What's the point of DIN rail terminal blocks?

rewireIT · Jun 27, 2023

I keep seeing these on pics of installations, mostly industrial, and just wonder what they're for? Are they fused?

Why put one in when we can go straight to the breaker instead?

James · Jun 27, 2023

It is a good way to joint the cables from outside the cabinet to inside it.
they are not fused (normally) but can be.

example, I build a panel to control 5 pumps
there are various float switches and pressure sensors involved plus of course 5 x 3 phase pumps to connect.

it is far easier to build a panel with all the terminals marked and at the bottom of the panel for someone else to wire up to than it would be for the installer to have to wire all the sensors and motor cables to the relevant contactors and plc inputs inside the panel.

plugsandsparks · Jun 27, 2023

There are many reasons why but, in general they are used often in Panels Boards that are designed , built and tested off-site. When on-site the electrician can then gland and terminate all remote cables to the relevant terminal block. This saves the electrician pulling the panel board apart to locate its upstream connection point, which may be a breaker or overload or contactor. They are provide a good isolation point for testing and fault finding.

rewireIT · Jun 28, 2023

Thanks you two; makes total sense and now i feel silly.

James · Jun 28, 2023

Not silly, you are now just a little more informed.

pc1966 · Jun 28, 2023

Just to add another advantage of the DIN terminals that you can link the terminals together using purpose designed jumper bars and that can be useful if you need, say, 4 cables connected to one without wanting to double-up wires, etc.

RS PRO Jumper Bar for Use with DIN Rail Terminal Blocks | RS

uk.rs-online.com

Also normally the green/yellow terminals have a clamp to the metal rail, and that is often useful for reliable low-impedance earthing. Of course there are some situations where you don't want that, like extending cables where you want to test the CPCs separately, but for panel building that is not so common.