In General

How does an air conditioner, heat pump, furnace and thermostat work?
How long should it take the air conditioner to cool or heater to heat my home?

Maintenance

What maintenance can a homeowner perform?
How often do I have to change my filters?
Where are my filters?
What type of filter should I use?
How do I replace my filter?
How often do I need professional maintenance on my HVAC system?
How often do I need my motors oiled?
How often do I need my ducts cleaned?

Furnaces

Where is my furnace fuse and how do I check it?
Where are my circuit breakers and how do I check them?
How do I light my furnace pilot?
What is a cracked heat exchanger and can it be fixed?
What will PG&E do for me?
Is it OK for the painters and sheet rock guys to run the furnace?
I occasionally smell gas near the furnace. Is that normal?
Why should I have hard pipe through the furnace's sidewall?
What is the problem with copper and brass gas connectors?

Air Conditioners

Where are my air conditioner fuses and how do I check them?
Where are my circuit breakers and how do I check them?
Do I need to add refrigerant to my system on a regular basis?
Do I have to repair a refrigerant leak?
Can I get Legionnaires disease from my air conditioner?
What is a micron gauge and why is it important?
What is superheat and subcooling?
 

Thermostats

How do I use my thermostat?
What temperature should I set my thermostat for?
Should I maintain a minimum temperature when I'm gone or just shut it off?
Will a programmable thermostat save me money over a mechanical 'stat?
I have a heat pump thermostat. How is it different from a gas furnace 'stat?
What is emergency heat on my heat pump thermostat?
I have a Sta-Tech system. What do I do?

New Equipment Installation

Which brand is best?
What size should my heater or air conditioner be?
What size should my ducts be?
What SEER rating should I get?
What AFUE rating should I get?
What's the most important factor in purchasing a heater or air conditioner?
Will a new heater or air conditioner pay for itself in a few short years?
What about the sales pitch that proved a new system would pay off in no time?
Do I have to pull a permit with the city or county?
Can I install a new air conditioner on an old furnace or evaporator coil?
Can I install a new furnace or evaporator coil on an old air conditioner?
Can I use my old ducts with my new equipment?
Can I use my old refrigerant lines with my new equipment?
What is the new 13 SEER standard about?
What effect will the new 13 SEER standard have?
What are the new Title 24 duct standards about?

In General

How does an air conditioner, heat pump, furnace and thermostat work?
Goodman has succinct explanations with good illustrations on their "Heating & Cooling 101" tab. The howstuffworks articles on air conditioning, heat pumps, heating and cooling system basics, and thermostats go into more depth. Their short video on air conditioning is excellent. Unfortunately some of their links lead to energy efficiency sales material that advocates the use of cooling hours as a method of calculating energy savings. I've commented on that issue here and here. Wikipedia also has some interesting articles that cover the topic rather broadly here, here, and here. And of course I cover a myriad of topics on this site, including my HVAC 101 articles which can be best found by looking at the site map.

How long should it take the air conditioner to cool or heater to heat my home?
Few homeowners realize that their HVAC system is not specifically designed to recover from a high or low temperature. Rather, it's specifically designed to maintain a particular temperature. For central Contra Costa a common design temperature during the summer is 97 degrees outside and 75 degrees inside. What that means is that a properly designed air conditioner will run nonstop to maintain 75 degrees inside when the outdoor temperature is 97 degrees. No where in the design criteria of an air conditioner or heater is there a number that tells us how quickly a system will heat or cool. How long it takes will depend on your home's mass, insulation, shading, etc. There are many good measures of how a system is performing. Recovery time is not necessarily one of them.

Maintenance

What maintenance can a homeowner perform?
Most manufacturers will tell you in their owner's manuals. Typically they recommend filter changes at a particular interval. That is the single most important thing you can do as a homeowner. If you do nothing else change that filter! They also often recommend that you hose off your outdoor condenser yearly AFTER first having disconnected power to it. You should keep flammables away from the furnace and airflow obstructions away from the furnace and condenser. Consult your owner's manuals for specific instructions for your particular equipment.

