SEER is Seasonal Energy Efficiency Rating. It's basically a benchmark that tells you how efficient a piece of equipment may be. Mostly you would use this rating when comparing different brands of equipment, to ensure that you're comparing similar products. A SEER is an indicator of how much electricity you can expect the unit to use - the higher the SEER, the more efficient the unit, and the less power it consumes while cooling your house. Of course, the higher SEER units also generally cost more.

AFUE stands for Annual Fuel Utilization Efficiency, and is a rating applied to gas furnaces. It is similar to a SEER for air conditioners in that it basically tells you how much gas the furnace will burn to heat your home. As with SEER, a higher AFUE rating means less gas consumption (and lower energy bills).

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There is no hard and fast rule, but a standard "rule of thumb" for R-22 home systems is about 15 - 20 degrees cooler than room temperature. So if your home is at 80 degrees, you would expect to have 60 - 65 degree air coming from your vents. This is a very rough approximation, mind you, and depends on many things - for example, if your home is extremely hot 90+ degrees) you most likely won't get that much temperature drop. Also, if your ducts run through your attic, you most likely will not get as much temperature drop during peak summer temperatures.

This could be caused by a number of things - bad indoor blower motor, defective thermostat or fan relay - but often it's caused by the system icing up on the evaporator (indoor) coil. Icing can be caused by many things, but the most common are (a) dirty filters and (b) low refrigerant charge. You can't fix the second, but you can change the filter. If your unit is iced up, here's how to thaw it out:

• Turn your thermostat's Heat-Off-Cool switch to the Off position
• Turn your thermostat's On - Auto switch (the Fan switch) to the On position
• Leave your thermostat in this position for about an hour, or until you feel a good volume of air coming from several vents
• Now turn the switches back to their original positions

Of course, you want to fix the problem that caused your freezeup. If the filter was really dirty, then changing it would probably fix the trouble. However, if the filter was not overly dirty (a light coating of dust, for example), you'll need to call one of the pros at Wrenn to straighten out your trouble.

The short answer is the temperature at which you're most comfortable. Of course, the lower you keep your thermostat in the summer, and the higher you keep it in the winter, the more power/fuel you'll consume so be reasonable with it. Most utilities suggest 78 degrees in the summer and 68 in the winter. Most people think that's crazy, of course, and keep the temperature around 75 year round. A good idea is to check your thermostat with an external thermometer. Buy a decent quality thermometer (they cost around $3 - $5 dollars at most department stores) and check the temperature of your home at various places in your home. Compare that with the setting on your thermostat to see if they match. If not, you may need a new thermostat, or the one you have may simply need to be calibrated.

Generally 12 - 15 years. Of course, this depends on several factors, among them how the system has been maintained, quality of construction, and environmental quality. Regular preventative maintenance has been proven to extend the useable life of your system, but many people only have their system maintained when it breaks down. Quality of construction is another factor. Some lower tier units just aren't built as well as other brands, and they don't tend to hold up well as they age. Units installed in corrosive atmospheres (i.e. chemical plants, etc) or along the coast tend to have short life spans as well. Of course, it's not at all uncommon to come across units which are 25+ years old that are working just fine. The power consumption is enormous, of course, but mechanically those units are in fine shape. I hate to say it, but the units being built today don't look to be able to stand up to 25+ years of work ... if you get 15 years of service out a unit installed today, I'd consider that about right. As with many other things in the world today, air conditioners just aren't "built like they used to be".

If you've built a relationship with your HVAC contractor and have used the same company for several years, the answer is easy - let them do the job. Otherwise, it's time to do some research. Call friends and neighbors, ask for recommendations. Get a couple of estimates (normally these are provided free of charge) and narrow your choices down to 2 - 4 contractors. Call your local Better Business Bureau to make sure all your finalist are in good standing. Ask each contractor about warranty, service, etc - in short, get as much information as you can. After arming yourself with this knowledge, make your decision but remember - the cheapest price is NOT always the best value, and the most expensive price will not necessarily get you the best job.

There are a few things which should set off the alarm bells in your common sense:

• If a salesmen calls you back and tells you "We've only got two of these left at this price" or "We'll knock xxx dollars off if we can start by Monday" or some other hard sell tactic, you're probably better off going with someone else
• If the company asks for money up front, check them off the list and move to someone else - no legitimate contractor requires a down payment.
• If the company wants to do the job on the weekends or after hours, you may be dealing with a "weekend warrior" who may be unlicensed, uninsured, and unbonded. This may not always be the case, of course. During times of peak demand companies often work long hours and weekends to try and keep pace with the demand.
• If the company "doesn't give written estimates", find another contractor. This guy is just looking to get his foot in the door.
• If the company says "we'll do this without a permit so you won't be hassled by the inspectors", find someone else. Either the company is unlicensed or they have serious problems with the local inspection department - either way, not good for you.

