Short answer: TS35 is the 35 mm top-hat rail defined by IEC/EN 60715, and it comes in two depths — 7.5 mm and 15 mm — which is the distinction that decides whether a heavy contactor stays clipped in place or falls off when the panel is shipped. The shallower rail is the default for MCBs, RCBOs, terminals and small relays; the deeper rail holds heavier devices more securely and costs enclosure depth. Alongside them sit two other profiles you will meet in older panels: TS15 for miniature terminals and the G32 asymmetric rail.
We export enclosures and DIN components as an independent trading company — not a manufacturer, and not an appointed distributor of any brand. Rail choice looks like a detail until a panel arrives on site with a row of contactors hanging by one edge.
What TS35 actually specifies
The rail is a cold-rolled steel strip formed into a hat section, 35 mm across the outside of the top, with a 1 mm nominal material thickness in the standard version and taller variants offered at 1.5 mm and 2 mm for heavier loads. Devices clip onto it with a spring-loaded foot or a screw-fixed foot, and the profile is symmetric, so a device can be mounted from either direction.
The dimension that is usually missing from a purchase description is the depth. A 35 × 7.5 rail sits the device 7.5 mm off the mounting plate; the 35 × 15 rail sits it 15 mm off, giving a deeper grip on the foot and more room behind the device for wiring that passes down the plate. Both accept the same 35 mm devices — the difference is retention and depth, not compatibility.
The four profiles you will meet
| Profile | Nominal size | Typical use | Watch out for |
|---|---|---|---|
| TS35 × 7.5 | 35 mm wide, 7.5 mm deep | MCB, RCBO, RCD, modular contactors, terminals, small relays, meters | Default choice; heavy devices can rock on the shallow grip |
| TS35 × 15 | 35 mm wide, 15 mm deep | Larger contactors, overload relays, heavy terminal blocks, devices with deep feet | Costs 7.5 mm of panel depth across the whole row |
| TS15 | 15 mm wide, low profile | Miniature terminals and small signal components in compact boxes | Not interchangeable with TS35 — different clip geometry |
| G32 | 32 mm asymmetric G section | Older installations, legacy terminal and relay ranges | Asymmetric, so devices only fit one way; mixed with TS35 rows only by using adaptors |
A panel that mixes profiles is not wrong, but each row should be built on one profile and the drawing should say which. Two rows at different heights also change the wiring duct layout, which is where the depth budget gets spent.
Depth is the hidden cost
An enclosure is bought for its internal depth, and every millimetre goes to one of three things: the rail, the device, and the space for wires to leave the device. A modular MCB on a 7.5 mm rail needs around 70 mm behind the door including wiring room; a contactor on a 15 mm rail needs more. Add a wiring duct between rows and the figure climbs again.
The usual planning rule is to allow 20–30 % spare rail length for future circuits, and to check depth against the deepest device plus the bend radius of the largest conductor that lands on it. A 4 mm² conductor bent into a 25 A terminal needs more room than the catalogue drawing suggests — and that room has to be behind the door, not in the imagination of the installer.
Steel, thickness and span
The rail is a beam, and it deflects. A 1 mm rail carrying a row of MCBs over a 600 mm span is fine; the same rail carrying four 95 A contactors is not. Three rules cover most cases.
First, support the rail with a screw at least every 200–300 mm, and always within 50 mm of each end of the row. Second, use the deeper 15 mm profile and 1.5 mm material for devices above roughly 40 A, and add supports where the row is longer than about 500 mm. Third, fit end stops at both ends of every row: a device that slides along the rail is a device whose terminal screws can loosen, and in a container shipment the whole row can shift as one block.
| Row type | Rail profile | Suggested support pitch | End stops |
|---|---|---|---|
| MCB / RCBO row | TS35 × 7.5, 1 mm | Every 250–300 mm | Both ends |
| Terminal row | TS35 × 7.5 or × 15 | Every 250 mm | Both ends |
| Contactor / overload row | TS35 × 15, 1.5 mm | Every 200 mm | Both ends, plus a screw-fixed device if vibration is expected |
| Meter and instrument row | TS35 × 7.5 | Every 300 mm | Both ends |
| Mixed retrofit row | Match the installed profile | As existing, add supports if devices rock | Both ends |
Mounting practice that survives a shipment
Cut the rail square and deburr both ends: a burr interferes with the end stop and can cut the installer. Fix the rail with pan-head screws and washers, not countersunk screws into a slotted hole, and do not rely on the rail as the protective conductor unless the assembly was designed for it — the rail is plated steel, and its continuity depends on screw torque, paint and corrosion over time. Where the rail is used for earthing, use a proper earthing terminal and a separate conductor.
Align multiple rows on a common horizontal datum rather than by eye: the wiring duct covers, the door-mounted devices and the labels all reference that datum, and 3 mm of drift across a 600 mm panel is visible. Leave at least 30–50 mm between the end of a rail and the enclosure wall for wiring and for the door hinge clearance.
Matching devices to the rail before ordering
Modular devices are defined in 18 mm units, so a 12-way board is about 216 mm of rail plus end stops. A three-pole contactor may be one 45 mm width but a much deeper foot, which is the case that fails on a 7.5 mm rail. Metering and control relays vary the most: some clip directly, some need a separate socket or a screw-fixed foot, and a few older ranges are G32 only. Check the foot type on the datasheet, not in the photo.
Voltage and frequency do not change the rail, which is why this is one of the few components that can be specified once for a project that ships to several markets — 110–127 V and 220–240 V systems use the same TS35 profile. What changes by destination is the enclosure, the certificate and the labelling language.
What to put on the purchase order
Profile and depth (TS35 × 7.5 or × 15), material thickness, length or pre-cut lengths, hole or slot pattern, finish (zinc-plated is standard; ask for the plating thickness if the site is coastal), quantity of end stops, and whether the rail is to be supplied with the enclosure as a fitted set or loose. Add the device list with weights if the panel is heavy — it is cheaper to specify a 15 mm rail at the quotation stage than to rebuild a row on site.
FAQ
Will a 35 × 15 rail take the same devices as a 35 × 7.5 rail?
Yes. Both are TS35, and the clip geometry across the 35 mm width is the same. The deeper rail gives a longer engagement on the device foot and holds heavy devices better, at the cost of 7.5 mm of panel depth.
Can I use aluminium rail instead of steel?
It exists, and it is lighter and corrosion-resistant, but it is softer and the retention force and earthing behaviour differ. For load-bearing rows and for any assembly that will be type tested, use the steel rail the assembly was designed around.
Does the rail need to be earthed?
Not automatically. If the assembly uses the rail as a protective conductor, that has to be a designed connection with a proper earthing terminal and a conductor sized for the fault current. A rail fixed with painted screws is not an earth path.
How much spare rail should a board include?
Twenty to thirty per cent of the used length is the usual planning figure, and it should be spare rail plus spare duct space, not just an empty gap at the end of a row that has no way to be wired later.
Related: Planning an enclosure in DIN modules · IP rating guide for enclosures · NP2 push buttons and pilot lights · NTE8 on-delay and off-delay relays · MCB range overview · Cross-reference an existing device · Request a quotation