Show a three- or four-way wire connection the way a hydraulic drawing shows a tee: a filled dot where the lines meet, tagged with a terminal block ID and the terminal numbers. A four-way +24 V branch — one feed and three coil taps — becomes four jumpered terminals, TB12/1 through TB12/4, all on wire number 201. You draw it three times, once on each document that needs it: the dot on the schematic, the same four terminals on the terminal strip drawing, and the strip position on the panel layout. Three documents, one link between each, and your panel shop never has to work a branch out on the floor.
What you need on the desk
Five items, before the first dot goes down on your schematic:
- The schematic, wire-numbered. One number per net, and every leg of a branch keeps the same number (201 in the worked example below).
- The terminal block catalog. It gives the block width, the two-conductor ceiling per point and the matching comb jumper. A compact 2.5 mm² block runs about 6 mm wide on typical terminal block datasheets.
- Jumper hardware. A jumpered group of 4 terminals needs 3 links, or one 4-pole comb.
- The panel layout drawing. Backplate, 35 mm DIN rail (IEC 60715) and wiring duct, so the strip position is drawn rather than guessed.
- NEC 312.6 for power legs. It sets the minimum wire-bending space at terminals for cabinets and cutout boxes; a feeder needs that depth between its terminal and the duct wall.
Draw the dot on the schematic
North American ladder drafting and IEC 60617 both use the filled dot for a connection, and IEC drafting adds a helpful default: a line ending on another line reads as connected, while a bare crossing reads as two nets passing without touching. The dot is the only thing telling the reader that your cross is a junction.
- Put one filled dot where three or more conductor legs meet at one potential.
- Wire-number the net once, and give every leg the same number: the legs differ by destination, not by name.
- Tag the dot with the strip ID and the terminal range — TB12/1-4, jumpered. Electrical CAD packages generate that tag from the terminal definition; on a paper drawing, you write it beside the dot.
- Count the legs: 1 feed + 3 taps = 4 conductors at one potential. That count sets the terminal count, the jumper count and the rail length in the next two drawings.
Signal nets that stay inside the cabinet get the same treatment; loop diagrams for signals that stay inside the cabinet keep each net traceable without adding hardware.
List every leg on the terminal strip drawing
The strip drawing is the sheet your shop wires from, and it is the document drawing sets most often leave out. Give it one row per terminal: terminal number, wire number, size, from, to, and the jumper as a bar drawn across the group. A sample row for the branch below reads: TB12/3 · wire 201 · 1.5 mm² · to K2 coil A1 · jumper 1-4.
Then the group rules:
- One conductor per terminal in a branch group. Two per point is the datasheet ceiling, not the target; one conductor per leg means you can lift any single load for testing without breaking the net.
- Jumper links = legs − 1, so a 4-leg group takes 3 links.
- Label spare terminals as spares. A blank row reads as an omission; a labeled spare reads as design.
The junction-box terminal drawing checklist covers the full column set, and grouping I/O and spares on terminal strips shows how to order strips so the spares stay useful.
Place the strip on the panel layout
The layout turns the strip into hardware. TB12 lands on 35 mm DIN rail (IEC 60715) at a drawn position, duct above it, strip label facing the door. Widths come straight from the catalog: five 6 mm blocks — four terminals plus one spare, the 20% margin — take 30 mm of rail. Leave about 1 in [25 mm] between duct wall and terminal row; that much rise lets a 1.5 mm² wire enter the block square. The duct run is drawn to the 50% interior fill that wiring-duct fill tables set as their maximum, citing NFPA 79-2012 section 13.5.2. For power legs, NEC 312.6 bending space sets the gap between terminal and duct wall instead. The backplate and DIN rail layout guide walks the whole arrangement, and you can drop the strip into a 3D enclosure model to check it before the metal is cut.
Worked example: a four-way +24 V branch
Assume a 24 V DC rail feeding three solenoid coils that all tap off one point. Coil draw is 0.5 A each — a worked-example figure you replace with your coil's datasheet value. Legs: 1 feed + 3 taps = 4 conductors on net 201.
