This page is about preventive maintenance for heating and air conditioning systems and why it is important.
Preventive maintenance keeps your HVAC equipment running with-in design parameters.
All mechanical equipment is designed to operate within certain limits. Air conditioning and heating equipment is no exception, and if not properly maintained, the equipment will exceed its design limitations with the result being earlier equipment failure and higher operating costs.
If preventive maintenance is not performed regularly or if it is done haphazardly, the equipment will require extensive and costly repairs at a later date that is sooner than it should be. This is not just a case of "pay me now or pay me later." It is a case of "pay me now or pay me considerably more, later," and lose reliability while paying higher repair and energy costs in the process.
Your best insurance against HVAC failure and cost containment is preventive maintenance.
Air conditioning equipment is designed to operate with a specific quantity of air passing over its indoor coil surface. When air filters are not replaced, they clog and become coated with dirt. Similarly, the indoor coils get coated with dirt. This dirt reduces the amount of air through the unit below the design limit, leading to higer energy costa and eventual catastrophic failure.
In the cooling mode, if there is not enough air over the indoor coil, the coil temperature drops. When it drops below the freezing point, ice forms on the coil, which further reduces the airflow, which further reduces the coil temperature. The compressor within the unit is a pump, which is designed to pump a vapor. As the airflow through the indoor coil drops, there isn't enough heat being removed from the air passing over the coil to vaporize the liquid refrigerant inside the coil. Thus, instead of receiving a vapor, the compressor receives liquid refrigerant.
This is called "liquid slugging". The effect of "liquid slugging" is similar to the effect of pouring liquid into the cylinders of a gas engine.
As liquids are not compressible, compressor pressure exceeds it's design limits, and the internal componenets are are destroyed little by little and sometimes very quickly. The air conditioning unit starts out requiring that its filters be replaced. Now it needs a new compressor.
Preventive maintenance or a new compressor? Ultimately, it's your choice.
In the heating mode, low airflow causes the heat exchanger to overheat. Heat exchangers are designed to operate at temperature between 120F and 200F. At higher temperatures, the heat exchanger oxidizes, its life-span is reduced, or it cracks and breaks. In either case, It makes far more sense to replace air filters regularly than to replace a heat exchanger costing far more.
Loose or broken drive belts cause the same problems that dirty filters cause. they cause the airflow through the equipment to be reduced below design limits. In addition, loose drive belts slip on the pulleys. This wears the groove in the pulley so that when the belt is replaced, the new belt is ruined in a shorter period of time by the worn pulleys.
Once again during preventive maintenance we must replace the $15.00 belt on a regular basis or spend much more replacing pulleys. (mostly pertains to commercial AC units.)
Air conditioning equipment is designed to operate between certain outdoor temperature limits. Cooling and condensing of the refrigerant vapour is designed to occur with a particular volume of air flowing through the condenser at a maximum outdoor ambient temperature. (Usually 115F)
If the finned surfaces of the outdoor coils are fouled with dirt, the ability of these coils to transfer heat is reduced and the airflow through the condenser coil is reduced (blocked by dirt and dust). When the ability to transfer heat is reduced, the operating temperatures and pressures of the air conditioning unit increase. A unit, designed to operate at ambient temperatures of 115F or more, may stop operating at an outdoor temperature of 90F. Due to the reduced heat transfer capability, the operating temperatures and pressures within the unit exceed the manufacturer's safe limit and the unit shuts down.
If the unit does not exceed the manufacturer's limits by enough to shut down, it will continue to run at reduced capacity and efficiency, and at an increased rate of wear and energy consumption due to the increased work load. A strong reason for preventive maintenance, reducing wear, costs and catastrophic failure.
Electrical relays are designed to open and close a certain number of times with a particular current load, before the contact points are damaged and relay requires replacement. If more than the design current is passed through this relay due to a motor working too hard, or low voltage conditions, the contact points overheat and become damaged. If the electrical contacts in a contactor (large relay) begin to get pitted, and the contactor is not replaced, eventually the air conditioners compressor motor or the fan motor controlled by the contactor will burn up and require replacement. Once again, if we exceed the design limitations of the device, or its anticipated life span, additional damage is caused.
Cheap to replace a relay or contactor during a preventive maintenance when compared with a motor or compressor replacement.
Bearings and other rotating parts are designed to have a useful life span of hundreds of thousands of hours, provided they are lubricated at appropriate intervals and are not overloaded due to vibration from defective drive belts or dirty blower wheels. If bearings are not lubricated regularly, they will overheat and eventually seize. When this occurs, the bearings fall apart, and the blower wheel, shaft, and housing are destroyed.
This is a prime example of a situation where inexpensive preventive maintenance was neglected with catastrophic results.
A unit operating with an insufficient refrigerant charge can ruin its compressor via two scenarios. The unit icing up due to a low-pressure condition causes the compressor to fail due to liquid slugging, as described before. The second type of failure is due to the fact that the compressor requires a certain quantity of cool refrigerant vapour to cool its motor windings. If the refrigerant charge is not sufficient, the motor within the compressor will overheat and burn up.
A preventive maintenance program would spot this condition and save you money.
The scenarios described all cause damage to occur slowly over time, usually without being noticed until catastrophic failure has occurred.
Regularly scheduled preventive maintenance on any HVAC or heating and air conditioning system lowers overall costs. It reduces emergency calls due to catastrophic failures, it results in lower energy costs and lower replacement costs. It reduces repair costs.
HVAC RULE: properly maintained air conditioning and heating equipment operates more efficiently, consumes less energy and lasts longer. Period!
Over the years we have noticed that customers who are well informed and have a basic understanding about Heating and air conditioning make better decisions and quite frankly are far less likely to be talked into a mistake or be mislead by bad HVAC contractors. Over the years they spend thousands of dollars less on energy, repair and capital costs.
Kelly's offers customized preventive maintenance programs designed to suit your specific needs.
Call for an estimate! 714-750-6583