How often do I have to change my filters?
That varies tremendously. Typically a residence doesn't need it changed more than 4 times a year. Often I find that just twice a year is enough. You may have noticed the filter manufacturer telling you to do it monthly. However, I've found only a few instances where that was true. If you're not sure, pull it out every so often and look at it. Ask yourself if the amount of dirt you see is enough to impede airflow in a substantial way. If not then put it back. Believe it or not a slightly dirty fiberglass filter will clean the air a little better than a new one. There are other variables and other types of filters. If you're not sure then replace it.

Where are my filters?
That varies tremendously. They can be in the furnace blower compartment, above the furnace or below the furnace. They can also be in one or more return air filter grilles that sit in the ceiling or on the wall. There are other possibilities. I'm hard pressed to tell you exactly without seeing your equipment. See the description below of how to change your filter for more details.

What type of filter should I use?
Under normal circumstances I recommend inexpensive filters. That's because a typical HVAC system suffers from low airflow, especially residential systems. Most duct systems, especially the return duct, are undersized considerably. Putting in high efficiency air filters only compounds the problem because they restrict airflow much more than the inexpensive filters. The so called washable electrostatic air filters are sometimes even worse. And to top it off, the increase in air quality is negligible when you consider how most people use their HVAC systems. An average house will exchange its entire volume of air with the outside eight times per day due to natural infiltration. When you consider all the hours in a year your HVAC system doesn't run a whole lot, especially in our relatively mild climate (locally at least). As such those expensive filters don't stand a chance against a typical home's natural air infiltration rate unless you take take proper measures.

Of course there's nothing wrong with high quality filters as long as the system is designed so that you'll have proper airflow with them in place. The Indoor Air Quality section of the installation page expands on that idea. And the last of the three paragraphs on mold brings up one reasons why you may not want high quality filters even if the system is designed for them.

How do I replace my filter?
This will vary tremendously from house to house. In all instances the filter's arrow should be pointing in the same direction as the airflow. Anytime you need to open the furnace you should turn the power to it off first.

• If your filter is in the return grille (some call it the cold air return or suction vent), there may be two little levers or two little nuts that you can turn by hand. The face of the grille will then swing open granting you access to the filter. The filter should sit in the frame of the grille and not above it. If you have more than one "return air filter grille" then each one should have a filter. If it's in the ceiling then you might want to turn the fan on. The suction will probably hold the filter in place so it doesn't drop on your head as you open the grille. But it may not, so be careful or you'll end up with a dirt in your face.
• Even when you don't have a return air filter grille there are occasions where people will unscrew a standard grille from the wall, ceiling or floor and stuff a filter in there. It's always a good idea to take a flashlight and look inside your return grille to make sure someone hasn't stuffed a filter in there.
• In some cases your filter will be above the furnace. There may be a door built into the sheet metal box on top of the furnace. Or you may have to take the blower compartment door off to access the filter through your furnace.
• In some cases your filter may be below the furnace. Under those circumstances you typically need to take both doors off of the furnace to access the filter. In some circumstances the filter just slides out through a slot that's under or next to the furnace.
• In some cases you may find that the previous tenant or owner didn't leave a filter in place at all. You must correct that immediately. If you believe it's been that way for an extended period of time then you should have the system inspected for fouling of the blower wheel, evaporator coil (if you have AC), etc.
• If the filter has a cardboard frame then it is most likely intended to be disposable. Your local hardware store will most likely have what you need. If they can't match your size exactly then get one that is just a little too big and fold over the excess. As mentioned above, I prefer cheap disposables over the more expensive variety because they breathe better.
• If the filter is a fairly heavy plastic material with a rigid frame then it is most likely a washable electrostatic air filter. Those can be hosed off. Use detergent if it's especially dirty. As I mentioned above, washable electrostatic air filters can be very restrictive to airflow. You might consider downgrading to a cheap disposable filter.
• If your filter is a light plastic material without a frame then it may be what's referred to as hog hair. If in good enough condition it can be washed out, dried and reused.
• If your filter has a cardboard frame and is several inches thick then you might have a media filter that will need to be purchased through an HVAC contractor, plumbing supply or something similar.
• If your filter is several inches thick with a removable core and plastic frame then it may be a Space-Gard or Aprilaire air filter. Replacing those requires a bit of effort that should be described on the replacement media's box. The replacement media will probably have to be purchased through a contractor or online.
• If you have a powered filter then it is most likely an electronic air cleaner (EAC). Those typically have two prescreens and two cells that need to be cleaned. Turn the EAC's power off. Take note of their position and direction before you remove the two cells and two prescreens. They only work correctly when installed in a very specific position and direction. I recommend soaking them in hot water with a mild detergent followed by a rinse. The next best choice might be to take them outside; spray them thoroughly with a mild detergent; let the soap work for a few minutes; and then rinse. Some EAC manufacturers suggest washing them in a dishwasher. I advise against that due to the potential for damage to both the EAC components and your dishwasher. Use caution because the cells often have thin metal blades or fins that can cause injury. The cells and prescreens must be bone dry before you reinstall them or you run the risk of shorting out your EAC.
  (These instructions are generic to the old fashioned EAC. There are quite a few relatively new products on the market such as Trane's CleanEffects filter that have very different cleaning procedures. Always follow manufacturer instructions for servicing your powered air cleaner.)

