I know I need AC and heat work, but how can I decide what I really need, without pressure from a sales person in my home?


Replacing Your Air Conditioning Unit

AC and heat systems are machines that wear out with age, like a car. As they get older, they require more frequent repairs, and lose efficiency and capacity.

A system that was 4 tons 12 years ago may only be producing 3.5 tons today. If your system is not keeping up, don’t assume you need to “upgrade” to a larger unit on your new system. Generally, Texas AC systems work hard, and start showing wear after 10-12 years. A 15 year old system is tired. You don’t have to wait for the system to die to replace it. An older system may well be 1/2 the efficiency of a newer one, so the power savings can pay for the new one alone.

As a rule, if the outdoor coils look beat, corroded, and dirty, and the air coming from the top of the unit is uncomfortably warm, your outside unit has probably lost its capacity to condense properly, and is wasting power. Replacing this unit will usually mean replacing the indoor coil as well, since you will probably be switching to the new R410a refrigerant, now required in all new systems. If you have gas heat, the coil is a separate box on it’s own, but if you have electric heat, the coil will be part of the air handler, which is blower, coil and electric heat strips in one.

Replacing an outdoor unit on a system with electric heat will mean replacing all the equipment. The gas furnace, on the other hand, you may or may not replace. They tend to work less in South Texas, so they don’t age as fast. The real concern with furnaces is that the heat exchanger may crack with age, and possibly introduce dangerous combustion gases into the home air flow. Truthfully, a minor crack in a heat exchanger may be almost impossible to check, but there are accepted procedures to do so. Another concern is rusted out burners, that can present a fire hazard. Generally, any sign of substantial rust is a good reason to replace a furnace. Rule of thumb: Systems 12 years old; consider replacing. 15 or more: Replace.


Energy Efficient Air Conditioners

Efficiency costs money, and sadly has little resale value. You must judge savings in power vs. time you will own system.

Minimum system seer is now 14, and your 12 year old system is probably 10 or less. You are already getting a 20% improvement or more. The cost upgrade to a 16 seer will probably cost 5-6 years to recover. What you need is a heat load analysis to figure out the savings. This will also determine the correct capacity requirements of your new system. Of course, if your old system seemed to work well, then you can replace with the same size system.

Another concern over efficiency is that super efficient systems tend to have larger coils and operate at somewhat higher temperatures. The downside is that while temperature efficiency is increased, the humidity removing capacity is reduced. A super efficiency system can actually make your home less comfortable in our humid Gulf Coast climate. The best solution is to get a two speed system that operates at low speed for a longer period, and removes humidity and runs highly efficient. Some contractors actually use undersized evaporator coils with thermostatic expansion valves to run them colder, and squeeze the most humidity possible out of the air. Actual efficiencies this way, however, are probably 12-13 seer.


Types of Residential Air Conditioners

In today’s competitive market, most manufacturers produce several lines of equipment to compete on all levels. I generally classify them into three groups.

Base line or “builder’s grade “ systems: These are mass produced standard efficiency systems that appeal to home builders, and other large volume markets. While not shoddy, they lack the safety features, and durability features of better lines. Many brand name manufacturers sell their products under other obscure names at a discount, to capture the low end market without attaching their name to “cheap” equipment. Often the same machine with a different tag.

Standard or medium efficiency systems: The systems most often purchased and installed, 13-14 seer range, with a variety of base warranties and simple add-ons, such as a loss of pressure switch, or hard start kits included. Usually features brand names.

Super efficiency and multi-stage systems: The best built systems, with efficiencies 15-18 seer, often two speed or dual capacity compressors. Usually utilize variable speed blowers as well. Warranties tend to be extensive, often 10 years parts and labor. These are the flagship models of any brand. If you want lowest sound levels, highest temperature control, highest humidity control, and greatest durability, these are the systems you are looking for. Usually these systems are offered by the more experienced and qualified dealers as well. Prices will reflect all of this.

All in all, brand choice should not make or break your deal. The installing contractor makes all the difference, both during the install, and in aftercare. It is well known that more equipment failures are due to poor installation practices, than faulty or bad manufacturing.


Choosing a Houston AC Contractor

Probably your biggest AC installation decision lies here.

First of all, your installer must have a Texas State Air Conditioning Contractor’s license. This means he has passed a state exam, and provided proof of liability insurance. This contractor’s license is not to be confused with a technicians license, which is another card that appears similar, but requires only a $25 fee to the state to register, and requires no experience or exam. It also does not give the holder the right to contract AC work, but only to work for a licensed contractor. Only you can verify the qualifications of your contractor, but you should be able to get references.


Upgrading Your Air Conditioner

If you change your condenser (outside unit), you may want to include a new electrical disconnect box at the unit, and a new weatherproof flexible “whip”.

Your existing concrete pad may be too small for the new unit, or damaged, and can be replaced with a new lightweight concrete pad. If you change your evaporator coil, it should include a new secondary, or emergency drain pan as part of the price.

You may want to add a secondary float switch, that will shut the system down if the secondary, or emergency drain pan backs up. Could save you a sheetrock ceiling. (Note : Vertical units, installed in closets have no secondary pans, but often a secondary drain pipe will be connected.) Your new installation may include a new supply plenum, which is the metal box connected to the coil that all the room ducts are connected to. The new plenum will be mastic sealed to the new coil, and the ducts start collars, or connecting points. The primary drains will connect to the coil, and must flow downhill.

If you change your air handler (electric heat) you should get a new drain pan that is larger than the whole air handler. The air handler will connect to your existing electric power lines and ducts (unless you get a new plenum). The return air side (entering from your intake) may be reused, or optionally the return plenum may be replaced. This is usually field fabricated in duct board, which is a semi-rigid fiberglass duct material. When finished, all the duct connections should be sealed airtight with a mastic sealant.

If you change your gas furnace, several things must be looked at:

  • Gas furnaces can be dangerous if installed incorrectly. Proper clearances must be met, gas lines installed leak proof, and in a manner so it cannot be easily damaged.

  • The vent pipe (flue) through the roof must be up to code, installed without screws, and properly terminated.

  • Thermostats are not automatically changed with a system change out, since many homes already have good electronic thermostats.

  • Older mechanical units with mercury bulbs are obsolete, and we now use electronic thermostats on all systems. These are available programmable, and non-programmable, to suit your preference. Several newer models are touch screens, with no external mechanical switches. Prices vary from $40 for a basic one to over $500 for top of the line programmable. Hint: for durability, stick with a brand name thermostat.

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