LLT ENGINEERING · Application analysis
Published · Updated
Waterproof Wiring for Horticultural Lighting: Trunk, Dimming
On a greenhouse lighting row, the AC trunk and the dimming run fail in different ways, so each connection point needs its own checks before assembly. This guide sets the working order — load mapping, part matching, termination, sealing, locking and verification — plus the conditions that stop the job.
Scope and boundaries
Applies to wire-to-wire, junction-box and distributor connections on horticultural lighting trunks and 0–10 V or DALI-style dimming runs using the LLT catalog configurations cited below; ratings are per listed configuration. The catalog tables give rated voltage, current per contact, conductor limits and cable ranges for named configurations, but they do not state AC/DC system assignment, pinout, torque values or dimming-protocol certification, so those items stay open until model drawings and project documents confirm them.
De-energize first, then fix the numbers that decide the job
None of the configurations discussed here is stated to support live mating or breaking: lock out the trunk, verify absence of voltage, and treat every termination and mating step as de-energized work. Then fix the inputs that decide selection — trunk voltage and AC/DC system, current per fixture and per branch, startup inrush, dimming protocol and pin count.
The check most often skipped is the pair of cable numbers behind every connector. Conductor cross-section in mm² and cable outer diameter in mm are two independent checks: the catalog conductor limit is only an upper bound for initial screening, and the cable sheath diameter must land inside the seal's adaptation range. A wire that fits the contact can still fail the seal.
- Trunk voltage and system type, plus the highest working voltage at the driver input
- Continuous current per fixture, fixtures per branch, startup inrush
- Dimming protocol and the pins for signal, auxiliary supply and shield
- Conductor cross-section and sheath outer diameter of every cable
Sources: LLT selection guide · Technical applicability
Map the trunk and count the load at the inlet
One feed usually serves a row of drivers, so size the inlet for the summed simultaneous load; adding branch outlets never raises the inlet allowance. Simultaneous loading, conductor size, ambient temperature and heat dissipation all move temperature rise, so per-contact ratings are a screening step, with final acceptance against the specification and project verification.
Each connection point on a horticultural lighting trunk needs its own voltage, pin-count and cable-diameter check against the exact catalog configuration, and an IP67 listing only holds when the pair is correctly mated, locked and fitted with a cable inside the listed sealing range. Decide point by point — driver input, branch take-off, dimming. Where power and signal share one shell, check each contact group separately and never add two groups' ratings into one number. Keeping dimming on its own connector is the lower-risk default when protocol, shielding or pinout is still unconfirmed, because a combined shell forces power and signal decisions into one part number.
Sources: LLT selection guide · Technical applicability
Driver input connections on the trunk
The driver-input configurations listed for lighting run from 250 V and 15 A per contact (LLT-M16-15003F1031) to 600 V and 35 A per contact (LLT-M25-35003F1031), each with its own conductor limit and cable sealing range. The 20 A M19 option carries an IP65 basis, not IP67, and its overmolded-with-cable structure arrives with leads attached rather than being soldered on site.
Reject two assumptions before ordering: a rating that does not state AC or DC is not a promise for your system, and three pins are not automatically a confirmed L/N/PE assignment. Pin allocation and grounding order come from the drawing, and whether fixtures need protective earth decides the pin count.
Sources: LLT public connector catalog
Dimming runs: protocol, pins and shielding
Confirm the protocol first — 0–10 V, DALI or something else — then count contacts for signal, auxiliary supply and shield, and set how shield grounding is handled under the controller's documentation. The 8-contact candidates listed for lighting (60 V threaded M12, 110 V M16 and 100 V M19 push-lock, 5 A per contact) are wiring examples, not protocol certification; not every system needs eight contacts.
Two cautions follow. The M12 candidate's protection level is not listed, so treat suitability as unconfirmed until documentation arrives. And an LLT M12 series name does not establish inter-mating with another vendor's IEC M12 A-code interface — check dimensions, coding, contact count and pinout on both drawings before mixing brands.
Sources: LLT public connector catalog · LLT selection guide
Branching hardware: junction box or pluggable distributor
T/X junction boxes and pluggable distributors are different maintenance strategies, not just different housings. The screw-clamp T box LLT-L25-35003T0001 (250 V, 35 A, cable Ø 10–16 mm) suits a fixed trunk; the distributor LLT-M16-15002F3254 (250 V, 10 A) lets a faulty branch drop out without disturbing the rest. The distributor listing states no cable diameter — confirm that value before ordering cable.
Seal each outlet to its own cable outer diameter, number the branches, and leave access so a faulty string can be swapped without cables hanging from the connectors.
