2

What's the proper bushing or coupling for stepping 1" EMT down to 3/4"? Does such a fitting (bushing?) even exist?

My searches for a 1" to 3/4" EMT adapter pretty much come up empty.

Goal: the top of the outdoor box I'm using to house some outlets has a female threaded fitting which works great for 1" EMT, but I'm running 3/4" so I need some kind of step-down.

Are the fittings in the tops of the outdoor boxes regular NPT pipe thread, so a 1" x 3/4" NPT galvanized bushing will work? (Or whatever NPT size the 1" and 3/4" EMT uses).

Box and fittings I was thinking of using

Gary Aitken
  • 191
  • 8
  • 1
    Are you trying to interface a 3/4" EMT to a 1" threaded hub? What sort of box is this? – ThreePhaseEel Sep 24 '22 at 03:13
  • 1
    @ThreePhase yes. The box is an old Midwest, I'm guessing 8" x 12". I think it may have been a temporary construction thing with a main breaker, a 220 and a 110. The main breaker was broken so I've removed that and I'm just using the 220 and 110. – Gary Aitken Sep 24 '22 at 18:10
  • Gary could you post some photos of "the top of the outdoor box I'm using to house some outlets has a female threaded fitting which works great for 1" EMT"? I'm worried that we are having terminology misunderstandings (e.g. hub vs. connector vs. coupling). – Armand Sep 25 '22 at 05:24

2 Answers2

2

I think you should search for "reducing bushing". Here's one I found (example only) but it seems to be sold in box quantities only. Why not check with a local or online electrical supply house?

enter image description here

Technically, EMT conduit isn't threaded itself, just via end fittings, while rigid and IMC are/can be directly threaded.

Edit: According to @ThreePhaseEel I was wrong thinking the threading of EMT fittings matches that of rigid/IMC threading. As TPE describes in their answer, there are apparently special fittings to convert EMT ends into female or male rigid pipe threading (which would connect to a threaded hub in a box).

Armand
  • 3,834
  • 5
  • 22
  • It sounds like the quantity issue is due to trying to shop online. Nobody wants to sell electrical gear online, or to be more precise, nobody wants *to ship* electrical gear by mail because the cost of shipping is usually very high relative to value. Also, since all electricians have local supply relationships and don't buy mail order, you're left with novices who don't know what they're doing, have exceedingly high returns and chargebacks, and are very hand-holdy. – Harper - Reinstate Monica Sep 24 '22 at 03:48
  • @Harper-ReinstateMonica Yes. I have found some supply houses with online operations that have been good to work with. I suspect it helps to be ordering items other than standard DIY items, like 3-conductor rated split bolts :) In my area, high commercial space rents have driven away the local open-to-the-public plumbing and electrical supply houses that used to be in the area. Perhaps one needs to develop a mapping app to identify local retail supply houses. – Armand Sep 24 '22 at 03:59
  • @Armand thanks, will try local supply house. I used to deal with them when doing more construction (barn, arena, house, etc.) but they generally say "wholesale only" and despite more-or-less being the builder I don't have a commercial license and am not going to pretend to be one. I would prefer to give them the business and don't mind paying some extra for it if it's not some outrageous pretend retail price. I used to avoid ACE only because they were always 2x the big box but recently bought ground rods at about the same so maybe that has gotten better. – Gary Aitken Sep 24 '22 at 18:23
  • @GaryAitken That Ace ratio still generally holds in my area :( – Armand Sep 24 '22 at 18:47
  • @Gary that's what happens. People find out ACE is more than big-box on certain items the big-box puts out there as loss leaders. Then they get angry and swear they'll NEVER set foot in a hardware store again. Then they get trapped by big box's poor selection. – Harper - Reinstate Monica Sep 24 '22 at 19:00
  • This isn't sufficient -- it gets the reducing done, but doesn't solve the much larger issue of getting the EMT into a threaded hub in a compliant way – ThreePhaseEel Sep 24 '22 at 19:05
2

You need the correct EMT-hub transition setup in addition to a reducing bushing

While it's true that you'll need a 1" to ¾" threaded reducing bushing (Bridgeport 1163 or equivalent) for this installation, that's not the only piece you need to make this work. You see, the threads on standard EMT connectors are designed to mate to the threads on locknuts, not the somewhat different threads found on the inside of the hub fitting sitting atop your construction power outlet box (cabinet), or on the inside of a reducing bushing for that matter. As a result, an inspector is within their rights to reject your installation if you simply slap a standard watertight (compression) EMT connector in your reducing bushing and call it a day.

Instead, you'll need to use a Bridgeport 291-RTNPT to make the EMT-hub transition work here. If you can't obtain one of those through your local supply house, your local inspector should accept a rig consisting of a EMT-RMC female-female transition fitting (Bridgeport 291-RT or equivalent) and a ¾" RMC nipple threaded into the reducing bushing instead.

ThreePhaseEel
  • 79,142
  • 28
  • 127
  • 220
  • Wow - that's knowledge! – Armand Sep 24 '22 at 19:18
  • Not sure I understand this. EMT is not watertight, at least not standard couplings. This EMT is running inside a shed, and the construction outlet box / cabinet is also inside the shed. Can't the normal EMT threaded male adapter with tightening ring be used to snug it down? Or are you saying I'm going to need water-tight couplings as well? – Gary Aitken Sep 25 '22 at 04:11
  • @GaryAitken -- by "threaded male adapter with tightening ring" are you referring to a *compression* EMT connector/fitting, or are you referring to a *setscrew* EMT fitting? – ThreePhaseEel Sep 25 '22 at 04:18
  • @ThreePhaseEel Gary might mean "lockring" when he writes "tightening ring". – Armand Sep 25 '22 at 05:20
  • @Gary Can you post photos of the "threaded female fitting" in the box you've got? – Armand Sep 25 '22 at 05:26
  • 1
    I've added an image of the box and the fittings (3/4") I was thinking of using on the 3/4" EMT going to and into the box. – Gary Aitken Sep 25 '22 at 15:15
  • @GaryAitken yeah, you're in a bit of an edge case with the three-sided shed and sideways rain, I'd talk to your inspector to see if you need a watertight run there – ThreePhaseEel Sep 25 '22 at 15:26
  • @ThreePhase The "tightening ring" I was referring to is apparently what is technically called a lockring. Thanks Armand – Gary Aitken Sep 25 '22 at 21:59
  • @GaryAitken -- locknut, really – ThreePhaseEel Sep 26 '22 at 00:53