Solar Connector & PV Wiring Guide - MC4, Fusing, Crimping
TECHNICAL GUIDE
MC4-Type Connectors: Where, Why, and How
Nearly every crystalline solar panel ships with MC4-type leads - the IP67 locking connector standard originated by Stäubli (Multi-Contact). This guide covers selection, crimping, fusing, and code items for PV installs from RV roofs to ground-mount arrays.
Where each connector goes
| Part | Use |
|---|---|
| MC4-type pair (M+F) | Panel-to-extension, panel-to-panel series strings |
| Branch / Y connectors | Parallel wiring - combining two strings (adds current: fuse it) |
| Inline MC4 fuse holder | Series fusing per NEC 690.9 when 3+ strings parallel; protects panel backsheet wiring |
| MC4 disconnect tool | Unlocking mated pairs - never pull by wire |
Fuse sizing
Use the panel label: fuse at the Maximum Series Fuse Rating (typically 15-20A for 60/72-cell panels). Fusing is required when three or more strings are paralleled - two strings can usually backfeed each other within panel ratings; three or more cannot. Inline MC4 fuse holders make this a 30-second field install.
Crimping - do it once, correctly
Use 10 AWG PV wire (USE-2/PV rated, sunlight-resistant) and a proper MC4 crimping tool with the hex die - not pliers. Strip 7mm, crimp the barrel, tug-test, then click into the housing until the tab locks. A bad crimp is the #1 cause of PV arc faults. We stock PV crimp tools and pre-terminated extension cables if you'd rather skip field crimping.
Compatibility - the honest version
Stäubli certifies intermating only between genuine MC4s (PV-KST4/PV-KBT4, $2.00-3.80 street). MC4-type connectors from every other maker - ours included - are built to the same interface geometry and IP67/TUV class and are used across the industry, but pairing brands is at the installer's discretion and some panel warranties reference connector origin. Best practice: keep connector pairs same-brand (both halves ours, or both Stäubli), which costs nothing when you're building extensions.
Why installers buy from us
Same TUV/UL-class connectors, fuse holders and branch pairs at distributor-direct pricing, same-day shipping from California, and volume terms for solar installers and RV/marine OEMs. Panels from major manufacturers (Qcells, REC, Canadian Solar, Jinko class) ship with MC4-type leads - our connector family fits that ecosystem.