The schematic gets one filled dot tagged TB12/1-4, jumpered. The strip drawing gets:
| TB12 | Wire | Size | From | To | Jumper |
|---|---|---|---|---|---|
| 1 | 201 | 1.5 mm² | PSU +24 V | — | 1-4 |
| 2 | 201 | 1.5 mm² | — | K1 coil A1 | 1-4 |
| 3 | 201 | 1.5 mm² | — | K2 coil A1 | 1-4 |
| 4 | 201 | 1.5 mm² | — | K3 coil A1 | 1-4 |
Jumper current. The segment nearest the feed carries all three coils: 3 × 0.5 A = 1.5 A. The middle segment carries 1.0 A and the far end 0.5 A, so you pick the comb for the 1.5 A segment from the block datasheet. Heat sits where the current is.
Rail length. 5 blocks × 6 mm = 30 mm of 35 mm rail, spare included.
Duct fill. A 1.5 mm² control wire runs about 3.0 mm OD, so one wire occupies π × (3.0 mm ÷ 2)² = 7.1 mm² of duct section. Four wires occupy 28 mm². A 25 × 40 mm duct offers 25 × 40 = 1000 mm², so the branch alone sits at 28 ÷ 1000 = 2.8%. The 50% cap binds on the whole duct run, so this branch's share is what you add up across all the nets in it. The strip-and-duct pairing here matches the layout of a full CNC control cabinet, scaled down.
Four terminals, 3 jumper links, 30 mm of rail: the whole branch is on paper before any wire is cut.
Checks when the set is done
Run the drawing set against this list before it leaves your desk:
- Every junction dot carries a strip ID and a terminal range; every bare crossing is two nets, on purpose.
- Jumper links = legs − 1: the 4-leg example shows 3 links, and the schematic tag matches the strip rows one for one.
- One wire number per net on every leg; destinations differ, the number does not.
- Every terminal on the strip drawing exists on the layout at its drawn rail position, and the duct above it stays inside the 50% fill.
- Lock the panel off, prove it dead, and ring each jumpered group end to end; a leg added on the floor then gets a row, a link and a revision number before hand-off.
Mistakes that cost the rating
The drawings carry the branch; the enclosure carries the water. When a branch leaves the box — a sensor spur running out along a washdown line, say — the hole it passes through decides the rating. Order the cutout with the enclosure rather than drilling in the field: a field hole above the gasket line wicks washdown water straight onto your terminals. Fit the gland at the box's own rating, because the weakest part sets the rating — an IP54 gland turns a washdown enclosure into a splash guard. Our stainless bodies are rated NEMA 4X / IP66 by the manufacturer; not UL listed, and 304 or 316L cutouts built to your drawing arrive in 10 business days from your approval of the drawing.
Start from the custom enclosure builder or the stainless cutouts page. The sensor-cable connection guide covers the gland side of that spur, and connecting a wiring trough without losing the rating covers extending the run while keeping the seal.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 6 × 6 × 4 in | 304 stainless | 6 x 6 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 8 × 6 × 4 in | 304 stainless | 8 x 6 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 10 × 8 × 4 in | 304 stainless | 10 x 8 x 4 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
How do you show two wires crossing on a wiring diagram without a connection?
Leave the crossing bare. With no dot, both IEC 60617 drafting practice and North American ladder style read the two nets as unconnected, so a bare cross means pass-through by convention. Put that convention in the title block as one line so every reader and every panel shop takes each dot the same way, and add a small hop at crowded crossings.
What jumper does a four-way branch need?
Count links, not boxes: 4 jumpered legs need 3 jumper links, or one 4-pole comb. The segment nearest the feed carries the whole branch: in the worked example, three 0.5 A coils put 1.5 A on the first link, 1.0 A on the second and 0.5 A on the last. Pick the comb for the 1.5 A segment from the block datasheet; heat sits where the current is.
Can a multi-way branch leave the enclosure through a field-drilled hole and a gland?
Order the cutout with the enclosure and keep the gland at the box's rating, because the weakest part sets the rating: an IP54 gland on a NEMA 4X box drags the whole assembly down to IP54. Factory-cut 304 or 316L cutouts sized to your gland drawing arrive in 10 business days from your approval of the drawing.
What changes when the branch carries power instead of 24 V control?
Same three documents, bigger hardware: power distribution blocks take one input and split it to several output terminals, each output keeping its own torque value from the datasheet. NEC 312.6 bending space grows with conductor size, so the strip drawing gains depth between terminal and duct wall, not just width.
