When sizing up a new air conditioner, heat pump, or HVAC unit, it is common to hear the pros throw around terms involving tonnage, saying for example, you need a 3-ton or 4-ton unit.  For reference, 4 tons is about the weight of an adult elephant!  But don’t be alarmed: they’re not talking about the weight of the unit!  This is a throw-back from the 1800’s and the term stuck.  You may also hear pros refer to the capacity of HVAC units in terms of BTUs.  Did you know these terms are related?  Here’s how they originated:

Historical Perspective

Before the modern air conditioner was invented, people used to cool buildings in the summertime using ice harvested from rivers and lakes. Gathering the ice from farther and farther north and shipping it down south, or storing it from winter until summer, meant a lot of ice was lost to melting.  A BTU, which stands for British Thermal Unit, is the amount of heat required to raise 1 pound of liquid water 1 degree.  But, when water is below freezing (less than 32 degrees Fahrenheit), the amount of heat needed to melt ice is 143 BTUs per pound.

How the Math Works Out

A ton weighs 2,000 pounds, so to melt a ton of ice it takes (143 BTU/lb) x (2,000 lbs) = 286,000 BTUs.  How quickly the ice will melt depends on how quickly you heat it.  If you apply the heat uniformly over a 24 hour period, the ice will have absorbed (286,00 BTU) / (24 hours) = 11,917 BTUs per hour.  That number is generally rounded up to 12,000 BTU/hr.  So, a one ton air conditioning unit has the capacity to cool up to 12,000 BTU/hr.

Sizing an AC Unit for Your Home

When comparing costs of different HVAC units, be sure you are comparing similarly-sized units.  Central air conditioning units frequently have the capacity coded into the model number: for example, model RDR36 would be a 36,000 BTU unit, or expressed in tonnage – with 12,000 BTUs being the heat needed to melt 1 ton of ice – the model RDR36 would be a 3-ton unit (= 36,000 / 12,000).

Multiple Factors Affect Sizing

If you have a 2100 sq.ft. home, a 2-ton heat pump will not be adequate; you’ll need maybe a 3.5 or 4 ton unit. Here’s where having a professional who can do a site visit helps. There are many things that contribute to sizing an HVAC system, other than the number of square feet you want to cool.  Here are just a few:

• How well the house is insulated and when it was built
• The numbers and sizes of the windows and doors in the house
• The color of the roof: darker ones absorb more heat
• The height of the ceilings
• The overall shape of the home: long narrow houses lose more heat (through walls) than a more square house of the same size.
• The size of AC’s condenser, and whether it is positioned in the shade or in the sun
• The efficiency of the cooling unit, often expressed as a SEER rating, or seasonal energy efficiency ratio (see our post What’s Your SEER?).

Moral of the Story

Knowing the number of BTUs that will be required to heat and cool your house effectively is not only important in choosing the right size furnace and air conditioning system, but it can also tell you whether your existing system may be too large or too small… yes, a system that is too large will not cool effectively, so bigger is not always better! (read our post Think Bigger is Better?)  Now that you know that tonnage does not refer to the weight of the unit, and how to convert from tons to BTUs, you can more readily compare units. Proving yet again that knowledge is power!

If you live in the Nashville and surrounding area, and need some help figuring out the right BTUs and tons for your home, we’ll be happy to help.  Plus, if you haven’t had your spring tune-up yet, now’s the best time!  Call on us at 615-802-2665.

Cooling an empty house – either when you’re gone during the day at work, or when you’re away for an extended vacation – seems like a bad idea since it uses electricity and energy, and wastes money. So, it’s natural to assume that the best way to save money is to turn it off when not in use, right?  Not so! Here’s why:

While you’re gone, the house heats up, but it does so unevenly – with some areas or materials retaining pockets of cooler air and others having pockets of warmer air.  This can cause condensation inside the walls, around pipes and around windows, while indoor humidity rises.  In Tennessee, it’s like we always say: it’s not the heat, it’s the humidity!  The increased humidity in your home attracts bugs and greatly accelerates mold growth.  Over time, this moisture and mold can damage a house, causing fowl smells, wood deterioration and warping, buckling of wallpaper, peeling paint, and can damage sensitive artwork, electronics, and bottled wine.  High humidity also greatly increases allergens in the air – bacteria, mold, fungus, and dust mites –  which get deposited in your living space.  Remember: the number one thing air conditioning provides is dehumidification!

What’s the Solution?

