Size calculation of terminal bars / terminal blocks
31. May 2023Updated on 22. March 2024stefan
General information
For terminal bars (and the terminal blocks they contain), the program calculates an automatic size that depends on the type and quantity of terminal bars they contain.
The aim of the calculation is to reserve sufficient space for terminal bars. It is rounded up deliberately to avoid undesirable space problems later when building the switch cabinet.
If you are not happy with the size calculation, you can select the option “Convert to placeholder” by right-clicking on a terminal bar in the tree. This creates a placeholder of (initially) the same size. Double-click on the placeholder to change the size manually.
Goal of the automatic calculations
There are a few important goals for the calculation that I would like to summarise in more detail:
The calculation is optimised for planning new state-of-the-art distribution systems
Terminal bars can also always be designed using placeholders => you can then plan freely in a 0.5 HP grid if the calculation for older systems does not fit.
No over-optimisation to mm:
You always plan a new distribution board with a bit of ‘breathing space’, things always change on the construction site, so you don’t want to end up with a distribution board that is too small. A ‘little’ too big (1-2 modules) is always okay.
Target group: Planners who want to plan quickly and pragmatically. Time is money -> generalised approaches are more important than detailed planning
Generalised approaches and standards beat checkboxes for fine-tuning
An important feature of stromlaufplan.de has always been: you cannot customise everything -> but what you design will work in many cases. This means that diagrams can be created quickly and pragmatically with just a few clicks. If you need finer planning details, you should purchase a CAD programme as a supplement.
The calculation should work equally well enough for Wago or Phoenix
Formulas for calculating the size of terminal bars
The following calculations can currently be made:
The number of terminal blocks required for each terminal bar is first calculated
For 230V, L/N/PE terminals are always used, then additional LL terminals (see below for special cases)
For 24V and KNX with simple LL terminals
If you use the “Modules calculation” export under Exports, you will find a spreadsheet where you can see the distribution of the terminals
For terminals <=2.5 mm² CS area:
Terminals are recognised with a standard width of 6 mm. This is suitable for Wago and also Phoenix and a separator plate here and there.
If there are more than 4 (L/N/PE) terminals in a terminal bar, a busbar is used in the calculation.
Generalised approach: 1.5 HP // 26 mm on top. Sufficient for one N-disconnect terminal + 1-2 busbar supports
With max. 4 (L/N/PE) terminals, it assumes that these are simply bridged, no busbar supplement
But: if there are too many (>=2) L/L terminals in between, then we will use the busbar anyway
No busbar for 24V or bus systems (they also have no L/N/PE terminals)
For terminals with a >CS area of 2.5mm² -> no longer calculated with two-tier terminals, each wire has its own terminal
4.0/6.0 mm² RK have a width of 6.2 mm
6.0/10.0 mm² RK have a width of 7.5 mm
10/16 mm² RK have a width of 10 mm
16/25mm² RK have a width of 12mm
A general 1 mm is added to each terminal: this covers the fact that a separator plate or separator wall is placed here and there
KNX (feed-through) terminals are set at 4 mm.
Both Wago and Phoenix offer various terminal types for KNX cables. These are usually narrower and enable a large number of KNX cables to be bridged in a small space. In our experience, a calculation of 4 mm per (double feed-through) terminal fits very well as a general rule for the various available systems.
Each terminal bar always has an extra 6 mm for an end clip for labelling
After the calculation is complete, the grid is rounded up to 0.5M.