PROFINET cable: what Type A, B, C and R mean, and why the flexible Siemens one stops at 85 m

Most PROFINET cable trouble is not bad cable. It is the right cable in the wrong place. Solid-core Type A run through something that moves. Flexible Type B pulled 95 m because everybody knows PROFINET does 100 m. A link with six plug connections in it that passed on a pocket tester. The jacket tells you the type. The rest is in the numbers below: what the type letters mean, the real length limits, how many connectors a link can take, the pinout, and how far to keep it from power.

What is inside a PROFINET cable

Two pairs. A standard 100 Mbit/s PROFINET cable has four cores, laid either as two twisted pairs or as a star quad, under aluminum foil and a copper braid. Cores are AWG 22. The sheath is green, RAL 6018, and the type has to be printed on it: "PROFINET Type A," "PROFINET Type B" and so on. Impedance is 100 ohms ± 15 ohms, delay skew no more than 20 ns per 100 m.

In a star quad the pairs are the opposite cores, not the neighbors. Yellow goes with orange, white goes with blue.

Star quad cross-section. The pairs run across the center: yellow with orange, white with blue.

Gigabit is a different cable altogether. 1 Gbit/s needs all four pairs, Category 5 or better, and 8-pin connectors, so the green 2-pair cable on most machines will not carry it whatever the switch is rated for.

On paper, what makes a PROFINET cable a PROFINET cable is the manufacturer's declaration of conformity. A generic shielded Cat5e can be perfectly good copper. It just has no declaration, and the connector and length rules further down only guarantee a working link when every part in it is a declared PROFINET component.

Type A, B, C and R: pick the letter by how the PROFINET cable moves

The letter is about movement. It says nothing about speed. And there is no Type D.

Type	Made for	Conductors	Worth knowing
A	Fixed installation, no movement after it is laid	Solid, AWG 22/1	The default for tray and cabinet runs
B	Flexible installation, occasional movement or vibration	Stranded, AWG 22/7	The one to use wherever there is vibration
C	Special applications, such as continuous movement in trailing chains or festoons	AWG 22, construction set by the manufacturer	Length and bend limits come from the maker, not the type letter
R	Robots: combined torsion and bending	AWG 22, construction set by the manufacturer	2-pair only. Tested to 5 million trailing-chain cycles, 5 million torsion cycles at ±180°/m and 1 million reverse bends

PROFINET cable types by application. The letter tells you how much movement the cable survives.

Two things from the floor. Vibration counts as movement, so a junction box bolted to a conveyor frame or a motor gets Type B even when nothing visibly travels. And Type B is not a trailing-chain cable. Occasional movement is a machine section that gets slid out for maintenance, a guard that gets opened. If it moves every cycle, it wants C or R.

The 100 m rule has an asterisk

Every PROFINET copper link is allowed 100 m end to end. Some cables get less. Flexibility, trailing-chain construction and flame-retardant materials can all pull the maximum length of a PROFINET cable below 100 m, and the manufacturer sets the reduced figure.

Siemens' two everyday 2x2 cables show how much that can cost:

Spec	6XV1840-2AH10 (Type A)	6XV1870-2B (Type B)
Conductor	Solid, AWG 22, 0.64 mm	Stranded, AWG 22, 0.75 mm
Category	Cat5e	Cat5e
Sheath diameter	6.5 mm	6.5 mm
Max length, FC RJ45 plug to FC RJ45 plug	100 m	85 m
Max length through an FC outlet RJ45	90 m	75 m
Min bend radius, single bend	19.5 mm	32.5 mm
Min bend radius, multiple bends	49 mm	52 mm
Max tensile load	150 N	150 N
Operating temperature	-40 to +75 °C	-25 to +75 °C
Installation temperature	-20 to +60 °C	-10 to +60 °C

The same 6.5 mm PROFINET cable in Type A and Type B, and what the flexible version gives up.

Spec Type B everywhere "to be safe" on a long conveyor and you have handed back 15 m before the first plug goes on.

The bend radius rows go the opposite way from what people expect, too. The flexible cable needs the bigger radius on a single bend, 32.5 mm against 19.5 mm. Flexible means it survives being moved. It does not mean it takes a tighter bend.

Count the plugs: four connector pairs, no patch cords

PROFINET does not use patch cords. Port to port is one end-to-end link, and when that link is built only from PROFINET components, has no more than four connector pairs and stays within 100 m, no acceptance test is required on it. Break any of the three and that guarantee is gone. Type C cable is outside it altogether: the component approach is not supported for Type C, so a Type C link follows what the cable and connector makers specify.

A connector pair is a plug and the jack it sits in. The ones at the device ports count. A bulkhead connector or a coupling with two sides counts as two pairs, unless its manufacturer declares it performs as a single connection.

Say a switch in the main cabinet feeds a drive out on the machine. The cable leaves through a bulkhead on the cabinet wall, then passes an inline coupler in a junction box halfway out. Switch port, one pair. Bulkhead, two. Coupler, two. Drive port, one. Six. Over the limit, on a 40 m run where every part is PROFINET rated.

One 40 m link, counted both ways. The inline coupler is what pushes it from four connector pairs to six.

Going past four is possible, but the job changes: the whole link then has to meet Class D channel attenuation, and the only way to know it does is to measure it. Pulling the coupler out is usually quicker.

