Category Archives: Furnace

Quality Installation and Maintenance of HVAC Equipment

The news this month has multiple stories about Heating and Air Companies being very busy with units not cooling or not cooling enough.Screen Shot 2016-06-24 at 8.49.56 AM Driving around town, I see most of these contractors have a sign out front looking for help. The wait time is up to two weeks.  In the 7 homes I’ve been in this week.  One had no working AC, one home was on it’s last legs, and two other homeowners were very concerned. For the 1st time in 7 years, I’m getting calls from my website asking if I can fix their AC unit.

This morning I found a report on HVAC Problems, Problem Identification and Repair.  I have scanned this 27 page report and these are the things that jumped out.

Background:  California has some of the toughest energy requirements for buildings, both new and remodeling of existing buildings. These is a direct result of the problems they had 15 years ago, with not enough electricity.  They resulted to black outs, (Utilitys were allowed to shut off electricity to various geographic areas).  and brown outs, (Utilities were allowed to provide only part of the electricity needed to a geographic area).  Both are not good.

These energy codes are generally referred to as Title 24.  A large part of the work in California the last few years has been testing and measuring how well the requirements are being met.  This report is just one small piece of that process.

Title 24 refers to the problems, their identification and repair as “Fault Detection and Diagnosis” or “FDD”

Screen Shot 2016-06-24 at 8.51.18 AM

The Report was working on the answers to these questions

  • Is FDD worth the investment, and what is the savings potential?
  • How effective are available FDD methods and what do they cost to implement?
  • What training is needed for effective FDD and is it being provided?
  • Are codes and standards working?
  • What are the major gaps and how can they be addressed?

This particular session and reporting was limited to:

 

  • System Types–new and existing residential only
    • Air conditioners
    • Heat pumps
    • Furnaces and air handlers
  • Fault Types
    • Low airflow
    • Refrigerant system charge, restrictions, and contaminants
    • Mechanical and electrical faults and faulty installation
  • Repair vs. Replacement Issues
    • Cost-effectiveness of FDD
    • Replacement refrigerants for R-22
  • Human Factors
    • Training and quality of maintenance
    • Homeowner knowledge and expectations.

The reporting included tests applied with standard AHRI methods. The tests were designed to determine the impacts on efficiency and capacity of a variety of conditions, including:

  • Airflow of 250 cfm/ton reduced energy efficiency ratio (EER) by 12% and has the potential to produce a false overcharge diagnostic due to freezing of the coil (the asterisk denotes an unofficial EER)
  • Liquid line restrictions (e.g. due to clogged filter-dryer or metering devices) reduced EER by 30% to 36% for non-TXV and TXV systems respectively
  • Only 0.3% Nitrogen in the refrigerant reduced the EER  by 18% with no TXV and 12% for the TXV-equipped system

Discussion pointed out that California Title 24 charge verification methods, which only measure superheat (for non-TXV) and sub-cooling (for TXV) systems, and ACCA Standard 4, for which only 3% of the procedures are related to energy performance. Also covered were  how improperly maintained vacuum pumps, test instrument error, and poor service practices such as use of rules of thumb contribute to the introduction of non-condensables, improper charge, and other faults.

John Proctor, PE presented a case for making improvements to California’s Title 24 standards, John worked with a team to inspect a large number of recently built homes to identify HVAC installation and performance issues. He began his presentation by defining an “incremental effectiveness ratio” that divides benefits of maintenance by the incremental cost to diagnose, repair, and ensure quality, which is fundamental to the question of the value of HVAC service. He proceeded to show a series of graphs from his experience and other studies that illustrate the deviations from the ideal for airflow, charge, duct leakage and efficiency, and non-condensables, as well as the incidence of occurrence of these defects.

For example, his graphs show:

  • 50% reduction in airflow reduces EER by 25%.
  • A refrigerant charge that is 70% of the recommended charge reduces EER by about 55%.
  • Leaving Nitrogen in the line set and coil at 20 psig before charging with refrigerant reduces the sensible EER by about 45%.
  • From his 2003 survey, more than 60% of the houses checked failed on refrigerant charge, airflow, and duct leakage, and more than 95% failed overall.

Many of these issues result from a lack of training and a lack of follow up by supervisors.

They had some specific things that could be done by builders, HVAC Contractors and home owners to ensure these items do not get missed.

I will read the report in more detail and have further comments.

You may read the entire report.

Indoor Air Quality Evaluations

The quality of the Indoor Air of our homes and offices is an important part of our health and comfort.

