Rooftop Solar PV Testing How to Check Solar Irradiance During Maintenance Malaysia
Rooftop Solar PV Testing – How to Check Solar Irradiance During Maintenance Malaysia
Rooftop solar PV systems are increasingly installed on factories, warehouses, commercial buildings and residential properties.
When technicians perform inspection or maintenance, one important question is:
How much solar radiation is actually reaching the PV modules at the time of testing?
A solar irradiance meter provides this information in watts per square metre (W/m²).
For Malaysian solar installers, electrical contractors and facility maintenance teams, portable solar radiation measurement can provide useful environmental context when evaluating PV system performance.
The VICI LX-107 Solar Power Meter is designed for portable solar radiation measurement and can be used for solar installation and related field applications.
Why Measure Solar Irradiance During Rooftop PV Maintenance?
PV electrical performance is influenced by available sunlight.
If a technician measures lower-than-expected electrical output, it is important to know whether the modules were receiving strong or weak solar radiation at that moment.
Consider two situations.
Situation A
PV output is lower than expected, but solar irradiance is also low because of heavy cloud cover.
Situation B
PV output is lower than expected while solar irradiance is relatively strong.
These situations should not automatically lead to the same troubleshooting conclusion.
Measuring W/m² helps establish the environmental conditions under which the electrical measurements were taken.
What Is W/m²?
W/m² means watts per square metre.
In solar measurement, it represents the incident solar power over an area.
A solar irradiance meter measures this incoming radiation directly.
It does not measure how much electrical power the PV system produces.
This distinction is important:
Solar irradiance meter → incoming solar radiation
PV/electrical tester → electrical characteristics of the solar system
Using the appropriate measurements together provides more useful information during maintenance.
Rooftop Solar Irradiance Testing Procedure
A basic field workflow can be carried out as follows.
Step 1 – Observe the Weather
Before taking measurements, note whether the sky is:
Clear
Partly cloudy
Overcast
Rapidly changing
Weather conditions can cause irradiance to change quickly.
Step 2 – Select W/m²
Set the solar power meter to display solar radiation in W/m².
This is a commonly used unit for PV-related irradiance measurements.
Step 3 – Position the Sensor Correctly
When the objective is to evaluate irradiance incident on the PV modules, sensor orientation should be relevant to the plane of the modules.
Do not assume that a horizontally positioned sensor receives exactly the same radiation as an inclined PV module.
Orientation matters.
Step 4 – Check for Shading
Make sure the technician, tools, roof structures or nearby equipment are not casting a shadow over the sensor.
Even temporary shading can change the measurement significantly.
Step 5 – Record the W/m² Reading
Record the solar irradiance together with the measurement time.
Step 6 – Take the PV Electrical Measurements
Perform the required PV measurements as close in time as practical to the irradiance reading.
This reduces the possibility of comparing measurements taken under very different sunlight conditions.
Example Rooftop PV Inspection Record
A simple field record could include:
Site: Factory rooftop PV
Date: __________
Time: __________
Weather: __________
Solar irradiance: __________ W/m²
Module temperature: __________ °C
DC voltage: __________ V
DC current: __________ A
String / Array: __________
Remarks: __________
Recording environmental and electrical information together creates a better maintenance history.
Why Malaysian Weather Makes Timing Important
Solar measurements are not static.
Passing clouds can cause the solar radiation reaching a rooftop to change rapidly.
For example, a technician may record one irradiance value and then obtain a noticeably different reading only a few minutes later.
Therefore:
Do not rely on one morning irradiance reading to represent conditions for measurements taken much later in the day.
When irradiance is being used to provide context for PV troubleshooting, measure it close to the corresponding electrical test.
Factory Rooftop Solar Maintenance
Factories are an especially relevant application.
Large industrial roofs may contain substantial PV installations, and maintenance teams may need to investigate changes in system performance over time.
Possible inspection areas include:
Solar modules
PV strings
Connectors
DC cabling
Inverters
Electrical panels
Shading
Module contamination
Hotspots
Mounting structures
A solar irradiance meter adds another useful measurement to this maintenance process.
Warehouse Rooftop PV Inspection
Warehouses often have large roof areas suitable for solar installations.
