LLT ENGINEERING · Application analysis
Published · Updated
M25 Power and Signal Connector: Mixed Pins and Ratings
An M25 power and signal connector is only a fit when each contact group is checked separately. If any power branch needs more than 35 A, or the cable jacket is outside the sealing range for that SKU, stop and check the drawing; this page cannot prove the rating for every mixed layout.
Scope and boundaries
Applies to LLT M25 circular connectors in 2–8 contact power layouts, 20/24 contact signal layouts, and mixed 2+6 or 3+8 power/signal versions with screw or self-locking coupling and panel or flange mounting. Rated values, wire sizes, sealing and mating conditions depend on the exact SKU, and IP67 is conditional on correct mating, locking and the specified cable seal.
Start with the actual load and cable
Start with the actual load and cable, then check the interface. An M25 power and signal connector is only a fit when each contact group is checked separately. The shell diameter tells you the envelope; it does not tell you the ampacity of the contacts inside.
Before comparing mounting styles, write down how many power branches, how many signal lines, the voltage and current of each branch, and the conductor size and jacket diameter of the cable. Those four items decide the layout; the M25 shell only has to accommodate them.
- Number of power poles and their actual current
- Number of signal lines and their voltage
- Conductor cross section in mm² and cable jacket OD in mm
- Whether the connector is panel-mounted, flange-mounted or an in-line joint
Sources: LLT selection guide · Technical applicability
Why mixed layouts split the rating
The M25 series is built around the idea of power and signal in one interface, but the ratings are not shared. Rated current is marked per contact or contact group, and adding the power group current to the signal group current does not give a valid connector rating.
In the 2+6 and 3+8 mixed versions shown in the catalog supplement, the power group is rated 20 A / 250 V and the signal group is rated 5 A / 100 V; the two groups must be checked separately. That is why a 3+8 layout can serve a motor plus sensors, but only if the motor draw stays within the power-group limit and the signal lines stay within the signal-group limit.
Sources: Technical applicability
Check the parameter table row by row
The public M25 table shows that 2-, 3- and 4-contact versions are rated 35 A at 250 V, while 5-, 6- and 8-contact versions drop to 20 A, and the 20- or 24-contact signal versions drop to 5 A at 100 V. Maximum conductor cross section also falls as contact count rises, from 4 mm² down to 0.3 mm².
Each row applies only to that specific contact count. The series maximum of 35 A does not transfer to an 8-contact or a 24-contact version, and the 4 mm² conductor limit on a 2-pin layout does not apply to a 6-pin layout. Use the row for the exact SKU, not the series headline.
Sources: Technical applicability
If the load is higher, stop and check
If any power branch needs more than 35 A, or the cable jacket is outside the sealing range for that SKU, stop and check the drawing rather than assuming the mixed layout will work. A larger conductor may carry the current, but if the jacket OD does not fall inside the sealing adapter range for that contact arrangement, the IP rating is at risk.
The same stop condition applies when the signal voltage exceeds the signal-group rating, or when the equipment side needs socket contacts and the supply direction has not been confirmed. In those cases, do not derate by guesswork; request the full pinout and dimensional drawing for the exact part number.
Sources: LLT selection guide · Technical applicability
Match the cable, not just the conductor
Conductor cross section in mm² and cable jacket OD in mm are separate checks. The conductor size sets the current capability of the termination, but the jacket OD must sit inside the clamping and sealing range of the backshell. Two cables with the same mm² can have very different outer diameters because of insulation thickness, shielding or the number of cores.
Do not assume a seal can be swapped or that a slightly oversize jacket will compress enough. Confirm the OD range for the chosen contact count and mounting style, and keep the cable bend radius and pull relief outside the connector body.
Sources: LLT selection guide · Technical applicability
Mounting and mating are separate choices
M25 versions are offered with screw or self-locking coupling, and with front-panel, rear-panel, flange or in-line mounting. The coupling style decides how the halves lock; the mounting style decides how the connector sits on the equipment. Pin or socket contact gender is also a separate choice from the housing gender, and the face view must be read with the correct orientation and keyway reference.
Same contact count does not mean two parts will mate. Check the interface dimensions, keying, contact gender and pin assignment on both sides; similar appearance is not proof of compatibility.
Sources: Technical applicability · Connection and wiring methods
IP67 is conditional, not automatic
The M25 series is described as IP67, but that rating depends on the selected configuration being correctly mated and locked, with the seal in good condition and the specified cable diameter properly sealed. An unmated connector, a damaged gasket or a cable outside the clamping range can break the protection.
IP67 also does not mean continuous immersion or high-pressure washdown; those are different test conditions. If the equipment will see long-term water exposure or cleaning jets, provide the depth, duration and cleaning method and ask for a configuration with the corresponding test record.
Sources: Technical applicability · IEC 60529 — Degrees of protection provided by enclosures
What this page cannot prove
This page cannot prove the rating for every mixed layout, and it does not provide test depth, duration or certification for a specific SKU. The 20 A / 250 V and 5 A / 100 V figures for 2+6 and 3+8 come from a catalog supplement; other mounting versions may have their own catalog pages.
If the load or cable data is missing, the practical move is to treat the layout as unconfirmed and request the full drawing instead of narrowing by shell size alone. Send the interface sketch, circuit list, conductor sizes, jacket OD and environment, and ask for the matching part number, face view and any applicable test or certification files.
Sources: LLT selection guide · Technical applicability
Source parameters
| Contact count | Rated voltage | Rated current | Maximum conductor cross section |
|---|---|---|---|
| 2 pins | 250 V | 35 A | ≤ 4 mm² |
| 3 contacts | 250 V | 35 A | ≤ 4 mm² |
| 4 contacts | 250 V | 35 A | ≤ 2.5 mm² |
| 5 contacts | 250 V | 20 A | ≤ 1.5 mm² |
| 6 contacts | 250 V | 20 A | ≤ 1.5 mm² |
| 8 contacts | 250 V | 20 A | ≤ 1 mm² |
| 20 pins | 100 V | 5 A | ≤ 0.3 mm² |
| 24 pins | 100 V | 5 A | ≤ 0.3 mm² |
Frequently asked questions
Can I add the power group current and signal group current to get the total M25 rating?
No. Rated current is specified per contact or contact group, not for the whole shell. Adding the two groups is not a valid way to rate a mixed connector; check each group against its own limit.
Does a 35 A M25 rating apply to every contact count?
No. The 35 A / 250 V rating applies to the 2-, 3- and 4-contact versions. The 5-, 6- and 8-contact versions are rated 20 A, and the 20- or 24-contact signal versions are rated 5 A at 100 V. Use the row for the exact contact count.
Is conductor size the only cable check for an M25 connector?
No. Conductor cross section in mm² affects current capability, but the cable jacket OD in mm must fit the clamping and sealing range of the selected backshell. Both values have to match the chosen SKU.
Does IP67 mean the M25 can be used underwater or under high-pressure wash?
Not automatically. IP67 covers dust and short-term immersion under defined test conditions with correct mating, locking and cable sealing. Long-term immersion or high-pressure cleaning needs separate verification.