Always use common sense safety precautions when servicing your filters. If you are not absolutely certain of what you are doing then do NOT proceed. Call a professional.

How often do I need professional maintenance on my HVAC system?
Manufacturers and governing bodies recommend yearly maintenance on your heater and air conditioner by a licensed professional. Yearly maintenance is not a bad idea. But at the same time you should be informed about the realities of maintenance.

How often do I need my motors oiled?
Somewhere between yearly and never. Almost all equipment manufacturers use sealed motors. It's been that way for a lot of years now. However, if you have older equipment then there is no guarantee that your motors are sealed. If not then they may need oiling every one to several years. To further complicate the matter, a very old motor which has not been oiled regularly can be damaged by the addition of fresh oil. Just a bit more explanation of that can be found here.

How often do I need my ducts cleaned?
Probably never. There are rare circumstances in which the service is justified. However, no major equipment manufacturer or governing body that I know of recommends the service as part of routine maintenance. In most cases it's an utter waste of time and money. Read my editorial on duct cleaning to learn more.

Furnaces

Where is my furnace fuse and how do I check it?
Typically your furnace fuse (if you have one) is the old fashioned round type that screws into a socket. Visual inspection is not always reliable. If the fuse window shows damage then it probably is bad. But if not it may still be bad. The surest way to check a fuse is with a multi-meter or continuity tester. If you don't have one, most hardware stores will check the fuse for you and sell you a new one if you need it. Be sure to buy the time delay style that is designed to be used with motors. You may have the t-type or the s-type. If you have a package unit then the only fuses you might have are the same as in an air conditioner. Modern furnaces often incorporate control fuses onto the circuit boards in addition to the main fuse. If you have a heat pump instead of a gas furnace, then the air handler most likely has fuses (IF it's fused) similar to an air conditioner's. Look here to see some examples.

Always use common sense safety precautions when checking fuses. Turn off power to the equipment BEFORE removing fuses. On rare occasion I find the polarity of the fuse holding device reversed, which can make replacing the fuse hazardous. If you are not absolutely certain of what you are doing then do NOT proceed. Call a professional.

Where are my circuit breakers and how do I check them?
You most likely already know where some or all of your circuit breakers are. They can be located in a closet, hallway, garage or some place else. The furnace and air conditioner should each have dedicated circuit breakers, unless you have a package unit - in which case there will be only one circuit breaker. The same is true of a heat pump. The indoor and outdoor sections should each have their own circuit breaker. The furnace circuit breaker should have a single pole (single switch). The air conditioner or package unit circuit breaker should be a double poled breaker (two switches attached to each other). It may be located at your circuit breaker panel in the house or sometimes it's located right next to the electrical meter outside. When checking the circuit breaker always reset it even if it doesn't looked tripped. Some breakers can trip and not look it.

There are always going to be exceptions to just about anything. For example, a ductless mini-split system typically has just one circuit breaker even though it has an indoor and outdoor component.

Always use common sense safety precautions when checking circuit breakers. If you're not absolutely certain of what you are doing then do NOT proceed. Call a professional.

