What size electrical junction box fits a 1-inch diameter cable anyway?

[Danny D]

Today I tried to connect a 1-inch wide flexible conduit to what was billed as a 1-inch outdoor junction box:

However, the 1-inch side of the old elbow clearly was too small to fit the threads in the 1-inch hole of the new reputedly 1-inch junction box:

Yet, the 1-inch side of the old elbow was just as clearly too large to fit the threads in the 3/4 inch hole of a 3/4 inch junction box:

Clearly I'm confused. Or I bought the wrong type of junction box. Does a solution seem clear to you?

[gfretwell]

Conduit is measured based on ID not OD but that is a nominal size. Your Carflex LFNC looks like 3/4" but you need a connector to get into that 3/4" threaded hub.

[Harry Johnson]

[RBM]

You have a piece of 3/4" nonmetallic flex. It looks like you have a 1/2" X 90 degree NM flex connector. You need a 3/4" NM flex connector. The larger threaded side of the connector is not pipe threads. it only threads onto the tightening nut that goes on the NM flex. If you want to install the 3/4" into the box with 1" openings, you'll need a 1" x 3/4" threaded bushing.

[John Grabowski]

*You are confusing trade sizes with actual dimensions of the conduit. Your flex has some writing on the outside of it which should include the trade size.

I have put together a chart of the actual dimensions of some conduits, however it does not have the flexible type that you have listed yet. The other conduit dimensions may give you an idea of what size you really need.

[trader4]

ide flexible conduit to what was

+1

Also, I would use a box twice that size. You have 6 wires entering the box, which is probably close to the limit for that box. It's also being put in to allow easy disconnect of the motor, so having some extra room is a good thing. And a larger box would allow for the addition of another wire if you decide to go to a dual speed pump at some point.

[trader4]

wide flexible conduit to what was

Actually, I went back and looked at the pics again. I thought it was a smaller box, but now I see it looks like we're looking at the side of the box. If it's about 4x4, that's what I had in mind.

[DD_BobK]

+1

[DD_BobK]

[gfretwell]

Carflex is the same size as the same trade size in PVC

[Danny D]

Does that mean that what I measured as the old 1-inch conduit and 1-inch elbow is actually a 3/4-inch conduit and elbow?

If that's the case, why doesn't it then fit the 3/4-inch junction box?

[Danny D]

Does that mean that what I measured as the old 1-inch conduit and 1-inch elbow is actually a 3/4-inch conduit and elbow?

If that's the case, why doesn't it then fit the 3/4-inch junction box?

[gfretwell]

That elbow is a 3/4" flex to 1/2" thread. You need a 3/4 to 3/4

[Danny D]

I had asked and the answer came back that it's to code to put the box on the concrete outside, as long as I use waterproof connections and a waterproof cover (all of which I already purchased).

[Danny D]

OK. If the large side of the elbow, which measures at 1-inch, is actually a 3/4 inch connection, then that means the existing conduit is 3/4 inch and not 1 inch as I had thought.

So I bought the wrong box (because I bought a 1-inch box).

However, that doesn't explain why the 3/4-inch threaded connector is still too large for the 3/4-inch box?

It's close, but the threads don't fit?

I'm wholly confused because 3/4 inch conduit doesn't fit the 3/4 inch box???

[Danny D]

Actually, the plan is to put the old 3/4 inch conduit into the junction box with a straight-through connector.

Then, coming out of the junction box, will be half-inch conduit that goes to the motors, with a straight through half inch connector on the end that screws into the motor body.

My only problem right now is figuring out why the 3/4 inch conduit doesn't fit into the 3/4 inch holes of the box. It makes no sense unless I'm assuming something that isn't the case (which it must be).

[trader4]

What you have doesn't work, so you have to take it back, right? You apparently have 3/4" liquidtight conduit. Measure the inside diameter. Go down to HD or wherever you bought what you have. Take a piece of the conduit with you or measure the inside diatmeter. I see markings on the conduit in the pic and I'll bet it even says what size it is. Find a piece of conduit at HD to use or take a piece with you. Then go to the parts bin and find the appropriate fittings, box, etc. Make sure it all works before you leave.

One fundemental problem that has been explained to you is that you have two different ends of that elbow. One end has threads that mate with the nut for the conduit. That end will never mate with the box. If that conduit is 3/4, then you need a 3/4" elbow. It fits 3/4 conduit on one side, 3/4 box hole on the other

[trader4]

I'm not sure what we're looking at in the pic. On the left, is there a bushing inside that conduit? That's what it looks like to me, a 3/4 conduit with a bushing inside. And what are you showing the end of on the right? The old fitting that went over the conduit on the left? If so, then what that appears to me is some different kind of liquidtight fitting that uses a seperate bushing inside the conduit and then the fitting itself goes over the conduit.

[Danny D]

I did exactly as advised, and found out the answer to the size enigma can only be had with experience, as measurements do not prevail when it comes to flexible conduit connection sizes.

It turned out that this fitting (that clearly measured at one inch diameter) isn't even close to what they call a one-inch fitting:

In fact (even though it clearly measures out at 1 inch), it's not even close to what they call a 3/4 inch fitting; it turns out that it is a half-inch fitting!

So, the end result is that the original conduit and both sides of the elbow were actually nominally half inch sizes all along!

[Danny D]

I guess I missed the clue stamped right on the elbow all along!

The enigma turns out to be that the elbow was 1/2 inch on both sides!

The clue I missed is that it was clearly stamped 1/2 inch, but it never occurred to me that this meant *both sides* were half inch (yes, even the side that measures out at 1 inch).

Note: The straight-thru connectors are stamped 1/2NPT.