Close the terminal cover door click, please.

This morning I am traveling to Melbourne Australia for a few days. While there I will be talking to one or two of end users about design - electro mechanical design, of our SCD5200 IO terminal assembly. The unique SCD5200 design has been stable since it's introduction 10 years ago, thereby begging a 'why change it ?' from our team as well as our end users.

SCD5200 remote terminal units are compact with a reasonably high density hard wired IO. The mix of IO type {Discrete,Analog} and DC/AC voltage levels {24,48,129} provides convenience but needs special design consideration.

The potential design change, would be based on a requirement to increase the insulation thickness of the end user wiring connecting to the assembly. No it's not about increased voltage levels, nor about an increase in accuracy, not current rating nor actual wire cross section.
By taking the thicker field wiring 450/700V per AS5000-3, directly to the RTU assembly, the end user avoids a step down in wire thickness, just to make the connection. However, thicker wiring from the field, when bundled in a confined space, takes up more cross-sectional area.

The Grey Door, Green Terminal Blocks, and Blue Wiring Guides

In 1992 a new compact model SCD5200 was released, being more compact than it's C50/RTU50 predecessor and featured a removable hinged cover. This cover, when closed restricts the available space for the 44 wires which run up the guide channel to the integrated terminal blocks. Now if we allow for 600 volt insulation on 1mm2 field wire and we use all the signals [i.e 44 wires] we are NOT going to be able to close the cover.

Thus - we need a bit more space for a bunch of wires - so the door could be closed. The width and height of the module is constrained by the form factor of the multi-module unit, which means we would need more depth.

The design question is how much and what other design constraints will follow on the way to higher insulation rating with the terminal cover closed.

If you might be affected by:-

1. a change in depth of the blue wire guide channel, increasing by around 10mm- 15mm and 
2. raising the terminal block entry height by an equivalent amount, 

, please consider making a comment or send an email.

For the next few weeks, we will keep the lines open on any suggestions and impacts, and keep readers up to date with any other developments pending.