How do I light my furnace pilot?
First you need to be sure that you actually have a pilot. Modern furnaces have eliminated the pilot in favor of hot surface igniters and other similar devices. Attempting to light a nonexistent pilot on a modern furnace could be dangerous. Second, even those furnaces that have pilots often have automatic ignition systems that light the pilot only when the furnace runs. Again, attempting to manually light the pilot of such a furnace could be dangerous. IF you are absolutely certain that your furnace's pilot has to be lit manually then these are basic guidelines:

• Turn the furnace power off.
• Give the furnace ten minutes to expel any residual gas.
• Your furnace's gas valve should have a knob that's labeled in some fashion to indicate three positions: "on", "off" and "pilot". Turn it to the pilot position. If your furnace does not have such a knob then stop immediately and consult the furnace's operating instructions or call a professional.
• There will likely be a button that you push right near the aforementioned knob to allow the gas to flow to the pilot. Or you may have to push the knob itself. Push and hold down the button. If it's quiet enough you'll hear the gas flowing when you push the button or knob. Sometimes it takes a good minute or more to purge the air out of the line before gas is actually flowing to the pilot assembly. If your furnace does not have such a button or knob then stop immediately and consult the furnace's operating instructions or call a professional.
• While continuing to hold down the button, use a long match or other similar device to light the pilot. Do not stare directly into the furnace but rather light the pilot while being offset from it. Should there be any residual gas that suddenly lights you could loose your eyebrows. The pilot can usually be found by following a 1/4" aluminum tube that typically goes from the gas valve to the pilot assembly. If your furnace does not have such a tube stop immediately and consult the furnace's operating instructions or call a professional.
• Continue to hold the button down for one minute after lighting the pilot.
• After you release the button the pilot should stay on. Turn the knob to the on position.
• Turn the furnace power back on.

If the pilot should go out more than once or twice in a season then you may have a problem that requires professional assistance.

These instructions are a supplement and NOT a replacement for the manufacturer's instructions. Always follow the manufacturer's instructions for lighting the furnace pilot. Always use common sense safety precautions when attempting to light your pilot. Turn off power to the equipment BEFORE doing so. If you are not absolutely certain of what you are doing then do NOT proceed. Call a licensed professional. Serious injury and even death can result from using improper procedures.

What is a cracked heat exchanger and can it be fixed?
The heat exchanger is composed of one or more chambers in which the fuel is burned and through which superheated exhaust gases travel. The fan blows air around the chamber(s) to pick up heat and bring it into the house. When a crack develops exhaust gas can escape into the house. A cracked heat exchanger cannot be properly repaired by any accepted trade practice. The heat exchanger must be replaced. If the furnace is very old then the heat exchanger may not be available. In such instances the entire furnace must be replaced. Even if the heat exchanger is available it's not always cost effective to replace it. Pictures and further explanation can be found here.

What will PG&E do for me?
PG&E (the local utility company) performs free safety inspections on combustion appliances. They'll also light your pilot light. It's important to understand that this can be a mixed blessing. PG&E acts very conservatively and has been known to red tag equipment erroneously. Just like any large organization they occasionally have employees who are not entirely competent. Over the years I have personally witnessed many cases of outright bogus diagnoses from PG&E. As I've indicated the same can be said of any large organization. I'm not picking on PG&E in particular. Nevertheless, it's a fact that a typical PG&E technician is not qualified in the same way a competent and seasoned HVAC professional is.

Is it OK for the painters and sheet rock guys to run the furnace?
No. See for yourself here. There are construction heaters built specifically for that purpose. The fact that painters and sheet rocks guys rarely use one is no excuse. Are they properly equipped tradesmen or are they hackers? Your $5,000 interior paint job will cost you $6,500 after you replace a motor, circuit board and who knows what else. Often times customers don't know it was the sheet rock dust and paint that caused the failure. It can take years for the contamination to slowly eat away at furnace components.

I occasionally smell gas near the furnace. Is that normal?
It might be. Read this Honeywell document and learn to learn more. You might be smelling normal leakage or you might have a potentially dangerous gas leak. If you smell gas constantly and/or in areas not near the furnace then you most assuredly have a problem gas leak. Locally at least PG&E will do a free safety inspection.

