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For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
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Figure 01
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Figure 01
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For EC&M Magazine
By Mike Holt, NEC® Consultant
Here's the follow-up to yesterday's newsletter.
This includes the answers to the questions sent, so you can see how you did.
Note: The answers to these questions are based on the 2020 NEC.
Q1: Under what conditions can EMT not be used and installed?
A1: 358.12 Uses Not Permitted
EMT is not permitted to be used under the following conditions:
(1) Where subject to severe physical damage.‚
(2) For the support of luminaires or other equipment.‚Figure 01
Q2: What is the minimum and maximum EMT trade size permitted?
A2: 358.20 Trade Size
(A) Minimum. EMT smaller than trade size ½ is not permitted.
(B) Maximum. EMT larger than trade size 4 is not permitted.
Q3: What is the maximum degrees of bends permitted for EMT in one run?
A3: 358.26 Number of Bends (360°)
To reduce the stress and friction on conductor insulation, the total bends (including offsets) between pull points cannot exceed 360°.‚
Author's Comment:
â–ºThere is no maximum distance between pull boxes because this is a design issue, not a safety issue.
Q4: What are the requirements for securing and supporting EMT?
A4: 358.30 Securing and Supporting
EMT must be securely fastened in place and supported in accordance with (A) and (B).
(A) Securely Fastened. EMT must be securely fastened within 3 ft of every box, cabinet, or termination fitting, and at intervals not exceeding 10 ft.‚
Author's Comment:
â–ºFastening is required within 3 ft of termination, not within 3 ft of a coupling.
Ex 1: When structural members do not permit the raceway to be secured within 3 ft of a box or termination fitting, an unbroken raceway can be secured within 5 ft of a box or termination fitting.‚
(B) Horizontal Runs. EMT installed horizontally in bored or punched holes in wood or metal framing members, or notches in wooden members at intervals not greater than 3 ft, is considered supported, but the raceway must be secured within 3 ft of termination.
Q5: What are the requirements for installing EMT couplings and connectors?
A5: 358.42 Couplings and Connectors
Couplings and connectors must be made up tight to maintain an effective ground-fault current path to safely conduct fault current in accordance with 250.4(A)(5), 250.96(A), and 300.10.
If buried in masonry or concrete, threadless EMT fittings must be of the concrete-tight type. If installed in wet locations, they must be listed for use in wet locations and prevent moisture or water from entering or accumulating inside the enclosure in accordance with 314.15.
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