It’s the little details in a project that can be easily overlooked, yet getting those details right can be as important as the rest of the job. In the HVAC industry, it can be something as simple as using the correct wire connectors for the installation.

I found this to be true once when I visited a condominium complex. I was apprised that a condensing unit in the complex was not running. A quick check of the voltage and fuses in the electrical disconnect ruled them out as possible causes for the identified failure. I then dropped the electrical control panel cover on the unit. I found the thermostat wires had separated and were not making contact. Thus, there was no current to the contactor coil.

Fortunately, the transformer was not shorted out.

The problem was that one wire connector was found on the floor of the electrical compartment (See photo), and it was easy to discern why low-voltage wires had separated. The thermostat wires were No. 20 AWG, while the wire connectors originally installed were rated for No. 10 to No. 12 AWG. (See Table 1.)

After installing the proper size of wire connectors, I checked five other condominium units. You’re probably wondering what I found. You guessed it - oversized wire connectors were installed on the five units. My speculation is that the remaining residences in the complex have the same problem. This problem could have turned out to be a very costly service call for all the condominium residents.

Conjecture would point to two groups who would have responsibility for this: the installing contractor and the local code office. Some or all of the following items may be the cause for the problem:

The contractor:

May have untrained installation staff,

Does/did not stock proper materials,

Did not have proper onsite supervision,

Did not inspect finished installations.

The local code office:

May have sent out an inspector who is not certified to inspect HVAC equipment,

The electrical control panel was not opened by the inspector.

Whatever cause(s) for the wire connector problem in this case, the lesson for all of us contractors and technicians is to be careful on the job when installing or servicing equipment, for a simple mistake could cause a big problem later.

Publication date: 01/29/2007