What a Way to Blow up a Blower!

Most residential and commercial HVAC equipment use centrifugal blowers to move air through duct systems.  The rate at which blower wheels turn is usually between 1000 and 1500 rev/min, depending on the application.  The point to be made is that blower wheels turn at a fairly slow speed.  Blower wheels that are attached directly to the motors that drive them turn at the rotational speed of the motor.  But, when the blower wheel is belt driven, the speed of the blower can vary depending on the size of the pulley attached to the shaft that drives the blower wheel.  If the size of the pulley attached to the blower shaft is twice as large as the pulley attached to the motor, the speed of the blower will be half of the speed of the motor.  If however, the blower pulley is the same size as the motor pulley, the blower will turn at approximately the same speed as the motor.  If the blower wheel is not designed for such speed, the centrifugal forces created by the rotational motion will cause the blower wheel to fail in a spectacular way.  The photos attached below illustrate the results.   

Blower louvers peeled away from blower ring

View of damage to blower louvers

2019 AHR Expo

Just returned from attending the Air Conditioning, Heating, and Refrigeration Expo held in Atlanta Georgia.  Some of the biggest names in the HVAC industry, such as Carrier, Trane, and York, were in attendance.  Along with cooling and heating equipment, those manufacturers that make specialty items such as boilers, compressors, piping, controls, motors and refrigerants were also in attendance.  Visitors, as well as vendors, came from all over the world to see new product lines as well as to showcase their products.  The trend, as has been the case for several years now, is to make machines more energy efficient.  Incorporating electronics to measure different parameters such as temperature and pressure, is now routinely done.  Depending on the type of equipment, manufacturers are also offering options on how the equipment is monitored.  Some owners prefer to let their on-site personnel keep up with the operation of their equipment while others are connected by internet to a servicing agency.

No matter how efficient or how well built a machine is, it will eventually fail.  Hopefully, when it does, there won’t be any property damage or personal injury.  But if there is,  the information collected during the Expo on various products will be invaluable in helping to determine the cause of failure and subsequent damage.  More specifically, the literature can be used to help identify a machine by model number, determine the pressure limitations, or establish the power requirements.

Fires and Appliance Safety

The weather has definitely gotten colder and heating systems are being put to the test. There are different kinds of systems; electric resistance, gas-fired forced air, hot water, and steam to name a few.  Regardless of the type of system, the potential for accidental fire is part of all heating systems.   During this time of year, it not uncommon for problems to develop which, when left unattended, can result in significant damage to homes and businesses.  For example, furnaces, both gas and electric, should be cleaned at least once per year; at the beginning of the heating season.  Some people think that just because they change their air filters every once-in-awhile maintenance is complete.  NOT SO!  Depending on the efficiency of the filter in use, some dust particles will pass through the filter media and accumulate on blower blades, motors, and heat exchanger surfaces.  The burning smell often detected when the furnace is first started is the result of dust accumulation.  If the furnace is never cleaned, dust accumulation can ignite and spread outside of ductwork.  Similarly, if the controls area is never cleaned, burners can become clogged resulting in poor combustion and sometimes, delayed ignition.  Delayed ignition of gas/air mixtures can become explosive and when ignited, can release a tremendous amount of heat with deadly force.  Poor combustion can also produce carbon monoxide which when inhaled can be deadly, especially to elderly people and young children with respiratory problems.  Similarly, electric heating systems such as heat pumps should be checked for proper operation as well as components that are in good working condition.  One of the biggest problems that should be guarded against is the wiring insulation that becomes brittle with age and cracks.  Exposure of conductors can result in short circuiting leading to a fire which can then spread to the structure.  Just because a circuit is protected with a circuit breaker doesn’t mean that a fire can never develop.  Circuit breakers are current limiting devices NOT thermal limiting devices.  Heat exchange coils, motor, fans, and blowers in heat pumps should also be kept clean.  Heat pumps come in different configurations such as air to air, air to water, and air to ground.  In the last two configurations, a fluid such as water or glycol is circulated to transfer heat to or from the heat pump.  In order to do so, a pump is used to circulate the fluid and must also be serviced at certain times.  Failure to do so can result in pump motor burnouts that could result in fire.  Remember, the pump and its motor are usually two separate components unless intentionally manufactured as a single unit.  Lastly, there is not much that can be done with hot and steam boilers except to make sure that the wiring is in good condition, stack temperature is not excessive, and piping is also in good condition.  Also, remember that piping can also be a source of ignition.  Hot piping can ignite combustibles if contact is maintained long enough.  Maintenance is the key to preventing fires in heating equipment.