Joe Marchese

Repairing refrigeration and air conditioning systems is not always an easy task. Occasionally technicians will encounter multiple problems on one system. If all of these problems are not initially discovered and resolved, the unresolved ones could lead to problems and more costly repairs.

Take this example of a repair scenario that resulted in additional work and a more costly repair:

A service technician is called out to service a computer room air conditioning system. Upon initial inspection, he discovers the main printed circuit board is burnt and needs to be replaced. He calls his office, gets a price on replacing the board, and discusses the repair with the customer. The cost to replace the circuit board is quite expensive - about $2,500. The technician obtains authorization to proceed with the repair, so he returns to the shop, picks up the new printed circuit board, and goes back to the customer to replace it.

Once the board is replaced, the technician goes to turn the system back on. Upon applying voltage to the system, the new printed circuit board begins to smoke and it fails - not a good thing for the service technician or the customer.

What happened? The technician begins to troubleshoot the system to discover why the new board smoked. Upon a detailed inspection, he discovers there is a short within the compressor that is causing line voltage (220 volts) to be fed directly back to the printed circuit board. This compressor has an internal overload that is wired through the low-voltage (24-volt) control circuit and tied into the printed circuit board. The compressor’s internal overload had shorted to the line voltage winding within the compressor.

When the compressor was energized, 220 volts were fed back to the printed circuit board. Now the new circuit board as well as the compressor will need to be replaced - again not a good scenario for the technician or the customer.

After further discussion with the customer, the technician discovers that the building had some major electrical issues in the past week. This could have caused the problem within the compressor that then caused the damage to the printed circuit board.

Could this problem have been avoided? Perhaps. If the technician had asked why the original board failed and what could have caused this to occur, he may have thought to look further into the system to find the compressor problem. This could have prevented damage to the new printed circuit board. Also, if the technician had learned early on that there had been a major electrical issue in the building, he may have looked closer at the system to see if any other components were damaged. This could have also led him to find the problem within the compressor.

Technicians need to think out- side the box and try to discover why components failed. It may not always be easy to find the root cause of the problem, but technicians should attempt to find it. Not doing this could lead to more costly repairs.
Publication Date: 07/07/2008