How to Conduct a Thermal Audit of Electrical Enclosures

A thermal audit of electrical enclosures can be revealing.

Statistically three out of ten enclosures are too hot for the power electronics and controls inside them. But this can be easily remedied with the addition of thermal cooling systems. The trick is identifying your problem areas quickly and efficiently, which brings us to the thermal audit. This is a safe, noninvasive method of identifying problem enclosures and specifying thermal cooling devices that will keep temperature at safe levels.

A thermal audit examines:

• Heat load of enclosed electrical equipment
• Temperature ratings of the installed equipment (upper and lower limits)
• Ambient temperature (typical and extreme)
• Environmental conditions
  1. Clean air (Type 1)
  2. Dirty or wet environment (Type 12, Type 4/4X)
  3. Closed- or open-loop
  4. Indoor or outdoor
• Maintenance and frequency of access requirements

Thermal audit – getting started

There are a few things to consider in preparation for an audit. How many enclosures do you have? Which are the most critical? Which will be difficult to get to? This preparation can help you prioritize your audit and plan the most efficient path.

Next determine who will conduct the audit. Two person teams are best, with one taking measurements and another recording findings. Temperature will be assessed at preferably two points, and dimensions will need to be recorded to compute interior volume.

Conducting the audit

In most cases the entire audit can be conducted without having to access the inside of the enclosure. Exceptions would be to confirm available power sources (for cooling devices), or perhaps to inspect a physical problem with the enclosure itself. Try to record measurements when your enclosures are electrically loaded, preferable at the higher end of their operating range.

Several data points will need to be recorded for each enclosure, including:

• Enclosure name/ID
• Open surfaces (surfaces that are not blocked, top/bottom/back/left/right)
• Minimum and maximum ambient temperature in your environment
• Your minimum and maximum desired operating temperature inside the enclosure
• Ambient temperature within 3 feet of the enclosure
• Temperature of the top surface of the enclosure.
• Enclosure material (ie steel).
• Mounting options for the cooler (top, side, interior)
• NEMA rating of the enclosure (12, 4X, etc.) 

Examining records and computing requirements

Thermal cooling devices will need to be selected for each enclosure not operating within the desired heat range. This is a two-step process where 1) the right technology is selected (ex. vortex or AC) and 2) the correct size is specified for the measured heat load.