Just exactly how does my A/C work?

Air conditioning is really not a very complicated process.  

Simply put, your A/C removes heat and moisture from the air inside the house.  It does so using a fairly complex system of copper tubes fans, valves, wiring, and other things that all play an intricate role in conditioning the indoor air.

1. The outdoor compressor and indoor condenser (in most cases) are two different yet linked components. The outside compressor is a small tank that sits inside that large metal box.  There is a motor with a fan attached just under the top of the compressor and some electrical and copper pipes that run into the house called the line set.
2. At the outside unit, the compressor physically compresses cool refrigerant gas under high pressure to form a hot vapor.
3. This liquid hot vapor is pushed through the smaller "liquid line" to the condenser coils inside the house.
4. The hot refrigerant liquid runs through an expansion valve inside the coil, causing it to evaporate and become cold gas again.
5. The cold freon gas flows through set of small tubes or the evaporator coil located just above (horizontal system) or just down stream from (vertical system) the furnace.
6. The fan at the air handler (bottom part of the furnace) then turns on and blows air across the evaporator coil.  The home's air becomes cold and travels through a the supply pleunum, supply ducts and finally into the rooms through the supply registers.  
7. The air is then sucked back or returned to the return air plenum located near the thermostat.  The air is filtered here before the warm ambient air is recirculated back toward the coil to start air circulation process all over.
8. The freon gas that has passed through the evaporator coil and picked up the heat and moisture from the air is then returned back to the compressor outside through a larger pipe called the "suction line", where the heat is removed from the refrigerant.  Then, refrigerant cycle starts all over again.  
9. The moisture removed from the air at the coil drips off the coil into a pan and drain out to a primary drain line.  This drain line runs water whenever the A/C is operating.  If the primary drain line clogs up with mold, the system should overflow into a secondary drain system (how to keep the primary drain line from clogging).
   

Never operate your compressor when the outside temperature is less than 60 degrees.  Because the system relies on outside temperatures of 70 degrees or better, there is a risk of damage to the compressor.  You always want to have your HVAC system serviced in the late spring to make sure everything is working for the coming summer.  Thinking your system cooled last year does not mean that everything is fine.  A system might feel cool but may not operating efficiently.  It may also be running out of refrigerant through a small leak that will crash your system in August.  


Regardless of they type of house you have, there are some necessary tasks you will have to do stay on top of things.  Learn more and keep up with your house with a free My Healthy House.com profile.  Stay tuned and make your house the best it can be.  

If you have any comments or suggestions on how this blog can be improved including suggested articles or constructive criticism, please send us feedback.

© Healthy House, Inc. 2009

Cleaning out your home's return air plenum.

It's like blowing your home's nose!

Your home's return plenum is a part of your HVAC (heating ventilation and air conditioning) system that is out of site and usually out of mind. The word plenum means a chamber intended to contain air, gas, or liquid at positive pressure. Simply put, its the box the air travels through.  In this case the return plenum is where home's ambient air returns to the HVAC system to be heated or cooled.  Since its hidden, most homeowners never look inside this part of the house.  This area often becomes a repository for all sorts of material such as dust, debris, pet hair, dust bunnies and even the dead bodies of pests. 

The return plenum gets dirty for two primary reasons:

• Improper sealing - The ducting and/or plenum is not sealed properly.  This is very common and renders an air filter mostly useless
  
• Deferred maintenance - Air filters haven’t been changed regularly or the filter becomes so dirty, blow-by occurs (more)
  

The return plenum is often located behind a metal grill on a wall, in the ceiling or in rare cases, on the floor of older homes. This area is the chamber behind or below the air filter depending on if the filter is located behind the grill or located under the air handler unit.

Cleaning out this area is very easy. Simply open or remove the grill (which ever applies).  Then, using a good flashlight, survey the area to determine if any build up is present and just how dirty it actually is.  Carefully vacuum out the box. Having the return plenum sealed while you have it open will reduce debris build up as well as dramatically increases the air quality of the home. A sealed plenum reduces cleaning and maintenance on the HVAC system's coil and ducts.  Sealing the plenum is easy but depending on how tight the space is, it may take some time to cover all the seams and joints with a sealant.  If your return plenum was built correctly, it will be lined with drywall or another approved material like fiberboard.  You shouldn't see framing like studs or the sole plate of the wall or any fiberglass batt material. Be sure to choose a sealant that is approved for indoor use by reading the product label.  You will be breathing the sealant fumes until the sealant cures.  

