Removing panel covers for electrical inspections
I have been asked on more than one occasion about the necessity for removing panel covers to perform an electrical inspection. There are quite a few companies that are inspecting the outside of panels with the doors closed, and only opening them if they see anything on the door.
This is not a good way to carry out thermography and usually it is an indication of inexperience and a lack of a basic understanding of infrared technology.
It is only in very extreme cases that an electrical anomaly will produce enough heat to be picked up on the outside of an electrical panel, and in cases like this the item is likely to be dangerous to open. Scanning panels externally as part of a survey can be helpful in determining if it is safe to proceed with removal of covers, but it should not be considered completion of a survey. This type of methodology will lead to missing up to 99% of problems, and gives false confidence in the reliability of the site electrical system. In order to successfully perform an electrical thermographic survey, all panel doors will have to be opened, and all covers removed. Where this is not possible, the equipment should be noted and it should be considered outside the survey as not being done.
Most materials used in the manufacturing of electrical panels are thermally opaque, and a thermal camera will only see the energy emitted from the surface. An infrared camera is not an x-ray machine and can not see through these materials, it will only see the heat energy emitted from the front of the panel door. While it is true that a bad connection will have a higher temperature, it is not true to say that this will always raise the temperature of the panel door to a significant level. This will only happen if the connection is extremely hot, close to the door and it has a significant mass. The doors need to be opened, and the flash guards removed in order to correctly perform electrical thermography.
The purpose of carrying out electrical thermography is to find electrical failures BEFORE damage occurs, if the doors are left closed, any problems found will have passed the point where a simple repair can be carried out, and a major shutdown of the equipment to carry out a repair is more likely. So the economics of only finding the really critical items will mean the cost of the repairs is significantly higher. The likelihood of unexpected failures also increases along with the potential for secondary damage. Unplanned shutdowns normally cost at least ten times more than planned ones, so we ideally want to try to reduce unplanned shutdowns. Simply put, opening the door allows for detection of small problems, that can be repaired easily and cheaply. Not opening the door means that you increase the chance of unplanned shutdowns, difficult repairs and will have significant cost implications.
Opening panel doors and removing covers also means that visual problems can be noticed, this ranges from evidence of rodents to cables that are obviously burned, other things like smells can be picked up by experienced personnel. As the fault cycle for electrical failure is very complicated, there are times when a bad connection can have a normal temperature even though damage has occurred, these can be easily observed visually when working with opened panels, and would be missed when viewing problems externally.
While the temptation is to perform thermography with the panel doors shut to reduce the cost and complexity of a survey, it is a false economy as the survey does not achieve its full potential, and does not reduce the number of potentially expensive failures.
External image shows no sign of problem.
Internal image reveals a problem