Here's the rub as explained in the linked Honeywell document: I have dealt with PG&E technicians and even HVAC tradesmen who were completely unaware of the fact that all combination gas valves will bypass a small amount of gas. I have personally witnessed situations where a technician detected normal residual gas and blamed what the customer was smelling on that. The customer then paid hundreds of dollars to have the gas valve replaced only to find out that the real leak was actually elsewhere. If anyone has condemned your furnace's combination gas valve because of leakage then ask them how exactly they came by that diagnosis. Ask them too if they're aware that ANSI allows for up to 235 cc/hr of valve leakage. If they are, then ask them if they know that the only way to accurately measure that leakage is with a Bubble-O-Meter. A fancy electronic gas detector is good at finding gas. But it can't measure how much there is.

Why should I have hard pipe through the furnace's sidewall?
The typical stainless steel flexible gas connector that provides your furnace with gas is very thin compared to the steel pipe that carries the gas most of the way. When the flexible connector goes through the furnace's sidewall there is an opportunity for it to chafe against the furnace and leak. Furthermore, in areas where there is lightening it has been documented that these connectors will sometimes arc to nearby objects and leak. You can see an example of a flex connector failure here.

What is the problem with copper and brass gas connectors?
In the "old days" it was not uncommon for natural gas to contain hydrogen sulfide in concentrations high enough that it would degrade the copper. Federal regulations now limit the amount of hydrogen sulfide to a level that won't adversely affect copper. Despite that copper is still not allowed by many inspectors, PG&E, etc. The brass connectors that were once available have a different sort of problem. Some of them used a solder joint that is prone to failure. The consumer product safety commission issued a warning about them here.

Air Conditioners

Where are my air conditioner fuses and how do I check them?
The air conditioner fuses (if you have them) are typically the cartridge type and will look like little shot gun shells. They'll usually be in a metal box on a wall next to your air conditioner. Visual inspection is not always reliable or possible. The surest way to check a fuse is with a multi-meter or continuity tester. If you don't have one then most hardware stores will check the fuse for you and sell you a new one if you need it. Be sure to buy the time delay style that is designed to be used with motors. If one of your cartridge fuses is blown then the other is likely weak. Replace both at the same time. Look here to see some example fuse boxes.

Always use common sense safety precautions when checking fuses. Turn off power to the equipment BEFORE removing fuses. On rare occasion I find the polarity of the fuse holding device reversed, which can make replacing the fuse hazardous. If you are not absolutely certain of what you are doing then do NOT proceed. Call a professional.

Do I need to add refrigerant to my system on a regular basis?
An air conditioner is a sealed system. You should almost never have to add refrigerant to it unless you have a leak. A good analogy would be that freezer that sat in grandma's garage for 30 years. A freezer works in the same way your air conditioner does. It has refrigerant just like the AC. Yet who ever heard of having to add refrigerant to a freezer? The difference is that a household freezer is made at a factory with stringent quality control in place. Your air conditioner often relies on field installers who got the job because they were low bid.

Do I have to repair a refrigerant leak?
No. The legal requirement to repair a refrigerant leak only applies when a piece of equipment contains 50 pounds or more of refrigerant. Often referred to as Freon or Puron, a residential air conditioner usually contains 5 to 15 pounds of it. A good reason to repair a leak is money. If you have to spend $175 each year to "top it off" then it won't take many years before it would have been cheaper just to fix it. On the other hand, if you only have to fill it every few years and your system is fairly old then the picture isn't as clear.

Can I get Legionnaires disease from my air conditioner?
Almost anything is possible. But the odds of getting Legionnaires disease from your air conditioner are virtually nil. The bacteria that caused the famous 1976 outbreak was spread by rooftop cooling towers. Cooling towers contain sumps full of very warm water, a perfect breeding ground for bacteria. A conventional residential air conditioner is nothing like a commercial cooling tower.

What is a micron gauge and why is it important?
Anytime the air conditioner's copper lines that carry refrigerant are opened air and humidity enter. Even the tiniest amount of water vapor left in the system will cause acid to form which will eat away at your compressor. A vacuum pump is used to remove water vapor and other contaminants. However, to ensure that all the water vapor is removed the level of vacuum must be less than .07% of atmospheric pressure. A refrigerant gauge would have to have over 1,500 hash marks in the space of less than an inch for it to measure such a pressure. It's not possible. Micron gauges are designed precisely for that purpose. Many if not most HVAC companies don't use micron gauges. Many don't even own one because most customers know nothing about them and because the adverse affects from not using one can take years to manifest (if they manifest at all). See the pictures.

