USA Building Codes: Inside Junction Boxes with Terminals?

[Stephen Tashi]

TL;DR Summary

Are there junction boxes with terminals that are designed for interior residential wiring?

(USA) building codes require that wires that are spliced together must be contained in electrical boxes that are accessible - e.g. you can't splice together wires in an attic. So one often finds electrical boxes for ceiling fans or electrical outlets also serving as junction boxes in the sense that they contain multiple wires spliced together using wire nuts. To me, a nicer way to make a junction box would be to have a dedicated electrical box that had terminals in it. However, in the USA, the only junction boxes I see for sale are designed for outdoor use with electrical conduit. Is there such a thing as a junction box with terminals that is designed for interior use? - something like an ordinary electrical box for outlets and switches, only with a set of terminals inside it?

( On the web, I find this type of 4 terminal junction box for sale by UK companies https://www.hawthornshop.co.uk/20-amp-junction-box-4-terminal-brown-661-p.asp Why is this such a common product in the UK? )

 

[Averagesupernova]

Not that I know of. What's wrong with wire nuts?

 

[Stephen Tashi]

Not that I know of. What's wrong with wire nuts?

The bad thing about wire nuts is the labor of cramming all the wires back inside a box after you have finished wire nutting them together.

 

[berkeman]

Summary:: Are there junction boxes with terminals that are designed for interior residential wiring?

(USA) building codes require that wires that are spliced together must be contained in electrical boxes that are accessible

One way might be to use a "barrier block" mounted inside the junction box. Usually these are used with the wire ends crimped into ring or fork connector ends, but you probably could use them with bare wire too. Check with your local Building Department to see if bolting these inside of junction boxes meets the NEC and your local building codes...

 

[Averagesupernova]

Check with your local Building Department to see if bolting these inside of junction boxes meets the NEC and your local building codes...

I doubt it will.

 

[Averagesupernova]

The bad thing about wire nuts is the labor of cramming all the wires back inside a box after you have finished wire nutting them together.

If you have not exceeded box fill limits, and I suspect you have since you state it in the manner that you do, 'cramming' the wires back in should not be an issue. Adding even more hardware inside the box is not going to solve your problem.

 

[Stephen Tashi]

One way might be to use a "barrier block" mounted inside the junction box.

I can find such terminal strips for sale in local hardware stores, but finding an economical junction box to hold them is the problem. I suppose I could mount a junction box designed for exterior use into the wall of a room just as one installs electric boxes for switches and outlets, but this seems overkill for interior work.

 

[anorlunda]

Connectors like these can replace wire nuts inside boxes. They are mostly used outside the USA, but they might be allowed by US electrical codes. I'm not sure.

 

[Stephen Tashi]

Connectors like these can replace wire nuts inside boxes. They are mostly used outside the USA, but they might be allowed by US electrical codes. I'm not sure.

I frequently use those "Wago" connectors and prefer them to wire nuts. However, judging by the exterior junction boxes I've seen, terminal strips make for more organized layout.

 

[Mark44]

However, in the USA, the only junction boxes I see for sale are designed for outdoor use with electrical conduit. Is there such a thing as a junction box with terminals that is designed for interior use? - something like an ordinary electrical box for outlets and switches, only with a set of terminals inside it?

Any hardware store or home improvement store will have different kinds of utility boxes (that's what they're called). The ones you described are for conduits that get screwed into the utility box. The ones for indoor application are made of plastic or stamped metal. They don't have terminals inside -- you insert the Romex (typically) cables into the utility box and join the appropriate wires with wire nuts.

The bad thing about wire nuts is the labor of cramming all the wires back inside a box after you have finished wire nutting them together.

Each type of utility box is rated for the maximum number of wires that can be attached inside it. If you're having trouble cramming all the wires in after connecting them, you're probably working with a utility box that's too small.

 

[Averagesupernova]

I would be curious to know what size box your are working with and how many cables enter the box with how many wires each? Also, will this box have a blank cover or house a switch/outlet?

 

[Merlin3189]

( On the web, I find this type of 4 terminal junction box for sale by UK companies https://www.hawthornshop.co.uk/20-amp-junction-box-4-terminal-brown-661-p.asp Why is this such a common product in the UK? )

Yes. In my experience that is the most common way of doing mains power junction boxes in the UK. Connections to switches and sockets use similar connectors.
I've never seen "wire screws" in power wiring, only, occasionally, inside equipment.
Also in UK we have the terminal strips, commonly called "chocolate block connecters", but in my experience they are less common for mains power junctions.

 

[Stephen Tashi]

I would be curious to know what size box your are working with and how many cables enter the box with how many wires each? Also, will this box have a blank cover or house a switch/outlet?

A typical situation: double gang deep (4 inch deep) box as a junction for 5 #12 Romex cables, each with 2 conductors plus a ground. Blank plate for a cover. I'm not saying that cramming the wires into the box is not possible. I'm saying the process is time consuming and the result is ugly when, for example, you want to make changes to wiring.

 

[Averagesupernova]

You are telling me you are using a 64 cubic inch box? I find that very hard to believe.
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I would really avoid if possible running 5 #12 cables into even a double gang box. Split off on an extra j-box instead.
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The box fill guide that I have shows that 5 #12 cables with two conductors plus ground will require a minimum of 27 cubic inch box. This is assuming internal clamps and no receptacles/switches.