There is not much sense in putting a lot of good insulation into a building if it is:

  • Not Structurally Sound
  • Not Healthy

What types of things can be done to improve the Indoor Air Quality of any home or property?

  1. The immediate environment of the structure must be kept separate from the inside.
  2. The required fresh air that is needed, in every one of our buildings, should be filtered and otherwise treated for comfort and to remove pollutants.
  3. The pollutants that are created during the normal operation of our building must be eliminated, removed, replaced, diluted or neutralized.
  4. Moisture in any form must be controlled , and then removed avoiding any accumulation.
  5. Any and all accumulations of moisture damage or animal infestation must be cleaned up and damaged building components replaced.
  • A Full Indoor Air Quality evaluation must address all of those concerns.
  • Full interior visual inspection
  • Full exterior visual inspection
  • Testing of the building enclosure to ensure the outside stays outside
    • Infrared Evaluation as part of the above testing
  • Inspection of HVAC Duct Work and systems that move air.
  • Combustion Safety Inspection on open combustion appliances
    • Moisture, Carbon Monoxide, N02, SO2 and others
  • Infrared and other testing for moisture accumulations.
  • Sample Collection of suspended and/or deposited material that are potential pollutants or irritants.
    • Examination and Evaluation by a certified Microbiological Laboratory of these samples.

This evaluation is typically completed in two visits to the home or business. Level I Evaluation and Testing is non-destructive and not invasive.

Level II Evaluation and Testing involves invasive inspections. These may be as simple as drilling a few holes for visual inspection or sampling. It may involve removing obviously damaged building material, that requires replacement, for example wet drywall.

Contact The Energy Guy for further information about an Indoor Air Quality Evaluation.

A Healthy Home Part 3 — Well Ventilated

Fresh AirA Healthy Home is well ventilated.  Everyone knows fresh air is important. This should be easy.  Well ventilated in more than just bringing in fresh air. The concepts are certainly easy, the details on the other hand take some thought and planning.  A new home ventilation strategy is fairly straight forward to design and implement. An existing home needs the input from the occupants and good analysis to address the problems. An effective ventilation strategy should address these issues in either new or existing homes.

  • Remove humidity, odors,, or significant problems from specific areas.
  • Remove stale, musty or other objectionable air.
  • Allow the occupants to choose fresh air sources that can be filtered or treated in other ways
  • Allow the occupants to choose to open windows when outside weather is appropriate
  • Allow the occupants to operate a system that can provide the amount of fresh air, to the appropriate places, in adequate amounts when needed
  • Provide fresh air when the outside air creates potential problems, such as Ragweed season or when other allergens are active
  • Provide air movement within the home, without the use of the expensive blower on the furnace or heat pump.
  • Allow minimal use of heating or cooling equipment during the shoulder seasons, when temperature changes are minimal, while keeping the home comfortable.

Billings QuoteHow much fresh air is needed?  Going back to the 1890’s, the number has been pegged at 30 CFM (cubic feet per minute) per person. This number was validated in a number of different studies and with the public health authorities in larger cities, dealing with large apartment buildings and recurring respiratory diseases.  I was pointed to the quote at the left by Allison Bailles. he located the original book on Google Books, page 20.

Beginning in the 1930s, research into changes in building techniques began to show the optimal number was closer to 15 CFM per person.  Some of the changes in construction included the increased use of forced air heating, moving from balloon framing to platform framing, increasing square footage, and the use of insulation in walls and attics. The formula changes from time to time and everyone has an opinion on details. The common point remains, fresh air is needed in every house.

Part of the Ventilation is removing air with a problem. Where is that?  Humidity is found in rooms that use hot water and basements.  Showers, tubs and cooking are the large sources of humidity.  The smells from food preparation and cooking can be very mouthwatering.  When the meal is finished and the refrigerator is full, the lingering smells become odors.  The answer is some spot ventilation in these areas. If your basement has a humidity problem, you can tackle that with a fitted sump pump cover to contain the humidity, and work to eliminate any water seepage.

vent fanSpot ventilation is a window that opens and an exhaust fan. The size of these fans is part of the formula that is specific to each home. The features of the fan are common to all homes.  It must be quiet. Builder grade fans are noisy. Noise in fans is measured in ‘Sones’. The Sone is a linear measurement of noise, compared to the decibels used by OSHA and others which is an exponential measurement.  Linear is better for quiet sounds, and decibels is better for loud noises. Fans should be less than 3 sones, and preferably less than 1 sone.  Reasonably priced fans are available that rate a 0.3 sones. A 1 sone fan is very quiet.