Generally speaking, yes you should. If, however, you've recently replace one component, you may not need to replace everything. For example, if your furnace was installed within the last 5 - 7 years you probably will be okay just installing a new condenser and coil. Beware of companies who insist on replacing everything, or who claim that you'll void warranties on your condenser if you don't replace your furnace - that's a load of horse hooey. Your condenser is ignorant of the type of furnace installed with it, and as long as the furnace moves sufficient quantities of air, you should be fine.

Of course, you can usually get a much better deal on a full system. And, an air conditioner should be matched to the correct indoor evaporator coil. Your installing contractor may tell you this, and he would be telling you the truth in that regard.

By doing a Manual J load calculation on your home. Manual J load calcs are worksheets put out by the Air Conditioning and Refrigeration Institute (ARI) that assist contractors in determining exactly what size comfort system should be installed in your home. There are some "rules of thumb" - in our area, 700 square feet per ton - but these don't always work, especially for older homes or homes with a lot of windows and doors. If you're unsure, ask your contractor about doing a Manual J load calculation. Don't be surprised is there's a charge for doing this, however - it takes a good bit of time and specialized knowledge to properly perform a Manual J calculation.

Packaged systems are "all in one" units. They combine a heating unit (aka furnace) with a cooling system, blower, and all the necessary controls and such needed to make the system run. Package units are large, normally much larger than split systems and are directly connected to your home's duct system.

Split systems have separate heating and cooling pieces. The heating section is installed in or under the house (along with the evaporator coil, which is part of the cooling system) and the cooling section is installed outdoors. The cooling section is connected to the evaporator coil with copper pipes - one large and one small. Basically, if you see two copper pipes running from your outside unit into your house, you have a split system.

Often the simplest way to determine this is to look at your thermostat. If you see an Emergency Heat or Supplemental Heat setting, chances are you have a heat pump. Of course, many times the thermostat has been changed, either by the homeowner or a weekend warrior, and the wrong type of thermostat has been installed. You can look at your outside unit; many times the words "Heat Pump" will be on the label somewhere. If your outside unit runs during the winter, then you have a heat pump. Otherwise, you can just give us a call and let us know the make and model of your unit and one of our techs will let you know exactly what you have!

You can, but you may be shooting yourself in the foot. Air conditioners not only cool the home, they also remove humidity. In sub-tropical climates, like the Southeastern US, this is as important as providing cooled air to the home. In order for an air conditioner to remove moisture, the system must be running, and an oversized unit generally tends to run for a very brief period of time and shut off. The system never gets the chance to dehumidify, which results in a cool, clammy home - not comfortable. It's okay to oversize your system a little bit - say 1/2 ton or so - but to double the size needed is just asking for mold and mildew problems, along with poor cooling performance.

All new air conditioners should come with a manufacturer's warranty. Most legitimate contractors also provide you with a one year labor warranty (some more, some less). Generally speaking, there should be NO charge to repair an air conditioner which is less than one year old. That said, there are some instances which could generate a charge for service:

• If the unit was struck by lightning or some other voltage surge, or was damaged by some other act of nature, your manufacturer's warranty will NOT cover this. Normally, however, your homeowner's insurance will cover the cost of this repair, minus any deductible.
• If the damage is the result of negligence (i.e. you didn't change your filter, or your unit is full of dirt and debris), your warranty won't cover this. Preventative maintenance is YOUR responsibility
• If the problem comes from some other area of your system, your warranty may not cover this. For example, if your contractor replaced your outside unit ONLY, and the indoor coil is now leaking refrigerant, your air conditioner's warranty won't cover that - nor would you expect it to. If, however, you had a full system replacement, then (barring natural causes or negligence), your system should be covered for any problem.

Of course, read your warranty papers thoroughly when purchasing a new system, and keep those papers in a safe place. Your equipment warranty is through your manufacturer, but your labor warranty is normally provided by your dealer.

