Loose Electrical Connections in HVAC Equipment

Loose electrical connections in HVAC Equipment can cause big problems and safety issues with HVAC equipment. A good maintenance check of any HVAC system will include checking for loose electrical connections or wires that are corroded or frayed in some way.

Loose Electrical Connections in HVAC Equipment

The picture to the top left is a picture I took after repairing a large rooftop unit where a loose electrical connection almost started a fire in a commercial building. You will see a large fuse and two smaller fuses that have an indication of smoke on them. There is also a fuse block in the middle part of the fuse block melted completely away.

Aluminum melts at approximately 1200 degrees Fahrenheit and the top center lug melted. Loose connections cause very high temperatures and the possibility of a fire. The smaller fuses are 100 amp fuses and the bigger fuse is 250 amps. I replaced two large fuses and all three small fuses along with the fuse block and a contactor that was damaged by the dripping hot aluminum falling into the coil of the compressor contactor. Typically, on start-up of new equipment including condensing units the first thing the startup technician checks is to make sure all the electrical connections are tight. This is an important check on any regular maintenance schedule so that this problem does not happen to you. It is a fact that an electrical connection, even new electrical connections, will eventually fail because of corrosion, vibration or other condition.

Disconnect Box with Loose Electrical Connections Exposed by Infrared Camera

Loose Electrical Connections in HVAC Equipment: Methods of Testing

Large Switchgear Equipment for a back-up generator

Working in a new data center we tested all the electrical and the mechanical equipment. Part of the tests was initial basic checks of the equipment before testing began. Part of the basic check was checking for loose electrical connections inside the equipment. Other things tested was the electrical connections on the batteries in the battery room. A data center can use hundreds of batteries for backup power if the power goes out. Since data centers have redundant power sources the batteries allow for power during the transition time from one power source to back-up. Putting the batteries under load an electrician used a thermal imaging camera to check all the connections on the batteries.

Surprisingly enough there were several loose connections found on the batteries that were tightened up. Whether you have a data center or you are just a homeowner these things need to be checked and preferably by someone qualified for safeties sake.

As always, SAFETY FIRST, make sure power is off before doing these checks!