What is superheat and subcooling?
Both terms refer to specific ways to check how much refrigerant your air conditioner or heat pump has. Measuring pressure is the most commonly used method of checking your refrigerant levels. However, pressure alone can be very inaccurate. Certain conditions like low airflow can cause refrigerant pressure to drop even though there's plenty of it. Checking superheat or subcooling is absolutely the most accurate way to check refrigerant levels. Unfortunately it's not often done. While I don't believe it's absolutely necessary under all conditions, I believe it is a necessity any time major repairs are performed and under other circumstances.

Thermostats

How do I use my thermostat?
Go to the thermostat manuals page linked under FYI on the menu above and find your manual. I have a variety of thermostats pictured and their model numbers listed. If I'm not hosting your specific thermostat's manual then there are links at the bottom of the thermostat manuals page that will take you to other sources. If you still can't find your specific model but have noticed other thermostats that look similar then try those manuals. Thermostat programming often follows similar conventions from one thermostat to another. If you have a digital thermostat and still can't figure it out then use the hold button. In almost all cases pressing hold tells the thermostat to hold its current temperature setting and ignore the program. If the thermostat is holding then you should see the word "hold" in the display. Just be aware that once you place the thermostat in the hold mode, it will hold indefinitely. The program is bypassed by the hold function. It'll be up to you to turn the thermostat off when you want the system completely off.

What temperature should I set my thermostat for?
The answer to that is the intersection of what makes you comfortable and how much you're willing to spend. In other words, there's no one answer that suits everyone. Surveys have found that in the winter a setting of about 70 or 71 degrees is what the greatest number of people find comfortable. It is my theory that the local utility company recommends 68 precisely because it's a couple degrees lower than that. What's more is that there are a lot of inaccurate thermostats out there. What you think is a setting of 70 degrees may in fact be a couple degrees higher or lower than that. Uneven houses tend to exacerbate the problem. While the thermostat may keep its area at 70 degrees, other parts of the house may be very different. Ultimately you should pick the lowest temperature in the winter and highest temperature in the summer that you feel comfortable with (and can pay for!). 

Should I maintain a minimum temperature when I'm gone or just shut it off?
In terms of energy savings, shutting the system down whenever possible is always your best option. The idea that letting the house temperature stray too far will somehow cost you more than just maintaining the temperature is an urban legend. However, there are other important factors to consider. The most important of which might be mold. A house that is allowed to cool down too much in the winter or a house where certain rooms are allowed to be much colder than others may develop condensation issues. Form enough condensation and you WILL have mold growing. There are simply too many variables to predict when mold may or may not grow.

Homeowners are strongly advised to be vigilant in controlling mold growth. Due to the impossibility of predicting what effects certain thermostat settings will have on your house, I make no recommendation about those thermostat settings. I merely advise you of some of the possible effects those settings will have.

Will a programmable thermostat save me money over a mechanical 'stat?
It depends entirely on the behavior of the occupants. In some cases the occupants tend to turn the furnace or AC on and forget to turn it off. In such instances a programmable thermostat could save you hundreds of dollars over the course of a year. But in other cases there are occupants who hate running the heater or AC and are miserly. In other words, they tend to run their system only when they feel extreme discomfort and they tend to turn if off just as soon as they can. In such instances a programmable thermostat could actually cost you hundreds in higher utility bills IF it's allowed to run the system when the occupants otherwise would not have.

I have a heat pump thermostat. How is it different from a gas furnace 'stat?
In terms of programming they're usually the same as any other. But unlike an average gas furnace, a heat pump typically has two stages of heat. The first is from the heat pump. It can be thought of as an air conditioner in reverse. The second is electric heat strips that reside in the air handler. Heat from the heat pump typically costs less than half that of heat from the electric strips. Some electronic heat pump thermostats have two lights or some other indicator to tell you when each stage is functioning. Keeping the second stage off will save you money. Typically the second stage activates when you raise the thermostat setting more than a couple degrees higher than the current room temperature.

What is emergency heat on my heat pump thermostat?
Emergency heat is a feature found on some heat pump thermostats. Should the outdoor unit (the heat pump) fail or otherwise give you concern then with the emergency heat mode you can turn it off and rely solely on the electric heat strips. Given the high cost of using only your electric heat strips you should repair the heat pump as soon as possible. In some cases I find that the emergency heat mode does not work due to improper wiring and other reasons.

