Do bolt heads on a NEMA 12 enclosure need gaskets or O-rings?
Short answer
Yes. Any intrusion into a NEMA 12 enclosure, including bolts threaded in from the outside, should be sealed with NEMA gasket material or O-rings if the original rating of the enclosure is to be maintained. NEMA 12 is an indoor rating: it protects personnel against access to hazardous parts, protects the housed equipment against ingress of solid foreign particles, and protects the contents against dripping or light splashing water, which roughly translates to the IP54 rating used in Europe. There is no value in specifying seals with a higher NEMA rating than the enclosure itself, because protection cannot be increased through over-sealing.
Any intrusion into the enclosure should be appropriately sealed if the original rating of the enclosure is to be maintained, so we recommend installing NEMA gaskets or O-rings around the bolts to ensure protection to the required level.
A NEMA 12 enclosure is intended for indoor use. It provides a degree of protection to personnel against access to hazardous parts, and a degree of protection to the housed equipment against the ingress of solid foreign particles. It also provides protection to its contents against the dripping or light splashing of water. This roughly translates to the IP54 rating that would be used in Europe.
Bolts threaded in from the outside break that seal in the same way any other penetration does, which is why each one needs its own gasket or O-ring.
There would be no value in specifying gaskets or O-rings with a higher NEMA rating than the original enclosure, as the protection of the enclosure cannot be increased through ‘over sealing’.
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