Laying cables sounds simple — but it's not always
A photovoltaic system on your own roof is one of the best investments you can make as a homeowner. But between installing the modules and generating the first self-produced electricity lies a critical step: cable routing. This is where most mistakes happen — often invisibly and with consequences that only appear years later.
Here are the 5 most common mistakes when laying PV cables — and how to avoid them from the start.
Mistake 1: Laying cables over sharp roof edges
Roof tiles, slate, and trapezoidal sheets have one thing in common: sharp edges. If a PV cable is laid unprotected over such an edge, it will wear through over the years. Wind minimally moves the modules, temperature changes expand and contract the cable — all this creates friction exactly where the edge is.
The solution: At every point where the cable touches a roof edge or is routed through an opening, mechanical protection is required. A cable gland with an abrasion-resistant sleeve permanently protects the cable — without rework.
Mistake 2: Only "somehow" sealing the roof penetration
A hole in the roof through which the cable runs must be permanently sealed. Many DIY enthusiasts use expanding foam or normal sealants — this works for a short time, but not in the long term. UV radiation, frost, and temperature fluctuations cause many sealants to crack after a few years.
The solution: Use a cable gland that is designed for roof mounting. These are designed to remain permanently sealed — without regular inspection or rework.
Mistake 3: Planning too little cable length
Cables that are too tightly stretched will tear when moved or expanded by heat. In addition, a tightly stretched cable causes problems with roof penetrations: It pulls on the entry point, stresses the seal, and in the worst case can pull the penetration out of its position.
The solution: Always plan a buffer — at least 20–30 cm extra for each penetration point. The cable must not have any mechanical tension at the penetration.
Mistake 4: Fixing cables without strain relief
Immediately after penetrating into the building interior, the cable must be secured. Without strain relief, the entire cable weight hangs at the penetration point — this stresses the seal and ultimately leads to leaks.
The solution: Immediately after penetration, secure the cable with a cable clamp or strain relief clamp. This takes the load off the penetration and protects the seal.
Mistake 5: Considering cable protection as "optional"
A PV cable is built for outdoor installation — robust, UV-resistant, designed for high temperatures. But "robust" does not mean "invulnerable." Without mechanical protection at the penetration point, the insulation can be abraded within a few years. The result: insulation faults, warning messages in the inverter, and in the worst case, a fire risk due to arc faults.
The solution: Do not treat cable protection at the penetration as an optional extra, but as part of the basic installation. A good penetration with abrasion-resistant cable protection costs little — damage later costs much more.
In a nutshell
The five mistakes at a glance: laying cables over sharp edges, poor sealing, too little cable length, missing strain relief, and no cable protection. Anyone who does these things right from the start will not have to worry about their cable routing for 20 years.
Are you currently planning your PV installation or do you want to retrofit an existing system? In the NEXCAPE® shop you will find cable glands with integrated abrasion protection — specially for use on pitched roofs.