I have a Sta-Tech system. What do I do?
Sta-Tech was a whiz bang zone system that was installed in quite a few homes locally some years ago. They have since gone out of business. A local entrepreneur provides manuals and other assistance at statechrepair.com. John Otteson owns and operates the business. You can reach him directly by calling (925) 699-4708. He has an extensive background in electronics and can repair your existing Sta-Tech system for a fraction of the cost of an entirely new zone system. If he doesn't answer, leave a message. There are very few service providers that really understand Sta-Tech systems the way John does. He's worth waiting on for a callback.

If you're not sure whether the problem is with your Sta-Tech system, your furnace or your air conditioner then give me a call. I'll help you figure that out over the phone.

New Equipment Installation

Which brand is best?
Any brand that High Performance Heating & Air installs. ;^) But seriously, you simply can't prove which brand is best. The reports from consumer ratings magazines hardly qualify as proof. They simply survey consumer experience. That experience was in fact determined primarily by the contractor, not the equipment. The contractor is the number one factor. Read this essay and believe it! It's unadulterated truth. I say basically the same thing here and here.

What size should my heater or air conditioner be?
That depends on a plethora of variables. Don't let anyone snow you with the "500 square feet per ton" rule of thumb or anything like it. It could turn out to be grossly inaccurate. A heat load calculation is what's required to know for sure. ACCA publishes Manual J, which is considered the standard in size determination. There are many Manual J based software programs that a contractor can use. If your contractor supposedly performed a Manual J calculation in 10 or 20 minutes then be skeptical. A proper Manual J calculation takes much longer, often times hours. Learn more here.

What size should my ducts be?
That too depends. ACCA's Manual D is the standard by which that can be determined. While determining duct size isn't nearly so complicated as determining heat load, it is very important. Make sure your contractor performs a Manual D calculation if you're getting new ducts. Learn more here.

What SEER rating should I get?
SEER is the rating that measures air conditioner energy efficiency. Currently the minimum SEER for an air conditioner is 13. In many if not most cases that is the best choice for our local climate. Higher efficiency models have the potential of being quieter, having more features and (obviously) are more energy efficient. In our relatively mild climate energy efficiency is often the weakest of those three reasons to upgrade to higher than minimum efficiency. The added capital cost can take a very long time to recover on your utility bill. You can see more here.

What AFUE rating should I get?
AFUE is the rating that measures furnace energy efficiency. Currently the minimum AFUE for a furnace is 80 percent. There are models that range from 80 to the upper 90's. The premium for a 90+ AFUE furnace ranges from moderate to high. A less than five year payoff is possible, depending on usage. But don't let anyone snow you. It's not guaranteed. The 90+ furnaces tend to require more maintenance and can have more failures than a basic 80+ furnace. As such energy savings can potentially be wiped out by higher maintenance and repair costs. A deeper discussion with an honest and competent contractor can determine what's best for you. You can see more here.

What's the most important factor in purchasing a heater or air conditioner?
There can be no question about it. The contractor is far and away the most important consideration. The brand you choose, the SEER rating, the type or features of equipment are all second to getting a good contractor. He is the final builder of your product and determines how well your system will work. Remember that you are not buying a stand alone appliance, you're buying a system. The manufacturer only provides the pieces. The contractor determines how they work. See this essay on what that means. I say basically the same thing here and here.

Will a new heater or air conditioner pay for itself in a few short years?
In the relatively mild climate of the San Francisco Bay Area there's almost no chance of that happening. (In more severe climates the odds obviously increase.) That's true even if your old system is 20+ years old. In my experience I find that your HVAC system will comprise less than half of your yearly energy usage. And even when replacing a very old HVAC system, that portion of your utility bill will be reduced by less than half. In other words, saving even 25% off of your total utility bill by simply replacing the furnace and air conditioner is not that common when installing entry level equipment. In some instances your utility bill may actually go up due to changes in occupant behavior. There are indeed circumstances where a new system saves its owner a tremendous amount of money. But in such cases the old system often had defects beyond that of just equipment age. Plus, big energy savings almost always requires the installation of expensive high SEER equipment. Contact me if you'd like further explanation.

