Watch Those Connections!

Some appliances such as stoves and dryers, do not come with line cords when the appliances are purchased.  As a result, consumers have to make separate purchases in order to use their new machines.  When attaching the cords to the appliance, pay close attention to the way the manufacturer requires that the line cords are connected.  For many do-it-your-selfers, this is no big deal.  It shouldn’t be a big deal for a professional electrician either.  However, we are all human and subject to making mistakes.  Case-in-point: the following dryer fire.  Although minor as residential fires go, the damage could have been much worse.  The photographs shown below illustrate how the manufacturer called for the installation of the line cord and the subsequent way, the cord was connected.

The manufacturer’s schematic drawing shows how the “hot” (red and black wires) lines of the line cord were to be attached to the L1 and L2 terminal block terminals.  The common line or white wire was to be connected to the N terminal on the terminal block.  Lastly, the green wire or earth ground, was to be connected directly to the appliance housing.  The photograph below shows how the white and black wires were reversed on the terminal block.

 

 

Since the common and earth ground points are electrically the same point, the dryer was, in effect, energized through the housing.  Anything in contact with the dryer housing, such as the exhaust duct, will also become energized.  Dryer ventilation ducts are usually coils of steel wire wrapped with a thin layer of vinyl or aluminum material.  As current flows through the steel wire, the external covering is heated.  If not stopped, the heat will cause the covering to melt and possibly ignite.

What’s Going on With Carrier and Goodman?

 

For a number of years, the Carrier Corporation has been manufacturing air conditioning equipment and selling their products all over the world.  Virtually everyone in the HVAC industry and a large part of the consuming public is familiar with the Carrier name.  To a lesser extent, the Goodman Company has also been manufacturing air conditioning equipment.  Although the Goodman Company is not was well known as Carrier, the two companies manufacture some of the same products.  Case in point: packaged terminal air conditioning units or PTACs as they are more commonly known.  These are units that are commonly found in motel rooms.  Recently, both companies recalled some of their PTAC units, Carrier on December 22, 2015 and Goodman on February 17, 2016.  But, the most troubling commonality is that the recalls are for the same problem.  That is, both companies recalled their products because their PTACS were equipped with line cords that could overheat and pose a burn hazard to consumers.  The only reason that line cords overheat is because they are sized too small for the unit’s load; i.e. the unit is drawing more current than the line cord can handle.  How does that happen?  This problem is not something that has been recently discovered.  It is not something that belongs to new technology innovations.  Any company that has been manufacturing an electrical device for any length of time has to know full well what the consequences are of undersized wiring for a specific load.  So, again how do companies like Carrier and Goodman get it wrong?  If the problem can’t be in the lack of knowledge, it has to be in the manufacturing process.  Maybe it’s time for some worker retraining.