UnknownFans are certified for air flow and noise levels by the Home Ventilation Institute. HVI certification is very common and includes both the Sone rating and CFM rating.  When installing a fan, you must consider the duct losses that will occur in meeting the required air flow.   The rates for bathroom air flow  are 50 CFM, and 100 CFM for a kitchen.  Do not expect to buy a 50 CFM fan for a bathroom and connect it to 6 or 8 feet of duct work, and obtain 50 CFM.  I have measured 30 CFM routinely in these set ups.

Most people understand that various parts of their body are just a part of the whole.  If you start some type of therapy, there may be a side effect. Physical Therapy starts and you end up with some sore muscles, aha!  Side Effect!  Start a therapy for cancer and your hair may fall out, aha! Side Effect!  Your home works the same way.  Each part is just part of the whole. Change something, aha! What is the side effect?

House-System-imgAll of the items in the list above are part of the whole. For an existing home, some specifics of that house may indicate concentration on one or another of those areas.  A home built in the 1920’s will benefit from a different approach then a house built in the 1980’s.

A new home should have the ventilation system that meets the general points above.  The natural ventilation provided when windows and doors are opened, or the mechanical ventilation system that allows filtered and perhaps treated fresh air brought in from specific places and in specific amounts, allow the occupants to make the system work as they need.

 

This post is part of a Series on A Healthy Home

 

 

Using One HVAC System for Two Areas

My first audit was triggered by the homeowner concerned that the upstairs was several degrees warmer than downstairs. Since we all have experienced Hot Air  goes up, it makes some sense.  In this case the difference was 15° F at 8:00 am, rising to 20° F by noon that August morning.  Yes, it was hot.

4 square craftsmanThere are a number of ways to help this out, for existing homes. Which one is best depends on the specific home, the existing setup and the homeowner.  For new homes, it usually falls to the HVAC guys to work out.

In a new 2 story home, it is common to see two HVAC units.  One in the basement for most of the home and one in the attic for the second floor.  Some builders, concerned with cost, or space considerations, will try a Zoned System.  You can also find Zoned Systems in single story homes, with the master suite on one zone and the rest of the home on another zone.

furnace bypass zoneTypically, the set up uses a bypass and several dampers to control the air.  The wisdom of this approach is that changing the air flow through the unit costs a lot of $$$$.

In the video below, John Proctor, goes through the measurements and calculations of using or not using a bypass and dampers to figure out exactly what is happening.  His conclusion:  The Bypass Damper set up costs 22% – 32% more.

This video is primarily written for HVAC contractors and others interested in the details and workings of air conditioning.  If all the numbers make your eyes glaze over, that is OK.  All you want is comfort, a Bypass dampened system may do that at a cost. It may have the cost and not do that.  So if you are considering a Zoned HVAC system,  tell your contractor —  ‘No Bypass Dampers’!  And refer them to this post.

What Happens After You Finish Your Part of the house, and Then The House Is Finished?

images-2Modern home building takes a lot of people. Concrete, Carpentry, Heating and Air, Paint, Drywall, Insulation, Electrical, Plumbing and many others. These professionals work on the house at various times. Usually there is a sequence, the foundation is done before the framing, the roof is done before inside work gets very far. Toward the end, it can get somewhat hectic. Everyone is trying to finish. The deadline is looming. Painters, trim carpentry, flooring, plumbing, final electrical installations are all happening.

One of the last things is the final work on the Heating and Air Conditioning system. This cannot happen until after the electrician is finished, and if you have a gas furnace, the plumbing must be there. Some of the work by the HVAC contractor was completed before the drywall went up. The duct work was installed and the inside unit of the system was probably put in place and hooked up to the duct work.

If the home is built on a 120 – 150 day schedule, the initial work, rough-in, on the duct system would happen about 1/3 of the way. Then about 2/3 of the waywall_duct, the Heating and Air techs are back to install the thermostat, the outside unit, hook up the electric and finish the job.

Last week, I went out to complete a rating on a new home. I had completed some testing on the duct system at rough-in. I used a Duct Blaster unit and testing the duct system for Total Leakage. I got a great number. There is a professional standard, issued ACCA (Air Conditioning Contractors of America) for this test. It is based on the size of the amount of air flow pushed through the system by the fan; in this case it would have been about 1,200 cubic feet per minute.

