What Protection Does a NEMA Type 12 Enclosure Provide?


A NEMA Type 12 electrical enclosure is designed for indoor use in relatively mild environments. However, it is a sealed enclosure that is not naturally ventilated so in most instances it will require the addition of enclosure cooling technology to keep the interior temperature below the thermal limits of electrical equipment in the enclosure. The protection provided by a NEMA Type 12 enclosure is as follows.

Indoor Use

These enclosures are designed for indoor use only and are not suited for locations where the enclosure is subject to the elements such as wind, rain, and snow. NEMA 12 enclosures are generally manufactured from painted steel to provide strength and rigidity to the electrical enclosure. Although plastic and fiberglass construction is also used, the strength, physical characteristics, and other properties of these materials must comply with appropriate specifications.

Sealed, Non-Ventilated

NEMA Type 12 enclosures are sealed and don’t have natural ventilation. The degree of sealing is limited only to what is needed to protect against dust and dirt. Because the enclosure is sealed, it may be necessary to provide enclosure cooling to manage the equipment heat load. The use of filtered fans is questionable because installation could invalidate the enclosure’s NEMA 12 rating. Alternative cooling methods that may be used include closed-loop systems such as air conditioning and air to air heat exchangers.

Circulating Dust

The enclosure provides protection against circulating dust such as that found in factories processing dusty materials. This includes fibers, lint, and flyings. It should be noted that this level of protection does not include wind borne dust, and in extremely dusty environments a NEMA Type 4 enclosure may be better solution.

Falling Dirt

This is similar to and an extension of circulating dusts, but is intended to take into account atmospheric dirt, usually present in older factories and facilities, which falls vertically.

Dripping of Non-Corrosive Liquids

The enclosure should provide sufficient protection against dripping liquids. Typically, this would include minor water leaks, water dripping from steam traps, and oil leakage from machinery. As it’s a requirement that the liquid be non-corrosive, no special corrosion protection measures are needed.

Normal Factory Environment

A NEMA Type 12 enclosure is intended for use in what would be generally understood as a normal factory environment. The protective measures required take into account the dust and debris that is likely to be released into the atmosphere by typical factory processes such as grinding, drilling, machining, manufacturing, and processing of raw materials.

The sealing of the enclosure is designed to protect electrical equipment from contamination. However, it’s important that thought is given to the heat load generated by the equipment in the enclosure, as this could cause an increase in the enclosure temperature unless adequate cooling is provided. For example, a heat load of 500 watts in an average-sized enclosure could increase the temperature by over 30 °F.

NEMA Type 12 Enclosure Cooling Solutions

Thermal Edge offers two closed-loop enclosure cooling solutions for NEMA Type 12 enclosures. The most economical solution is the UL approved air to air heat exchanger, which is compatible with normal enclosure heat loads. This novel solution uses heat pipe technology that exploits the latent heat of evaporation of a refrigerant to remove heat from the enclosure and requires no power apart from that required to drive two air-circulation fans. Its only limitation is that the ambient air temperature must be lower than the required enclosure temperature.

Alternatively, Thermal Edge’s range of UL approved enclosure air conditioners with capacities from 1,000 BTU/H through to 20,000 BTU/H will provide effective cooling under all conditions. Contact sales today to learn more about our enclosure cooling systems.