Sources: LLT public connector catalog · LLT selection guide
Termination, sealing and locking in order
Follow the order the model drawing sets: strip and terminate — solder for the wire-to-wire solder configurations, screw-clamp at the T box — keep sealing faces clean, confirm each seal is seated, then lock, by push-lock or thread depending on the part. Torque values and strip lengths are not published with these tables; take them from the model documentation, not from habit.
IP67 indicates dust-tightness and short-term immersion protection under specified test conditions, and the rating depends on a correctly mated and locked pair, intact seals and a cable of the specified outer diameter. Unmated ports, the far cable end and the device opening each need separate treatment. Locking cannot be judged by appearance alone: confirm engagement by the method the model document defines, and where none is defined, raise it before energizing.
Sources: LLT selection guide · Technical applicability · IEC 60529 — Degrees of protection provided by enclosures
Support the cables, verify the assembly, and know when to stop
Give every cable independent support so no connector carries hanging weight, leave room for the locking motion and the cable bend, and cap unused dimming outlets with their matching covers. After assembly, check wiring against the pinout, clamping state and locking state, then verify under the project process before energizing.
If the cable outer diameter falls outside the listed sealing range, stop and re-select the connector or the cable instead of assembling anyway; if it falls inside, proceed with termination and locking exactly as the model drawing specifies. Stop as well when a seal is cut or deformed — replace it only through a method documented for that model — when the mating pair disagrees in keying, contact count or contact gender, or when pinout and torque drawings are missing.
To close the open items, submit the fixture list, branch currents, cable outer diameters, protocol and target part numbers to the engineering team; ratings belong to specific configurations, not series names.
Sources: Technical applicability · LLT selection guide
Source parameters
| Part no. / structure | Contact count | Rated voltage | Rated current / contact | Mounting method | Conductor cross section / cable outer diameter | Protection / basis |
|---|---|---|---|---|---|---|
| LLT-M16-15003F1031Push-lock · solder | 3 pins | 250 V | 15 A | Wire-to-wire | ≤ 1.5 mm²Cable Ø 3.5–8.5 mm | IP67Catalog p. 40 |
| LLT-M19-20003F3034Push-lock · overmolded with cable | 3 pins | 250 V | 20 A | Wire-to-wire | ≤ 2.5 mm²Cable Ø 3.5–12 mm | IP65Catalog p. 60 |
| LLT-M25-35003F1031Push-lock · solder | 3 pins | 600 V | 35 A | Wire-to-wire | ≤ 4 mm²Cable Ø 3.5–13 mm | IP67Catalog p. 79 |
Original table and applicability
| Part no. / structure | Contact count | Rated voltage | Rated current / contact | Mounting method | Conductor cross section / cable outer diameter | Protection / basis |
|---|---|---|---|---|---|---|
| LLT-M12-05008F1051Threaded · soldered wire | 8 contacts | 60 V | 5 A | Wire-to-wire | ≤ 0.2 mm²Cable Ø 3.5–6.1 mm | Not listedCatalog p. 20 |
| LLT-M16-05008F1031Push-lock · solder | 8 contacts | 110 V | 5 A | Wire-to-wire | ≤ 0.3 mm²Cable Ø 3.5–8.5 mm | IP67Catalog p. 40 |
| LLT-M19-05008F1031Push-lock · solder | 8 contacts | 100 V | 5 A | Wire-to-wire | ≤ 0.5 mm²Cable Ø 6–10 mm | IP67Catalog p. 59 |
Original table and applicability
| Part no. / structure | Contact count | Rated voltage | Rated current / contact | Mounting method | Conductor cross section / cable outer diameter | Protection / basis |
|---|---|---|---|---|---|---|
| LLT-L25-35003T0001See catalog for structure · screw-clamp wiring | 3 pins | 250 V | 35 A | T three-way junction box | ≤ 2.5 mm²Cable Ø 10–16 mm | IP67Catalog p. 111 |
| LLT-M16-15002F3254Threaded · overmolded with cable (soldered) | 2 pins | 250 V | 10 A | Distributor | ≤ 1 mm²Cable Ø not listed | IP67Catalog p. 114 |
Frequently asked questions
Is IP67 enough for a permanently wet greenhouse?
IP67 covers dust-tightness and short-term immersion under defined test conditions with the pair mated and locked. Standing water, long-term immersion and high-pressure washdown are different tests; provide depth, duration, medium and cleaning method and select a configuration with matching verification.
The catalog conductor limit is larger than my wire — can I terminate it?
Only as a first screen. Check the terminal's lower conductor limit, strand structure and termination process too, and confirm the cable sheath diameter sits inside the seal's adaptation range before committing.
Will an LLT M12 plug mate with another brand's M12 A-code socket?
Not by name alone. Mating needs matching interface dimensions, locking structure, coding, contact count and pinout on both drawings, plus validation; confirm both sides before mixing brands.