit referred to as the evaporator. These must be matched correctly each other and the furnace (the blower fan is there) to achieve a specified SEER Rating. SEER is Seasonal Energy Efficiency Ratio.

For a user friendly description on the magic of Air Conditioning, a link to Energy Vanguard’s Blog Post on the subject.

The American Heating and Refrigeration Institute (AHRI) certifies furnaces, and air conditioners. Here are 3 entries with the same condenser/evaporator match with different furnaces.

AHRI Number      Model No Cond.        Model No Evap        Furn No              SEER

4137591                 24ABC630A**30       CNPV*3621A**        58HDV040–12        15

3630546               24ABC630A**30       CNPV*3621A**       58CV(A-X)090-16    16

3630606              24ABC639A**30        CNPV*3621A**       58CV(A-X)0110-16  15.5

As you can see here are 3 different furnace units partnered with the same outdoor unit and indoor coil. They are rated for different efficiency levels.

If you would like to look up your units, the information is on the data plates. You need the model numbers.

  • The evaporator coil plate is on the inside unit, usually the easiest to find. The evaporator will be either above or below the furnace, appearing to be in the ductwork.
  • The condenser unit is on the outside unit, usually it is on the side by the copper tubing. The furnace data plate is usually found in the burner compartment of the furnace.
  • If you have the original paperwork for your units, the model numbers may be there. After collecting these numbers go to AHRI Directory

If you are buying a new HVAC system, ask your contractor for the AHRI certification numbers and look up for your self, the efficiency ratings.  Unfortunately I have seen many new systems the Home Owner was told is a High Efficiency Unit, only to find the matching process did not meet the Sales Hype!  If you would like some help in this process, The Energy Guy can help. Contact me for details.

For Part III

Common Approaches to Heating and Cooling Your Home Part 1

Homes in Kansas are heated by several methods. These range from wood stoves to various types of solar heating.  The most common method is a central forced air unit. These are found both as a sole method and sometimes in combination with other methods.

Forced Air Heating and Air Conditioning

Forced Air units have several things in common. Duct work to distribute the conditioned air to various parts of the house; a blower fan, known as an air handler; and a source of hot air and a source of conditioned air.

FurnaceTraditionally, the warm is created by burning a fossil fuel, either electricity or a gas (natural gas or propane). The cool conditioned air is created with an electric compressor and outside condenser coil with an evaporator coil in the plenum.  These relatively common units have been updated in terms of efficiency over the years.

During the past 20 years homes are starting to use one or another type of heat pump to do the work of these units.  Moving heat is more efficient than burning a fossil fuel to create heat.  All homes have one or more heat pumps; these are known as a refrigerator or freezer.

Instead of converting energy in the form of gas or electricity to heat by burning a fossil fuel, as a furnace does; the heat pump uses electrical energy to move heat. It moves the heat in or out of your home.

Air Source Heat Pumps are the most common heat pumps found in homes today.  This can be an efficient way to heat and cool your home. ASHPs are more common south of Wichita than north, since they are not as efficient in cold weather.  The other type of heat pump that has been gaining in popularity  is the Geothermal Heat Pump. The cost to install a Geothermal system is dropping.  Geothermal uses heat from the Ground and is more properly referred to as a Ground Source Heat Pump.

The Geothermal Approach to Heating and Cooling Your Home

Geothermal is the popular name for a Heat Pump using a Ground Source for heat transfer.  During times when the air outside your home is cooler than you choose to have your home, this heat pump transfers heat from the ground, below the frost line, into your home.  During times when the air outside your home is warmer than you choose to have your home, this heat pump transfers heat from your home, into the ground, below the frost line.

What is the temperature of the ground, below the frost line?  It is very close to the average annual temperature of your area. In Wichita, that is about 54° F.

A Ground Source Heat Pump, can be very efficient, because it transfers energy.  It does not convert energy from electricity or gas to heat.  In the winter, it moves heat from the 55 degree source to warm your house.  In the summer it discharges the heat removed from your home into the 55 degree source.

The Traditional Heat Pump Approach

An Air Source Heat Pump transfers heat to and from the air outside your home. During times when the air outside your home is cooler than you choose to have your home, this heat pump transfers heat from the outside air into your home.  During times when the air outside your home is warmer than you choose to have your home, this heat pump transfers heat from your home, to the air outside.

The ASHP is an air conditioner with a reversing valve for winter usage. There are some small technical differences. You can use this concept to understand how it works.

This approach works great and yields great efficiency when the temperatures vary outside between  a low of 40 and a high of 80. In climates with lower or higher temperatures the ASHP has to work much harder to find heat in 20 degree or lower air outside in the winter to heat your home. These units are usually set up with electrical resistance heating for lower temperatures. This can be expensive.  In the summer the ASHP is trying to discharge heat from your home to a much warmer outside, this reduces the efficiency.

These disadvantages cause some people to bypass the ASHP.  Others have had bad experiences with some of the early units.  They have improved over the last few years and make a strong showing.

This is Part I of a III Part Article.  Here is Part II