Different parts of the roof may also experience different conditions because of:
Roof orientation
Nearby buildings
Ventilation structures
Water tanks
Trees
Antennas
Other rooftop equipment
When comparing different areas, technicians should ensure that irradiance measurements are performed consistently.
Does Low Solar Output Mean the Panel Is Faulty?
Not necessarily.
Lower output can occur for many reasons, including weaker sunlight.
Other potential factors can include shading, contamination, module temperature, wiring problems, connector issues, equipment condition and system configuration.
This is why troubleshooting should rely on multiple relevant measurements rather than a single electrical reading.
A solar irradiance meter helps answer one specific question:
What were the sunlight conditions when this PV measurement was taken?
VICI LX-107 Solar Power Meter for Rooftop Testing
The VICI LX-107 Solar Power Meter provides portable solar radiation measurement for field applications.
Functions include:
W/m² Display
Suitable for solar power measurement.
BTU Display
Provides an additional unit for relevant applications.
MAX / MIN
Useful for observing changing solar radiation.
Data Hold
Allows the displayed measurement to be held for easier reading and recording.
Its handheld format makes it convenient for technicians moving between different rooftop measurement points.
Using MAX/MIN During Changing Solar Conditions
Cloud movement can make solar radiation fluctuate.
MAX/MIN functionality can be useful when the technician wants to observe the range of readings occurring during a measurement period.
However, MAX/MIN values should still be interpreted according to the purpose of the test.
For PV troubleshooting, the irradiance corresponding to the electrical measurement remains particularly important.
Solar Irradiance Meter vs Thermal Camera
These instruments answer different questions.
Solar Irradiance Meter
Measures the incoming solar radiation.
Thermal Camera
Shows temperature patterns that may help identify abnormal heating or hotspots.
They are complementary rather than interchangeable.
For more comprehensive PV maintenance, technicians may use solar irradiance, electrical and thermal measurements together.
Recommended Solar PV Maintenance Toolkit
Depending on the job scope, a rooftop solar technician may carry:
Solar irradiance meter
Digital multimeter
DC clamp meter
PV tester
Insulation resistance tester
Earth resistance tester
Temperature meter
Thermal imaging camera
The correct combination depends on whether the job involves routine inspection, commissioning, preventive maintenance or fault investigation.
Who Can Use the VICI LX-107?
The LX-107 can be relevant for:
Solar Installation Companies
For field solar radiation measurements.
PV Maintenance Contractors
For recording irradiance during inspection and troubleshooting.
Electrical Contractors
For solar-related projects and measurements.
Factory Engineering Departments
For maintaining industrial rooftop PV installations.
Facility Management Teams
For commercial building solar maintenance.
Universities and Research Laboratories
For solar radiation experiments and research.
Portable Solar Irradiance Meter Malaysia
A portable W/m² meter can be a practical addition to a solar technician's field toolkit.
The VICI LX-107 Solar Power Meter is particularly relevant where the requirement is straightforward portable solar radiation measurement rather than a complete advanced PV analysis system.
For more specialised solar testing requirements, additional PV-specific instruments may be required.
VICI LX-107 Supplier Malaysia
MTM Precision supplies testing and measurement instruments for solar installers, electrical contractors, factories, engineering teams and industrial users throughout Malaysia.
Customers can contact MTM Precision for information on the VICI LX-107 Solar Power Meter and other instruments suitable for solar PV testing and maintenance.
Contact MTM Precision
MTM Precision Sdn Bhd
Website: www.mtmpre.com.my
Email: mtmpre@yahoo.com
WhatsApp: 016-660 7346
Showroom & Service Centre
No. 29-1 & 29-2, Jalan Bandar 18,
Pusat Bandar Puchong,
47160 Puchong, Selangor, Malaysia.
Serving customers throughout Selangor, Kuala Lumpur, Johor, Penang, Perak, Negeri Sembilan, Melaka, Pahang, Kedah, Perlis, Terengganu, Kelantan, Sabah and Sarawak.
Need a solar irradiance meter for rooftop PV maintenance in Malaysia? Contact MTM Precision for VICI LX-107 availability and solar testing equipment enquiries.
08 Sep 2026