While you're at it, look for water stains in this area and check to see if air is getting past your air filter.  This section might not apply to those of you who have an inline HEPA filter.  If your air filter is located below the air handler, remove and look into the lower panel on the air handler to see if it's dirty in the fan area.  If you filter is located behind the grill, the 1" lip where the filter sits will show dust that has missed the filter (blow-by).  If you find dirt has bypasses the filter, consider relocating the filter from the under air handler to a return grill filter type.  If you already have a return grill filter, consider weather stripping the 1" lip so the stripping is between the filter and frame.  This will form a good seal and prevent blow-by.  

If your air handler/furnace/coil are located directly above this area, there is a good change water has overflowed or will over flow the A/C's primary drain line.  Consider installing a primary drain overflow kill switch especially if you have any carpet or wood flooring you don't want destroyed if the primary drain does overflow.  Maintaining your primary drain by pouring about a cup of bleach in the beginning of the primary drain will help prevent these overflows.

Frequency: Check every three years

Difficulty: Easy

Tools Required: Household vacuum cleaner and a screwdriver

Completion Time: 15 minutes

Regardless of they type of house you have, there are some necessary tasks you will have to do stay on top of things.  Learn more and keep up with your house with a free My Healthy House.com profile.  Stay tuned and make your house the best it can be.  

If you have any comments or suggestions on how this blog can be improved including suggested articles or constructive criticism, please send us feedback.

© Healthy House, Inc. 2009

Utility saving case study. How much can you save?

Have you ever taken a close look at your home's utility usage and what you can do to reduce?

I did a utility consumption study on my home recently just to see if a few cultural/behavioral changes made any measurable difference in my overall utility bills from one year to the next.   I'm adding actual data from my personal home in the form of graphs from the City of Austin to illustrate the study.  

We have a 1994 single story all brick 2,100 square foot home in Austin, TX that has a gas water heater and furnace.  However, the gas utility was not part of this study simply because there was no real change in that particular service based on the changes we implemented.  I might also add that the year 2009 in central Texas was one of the heaviest droughts in history and still our usage dropped simply by paying attention to what we do on a daily basis.

My wife and I are 42 years old with two children (ages 7 and 9).  

Electrical savings
During the year 2008, we lived normally.  The only cultural/behavioral changes made in 2009 were the following:

• Night lights used during the night were changed from the sensor type to manual switch type.  They were manually turned on just before bed and turned off each morning upon rising.
• The HVAC's programmable thermostat was adjusted one degree higher in the summer and one degree lower in the winter.
• All unused appliances were unplugged including toaster, coffee makers, battery chargers, phone chargers, etc.
• We turned off our 3-4 computers each evening when going to bed and turned them back on when needed.
• Tried to be diligent turning off lights when we were not in a particular room.
  
• It seems I was a bit more aggressive on paying attention to these proposed changes from June on based on the graph below.  I'm betting the results would have been substantially better if the plan were followed more closely all year.
  

The overall cost of electricity for our house in 2008 was $1,495.60 for a total of 15,571 Kilowatt hours.  Comparing that to the electrical cost of 2009 at $1,259.93 for 12,725 Kilowatt hours resulted in a savings of $235.67 over 2009.  We lowered our monthly average electrical cost from $124.63 to $104.99 per month. 

Water savings

• When we went to the bathroom and only liquids were deposited, the commode was only flushed once every two to three uses.
• The irrigation system was turned on in May and turned off in September but left on all year in 2008.
• When brushing teeth or shaving, the water was turned off.
  

The overall cost of water for our house in 2008 was $896.66 for a total of 209,900 gallons.  Comparing that to the water cost of 2009 at $388.35 for 92,600 gallons resulted in a savings of $508.31 over 2009. We lowered our monthly average water use from $74.72 to $32.36 per month. 

So, by slightly adjusting the way we think about using water and electricity, we saved  $743.98 in 2009.  We will continue making slight changes in 2010.  Some of those changes will be sealing our HVAC ducting and better weatherproofing our home starting in January 2010.  Check back next year to see the savings.


One of the features we plan on implementing on http://www.myhealthyhouse.com are ways to monitor a home's utility consumption as well as teach homeowners what they can do to save money.  Learn more and keep up with your house with a free My Healthy House.com profile.  Stay tuned and make your house the best it can be.  