The standard is 10% of system air flow or in this case 120 CFM. In a previous blog post, I discussed a test where the system leaked over 100% of system air flow. This is an important test, because it can be compared to the test done at rough in.ACCA_5

The rough in test for Total Duct Leakage came in at 4.8% of system air flow. This is a very good number and typical for this HVAC contractor. Now at final, the total leakage was 16%. Wow! What happened?

I cleaned up and left the house about 6:00 for the weekend. Sleeping on the ‘What Happened?’ seemed like a great idea. I did just that.

Tuesday, I went back to take another look. I would conduct some additional testing to see if the leak(s) could be isolated. I started by removing the grills that fan the air out through each room. That would be easy and fast. So, the first few looked pretty good. It was going fast, I kept going and half way through I found one that showed some problems. At the end 1/3 of these grills had a significant problem.

Duct BootAs you can see the vent in the wall, had the drywall cut too large for the duct. The openings ranged from a quarter inch to over an inch wide, all around the opening. The air instead of 100% leaving the duct system into the room, was being pushed back into the wall. The idea of the duct system is to put the hot or cooled/dehumidified air into the room where the people are. A grill can do a great job of sending the air into various parts of the room. A good grill for one place may be absolutely the wrong grill for another place. Grill manufacturers refer to this as ‘Throw’. If you have the wrong throw on your grill, you aren’t getting much comfort from your system.

The infrared image, below, shows the outside of a wall in the winter (It was 20° F that morning). The hot area below the window is from the grill directing the heat up the wall, not out into the room. I found this condition on an audit last winter and made two alternate recommendations for the home owner. The cost was less than $20.00 for either one. The problem was fixed the same day by the homeowner.exterior_wall

Back to fixing the leaks! I filled the cracks and gaps in the poorly cut openings, replaced the grills and then set up to re-test the duct system. The leakage was back to the original number.

This shows the value of testing your work. We work with Quality Control Systems in our everyday work life. As consumers we depend on the quality of the products we buy. We see how companies respond when they are faced with a quality issue. A number years ago a lot of Tylenol was recalled. A few bottles had been tampered with, not really the manufacturer’s fault. They recalled anyway and their customers were well served. In the past few years, several auto manufacturers have had some problems with their cars, and they did not promptly recall the cars to fix the problem.

qcApplying good quality control lets the customers and the management of a company know the level of quality. The company can make drugs, cars, or install your heating and air system. In this case the quality work done by the Heating and Air techs was changed by another person working on the job. Good quality control found the problem. The fix took only a few minutes. Now the home buyer will not experience the discomfort from a badly installed duct system. I will not get a call in a few years because the home owner is not comfortable. The heating and air techs will not have a lot of call backs.

My thanks today goes to the crew at Cooks Heating and Air in Wichita. They did the quality work and deserve the credit. I am lucky to be able to work with people like this.

What % Of The Cost of a New Home Cost, Does The HVAC System provide? 5%, 10% ,15%???

This question was raised this morning on one of the professional discussion forums. Below is my response. Included is a link supplied by Richard McGrath in another response.

Let’s use a water bucket and a faucet for an analogy.

Take a page from the British Navy a few hundred years ago. They learned to tar the joints of their wooden hulled ships. Perhaps that’s why British Seamen are called ‘Tars’.

taringshipIf you build your bucket with wood, you do something to stop the leaks. To use the bucket, you have a faucet to put water into it. If you put less money into the bucket stopping the water loss, you will need to put more water into it all the time, and need a larger capacity faucet. That will cost more money. The reverse is also true.

The question is ‘what should our faucet cost’? Most people would look at it and say not much! For a half million dollar house you might get answers from 2-4%. Some would say less. A faucet system is not just the part you see sticking out of the wall? The system includes pipe from the source of water to the house, to the various rooms where water is needed. You can’t buy a $10 faucet and claim to have a faucet system.

For this question, you can’t buy a furnace and AC unit and claim that is the system. You must have a Thermostat and some way to get the heat and cool to the various rooms of the home. For an effective faucet system, you put some thought and effort into the design. The same goes for an HVAC system.

What is the bucket in our house? Sometimes it is called the thermal envelope, sometimes Thermal Enclosure. It is formed by a continuous thermal boundary that is aligned with a continuous air barrier. Pretty simple in concept, Not as easy to execute. Put some time and effort into the design; then put some effort into the execution.

