The purpose of this guideline is to help qualified individuals maintain and inspect PV systems with BFIRST Ventilated Skylight (SL) modules safely.
Safety requirements & personal protective equipment
Qualification to conduct such inspections is earned by direct on the-job training under qualified supervision or through training programs offered by accredited educational institutions or manufacturers. It should be noted that many testing and maintenance activities require two people to be performed safely and efficiently.
Major safety requirements during PV servicing include
- use personal protective equipment (PPE),
- perform lockout/ tag out procedures(LOTO),
- observe of and comply with all PV-specific system signage and warnings.
PPE includes fall protection, arc flash protection, fire protection, injury protection equipment, as indicated below
- fire-rated clothing,
- rubber-insulating gloves,
- rubber sole shoes with good traction,
- protective eyewear,
- safety belt.
Extra equipment: Lift, crane or scaffold
Lockout/tag out (LOTO) procedures are designed to ensure safe working practices and must be strictly followed whenever systems are de-energized prior to servicing.
Lockout/tag out steps include:
- notify others that the equipment will be shut down,
- perform a controlled shutdown to power down the equipment,
- lock and tag all energy isolating devices,
- de-energize the inverter,
- allow a minimum of five minutes for the dc bus capacitors to discharge after disconnecting the power
- verify that the equipment is completely de-energized by attempting to cycle it, and
- verify that the equipment is completely de-energized by testing for voltage with a voltmeter.
- Always remember the “DO NOT DISCONNECT UNDER LOAD” rule, so:
Do not open a string combiner fuse holder without first confirming that there is no current flowing on the circuit.
Do not disconnect (unplug) module leads, jumpers, or homerun wires under load.
Detailed Visual Inspection
Frequency of inspection:
(A) annual, once a year
(S) semester, every six months
(Q) quarterly, every three months
- (A) Inspect PV modules for defects that can appear in the form of burn marks, discoloration, delamination, or broken glass. If found, it is strongly recommended to replace module, in order to remove danger of fire.
- (Q) Check modules for excessive soiling from dirt buildup or animal droppings. (See chapter 5.‘Array Washing Procedure’ for proper procedures of cleaning an array.
- (A) Ensure that the module wiring is secure and not resting on the roof, hanging loose and exposed to potential damage, bent to an unapproved radius, or stretched across sharp or abrasive surfaces. If found, straighten and re-tighten wiring.
- (A) If possible, check junction box and micro-inverter box behind the modules, if they have any cracks or displaced cable glands or water accumulation. If found, it is strongly recommended to replace module, in order to remove danger of fire.
- (S) Ensure roof drainage is adequate, roof drains are not clogged, and confirm that there are no signs of water pooling in the vicinity of the array. If required, remove leaves and dirt from gutters to unblock water flow.
- (Q) Check for new shade items such as a satellite dish. If found, move new shade items.
- (A) Confirm proper system signage is in place.
- (A) Inspect racking system for defects including rust, corrosion, deformation, sagging, and missing or broken clips or bolts. If found so, a)check for proper corrosion resistant materials such as stainless steel, or for barrier materials that reduce corrosion and repaint material, b)replace broken, deformed or missing parts, after correcting root cause.
- (A) Check for signs of animal infestation under the array. Wearing PPE to prevent bites and stings from insects, snakes, and vermin, clean up infestation.
- (A) If sprinklers are used to spray the array, check that the water is free of minerals (demineralized) as these minerals can cause gradual performance degradation.
- (A) Inspect conduits for proper support, bushings, and expansion joints, where needed.
- (A) Check the integrity of the penetrations on the roof to ensure they are watertight. If not, repair defect by a) replacing the whole anchor rod with injectable mortar or b) apply waterproof sealants on the penetration.
- (A) Open the door to the AC and DC disconnect(s) and check for torque marks on the connections. Torque marks are made when lugs have been tightened to the proper torque value. Ideally they are applied during initial installation, but if not, the technician can mark the lug after torqueing during a maintenance visit. A proper torque mark is made with a specialized torque marking pen. The mark is a straight line through the lug and the housing. Over time, if the line separates between the lug and the housing, it shows that the lug has moved and needs to be re-torqued.
- (A) If a weather station is present, ensure that the sensors are in the correct location and at the correct tilt and azimuth. A global horizontal irradiance sensor should be flat, and a plane of array irradiance sensor should be installed to the same pitch and orientation as the array. Irradiance sensors should be cleaned to remove dirt and bird droppings.
- IMPORTANT: Once again, access to electrical wiring by all unauthorized persons is restricted.
Array Washing Procedure
Depending on the site conditions, an annual, semester or even quarterly cleaning may pay for itself in gained production. Some sites have more accumulation of dirt and other buildup than other sites. Depending on the tilt of the array and amount of seasonal rainfall, the soiling can have a dramatic impact on the overall production of the system.
- Wear rubber sole shoes with good traction to prevent slips and falls
- A lift may be needed to access the array. Follow aerial lift safety procedures, including wearing a harness if required.
Bear in mind that you are NOT to:
- walk on the modules. Use non-conductive extended reach broom and hose handles to reach modules
- use high pressure water,
- use harmful chemicals,
- use cold water when the module glass temperature is hot or use hot water to clean cold modules. Thermal shock from the temperature difference between the glass surface and the water can result in fracturing or breaking of the glass.
Before Washing Modules
- Inspect the array to confirm that there are no broken modules (shattered glass). Never spray broken modules with water. Perform a safety evaluation of the site looking for safety hazards such as trip hazards or areas that will become excessively slippery when wet.
- Plan for water runoff. If the site has a storm water prevention plan in place, determine how the used water will be collected and disposed of. If harmful chemicals are not used during the cleaning process, drain guards can be used to filter out sediments.
- Be aware of trip hazards introduced by having hoses spread throughout the property, cone off area if needed.
- Determine whether the module cover glass is too hot and will be damaged by coming into contact with cool water. Depending on the local climate and time of year, it may be best to limit washing activities to the morning or evening hours.
- Identify the water source to be used. Ideally, there will be a source of water near the array. If not, it may be necessary to bring in water from an outside source, which will involve a tank or water truck.
- Determine the best method of getting water to the modules. Typically, a ¾-inch garden hose is used to connect to a spigot near the array.
- Set up hoses and tools.
- If required, block or install drain guards for filtration or water capture purposes.
- Take a baseline production reading of the system, noting both kilowatt-hour (kWh) output of each of the inverters and weather conditions including temperature and irradiance.
- De-ionized water is preferred to prevent spotting and calcium buildup.
- Normal water pressure of 50-70 psi is recommended; do not use high pressure washers.
- If high pressure washers are necessary, hold the pressure source far enough away from the modules to prevent damage. As a rule of thumb, if the stream is too strong to comfortably hold one’s hand in, it is too much pressure for the modules.
- Spray the modules with water.
- Use a soft-bristled brush to get stubborn dirt off.
- If needed, use a non-damaging soap.
- Use extensions with tools to be able to reach extended distances.
- If needed, wipe modules dry.
After Washing Modules
- After the system returns to steady-state temperature (i.e., there is no remaining impact from the cooling effect of wash water), take another production reading of the system, noting both kWh output of each of the inverters and weather conditions including temperature and irradiance.
- Clean up tools.
- Remove any drain guards or blocks.
- Record the washing in the maintenance log.
- Compare production of the clean system to the previous production values.
Text written by HERON, Greece