There really is no "normal" cycle for an air conditioner - it all depends on the size of the system, whether it's properly sized for the house, how much "load" (i.e. heat) is on the house, etc Assuming an outdoor temperature of 85 degrees and an indoor setpoint of 76, a system that is properly sized, in proper working order, installed in a home with adequate insulation overhead and underneath with good windows and doors should run about 20 - 30 minutes before cycling off. It would typically stay off about 15 - 20 minutes. Of course, as the outdoor temperature goes up, your unit will have to run longer to compensate for this. When temperatures top 95 degrees - especially with high humidity conditions - you can pretty much expect your system to run significantly longer.

Technically speaking, "Freon" is a trademark used by the Dupont corporation for their line of refrigerant products. It's come to be a standard, however, much like "Xerox" has to the copy industry. Freon - or, more correctly, R-22 - is a chemical that is used by air conditioning systems to move heat. There are many different type and formulas of refrigerant; your home air conditioner likely uses R-22 (although some newer models are using R-410), while your car probably uses either R-12 or R-134a. All these are blends of chemicals; R-22 is actually "chlorodifluoromethane", while R-12 is dichlorodifluoromethane - quite a mouthful, and it's much easier to say "R-22" or "R-12".

Time to remember basic high school physics - There is no such thing as cold, there is only absence of heat. Air conditioners work by removing heat from inside your home, thereby making humans feel more comfortable. Heat is removed by the refrigerant in your system. Your indoor blower pulls warm air from inside your home through your return vents, and pushes/pulls that air over your indoor coil (also known as your evaporator coil). Your evaporator coil is full of refrigerant, and as the warm air passed through the fins of the coil, that air transfers it's heat to the cooler refrigerant inside. The refrigerant is then pumped back outside (the compressor does this) where the heat is dissipated. This is a VERY simplistic explanation, of course.

Your system capacity depends on various things - the size of the condenser, the length of the refrigerant lines, etc. Most systems have the "system charge" stamped on the outside of the unit, but those are simply rough estimates. Your technician can give you a much better estimate of exactly how much is needed after an onsite review of your system and the various components.

Technically speaking, yes you can. However, unless you have an EPA card that says you're certified to possess chlorine-based refrigerant, then attempting to do so would be a violation of the law. I doubt Big Brother is going to throw you in jail for it, but look at it from a cost standpoint: You'd need a set of gauges, a superheat thermometer, and a jug of refrigerant (total cost: around $500), and then you'd need the technical expertise and experience to know how much refrigerant to add (too much is worse than not enough). And, if you add too much refrigerant to the new Scroll compressors, you can permanently damage the compressor ... all in all, you're better off have one of the pros at Wrenn correct your refrigerant charge

In the early days of heat pump technology, heat pumps had a poor reputation for heating - poor, mind you, but well deserved. They produced lukewarm air (if you were lucky and the sun was shining just right) and generally were little better than a space heater. Today's modern heat pumps, however, don't have those problems. Most can produce heat which rivals a gas furnace, and they're extremely efficient. That said - watch out. Some of the less expensive brands use outdoor thermostats to automatically bring the electric heat strips on when the temperature drops below a setpoint (usually around 45 degrees), while better built systems can handle the load even when the temperature drops. Of course, the most important thing about heat pumps is to have the system properly installed and serviced. The old saying "I'd rather have a cheap system put in properly than an expensive system put in my monkeys" makes a lot of sense.

Heat pumps have backup or supplemental heat. Normally, this is in the form of electrical heat strips. These heat strip come on at various times - for example, when the unit goes into defrost, or when the inside temperature drops more than a few degrees below the thermostat setting. However, these strips can also be used to provide heating in the event of a compressor or other system failure. You should not use emergency heating for "normal" heating, however, since it's quite expensive.

That's not really smoke (at least we hope not), but more likely it's steam. Your heat pump is a lot like a frost-free refrigerator - both will "ice up", but both also have a defrost cycle that will help to thaw the system as needed. If you happen to be outside when your heat pump goes into a defrost cycle, you may hear some strange noises (a "whooshing" sound, perhaps, or a loud clattering noise), followed by a cloud of steam coming from your unit. This is perfectly normal - the unit is using the heat produced by the system to defrost itself, and when it's finished it will restart in heat mode and continue to heat your house like always. Of course, if this happens during a mild day, or when there is no visible ice on the coils, you may have a problem - time to call in the pros at Wrenn Heating and Air.

Possibly, but normally this is a sign of a much more serious problem. Often this means your compressor or fan motor has "grounded" or "shorted" out, and these are repairs a typical homeowner normally can't perform. It could be something as simple as a burnt wire, but anytime your 230 volt breakers are tripping it's time to call in the pros as Wrenn.