Choose your insulation types and amounts carefully.  Each have advantages and disadvantages. Air seal the building. All fibrous insulation types allow air to flow. That flow will decrease or eliminate the value of the insulation.

Properly flash and seal the openings for windows and doors. Specify the U-factor and SHGC for the windows. Calculate the correct overhang for the eaves. You want to have them cast a shadow over the whole window at noon on June 21st.

Properly air seal the home. Install your WRB (water resistant barrier) correctly. That means following manufacturer’s directions. Wrap types mean gasketed nails, properly lapped and taped with approved products. You can use factory applied WRB to the OSB or a site applied liquid to the house. Air sealing doesn’t stop there. Fill each 1 inch hole the electrician drilled with caulk or foam, most wires running through those holes are about 1/2 inch. Then seal the joints of the wall and ceiling drywall on the attic side. Caulk or froth pac work. You can flash 1 inch of CC SPF also.

Now your house, bucket, is not very leaky. So you don’t need a big faucet. Big faucets relate to size of the HVAC system, they also directly relate to the cost to install. You also have the cost to operate.

After you have a well built air leakage controlled envelope, then you can consider the HVAC system. ??Two choices to start with: Hydronic or Forced Air. Forced air is most common in this area, we will persue that route.

After choosing Forced Air, you can choose gas fired heat or an electrically driven heat source. Again 2 choices. ??With a gas fired heat source you will have conditioned air leaving the ducts at 100 – 110° F. With an electrically driven source the air will leave the ducts at 85 – 95° F noticeably cooler. That will make or break many people on their choice and ultimate satisfaction with their HVAC system.

Gas fired comes in primarily Natural Gas and Propane. Availability is the key here. ??If you choose a gas fired system – go sealed combustion on the furnace and either sealed combustion or fan assisted drafting on the DHW.

If you choose to go with an electrically driven system, you can choose a Heat Pump or an electric furnace. If you choose an electric furnace, IMO you will not be pleased with your operating costs. They will be through the roof and you will invest any capital cost savings in operating costs very quickly.

That leaves a heat pump with Two Choices. You can choose an Air Source or a Ground Source. ??With a well designed and built duct system, meeting the standards for leakage and design for the Energy Star 3.0 program; a ASHP with variable speed ECM motor (which may be overkill) including actual Manual J, S, and D work ups around here will cost between 9 – 15 K. A gas fired system will be very similar in price, as would a dual fuel system.

If you opt for a typical closed loop Ground Source set up, including all of the above, wells and piping your capital cost will run between 25 – 35K. (noted for the next 27 months a 30% tax credit is available, but not considered in this article.)

In this area new construction homes range from 125,000 to 7 million. ??So the lower end is in the 7 – 12 % range. The more reasonable price of 500,000 for a high end spec home in the area results in the 3 – 7% range.

The question of percentages is silly. Builders may like them, but most homeowners will have their eyes glaze over if you bring this up. The goal is to sell homes, not HVAC systems. A home is supposed to be comfortable. Many new ones are not. This link goes into depth on this issue. http://www.healthyheating.com/Thermal_Comfort_Working_Copy/comfort.htm#.Uj9kLr7D_5o

The equation of importance is capital cost to operating cost. Those are best approached with some modeling. I recently completed a model for a 3K sf home with R-25 ICF V 2×4 16OC construction. The operating costs were in the $1,500 range for our utility rates. The HERS Score was 54.

Substituting a GSHP brought the operating costs down by $200 per year and increase the capital costs by 10K. ??The customer opted for the ASHP and ICF over the GSHP and typical construction. He chose where to put his money.

I see a trap in logic using percentages. I provided new construction pricing around here. My cousin in California deals with homes on the bottom range in the neighborhood of 500,000. That makes a hugh difference in the % equation. So try rephrasing the question to get some more accurate results. Leave out the percentages.

The Energy Guy Does Rounding For 3rd Graders

I was recently asked to make a short video for children 8 – 9 years old. The subject was to involve how I use rounding in my job.

I chose to use measuring a house to obtain the size in cubic feet and relate that to choosing the size of the furnace. I varied the measurement on each side of the house by 6 inches.  The measurement rounding was shown to be accurate enough for this need. In this case the accuracy requirement was not needed due to furnace engineering issues, not the ability of someone to measure to the nearest inch or 6 inches.

Enjoy the video – help some kids! Thanks to the Third Grade Teacher, Grace for including me.  Here is the video on my You Tube Channel

http://youtu.be/xhZvH4RLY6U

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