The best solution is to turn the air conditioning down a few degrees but not completely off when not in use.  If you’re going to be gone for less than 12 hours, we recommend turning the thermostat up by no more than 4-6 degrees.  This way, you won’t come home to a humid, stuffy house and your air conditioner will not have to work very hard to cool the house down to your “normal” setting.  On the other hand, if you’re going away on vacation for a week, we recommend turning your thermostat up by no more than about 7-10 degrees.  This will allow you to save the maximum amount on cooling without risking damage from humidity.  A good rule of thumb to keep humidity at bay is to never set your thermostat higher than 82 degrees.

Programmable Thermostats to the Rescue!

Here’s where having a programmable thermostat is ideal.  You can set it to automatically be a few degrees higher during the portions of the workday when you are away, so you won’t need to remember to do this manually each day. Most thermostats also have an “away” setting you can use while on vacation.  Don’t want to come home to a hot house?  Many smart thermostats give you the ability to reset the temperature remotely, so you can turn down the temperature a couple of hours before you return.

Other Summer Vacation Tips

Do not steam clean carpets during the summer. This will increase humidity and cause moisture to be retained in the carpet and padding (especially if you’re turning the thermostat up!), and thus increases the mold and allergen problem.  It’s best to clean carpets during the winter months, when humidity is lower, and room heat can aid in drying the carpet and pad more quickly.

Do not leave exhaust fans on while you’re on vacation.  This only serves to exhaust the already cooled air and makes your air conditioner work harder.

Remove any standing water in the house – whether from a pet’s water dish (assuming you’re not leaving your pet behind), or in saucers around plants.  Water your plants the night before and pour out any excess water just before leaving.  Many plants are able to take in moisture from the humidity in the air, and leaving standing water around only attract bugs and mold… especially if you are raising the thermostat up several degrees.

Check out our many posts for more helpful tips to get the most out of your heating and air-conditioning year round.  If you live in the Nashville and surrounding area, Interstate AC Service is here for you!  Call on us at 615-802-2665.

Counterfeit and illegally imported refrigerants have existed in the HVAC industry for years. With R-22 increasing in price due to the government phase out (see previous post An Update on the Refrigerant R-22), people are doing anything they can to get their hands on cheaper solutions. Some refrigerants coming into the U.S. from other countries are not just imported illegally, but they are counterfeit, posing safety and health concerns to technicians and consumers. If you are having your air-conditioning system serviced, be alert to the various scams out there!

Unapproved Substitutes

Several companies have been penalized by the federal government for illegally marketing and selling other hydrocarbon products such as ES 22a as a replacement for R-22. (see  EPA vs EnviroSafe and EPA vs Northcutt).  According to the EPA,  use of ES 22a –  a refrigerant meant for window air conditioning units – creates the potential for explosion and fires, and is a serious risk to human health and the environment. R-22 air conditioners weren’t built to handle the level of pressure or flammability these substitutes pose. In particular, R-22a, which uses propane, creates a fire hazard. Approved alternatives to R-22 do exist, such as R-422D, so check with your HVAC contractor.

Unapproved Additives

Some vendors have blended the refrigerant with flammable substances such as propane and butane, or with a pine-scented odorant (see R-22a Safety). These have been sold under the names OZ-12®, HC-12a®, and DURACOOL, to name a few. Use of flammable refrigerants as a retrofit in equipment that was designed for non-flammable materials presents risks to consumers, equipment, and service technicians, and will void your equipment’s original manufacturer’s warranty. There are stories where the compressor burst into flames, the technician sustained serious burns, and the siding was melted off the house!

Counterfeit Refrigerants

Some counterfeit or contaminated refrigerants have counterfeit labels on the cylinders and packaging, so you can’t tell what’s actually inside. Contaminated refrigerants can cause a variety of issues, ranging from increased energy use and decreased cooling performance, to significantly reducing the operating life of your system, and causing injury and equipment failures.  Plus, many counterfeit  products contain ozone-depleting substances which are illegal. In China, 18 people were arrested from 4 criminal gangs, and 5 illegal production facilities were found, along with 11 storage warehouses and 2 sales offices. Over 28,000 canisters of fake R-134a and other refrigerants were confiscated along with 20 tons of raw materials (see report here).

Contaminated Refrigerants

Many refrigerants, including R-22, R-134a, R-404A, and R-410A, have been found to be badly contaminated (see report here). One of these contaminants is methyl chloride (also called R40 or chloromethane). It reacts with the aluminum and metal alloys used in the internal components of your HVAC system, causing corrosion and a volatile by-product that burns on contact with air. Exposure of the system’s contents to air and/or moisture could result in production of a strong acid and violent chemical reaction. This contaminant was responsible for a fatal apartment fire in 2014.