If you have any comments or suggestions on how this blog can be improved including suggested articles or constructive criticism, please send us feedback.

© Healthy House, Inc. 2009

The importance of replacing your HVAC air filter

Clean air filters keep your HVAC system and the air you breath clean!

Your HVAC (Heating, Ventilation and Air Conditioning) systems air filters should be changed not when they're dirty but on frequently planned intervals. Your home's air filters are like your cars oil filter. Only clean oil works effectively as a lubricant. If you wait to change your car's oil and filter when it’s dirty, the performance and fuel efficiency of the engine decreases. This is the same for your home's HVAC system.  

There are many different kinds of air filters. Each has pros and cons. Below  is a list of most filters available from cheapest to most expensive:

• 1" unframed spun plastic cut from bulk material.  This material is the cheapest.  It does not have a frame so it fits poorly and allows many particles to escape the filter.
• 1" framed spun fiberglass.  These are usually blue or white.  They are low cost but do not capture small particles.  They must change often (monthly).
• 1" framed pleated paper media.  These are usually gray or white with deep one inch pleats. The cost can be up to five times a fiberglass filter.  These are preferred as the most effective filtration material.
  
• 1" washable media.  These area usually black in a metal silver colored frame.  These last longer but must be washed and dried monthly creating quite a hassle.
• Return air grill HEPA filter system.  This a four inch deep pleated filter with a 1” extension frame that fits existing return air grills where the air is returned to the HVAC system.  They are more costly than 1” pleated filter but last much longer and filter more material resulting in fewer changes per year.  Typically, this type of filter is changed twice a year.
  
• The in-line HEPA filter fits in box next to or under the HVAC system.  This system last much longer than a standard 1" pleated filter thus requires fewer changes per year.  However, the initial installation of the in line box is more costly to install.
• Electrostatic filter systems.  These are electrically charged so there is a risk of electrocution.  Since the system is permanent, it lasts longest but is costly to install but this system filters the most material.
  

Filters should always be changed or cleaned based on the manufacturer’s recommendations. It is probably the easiest thing to do to keep your HVAC system clean, running efficiently, reduce your maintenance costs and extend the overall life of your system.


Most homes have the filters located as the first point of air intake but some have them located near the main HVAC system as an inline box. If yours is not part of an inline system, it will be located on a wall, on the ceiling, under the furnace or more rarely, in the floor. It is almost always located near the HVAC unit’s thermostat. Since room temperature air is pulled from the house into the return plenum where the filter is located to be heated or cooled, measuring the air temperature with the thermostat near the return is just makes sense.


You home's filters are installed using one of three methods. In most cases, the filter is located in a return air grill that folds open to reveal a one inch frame that holds the filter. If the furnace is in a closet, it may be located under the furnace’s blower unit.  These are usually either held down with a U-shaped wire or end clip.  A HEPA (High Efficiency Particulate Air) is usually slid into a 4" or 5" wide in-line HEPA filter box either under the blower unit or before the furnace (if the system is horizontally oriented). HEPA filtration is considered the best type of filtration since it stops the smallest particles from entering the core of the HVAC system. Only electrostatic systems can filter out more than a HEPA filters. In most cases, the in-line filters are simply slid out and new filters slid into their place. By far, the most difficult filter to change is the one that fits under the blower and is held down by the U-shaped wire or end clip. This design seems to be weak and allows the edges of the filter to be pulled up by the vacuum of the blower when the unit is on.


It’s always a good idea to have more than one filter on hand for each size your house uses. This will save you from having to make special trips to the hardware store for this frequent and very important task. Filters are not created equal so decide which system is right for your home but try to choose a filer with a sturdy frame. I personally use a Honeywell 4” HEPA return grill filters that fit in my home’s ceiling return air grill. This is a specially designed filter that uses the in-line HEPA concept but allows you to insert in to a standard 1” return air frame. They are not easy to find and I’ve never seen one at a hardware store. I use “return air grill media filter" as keywords to search the Internet for companies that sell this unique filter. Buy a case at a time and you’ll have several years of filters on hand.

Regardless of they type of house you have, there are some necessary tasks you will have to do stay on top of things.  Learn more and keep up with your house with a free My Healthy House.com profile.  Stay tuned and make your house the best it can be.  

If you have any comments or suggestions on how this blog can be improved including suggested articles or constructive criticism, please send us feedback.

© Healthy House, Inc. 2009