Solar Panel Installation and Repair, in detail

Every roof mounted panel needs a bracket, every bracket needs a fastener, and every fastener is a hole through a membrane that was keeping water out. That is the real risk in a solar install and it is where cheap installs fail. On EPDM or TPO, brackets get bedded in a self levelling sealant compatible with the membrane and Dicor goes over the fastener heads. On a fiberglass roof the substrate gets checked for solid backing before anything is drilled, and where a rafter is not where a bracket needs to be, a backing plate goes in rather than a screw into thin decking.

Adhesive mounting with no penetration at all is available, and it is the right choice on some roofs, particularly aluminium skinned trailers and coaches whose membrane is near the end of its life. It costs more in surface prep and it removes the failure mode entirely. Anybody quoting a solar install without asking the age and type of your roof is quoting half a job, and the leak that turns up eighteen months later will cost more than the array did.

• Membrane type and age confirmed before any hole is drilled
• Brackets bedded in a sealant compatible with EPDM or TPO
• Backing plate fitted inside where no rafter lands under a bracket
• Dicor over every fastener head, then photographed into the job file

Rigid framed panels sit on brackets with an air gap beneath them, run cooler, produce more for their rating, and last for decades. They are also heavy, tall enough to matter at a low clearance, and they occupy roof space in fixed rectangles. Flexible panels bond flat to the roof, add almost no height or weight, follow the curve of a van roof, and are the honest answer on a Sprinter with a rounded skin. What they do not do is last as long, because they run hot against the roof surface and heat is what degrades a cell.

Replacement is the other flexible panel problem. A bonded panel that fails after five years has to be cut off the roof, the adhesive residue cleaned away, and the surface repaired. A rigid panel that fails comes off in ten minutes on four bolts. For a van build where height and curvature decide it, flexible is correct and worth the trade. For a flat fiberglass roof on a fifth wheel, choosing flexible to save a little on the invoice is a decision the owner regrets twice.

A PWM controller connects the array to the battery and throttles that connection, which means the panel is dragged down to battery voltage and the difference is simply lost as heat. An MPPT controller converts instead, so it can run a higher voltage array into a twelve volt bank and keep most of that difference. On a cool morning with a high voltage panel the gap is substantial. MPPT is what goes on almost every install here, and the exception is a single small panel used only as a maintenance charger, where the controller would cost more than the extra harvest is worth.

Series and parallel wiring belongs to the same decision. A series string raises voltage and suits an MPPT controller, and it also means one shaded panel drags the whole string down. Parallel keeps panels independent under partial shade and needs heavier cable. RV roofs are shaded unpredictably by air conditioners, vents and antennas as the sun moves across, so we usually run a hybrid arrangement rather than one long string, and the controller gets sized to the array rather than to the battery.

The roof is already occupied. Two air conditioners, a bathroom vent, a kitchen vent, a refrigerator vent, a plumbing vent, a TV antenna and possibly a satellite dome are all up there, and every one of them casts a shadow that moves through the day. Panels get placed where midday shading is least, with service access retained around each air conditioner shroud, because somebody has to lift that shroud in three years without dismantling an array. Walkable paths matter just as much on a coach where a technician has to reach the front cap.

What that adds up to is less capacity than the roof area suggests. An owner who measures the roof and calculates six panels usually fits four once clearances and shadows are respected, and handing that number back at the estimate is better than discovering it at install. Where more capacity is genuinely needed, the answer is frequently a portable panel with a side plug rather than cramming the roof and blocking access to everything on it.

• Minimum clearance kept around every air conditioner shroud for future service
• Refrigerator and plumbing vents left unshaded and unobstructed
• Antenna and dome sweep arc mapped before panel placement is fixed
• Walk path preserved to the front and rear roof edges

Cable has to get from the roof to the controller and every route is a compromise. The refrigerator vent is the usual answer on a coach with an absorption unit, because it is already an opening to the outside, it drops straight into the interior, and no new penetration gets created. A plumbing vent stack works on some layouts. Where neither exists, a proper roof gland gets fitted, bedded and sealed the same way a bracket is, and never a drilled hole with sealant smeared over the wire.

Cable inside a vent chase is protected in loom and routed clear of the burner and the flue, which is a detail some installers skip and which matters a great deal on a gas appliance. On a van conversion the run usually goes down a corner pillar behind trim, and on a fifth wheel it drops through a wardrobe. Every foot of that run is labour, and mounting the controller close to the battery bank rather than close to the panels keeps the long section at higher array voltage where losses are lower.

The question every solar customer asks is whether the array will run the air conditioning, and the honest answer is usually no, not in the way they mean it. A rooftop unit draws a large continuous load and starts against a compressor. A roof full of panels on a good day produces energy across the whole day rather than a large instantaneous output, so what actually runs an air conditioner is the battery bank, with solar refilling it slowly afterwards. Running one unit through an afternoon means a large lithium bank, a substantial inverter, and usually a soft start on the compressor.

What solar does very well is everything else: lighting, the water pump, a refrigerator control board or a twelve volt compressor unit, fans, laptops, and keeping a bank topped up through storage so it does not sulphate. That is a genuine change in how a coach can be used. Promising air conditioning off a modest array is how owners end up disappointed by equipment working exactly as designed, so the numbers go in front of people before anything is authorised.

An aftermarket array is not factory equipment, and on a claim that distinction matters. If hail, a branch or a collision damages it, the carrier needs evidence it existed and what it cost, which means the install invoice and photographs. Owners who paid cash for an install years ago and kept nothing get a fight they usually cannot win. We keep the photographs and the parts list in the job file for exactly that reason, and a copy goes to an adjuster on request without anybody having to hunt for it.

The other claim angle is a roof repair on a coach that already carries an array. Removing and refitting panels is real labour that belongs on the estimate, and it is a line adjusters question until it is documented with photographs. Where an array sits over a membrane that then needs replacing, the removal, the new membrane and the refit are three separate operations, and pretending otherwise leaves either the shop or the owner short at the end.