Not really, but you can certainly help your system to operate at peak performance by following a few easy tips:

• Keep filters changed monthly
• Keep debris and shrubbery away from your outside unit
• Keep furniture and other obstructions away from your vents

Most appliances with a standing pilot will have instructions printed on them somewhere. However, be warned - follow these instructions exactly, since failure to do so can result in explosions or fire. If you're not confident that you can safely relight your pilot, call someone else to do it for your. Our service techs can do this for you, and perform a routine maintenance check while where there.

Yes, we can perform a carbon monoxide test to see if your has elevated levels of CO. However, your best defense against CO leaks is proactive maintenance. Have your furnace inspected annually, including your flue pipe and/or chimney. Be aware of odd odors around your furnace (CO gives off no odor, but often a blocked flue gives off a "gassy" smell, since the burners normally don't operate correctly with a blocked flue). If your flue goes into a common chimney with a fireplace, make sure to install a cap on the chimney to prevent leaves, birds, and other debris from lodging in the chimney. And always, always install CO and smoke detectors in your home - and change the batteries every year!

That depends. If you have a heat pump, and you see water around your outside unit in the winter time, it is probably coming from the defrost cycle. If you see water around an indoor unit, however, this is NOT normal and could potentially cause serious damage to your home. Unless you are confident that you can troubleshoot and repair the problem, it's time to call the pros at Wrenn Heating to handle this situation.

Often this is expected behavior, especially if your a/c is less than 10 years old. Modern digital thermostats incorporate a delay system that doesn't allow the system to come on for 3 - 5 minutes after the call for cooling. Some use a "delay on break" scenario, where the timer starts when the system turns OFF - thereby reducing the lag on the next startup. Some condensing system also have delay timers built into them, which can lengthen the amount of delay. Furnaces have always had delays when turning on. Electric furnaces use sequencers to "stage in" the heating elements, and those sequencers also control when the fan turns on and off. Older gas furnaces used temperature switches to turn the fan on/off; modern furnaces use circuit boards to do this, but both have a 2 - 5 minute delay between the time thermostat calls for heat and the time the blower comes on. This is done to avoid cold drafts. By allowing the furnace to heat up before turning on the blower, we can lessen the impact of the initial blast of cool air while the system clears the duct system.

Modern air conditioning systems often use fan delay timers to keep the circulating fan running after the thermostat is satisfied. The reasoning is pretty simple: The evaporator coil is still cold, so it makes sense to get all the cooling you can for the money you're spending in energy. Furnaces have always run for a short time after the call for heating has ended. This, however, is more of a safety feature than anything else - the fan cools the furnace so you don't have a superheated box sitting in your attic or crawlspace. Normally, your fan should run about 90 seconds or less after turning off your thermostat. If the delay is significantly longer than that. contact Wrenn Heating for service.

A programmable thermostat allows you to set different temperatures at different times of the day. Some of them allow you to program each day individually (these are known as "7 day programmable") while other only allow you to program the weekdays as a group, then Saturday and Sunday individually (these are known as "5-1-1" programmable). Programmable thermostats can save you money if used correctly, and if they fit your lifestyle. If you and other members of your home are always gone during a particular time (for example, if everybody goes to work at 8:00 a.m. and doesn't return home until 5:00 p.m.) then you can set your programmable thermostat to raise or lower the temperature during those times. If your family has a set schedule, then a programmable thermostat will save you money on your power bills.

Most modern programmable thermostats have "adaptive logic" circuits, which is just a fancy way of saying that they will bring the system on early enough to be at your selected comfort level at the time you select - for example, if you program the thermostat to bring the house to 75 degrees at 5 p.m., a thermostat with adaptive logic will sample the house temperature throughout the day and turn the system on far enough in advance to have the home at 75 degrees at 5 p.m. Thermostats without adaptive logic would simply turn the system on at 5 p.m., regardless of the home's temperature.

This could be caused by many things, but is most likely a duct problem. You could have a duct that has come loose or is broken. If the problem has been ongoing, it could be a design problem. Unless you're pretty handy with a pair of snips, it's probably time to call in the pros at Wrenn to take care of this.

In some cases, external forces can cause this - for example, if you cut down a large tree in your yard you may find one room becomes a little warmer in the summer. Inadequate home insulation can cause this problem as well, especially with blown in-type insulation. This tends to pack down over time, ultimately leaving you with poor insulation and poor cooling.