 

[Stephen Tashi]

You are telling me you are using a 64 cubic inch box?
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No, I'm not saying that.

I mean a typical double gang deep box: 32 cubic inches: https://www.amazon.com/dp/B000GAWYZ8/?tag=pfamazon01-20

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The box fill guide that I have shows that 5 #12 cables with two conductors plus ground will require a minimum of 27 cubic inch box.

So 32 cubic inches should be enough - correct?

 

[Averagesupernova]

No, I'm not saying that.

I have try very hard to see that didn't say that. But that aside, yes, according to the box fill calculator I have it will work. But my suggestion is still to avoid that many #12 cables into a double gang box. #14 is a lot easier to work with and of course the box fill calculator will allow more #14 wires than #12 so I've found its not so bad to stuff that many into a box if it's #14.
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You mentioned making changes to wiring in the future. If my 27 cubic inch figure is right, and you want to make changes later, there isn't much you can do. You can add another cable and you will be approaching 32 cubic inches. If you decide you add a receptacle you will also be approaching the limit if not over the limit. I just wouldn't figure it that close.
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All that aside, is that Amazon link you posted selling ONE box for that kind of money? I about spit my teeth out when I saw the price. Lowe's has it for $1.72.
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https://www.lowes.com/pd/CANTEX-2-Gang-Plastic-New-Work-Electrical-Box/5001743605

 

[pbuk]

Yes. In my experience that is the most common way of doing mains power junction boxes in the UK. Connections to switches and sockets use similar connectors.
I've never seen "wire screws" in power wiring, only, occasionally, inside equipment.
Also in UK we have the terminal strips, commonly called "chocolate block connecters", but in my experience they are less common for mains power junctions.

This used to be the case but now Wago and similar connectors have largely replaced old fashioned junction boxes and chocolate blocks.

Apart from being a similar price and much easier to work with they have the advantage that you CAN install them in inaccessible locations e.g. under floorboards because they are deemed 'maintenance free' - there are no terminal screws to work loose.

Note that wire nuts have never (in my lifetime anyway) been legal for mains voltage in the UK.

 

[Stephen Tashi]

Note that wire nuts have never (in my lifetime anyway) been legal for mains voltage in the UK.

It's difficult to understand from a USA perspective how to do without them!

For example, if I have a box where a 2 conductor cable is bringing power to a two-pole light switch, I'd typically wire-nut the neutral wire on the cable to the neutral wire to the light. The hot wire from the cable and the hot wire to the light would be attached to terminals on the switch.

Wiring 3-way switches involves even more wire nuts.
https://www.familyhandyman.com/project/how-to-wire-a-threeway-switch/

 

[pbuk]

It's difficult to understand from a USA perspective how to do without them!

For example, if I have a box where a 2 conductor cable is bringing power to a two-pole light switch, I'd typically wire-nut the neutral wire on the cable to the neutral wire to the light. The hot wire from the cable and the hot wire to the light would be attached to terminals on the switch.

In the UK we don't normally bring neutral to the switch: the switchable connections are all made either in the ceiling rose or a junction box (which must now either be accessible or maintenence-free - rarely used now).

Wiring 3-way switches involves even more wire nuts.
https://www.familyhandyman.com/project/how-to-wire-a-threeway-switch/

Firstly we call that a 2-way switch (in what sense is it 3-way?). Here we only have 3 conductors (+ earth) to the switch, again the neutral is only in the rose or [edit terminal block] junction box.

https://www.lightwiring.co.uk/two-way-switching-3-wire-system-new-harmonised-cable-colours/

When exceptionally you have to make an 'extra' conductor connection in a wall box then traditionally it would have been the aforementioned chocolate block or a crimped connector, twist on connectors (wire nuts) not being legal. Now Wago and similar connectors are approved for this use and have taken over.

 

[Stephen Tashi]

Firstly we call that a 2-way switch (in what sense is it 3-way?). Here we only have 3 conductors (+ earth) to the switch, again the neutral is only in the rose or terminal block.

A pair of switches that can be wired so each can turn a light on or off independently is called (in the US) a pair of 3-way switches. When a light needs only one switch, it is less expensive to use a 2-way switch for the job. The 2-way switches have 2 terminals plus a terminal for ground and the 3-way switches have 3 terminals plus a terminal for ground. I haven't thought about the literal interpretation of the "way" terminology.

In the UK we don't normally bring neutral to the switch

Likewise in the US, a more common way to wire a light that needs only a single switch is to use a "switch loop", which uses two wires in the same cable to take power to and from the switch. (The old way of doing this was to use a 2 conductor cable and put a tag of tape around the end of the white wire in the cable to indicate that it is not a neutral. The updated way requires using 3 conductor cable and using the black and red wires for the switch loop.)

Since (I'm told) some fancy light control devices want a neutral wire, the fancier way to wire a light is to bring both the hot wire and the neutral wire to the switch box.

 

[Averagesupernova]

In the USA it is irrelevant whether the source cable stops at the ceiling box first or stops at the wall switch box first. It's getting to be common to require a neutral at the wall switch box just as @Stephen Tashi described for occupancy sensing switches that require a neutral. This means a 3 wire cable between the ceiling light and the switch. If the source stops at the switch first then it can often be desirable to have a 3 wire in order to have a constant hot at the ceiling for a ceiling fan, or just to feed the next device on the circuit. More than once I've run 3 wire cable between just in case.