Safety Against Burns From Hot Touchable Parts of Electrical Equipment

Touchable parts of electrical products and equipment can be thermally hot. Unintentional contact with hot surfaces during the normal operations of products may cause burns, and severity depends on the thermal resistivity of the material of the exposed part, the contact duration, the contact pressure, and skin conditions (i.e., dry, water wet, etc.). Currents flowing through equipment surfaces due to intentional choice or wiring errors can also elevate their temperatures, compounding the thermal effect; this causes an increased risk of triggering explosive atmospheres and fires in locations where combustible/flammable materials are processed or stored. In this paper, in light of applicable technical standards, the authors discuss and propose applicable burn thresholds, and permissible contact times with hot parts, based on different groups of users who may unintentionally touch the surfaces. The risk assessment of burning can be performed by comparing actual maximum temperatures of parts of electrical equipment against safe temperatures that a person may withstand for a given time without suffering a second degree burn.

I. Introduction

Electrical apparatus in industrial, commercial, and residential environments are thermally insulated. However, surface temperatures of insulated equipment and appliances, which are likely to be unintentionally touched during their normal operations, may still be high enough to expose persons to the risk of burns. Hot surfaces of overheated electric conductors, conduits, or other energized equipment will cause injury if in contact with the skin [1]. It is also important to note that surfaces of enclosures continually exposed to sunlight may easily reach high temperatures, even if the equipment is not energized.