In our next post, we’ll tell you what the HVAC industry is doing to fight back and what you can do to avoid becoming a victim of fake refrigerants.

Perhaps you’ve read or listened to one of our earlier posts entitled “Fix the Refrigerant Leak Now!” so you know how expensive refrigerant leaks can be! With the phasing out of R-22, a “shot of Freon” (as it is often called), could run you $400 or more. And there’s no telling whether that will last a couple of months or a couple of weeks! Plus, it is detrimental to the environment, causing a depletion of ozone in our upper atmosphere. If you recharge the system several times, the oil in the compressor will deplete enough to damage the compressor, and then you may require a major and expensive repair! A properly-working air conditioner does not consume or use up refrigerant, so if it is running low on refrigerant, there is a leak somewhere in the system. But where? In this post, we’ll talk about the most likely culprits.

Schrader Valve

The Schrader valve, also called the core valve, or service valve, is the port you hook up to when servicing the system. That’s why finding a leak here can be so elusive: while it is in use, it doesn’t leak. It’s only when it is not engaged that the leak can be detected. Often, this can be as simple as putting a soapy solution around it and watch for bubbles to form, or using an electronic leak detector. The Schrader valve can become leaky when debris gets stuck in it, or when the rubber o-ring deteriorates. It used to be that to swap out the valve with a new one required removing all the existing refrigerant in the system (pumping it down) first. But now there are some specialized tools that allow you to swap out this valve while the system is still under pressure. After swapping it out, the system can be topped off with refrigerant. Consider yourself lucky if this is the problem because it is easily repaired.

Condenser Coil, Evaporator Coil, or Accumulator

The evaporator coil picks up heat from indoor air, and the condenser coil releases heat into outdoor air, so these coils are essential for heat exchange. Either or both can develop leaks over time. In some cases, you may be able to hear the hissing sound emanating from the coil and can determine where the leak is. What’s more likely is that the coil has developed microscopic “pin holes” in several places. That’s because these coils are typically made out of copper, which is particularly susceptible to pollutants such as formaldehyde which is often found in our homes in flooring, furniture, hairspray, and cleaners. Formaldehyde turns into formic acid which causes corrosion on the inside of the tubing. Ironically, newer systems that meet the government’s mandate for increased efficiency may be more susceptible to these kinds of leaks. That’s because A/C manufacturers found they can raise the efficiency of their equipment by using thinner copper in their evaporator coils, thus allowing faster heat transfer. Some A/C manufacturers have switched to aluminum coils to lessen the probability of this type of corrosion. Heat pumps typically have accumulators made of steel, which will rust over time.  Any of these types of causes are very expensive to address because they require replacement of the coil or accumulator which is a very expensive part, plus it requires a complete depressurizing of the system (withdrawing all refrigerant or “pumping down”).

Joints, Seals, Lines and Tubing

Vibration of running the system, as well as environmental pollutants, can cause joints, rubber seals and copper tubing to weaken, split, separate, or rust. A lawn mower or nail may have punctured a line. Steel parts will rust if not galvanized or made rust-proof. Age is also a factor, because the system is under high pressure causing the walls of the tubing to thin and weaken over time. These leaks can be hard to find and may require disassembly of the unit. To locate the source of the leak may involve injecting a tracer (a fluorescent dye) into the system and then re-checking the system about 10 days later using a UV lamp to see where the dye has leaked out. Once the source is found, the joint, connection, or hole in the tube can be fixed by re-soldering, cutting it out, replacing it or by-passing it. The diagnosis and repair of these conditions can be time-consuming and thus expensive.

A Dilemma

Depending on the age of the air conditioner or heat pump, and the type of refrigerant it uses, you may be faced with a dilemma: You may need to consider replacing it rather than repairing it. Weighing the costs can be tricky, so you’ll want to read our post entitled “Repair vs Replacement.” Keep in mind it is possible to repair one refrigerant leak and have another one develop in a different location shortly thereafter. Whatever you decide, doing nothing is not an option. Sure, the cost to repair or replace your system may be higher than simply adding another “shot of Freon,” but not repairing a leak causes recurring expenses that will only escalate, risks major damage to your system that could be even more costly, and injures the environment.

DIY? Not!

Finding the source of a refrigerant leak requires the use of specialized tools and supplies, specialized training, and is something few homeowners can do themselves.  Recharging the system with refrigerant whether the “old” R-22 or R-410A equivalent, or the new refrigerant R-422 is definitely not something a homeowner can do since it requires a government license to order and use these refrigerants. Depend on the experts at Interstate AC Service to diagnose the source of your leak, fix it, recharge your system, and get your air conditioner operating at peak efficiency.