by User Not Found

In our industry, we not only anticipate the change in seasons, but from a business perspective, we like cold winters and hot summers.  It can influence the demand for new equipment and the amount of service needed on installed equipment.  The winter months mean that we’ll be seeing more use of our heating appliances.  During the summer months we have a greater need for our air conditioning and refrigeration equipment.  In either case, the more the equipment operates, the more wear and tear we see on it.

It makes sense that the more the equipment operates, the sooner it will require service or replacement.  But there’s more to it!

Operating cycles are an important factor in product life, but operating conditions also have a tremendous influence on it.  And one of the major factors in operating conditions is temperature.  When materials get hot, they expand.  When they cool, they contract.  In the case of the coils in a motor, contactor, relay, transformer, and the like, as power is applied, heat develops in the winding as a result of resistance through the coils.  As the winding heats up, the circumference of the wire in the winding expands.  It takes sophisticated equipment to measure this miniscule change, but this increase in size puts stress on the insulation that is around the wire.  If the winding temperature exceeds normal operating conditions the insulation will fail, causing failure of the product.  When products identify their ambient temperature rating, this is an indication of what the maximum temperature around that product can be to avoid premature failure.  Usually the ambient temperature is shown in Celsius.  Below is shown typical ambient ratings that might be seen on HVAC/R Motors.

80°C/176°F

70°C/158°F

60°C/140°F

50°C/122°F

40°C/104°F

Typical Ambient Ratings

In order to get the longest life out of a product, it should be matched to the conditions it will be operating within.  It’s probably not a good idea to install a condenser fan motor rated for 40°C in a unit mounted on a restaurant rooftop next to an exhaust fan venting a cooktop.  The additional heat of being mounted in the sun next to an exhaust fan blowing hot air from the cooktop will result in motor failure in short order.  The same can be true for other electrical components.

As a rule of thumb, if the winding temperature of a motor is increased by 10°C/18°F, the life of the motor is reduced by 50%!  This same rule of thumb can be applied to capacitors.  Some capacitor manufacturers say that the number may be as low as 6°C - 7°C/10.8°F – 12.6°F.

Is there anything that can be done to help protect products from damaging heat?

·      Select products by the ambient conditions in which they will be operating.

·      Try to keep products out of the sun as much as possible.  If the capacitor can be mounted on the “north” side of the condensing unit instead of the “south” side, the effects of heat from the sun may be reduced.

·      Do not block vent holes with mounting brackets, covers, guards, debris, etc.

·      Keep coils clean for good airflow.

·      Be sure that the system is properly charged to avoid overheating of the compressor.

·      Check all filter driers to assure that they are not clogged.

·      Allow as much ventilation around capacitors as possible.  Do not

o   Tape capacitors together

o   Install capacitors in their box or original packaging

o   Wrap with foam tape to silence any vibrations

·      Make certain that all electrical connections are clean and tight to prevent heat from resistance.

By being aware of the affect of heat on components, and taking steps to reduce heat where possible, system and component life could be extended.

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