Strapping nipples

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Dbarrett

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What is the rule on strapping conduit less than 18”? I thought it was considered a nipple and did not need a support but now I can’t find the code.


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It depends upon the type of conduit you are using. If the conduit requires a strap within 12" of a box (e.g. PVC), then a strap is required. I would center it on the 18" nipple. If a strap is required within 3' of a box (e.g. EMT), then the boxes on either end of the nipple are the support for the other side so no additional strap is required.
 
Sorry, so to clarify. The boxes or fittings on either side of emt less than 3’ are considered the support? Thanks for explaining


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Dbarrett said:
Sorry, so to clarify. The boxes or fittings on either side of emt less than 3’ are considered the support? Thanks for explaining
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To be technical: the boxes, not the fittings. The boxes are fastened down. The fittings are not. A conduit body doesn't count as a support point for this same reason. It's not fastened down. If the box is free floating for some reason, then it would not count either.
 
All EMT nipples require support even one that's 2" long. There was one code cycle where you could have up to 18" nipples unsupported but that didn't last long.
 
infinity said:
All EMT nipples require support even one that's 2" long. There was one code cycle where you could have up to 18" nipples unsupported but that didn't last long.
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A 2" nipple of EMT is no longer than the back-to-back bodies of the setscrew connectors. I would think the nipple would need to at least have a plain cylindrical section long enough to even fit a strap on it, before requiring a strap.
 
Carultch said:
A 2" nipple of EMT is no longer than the back-to-back bodies of the setscrew connectors. I would think the nipple would need to at least have a plain cylindrical section long enough to even fit a strap on it, before requiring a strap.
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That's the rub, even if you cannot fit it between the connectors it is still required. This is one of the few very dumb code sections which I violate often. :angel:
 
My thought on this has always been if you had something like a 3 inch RMC 24" long between two large cabinets and you are forced to put a strap on it by code, is the strap supporting the conduit or is the conduit supporting the strap? You can mix and match raceway sizes and types and even tweak length a little and still say the same thing for most of them.
 
This is one of those things where in my opinion the code should be revised to allow leeway to installers and AHJs. (I mean, I haven't had issues with AHJ's requiring me to strap short pieces of conduit that was secure in fittings. But if people are...)

Take for example a piece of EMT, 18" long, with no bends, installed between two set-screw fittings on two enclosures that are securely fastened to the same wall. That ain't goin' nowhere. It doesn't need to be strapped.

Now take the same piece of EMT, put a 90deg bend in the middle of it, and move one of the enclosures up so that the EMT enters from the bottom instead of the side. That elbow will wobble around a bit and arguably needs a strap.
Now try to write a code section that precisely covers all the other examples. :slaphead: This is one of those situations where I'd be okay with undefined language that the AHJ gets to interpret (i.e. similar to 'subject to physical damage).
 
jaggedben said:
Take for example a piece of EMT, 18" long, with no bends, installed between two set-screw fittings on two enclosures that are securely fastened to the same wall. That ain't goin' nowhere. It doesn't need to be strapped.
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I could see the EMT size being taken into consideration here. A 1/2" EMT nipple 18" long might need midway support where a 2" EMT nipple 18" long might not. Maybe it should be a given multiple of diameter.
 
LarryFine said:
I could see the EMT size being taken into consideration here. A 1/2" EMT nipple 18" long might need midway support where a 2" EMT nipple 18" long might not. Maybe it should be a given multiple of diameter.
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That's why I think it should be vague, something like 'a length less than 18" shall be permitted to be mechanically secured by associated fittings'. Let reasonable people decide if it's 'mechanically secured'.
 
jaggedben said:
That's why I think it should be vague, something like 'a length less than 18" shall be permitted to be mechanically secured by associated fittings'. Let reasonable people decide if it's 'mechanically secured'.
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I don't have much issue with that but think it should be 3 feet especially if we don't need a first support until 3 feet on other runs.
 
kwired said:
I don't have much issue with that but think it should be 3 feet especially if we don't need a first support until 3 feet on other runs.
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I agree, two solidly mounted boxes on a block wall with a 36" piece of EMT between them isn't going anywhere. They should have at least left the 18" exception in place.
 
infinity said:
I agree, two solidly mounted boxes on a block wall with a 36" piece of EMT between them isn't going anywhere. They should have at least left the 18" exception in place.
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If you have 3 feet then a piece of unistrut to attach it to, it is kind of similar situation. Then they even let you go up to 5 feet in certain situations where you don't have structural means within 3 feet.
 
jaggedben said:
Which code cycle was that?
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From the 2008 NEC:

358.30(C) Unsupported Raceways. Where oversized, concentric
or eccentric knockouts are not encountered, Type EMT
shall be permitted to be unsupported where the raceway is
not more than 450 mm (18 in.) and remains in unbroken
lengths (without coupling). Such raceways shall terminate
in an outlet box, device box, cabinet, or other termination at
each end of the raceway.
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