Set Screw Fittings in Chicago Plenum
- Thread starter mak134
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kwired
Electron manager
- Location
- NE Nebraska
Unless you have local rules that state otherwise NEC is fine with set screw fittings for this application. They are no more or less an issue than the boxes typically used or even FMC or AC/MC cables often used.
Someone think there is an air leakage issue? Maybe a caulk or other coating can be applied that is rated for plenum use. Still pointless if you don't have sealed boxes or have FMC, AC or MC.
Someone think there is an air leakage issue? Maybe a caulk or other coating can be applied that is rated for plenum use. Still pointless if you don't have sealed boxes or have FMC, AC or MC.
texie
Senior Member
- Location
- Fort Collins, Colorado
- Occupation
- Electrician, Contractor, Inspector
As Kwired said. Is this a local thing? Makes no sense. Like putting a screen door on a submarine.
growler
Senior Member
- Location
- Atlanta,GA
As others have asked, is this a local code amendment or could it be a job specification ? I have been on jobs in the past where compression fitting where required simply because that was the choice of the engineers that provided the specifications.
The first question should be who is requiring them to be changed and for what reason?
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
I am not a huge fan of the set screw type EMT connectors since I have seen a fair number of loose ones. never seen a compression fitting come loose. It probably happens, but I have not seen one.
MAC702
Senior Member
- Location
- Clark County, NV
I've seen more compression fittings come loose than set-screw, but that's because they are found in places where the installation is more likely to be abused. However, in both cases, I think the reason was because someone couldn't be bothered to tighten them properly or secure the conduit properly.
Same here. On one hospital project the specs did not allow compression emt fittings, this I liked and I asked the engineer why he wrote his spec that way, he said he knew a screw is easier to tighten than trying to get two pairs of channel locks into tight spaces .
Roger
growler
Senior Member
- Location
- Atlanta,GA
I really wasn't trying to start a debate over which is better, set screw or compression type connectors but to point out that if the requirement for compression fitting is in the job specs ( and it may well be) then they will have to deal with owners and possibly design engineers to see what they will accept.
I have had a bit of trouble over the years tying to get some electricians to understand the difference between Code and job specs. A red car may be as legal as a black car but the the customer ordered a black car then legally that's what he is supposed to receive. If someone can talk the customer into accepting a different color then that's OK but they shouldn't count on it.
grich
Senior Member
- Location
- MP89.5, Mason City Subdivision
- Occupation
- Broadcast Engineer
Perhaps the rationale is that air (and smoke) movement between the inside of the conduit and the plenum space is better controlled with a compression fitting...IDK.
kwired
Electron manager
- Location
- NE Nebraska
Makes some sense, but only if you also use completely sealed boxes with gaskets on the covers.
synchro
Senior Member
- Location
- Chicago, IL
- Occupation
- EE
300.22(C)(1)(a) of the 2018 Chicago Electrical Code (a modified version of 2017 NEC) specifically lists EMT with gland-nut (aka compression) fittings as one of the approved raceways for plenums, which implies the set-screw type is not allowed in this application.
Sorry for the blurry image from an on-line viewer access to the code.
Sorry for the blurry image from an on-line viewer access to the code.
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- Occupation
- Licensed Electrician
Get me that man's name and will send him a case of the beverage of his choice and an annual donation to his favorite charity.
StarCat
Industrial Engineering Tech
- Location
- Moab, UT USA
- Occupation
- Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
I am absolutely on the same page and use nothing but compression style connectors across the board. The other thing is, I wish I had a large bill for every time I have seen a Journeyman ever so gently tighten a lock nut with the heel of his hand and call it good.
- Occupation
- Licensed Electrician
I've assembled lots, and I've demoed lots of EMT. If the quality of the fittings and installation are the same set screw is tougher every time. Not only do set screw install easier and more reliably because they simpler, that little 1/532 of an inch of bite that compression has strips out quite a bit easier than a set screw divot.
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