THE WOODLANDS -- It's an all too common scenario. You find a house you want to buy and have it inspected. The general inspector recommends that the air conditioning system be serviced so you ask the seller to get this taken care of. The seller calls out an air conditioning technician who determines that the air conditioner is low in refrigerant (sometimes referred to by the brand name Freon or Puron), and charges the system so that it will cool properly. What's wrong with this picture?
A sound, properly functioning central air conditioner is a hermetically sealed system. The refrigerant which travels from the outside condenser coil through the refrigerant lines and into the inside evaporator coil and then back out again will never need to be topped-off or added to unless it is leaking somewhere. Your air conditioning system does not consume nor does it burn refrigerant. Once an air conditioning system is leaking refrigerant, this problem will never go away on its own but will only get worse over time as the leak grows in size. A small percentage of the time the refrigerant will be leaking from a valve, seal, or gasket which can be inexpensively repaired or replaced. However, the vast majority of the time, the leak will be in the condenser coil or the evaporator coil itself. When this happens the actual coil or the entire unit will need to be replaced.
The only way to know where the system is leaking refrigerant is to have a leak search performed. A reputable air conditioning contractor who adds refrigerant to the air conditioning system of a home that is for sale or that is under a sales contract will tell the homeowner that a leak search should be performed. Sadly, in many cases the ac technician will not take the time to advise the homeowner of the need to conduct a leak search and the well-meaning seller will believe that he has done his part and had the air conditioning system serviced as requested. In other cases, the technician may recommend a leak search, but the homeowner will refuse in order to avoid what may be a costly repair. Either way, once refrigerant has been added to the system, the air conditioner will keep the house nice and cool until the refrigerant begins to leak out again. In fact, if a system has recently been charged with refrigerant, there is no way for a general inspector or even an ac specialist to detect that the system has a leak.
The catch is that sooner or later, the system will leak more refrigerant. If it's a slow leak, it may hold an adequate charge for a year or two. If it's a moderate leak, it may hold a charge for several months. Sometimes, if the leak is quite large or if there are multiple leaks, the system could lose the refrigerant in a matter of weeks or even days. It is not only costly to regularly add refrigerant to a leaking system, it is also a violation of EPA regulations. If you buy a house and the air conditioner needs refrigerant, a reputable ac contractor will charge it up once or twice (if the leak is not large) but afterwards he will refuse to add refrigerant again until the system has been leak searched and the leaking components have been repaired or replaced. In other words, unless the leak is coming from something simple like a gasket or valve, once ac equipment starts leaking refrigerant, its days are numbered.
Due to the high cost of steel and copper and to the ever more stringent efficiency requirements the governemt has placed on heating and cooling equipment, these are among the most costly appliances a homeowner will have to replace. Purchasing a home with used air conditioning equipment is definitely a case of buyer beware. If an inspector recommends that the air conditioner be serviced, tell the seller that if the ac technician has to add refrigerant, you want the ac system leak searched at the same time and request an estimate for the cost of repairing the leak (or replacing the leaking equipment) before you close on the house.
The possibiity that you may have to replace the condenser unit and/or the evaporator coil is not the only problem with buying a home with an air conditioner that has been topped-off with refrigerant. When the refrigerant leaks again (and it will), the system may run constantly causing either the condenser unit or the evaporator coil to freeze-up. The freezing up and the subsequent defrosting of the evaporator coil (most often located in the attic) can lead to serious water damage.
A final note: air conditioning systems are best inspected on hot, humid days. If the temperature is too cool, it will be impossible for an ac technician to get a dependable pressure reading and determine whether the system is properly charged with refrigerant. This means that he will not be able to tell if the system is leaking refrigerant. Likewise, rainy days can make accurate refrigerant pressure readings impossible and will also prevent an inspector from opening the outside condenser unit to inspect the electrical components.
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