What about the sales pitch that proved a new system would pay off in no time?
A lot of contractors are using formulas based on "heating degree days" and "cooling hours" to calculate your energy savings. In my opinion these contractors are a part of the group I refer to in my essay on service calls as energy savings racketeers. The aforementioned formulas often bear little resemblance to reality. In some cases contractors have been known to project energy savings two to three times higher than what actually manifested. A real estimate of energy savings will use your past utility bills to establish baseline and HVAC system usage. From there you can get a reasonably close projection. More on that here and here.

Do I have to pull a permit with the city or county?
In virtually all cases, yes. Unfortunately permits are often not pulled by contractors who "lowball" their price in order to save money and/or time. An article on permits published by the Concord City News is posted here. You can see further explanation here.

Can I install a new air conditioner on an old furnace or evaporator coil?
Using an old furnace with a new air conditioner is not a problem as long as the old furnace can deliver the required airflow. When it comes to the evaporator coil you can sometimes use the old one, but it's not ideal. An air conditioner's capacity and energy efficiency are certified only when matched with the proper evaporator coil and airflow. Since the minimum SEER rating for newly manufactured air conditioners increased from 10 to 13 on 1/23/06, the likelihood of having a problem using old evaporator coils has increased.

Can I install a new furnace or evaporator coil on an old air conditioner?
Usually. While the air conditioner relies on the furnace for airflow, the furnace has no comparable reliance on the air conditioner. The air conditioner's performance should remain unaffected or even improved by the installation of a new furnace or new evaporator coil as long as the tonnage rating is the same or higher.

Can I use my old ducts with my new equipment?
Usually. However it is very important that they be evaluated. Most systems do not deliver the airflow they're rated for because of undersized and leaking ducts. When you don't have proper airflow you are not getting the capacity or efficiency you paid for. Your old ducts may be useable but may need repairs or upgrades.

Can I use my old refrigerant lines with my new equipment?
Usually. If the refrigerant lines are all copper they could potentially outlast three equipment life spans. They may need to be replaced if they're not entirely copper. Some old systems used what looks kind of like a rubber hose. That hose is not likely to last through two air conditioners. If the copper lines are too small for the new equipment then they should be replaced. A reduction in capacity ranging from small to significant will result from using copper lines that are too small. If you're converting from an R-22 system to an R-410A system then there may be the need to change the lines if most of the old oil can't be removed. And finally, if the old lines are severely contaminated from a burn out then it's usually best to replace them.

What is the new 13 SEER standard about?
Air conditioners manufactured after 1/23/06 must meet a minimum efficiency of 13 SEER (Seasonal Energy Efficiency Ratio). What that means is that manufacturers will no longer be able to make the entry level 10 SEER equipment that was so commonly sold. Existing 10 SEER equipment can still be bought and sold. However, most manufacturers have done their best to get rid of their existing 10 SEER supply. Furthermore, some building departments are more strict and will insist that only 13 SEER equipment be installed even if a 10 SEER unit was legally acquired.

What effect will the new 13 SEER standard have?
When compared to the previous minimum of 10 SEER, the most obvious effect is an increase in price. Our industry has already faced a considerable increase in costs due to the worldwide demand for metal. 13 SEER equipment uses a lot more copper than lower efficiency models. Second, system mismatches will become increasingly problematic. I mentioned above that you can put a new AC on an old evaporator coil but that it's not ideal. In some cases that which was once not ideal with a new 10 SEER AC will become a nightmare with a 13 SEER AC. You might need to change the metering device and/or the whole evaporator coil in order for a 13 SEER system to work right. Equipment manufacturers are insistent that the evaporator coil be replaced when installing a new air conditioner or heat pump.

What are the new Title 24 duct standards about?
As of October of 2005 new California Title 24 standards took effect. Title 24 as it relates to HVAC once concerned itself primarily with new construction. But the new standards affect the replacement market in ways unseen before. If you replace any of the three major components of your HVAC system (furnace, AC or evaporator coil) then you may be required to have your ducts tested for leakage. If your duct system exceeds a certain amount of leakage then you may be required to have them sealed. The same goes if you need to replace more than a certain amount of duct. A detailed explanation is here.

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