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Are EMT offset connectors or any EMT connectors or fittings Listed for use with threaded hubs, such as on a conduit body or Myers hub?

Posted By Underwriters Laboratories, Monday, May 01, 2006
Updated: Monday, February 11, 2013

Question: EMT offset connectors

A common practice I see in the field is EMT offset connectors screwed into hubs on outdoor enclosures. Are EMT offset connectors or any EMT connectors or fittings Listed for use with threaded hubs, such as on a conduit body or Myers hub?

Answer

All hubs are intended for use with threaded conduit, not fittings. Hubs are provided with a tapered thread, and so is threaded conduit such as rigid metal conduit or intermediate metal conduit (IMC). EMT fittings have a straight thread and are designed for use with a lock nut, intended to secure to an enclosure through a knock out or punched hole.

When the straight thread of the connector or fitting enters a hub in a wet location, the wet location rating may no longer be valid because the wet location rating of the hub depends on the tapered thread engagement of the tapered conduit thread into the tapered thread of the hub. With a straight threaded connector, the thread of the connector never locks into the tapered thread of the hub, therefore not providing a seal to keep out moisture.

An EMT fitting marked for use in a wet location is provided with or is used with a gasket between the fitting and the hub. When the fitting is tightened the gasket can be squeezed out from between the fitting and hub and may not provide a means to keep out moisture. Other considerations with straight threaded connectors into a tapered threaded hub may be grounding.

Depending on the installation of the straight threaded connector into the hub, the contact may not be tight enough to assure an effective groundfault current path. The connection of straight threaded connectors, such as EMT connectors, is not evaluated with hubs as part of their Listing. Hubs are Listed under the product category Conduit Fittings (DWTT).

EMT fittings are Listed under the product category Electrical Metallic Tubing Fittings (FKAV). The Guide Information for DWTT can be located on page 22 in the White Book and FKAV on page 33 or online by entering DWTT or FKAV at the Category Code search on UL’s Online Certification Directory located atwww.ul.com/database.

Tags:  May-June 2006  UL Question Corner 

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