Junction Boxes

[gbeichho]

Location: Ontario, Cottage
Reading Knights book, he tries to discourage people from using junction boxes:

"Use junction boxes sparingly, only where you absolutely have to. Usually all your joints are made up in light, switch or plug outlet boxes."

I've got 2 outdoor recepticles at the opposite ends of the cottage with the breaker box in the middle. It seems like a massive waste of wire (let alone running extra wire in outside walls) to run the circuit from one recepticle to the other.

Is this a case where I can justify using a junction box in the attic (assuming the location meets code requirements... I have 1 M head clearance)?
Or should I use a pigtail in the breaker box to join the two circuits?

Thanks

George

[Homer]

Just use a j-box where it's convienient to do so. The only reason that you need to limit the number of "needless" j-boxes is because of workmanship. Some dwellings have j-boxes all over the place, many of which are not really serving any purpose(3 j-boxes where only 1 well thought out j-box is appropriate).

If the attic is convienient put one there or else put one right beside the panel.

Just be aware that there's a rule [12-3034(1)] that you may not use a panel for the purposes of making junctions. The only real exception is if you replace an existing panel and the existing runs are too short to make the breaker / lug connections, then you can make junctions to lengthen the conductors. This differs from NEC rules where you're allowed to make junctions in panels.

Homer

[Wgoodrich]

There is a second reason and a third reason to limit junction boxes. The more junction boxes you have the more junctions you have as well as the more complicated it gets to diagnose a loose connection in one of those many junction boxes. A second relates to the first the more junctions you create the more risk of fire you have. Junctions of branch circuits are the most common cause of fires in a dwelling.

Good Luck

Wg

[Homer]

There is a second reason and a third reason to limit junction boxes.
Yes, in my haste I omitted what I thought was obvious(always a bad thing to do). If the quality of the workmanship is good (well thought out) that usually indicates that those junctions are generally of good quality, are a low fire risk, and generally don't need much troubleshooting.

Homer

[joed]

I don't believe splices are legal in the breaker box in Ontario. You could mount the junction box right beside the panel.

[gbeichho]

I'm curious how junction boxes are such a source of fires? Is this because they're left open? (no cover plate)

I thought that the reason for plastic and metal boxes was that they could contain sparking and protect surrounding environments from heat and ignition.

Very interesting.

I can say right now that the cottage has several uncovered junction boxes not mounted and not closed just laying on the top of the ceiling in the attic (amoungst fiberglass insulation). There are also several cases of splices without any J-Boxes, but I'm progressively eliminating that situation as I manage to rewire major sections.

I've not had to put any J-boxes in for my replacement runs yet, but this particular case (with two outdoor recepticles on opposite sides of the structure) seems to warrant one.

George

[Homer]

I'm curious how junction boxes are such a source of fires? Is this because they're left open? (no cover plate)
A lack of a cover plate spells a real fire hazard. The reason why junction boxes are a source of fires is the simple fact that any splice is a "weak point" in the circuit.

When a fault occurs such as a short to ground or a short to neutral, for the first few milli-seconds a very large "slug" of current will flow in the circuit before the breaker/fuse opens the circuit. You may have noticed that your breakers and fuses are labelled with 10,000 AIC (Amps Interrupting Capacity). In a residential setting, you have an available fault current of around 10,000 Amps from the transformer limited by the impedance of the windings and the resistance of the conductors to and in your home. The fuse/breaker must be able to interrupt this huge slug of current. If the fuse had too low an interrupting capacity, the current may continue to flow through ionized metal vapors inside the device until it eventually exploded.

That said, when this high current flows through a splice, it is subjected to intense stress and may fail or arc. Some people who have wirenutted the HOT and Neutral conductors together by mistake and flip the breaker back on have seen sparks from the splice even though it may have been a "good enough" connection for typical use.

I hope this reinforces the need to make very high quality splices.

Homer

[gbeichho]

Now I'm curious about "Good" splices. I always use Marrettes to splice wires inside the boxes. I put the wires together and then continue twisting until I feel a lot of resistence.

George

[Wgoodrich]

Very commonly people will try to install too many wires in a wire nut getting only half of the conductors inside the wirenut threads then the others just touching making them work when tested but under load the loose connection starts frying and will start an electrical fire. Many times this happens with no problem breaking the bad connection within the box when load is applied. However many cause undo overheating of the conductors and melt down the insulation beyond the box next to the stud then a fire starts.

Many will try to twist wires together then install a wire nut. Problem is they end up with such a wad of conductors the wire nut never makes a compression connection on those wire thus creating a twisted wire connection again overheating as discribed above.

Follow listing and labeling as well as manufacturer's installation instructions with your wire nut installations all contained in a box enclosing all connections and you should be fine.

Human error and misunderstanding is the most common cause of fires. That is why many giving their time freely to help with guidance for do it yourselfers and electricians in this forum, to promote knowledge hoping to save a life or two along hte way for those that don't know they don't know.

Good LUck

Wg

[gbeichho]

I always have the marrette box cutout handy to make sure it's supports the number of wires I'm using.

The biggest issue I've run into is with boxes and the number of conductors. I'm using plastic boxes when I can, because they have the biggest space inside. But I have still run into several cases where I have trouble fitting the wires back in.

One recent example was a heater thermostat. It has the source run, (14/2), the run to the heater (14/2), a source wire splice to a second thermostat (14/2) and the 4 wires for the DP thermostat. I was within the box fill limits, as I only had 5 caps and 8 wires, but I had a heck of a time fitting it all in (especially with the recommended 6" of wire). I had to cut down the wire lengths to get it to fit.

[blueshrike]

Is there a limit to the number of conductors in a junction box. Right now I have a j-box with one incoming pair and two out going pairs. Can I add another outgoing pair to that? (Assuming the wire nuts I get are large enough for fourn #14 conductors).

Is the size of the junction box relevant? Cause further away there is a double stacked junction box with the same config. 1 Pair in , 2 pairs out. Should I use that one instead. All things considered, I would prefer to use the other circuit cause there is less on it.

Thanks for your advice!

-jacques.

[Homer]

Is there a limit to the number of conductors in a junction box. Right now I have a j-box with one incoming pair and two out going pairs. Can I add another outgoing pair to that? (Assuming the wire nuts I get are large enough for fourn #14 conductors).

Is the size of the junction box relevant? Cause further away there is a double stacked junction box with the same config. 1 Pair in , 2 pairs out. Should I use that one instead. All things considered, I would prefer to use the other circuit cause there is less on it.

Thanks for your advice!

-jacques.
Yes, the size of the junction box is relevant!

You are dealing with the issue known as "Box Fill". The rules in Canada are slightly different than in the US for calculating this.

If you have an 1.5" deep, 4" octagonal j-box you are allowed to have up to 9 #14 wires and 3 caps. Other combinations of wires and caps are allowed also but this covers your case.

You would have a total of 8 #14 wires (ground wires don't count) and 3 wirenuts.

Homer

[Unregistered]

Do all junction boxes have to have access in Ontario? I'm asking this because our builder had to fix some of the siding on our house, the workers cut through the electric wire for our dryer and as far as I can tell the electrician must have just joined the 2 wires in a box and they put the siding back up, so I'm concerned there is a junction box in my wall with no access....wondering if this violates code? Thank you.

[Homer]

Do all junction boxes have to have access in Ontario?Yes.

... so I'm concerned there is a junction box in my wall with no access....wondering if this violates code?Yes this violates code.

They need to run a new cable at least to a point where it can be spliced in an accessable JB.

Homer