Efficient Air Conditioning

Efficient Air Conditioning – What you need to know

Electricity can be pricey these days. If you want to install or upgrade your air conditioning system, you should be aware that there is a wide range of quality out there. This is one of those things that pays for itself if you have it done properly. It’s worth it to do a little research. If you’ve already been reading up on cooling units, you may have repeatedly come across this acronym: SEER. Let’s discuss this first.

What is SEER? What is the difference between SEER and EER?

SEER (Seasonal Energy Efficiency Ratio) is a measurement of the efficiency of a cooling unit over the span of a whole season. More specifically, it is the cooling output during a typical season divided by the total energy input during that time. EER, on the other hand, is the same ratio applied to a specific set of conditions, instead of the whole season.

So what does all this mean? Basically, a higher SEER/EER rating means a more efficient air conditioning unit. But this rating isn’t everything. In terms of overall energy efficiency, it’s one small piece of the puzzle. Correctly sizing your ac unit and corresponding ducts is necessary if you want the SEER rating to mean anything. You wouldn’t exactly call a hybrid car fuel efficient if it had monster truck wheels installed on it, and you wouldn’t call a 13 SEER 5 ton (large!) air conditioning unit efficient if it’s setup for a house with moderate to low cooling loads. Lastly, if you want to significantly reduce energy costs on air conditioning, you’ll want to tighten up your air sealing and insulation as well.

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Unit size – How do I know the right size for my air conditioner?

Unfortunately, most technicians and contractors do not take air conditioning (or furnaces!) unit sizing very seriously. They will often use a general rule to estimate, and usually end up with an oversized unit. An oversized unit will constantly cycle on and off, resulting in low efficiency and inconsistent temperatures.

A more thorough HVAC technician will use the ACCA manual J and S to determine proper air conditioning unit size and air flow. This approach will determine the cooling load needed for each room, taking into account room size, insulation, building materials, orientation and climate. Add all those room cooling loads up, and you then know how big of an air conditioner the home needs. Ideal efficiency and comfort are achieved by minimizing static pressure (air flow resistance in the entire system), and fine tuning the air flow to each room. Additionally, it is important to size your cooling unit in conjunction with your furnace, since they will share the fan and duct system. Having greatly mismatched units would be uncomfortable, inefficient and could greatly damage your air conditioner coils.

Refrigerant – which is best?

Or first of all, what is it? A refrigerant is a substance that enhances the efficiency of a cooling system by means of a reversible phase transition, between liquid and gas. Water, for example, can be used as a refrigerant in some situations (non residential AC applications). Gradually, we have been discovering that many previously used substances were toxic to humans or harmful to the environment (or both). For example, various types of hydrochlorofluorocarbons (HCFCs), particularly R-22, are now known to cause ozone depletion, and are gradually being phased out, in accordance with the Montreal Protocol, the goal of which is to reduce the U.S.’s consumption of HCFCs by 99.5% by 2020.

But it’s happening slowly. Existing units that have been using R-22 are allowed to continue using it. Newly installed systems, however, are being designed to work with the new line of refrigerants, primarily R-410A, which does not cause ozone depletion. In fact, the Environmental Protection Agency (EPA) has already taken action to drive the price of older refrigerants way way up. It can cost 4 or 5 times as much to service an older air conditioner than a new one that uses R-410A.

Why do you need to know this stuff? Besides the environmental concerns, it’s important to be aware of it, because:

1. If you’re servicing an existing unit, you may have to use R-22, unfortunately, because your older system will not function properly with R-410A. This has become very expensive relative to servicing new air conditioners.

2. If you’re installing a new system, make sure your technician is properly trained in the installation and service procedures for systems that use R-410A. Don’t take it for granted – this is fairly new and not everyone knows how to work with it yet.

Frequently Asked Questions: Air Conditioning

a) How do I find out my Air Conditioner size?

First, take a note pad and pen and go outside to your outdoor air conditioner unit. Look for a label that looks something like this

The good news is, it is very simple to find the size of your air conditioning unit. Find the first number on there that is divisible by 6. In this case it is 60. Now just divide this number by 12. Done! Now you have your air conditioner size. The units are in tons of refrigerant charge. In this case, it is a very large, very oversized 5 ton unit. Units come in half ton increments so don’t be surprised if you see something like 2.5 tons (or “30” as it appears on the label).

Look at the Model # again and write it down along with the Serial, and Brand. You can use these to look up the age and SEER efficiency online (they don’t make it easy on you though).

b) How often should I have my Air Conditioner serviced?

It is a good rule of thumb to get it checked and serviced once a year or just over. The outdoor unit fins can be cleaned, the refrigerant charge should be verified and further charged if necessary. A good HVAC home performance service person can also let you know what the watt draw is.

c) Is 15 SEER efficiency, or higher, worth it?

The answer to this question depends on a few things. If you are already paying a lot in electricity (top tier usage rates) then a reduction of electrical usage is more rewarding due to the fact that it may knock you down a tier or two and therefore lower your month to month rates. The higher your existing electricity bills, the faster the Return On Investment for a 15 SEER+.

Here’s a factor that may seem like common sense to you, but still needs mentioning. Do you use your Air Conditioning a lot? Many people have high tolerance for hot summer weather and only use it 5 to 10 days a year. Many people just set the thermostat to 75 or 78 and let it run whenever they are home. The second type of homeowner could easily justify paying a little extra for a 15 SEER or better.

How old is your existing Air Conditioner and is it oversized? If its over 10 years old then you may want to seriously consider upgrading. Also, most air conditioners are oversized. End of story. It is very rare indeed to find an AC that matches the cooling needs of the home. Contact a home performance professional to calculate the cooling loads of your house and find out for sure. It is a common misconception to think that by maintaining and old air conditioner you will be doing a service to the environment. Older air conditioners use a refrigerant that is very harmful to the ozone. The technician replacing the unit will recycle the units and properly dispose of the refrigerant in accordance with EPA standards.

 d) What other types of Air Conditioners are there for homes?

Air Conditioning units come in various types in a residential setting. The most common by far is a standard split system with an outdoor condenser and indoor coils connected to a forced air duct system. Window ACs are another type and are by and large much less efficient and effective. If you only need to cool a small space then consider a mini split heat pump. Although called a “heat” pump, it can cool as well. The heating aspect of a heat pump is just simply an Air Conditioner running in reverse. There are a variety of heat pumps with a huge variety of applications and efficiency ratings. A “Mini-Split” heat pump numbers among the most efficient and does not require a duct system.

mini split heat pump indoor cassette

Get in contact:

[dropshadowbox align=”none” effect=”lifted-both” width=”640px” height=”” background_color=”#ffffff” border_width=”1″ border_color=”#dddddd” ]For more information about air conditioning, call (925) 363-4498 to speak to a technician or schedule an Energy Assessment. You can also e-mail:  info@epbuilders.com[/dropshadowbox]