PROFINET cable pinout for RJ45 and M12

Signal	Wire color	RJ45 pin	M12 pin (D-coded)
TD+	Yellow	1	1
TD-	Orange	2	3
RD+	White	3	2
RD-	Blue	6	4

4-wire PROFINET cable pinout. Both ends are wired the same.

Yellow with orange, white with blue: keep the pairs together. No crossover cable, either. The active devices do autocrossover, so a straight-through link is correct.

Gigabit runs go to 8 pins, wired T568A or T568B. Either works, provided the whole installation picks one before the first plug goes on. When you write it down, name the pairs by color. "Pair 1" does not get used the same way everywhere, and two drawings can mean two different pairs by it.

Siemens FastConnect plugs take the cores in insulation displacement contacts. If a plug comes off and goes back on, cut the end off and strip it fresh, otherwise the contact may not seat fully. The 2x2 plugs come with three cable outlets: 180° for SIMATIC NET modules and SCALANCE devices (multi-jack ones included), 90° for ET 200 and PN/PN links, 145° for SINAMICS and SIMOTION. All three are Cat5, 10/100 Mbit/s. Gigabit needs the 4x2 plug and a 4-pair cable.

FastConnect RJ45 plugs with a 180° outlet (left) and a 90° outlet (right). The device the plug goes into decides the angle.

Laying a PROFINET cable: distance from power, bend radius and the shield

Separation depends on the containment the data cable and the power cable run in.

Cable containment	Minimum separation S
No electromagnetic barrier	10 mm
Open metallic: wire mesh basket, or steel tray under 1.0 mm wall	8 mm
Perforated metallic: steel tray 1.0 mm wall or more, 20% perforated or less	5 mm
Solid metallic, equivalent to steel conduit with a 1.5 mm wall	0 mm

Minimum separation between a PROFINET cable and power cabling, before factor P.

Then multiply S by factor P, which counts 20 A, 230 V single-phase circuits in the run: 1 to 3 circuits is 0.2, 13 to 15 is 1.0, 16 to 30 is 2. A three-phase cable counts as three circuits, and anything over 20 A counts as multiples of 20 A. Recommended distance is twice the minimum. Twenty 20 A circuits, with data and power both in open wire basket: 2 × 8 mm × 2 = 32 mm.

Those figures assume long parallel runs beside unshielded power. On short parallel stretches inside a machine, or with shielded power cable, going below them is allowed.

On bend radius, 10 times the cable diameter for a single bend and 20 times where it gets bent repeatedly is the safe default when you have no datasheet. With one, use its number. On a 6.5 mm cable the default says 65 mm, while the 6XV1840-2AH10 is rated for 19.5 mm. Pulling needs more radius than the installed bend, and the risky moment is dragging it over a sharp corner. Put a guide pulley there.

The shield connects at both ends, normally through the metal plug, and every device also gets its own local ground. Grounding one end only is a habit people bring from other cable types. On PROFINET it takes the shield out of play at the high frequencies it is there for.

What a pocket tester tells you, and what it does not

Look first. Count the connectors, check the bends, the separation, the strain relief. Then the simple line tester. On a 2-pair cable it shows conductors 1, 2, 3 and 6 plus the shield and nothing else, which is correct. What it checks is correct connection of each wire and the shield, short circuits, and split pairs.

It does not measure the cable. Length, near-end and far-end crosstalk, attenuation and reflections need an acceptance tester that meets Class D plus the tighter 20 ns delay skew. With all-PROFINET components that test is optional. I would still run it on any link with a coupler in it, or any link you may end up arguing about later, and keep the printout with the drawings.

PROFINET cable questions that come up

Can I use a regular Ethernet cable for PROFINET?

It will usually link up, since 100 Mbit/s only needs pins 1, 2, 3 and 6. What a regular cable lacks is a PROFINET manufacturer's declaration, which puts the link outside the connector and length rules above and leaves measurement as the only proof it is good. For a bench test, fine. On a machine that ships, use declared PROFINET cable.

What is the maximum length of a PROFINET cable?

100 m end to end for copper, as a ceiling. Flexible and special cables can be rated lower. Siemens' 6XV1870-2B Type B is rated 85 m plug to plug, and 75 m through an FC outlet.

Is PROFINET cable Cat5e or Cat6?

The usual 2-pair version is Cat5e, and both Siemens 2x2 cables above are. A 4-pair version for gigabit has to be Category 5 or better. A higher category on its own does not make a cable PROFINET. The type marking and the declaration do.

Should the PROFINET cable shield be grounded at both ends?

Yes. A correctly fitted plug at each end normally makes that connection for you. Each device then needs its own local ground on top.

Before you order cable and plugs

Measure the run, count the connector pairs and decide whether anything moves before you pick a letter. For fixed runs we keep the 6XV1840-2AH10 Type A standard cable. Where there is vibration or occasional movement, the 6XV1870-2B Type B flexible cable, with its 85 m in mind. For the ends, the 6GK1901-1BB10-2AA0 FastConnect plug with a 180° outlet and the 6GK1901-1BB20-2AA0 with a 90° outlet, plus the 6ES7193-6AR00-0AA0 BA 2×RJ45 BusAdapter for ET 200SP stations. Not sure which outlet a port needs? Send us the device's catalog number and we will check before the PROFINET cable gets cut.