Terminal boxes vs connectors 1

[MarcT]

Hi everyone,

I am wondering about the difference between connections made in a terminal box as opposed to the connections in a dedicated connector. As a mechanical engineer this really isn't my cup of tea, but I'm trying to understand this requirements behind the two different situations to be able to make design choices.
What puzzles me is that for terminal boxes like in this image both CSA and UL standards require a certain amount of air volume in the box (123 cc total or 24 cc per conductor).

When you use a connector such as these from TE to make the same electrical connection (same voltage/amp requirements) there is no air volume requirement.

So why is this the case? And might it be allowed to use the principles of the terminal box (screw a conductor to a terminal) while circumnavigating the air volume requirement by for example closing off the connection terminals to a similar degree as in a connector?
Before you ask why I would want this; standard connectors in the required rating are too large for our purpose, but terminal blocks aren't.

I hope someone can help me make sense of this.
Thanks!

 

[Black Phoenix]

SparWeb - mainly because the procedures were followed incorrectly by the technician.

The connecting boxes are mounted to the chassis, which sits on good suspension, so there's little vibration (not enough to cause any things to come loose before the next checkup!). The motor cables are flexible and tied to a beam, to which they transmit mechanical forces that arise from train dynamics, leaving the connecting box itself "relaxed".

I don't know if this is relevant to the topic, but here's for example a typical connecting box on one of old trains (if I'm not mistaken, it's made of bakelite):

https://i.imgur.com/UQXeKuY.png

Other connection boxes are made of metal (

https://i.imgur.com/X8JVIDz.png

for example). Terminating wires to those 'hooks' that are bolted on are also a prone to problems...

 

[MarcT]

1 The wire space rules do not apply to terminal boxes that are part of a motor.

Could you tell me where you found that? If what you say is the case it would solve our problems, but when I look at the CEC I can only find teh following. There is nothing there about inclusivity or exclusivity in certain cases.

4.13 Boxes for Wiring Terminal Parts
4.13.1 Size
Boxes, either integral with or attached to equipment, shall be of sufficient size to accommodate wiring joints or terminal
blocks without crowding.
4.13.2 Construction
4.13.2.1
Boxes shall have removable plates to facilitate connection and inspection, and no conductor shall be brought out
through such plates.
4.13.2.2
Boxes for use in nonhazardous locations shall have no openings other than those which are required for support and
connections and which will be filled or covered when the box is in use.
4.13.2.3
Where conductors pass through an opening from the enclosure of a device to a terminal box
(a) the edges of such openings shall be well rounded to prevent abrasion of the conductor insulation;
(b) a bushing shall be used to protect the conductor insulation; or
(c) the opening, with the conductors in place, shall be filled with an insulating compound that will prevent the conductors coming in contact with the metal surrounding the opening.

 

[waross]

CEC Canadian Electrical Code? It doesn't have a rule 4.13
Our code applies to junction boxes installed and wired in the field.
There is a table in our code that lists the volume required for each different gauge of wire.
Motor terminal boxes are not covered by this code. The motor manufacturers work to different codes.

Bill
--------------------
"Why not the best?"
Jimmy Carter