Practice and Technical Analysis of How to Conduct UL Rain Test Based on UL Water Spray Test Device

Abstract
In the R&D, production, and factory inspection of electronic and electrical products, lamps, electrical cabinets, and other equipment, the UL rain test is a key method to evaluate the physical performance and safety reliability of products under simulated rainy weather conditions. Traditional rain test equipment has problems such as low standardization, insufficient precision in test parameter control, and non-standard operating procedures, which easily lead to deviations in test results and affect the judgment of product compliance. This paper takes the LISUN JL-UL Water Spray Test Device as the core, and combined with its design features that comply with international standards such as UL, ANSI, and CSA, systematically expounds the complete process of “how to conduct UL rain test“, including key links such as pre-test preparation, equipment debugging, parameter setting, test execution, and result determination. At the same time, by analyzing the technical parameters and structural advantages of the device, its reliability in standardized testing is verified, providing practical guidance and technical references for enterprises to standardize the conduct of UL rain tests and ensure product quality.

1. Introduction
Electronic and electrical products will inevitably face complex climatic environments such as rain and humidity during actual use. Rainwater intrusion may lead to problems such as reduced insulation performance of products, short circuits in circuits, corrosion of mechanical structures, and even safety accidents. To ensure that products can still maintain stable performance and safe operation under rainy conditions, Underwriters Laboratories (UL) has formulated a series of rain test standards (such as UL1598, UL153, UL1703, etc.), which clearly specify test methods, equipment requirements, and judgment indicators.

The core of the UL rain test is to simulate real rainy scenarios through standardized equipment to comprehensively assess indicators such as the waterproof performance, structural stability, and electrical safety of products. The JL-UL Water Spray Test Device developed by LISUN Group is manufactured in strict accordance with standards such as UL60507-ENGL 1999, ANSI Z21.10.3-2004, and CSA4.3-2004. It integrates the functions of UL rain test and 45° water spray test and is a dedicated device for enterprises to conduct UL rain tests. This paper will take this device as the carrier to detail the technical issues of “how to conduct UL rain test”, helping testers master the standardized test process and improve the accuracy and reliability of test results.

2. Technical Characteristics and Standard Compliance of LISUN JL-UL Water Spray Test Device
Before answering “how to conduct UL rain test”, it is necessary to first clarify the technical foundation of the test equipment – the structural design and standard adaptation capability of the LISUN JL-UL Water Spray Test Device are prerequisites for ensuring test compliance.

2.1 Core Structure and Functions of the Device
The LISUN JL-UL Water Spray Test Device is composed of two core components, corresponding to different types of UL rain test requirements. Its structural and functional characteristics are as follows:
UL Rain Test Device (Upper Component): Equipped with 3 original imported UL laboratory nozzles. The distribution of the nozzles strictly follows the size requirements of Figures 38.1 and 38.2 in the UL standard. It can simulate a “vertical rain” scenario and is mainly used to test the waterproof performance of the top and side surfaces of products. It is suitable for products such as lamps and electrical cabinets that need to be tested for vertical rain protection.

Water Spray Test Device (Lower Component): Equipped with 1 UL standard nozzle, which can be adjusted to a 45° angle to simulate an “inclined water spray” scenario. It is used to test the waterproof performance of the bottom and inclined surfaces of products and is suitable for electrical components, small electronic devices, and other products that may come into contact with rainwater from below or the side.

The device frame is made of formed aluminum material, which has both structural stability and easy cleaning; the nozzle frame can be freely lifted and lowered through a hand-cranked stainless steel wheel device, allowing the nozzle position to be adjusted according to the height of the test sample; the base of the bracket is equipped with universal casters with brakes, which facilitates the movement and fixing of the device in the laboratory and improves operational flexibility.

2.2 Standard Compliance and Technical Parameters
The core advantage of the LISUN JL-UL Water Spray Test Device lies in its high standard adaptability. It can meet the test requirements of multiple UL and international standards, and at the same time ensure test repeatability through precise parameter control. Its key technical parameters and standard compliance are shown in Table 1:
Table 1 Core Technical Parameters and Standard Compliance of LISUN JL-UL Water Spray Test Device

Category	Specific Content
Applicable Test Types	UL rain test (vertical rain), 45° water spray test
Complied Standards	1. Basic design standards: UL60507-ENGL 1999 (Figures 38.1, 38.2), ANSI Z21.10.3-2004 (Figures 10/11), CSA4.3-2004   2. Product test standards: UL1598 (lamps), UL153 (portable lamps), UL154B (power tools), UL1703 (photovoltaic modules), UL8750 (LED lighting), UL1741 (inverters), etc.
Nozzle Configuration	3 original imported UL nozzles (upper part, for rain test), 1 original imported UL nozzle (lower part, for water spray test)
Pressure Control	Each nozzle is equipped with a “Hongqi” stainless steel pressure gauge to monitor water pressure in real time and ensure stable pressure (the standard requires water pressure usually to be 80-100kPa, which can be adjusted according to standards)
Nozzle Spacing and Size	Strictly follow the dimensions in UL Standard Figure 103.1: A=710mm (28inch), B=1400mm (55inch), C=55mm (2-1/4inch), D=230mm (9inch), E=75mm (3inch)
Nozzle Lifting Range	Supports height adjustment of 0-1500mm (adapts to samples of different sizes, such as large electrical cabinets and small lamps)
Material and Protection	Frame: Formed aluminum material (rust-proof, easy to clean); Nozzles: Stainless steel material (corrosion-resistant, ensuring stable water flow)
Movement and Fixing	Universal casters with brakes, load-bearing ≥500kg, displacement deviation ≤2mm after braking

3. Complete Process of How to Conduct UL Rain Test Based on LISUN JL-UL Water Spray Test Device
The core of “how to conduct UL rain test” lies in following a standardized process. Combined with the operational characteristics of the LISUN JL-UL Water Spray Test Device, the test process can be divided into six key steps: pre-test preparation, equipment debugging, sample placement and fixing, test parameter setting, test execution, sample processing and result determination. Each step requires strict control of details to ensure test compliance.
3.1 Pre-Test Preparation: Clarify Standard Requirements and Sample Status
Before starting the test, two core preparation tasks need to be completed to avoid invalid tests due to insufficient preliminary planning:
1. Determine Test Standards and Parameter Bases: According to the type of test product, check the corresponding UL standards (for example, UL1598 should be referred to for testing lamps, and UL1703 for testing photovoltaic modules), and clarify the specific requirements of the standards for “rain intensity, test duration, and sample posture”. For example, UL1598 stipulates that the UL rain test duration for lamps is 10 minutes, and the water pressure should be stably maintained at 80kPa; while UL1703 requires a test duration of 30 minutes for photovoltaic modules, and the water pressure can be adjusted to 100kPa.
2. Sample Preprocessing and Status Inspection:
Ensure that the test sample is in the “factory state” or “simulated actual use state”. Components that need to be installed (such as lamp shields and electrical cabinet doors) should be fully assembled according to the instruction manual, and waterproof structures should not be disassembled without authorization.
Check whether there are damages, cracks, or other defects on the sample surface, and record the initial state of the sample (such as insulation resistance value and mechanical structure integrity) to facilitate comparison and judgment after the test.
If the sample is an electrical device, it is necessary to connect a simulated load according to standard requirements (for example, lamps need to be connected to a rated voltage power supply, and electrical cabinets need to be connected to a simulated circuit) to ensure that the sample is in a “working state” during the test and assess the impact of rain on its operating performance.

3.2 Equipment Debugging: Ensure the Device Meets Standard Requirements
The debugging of the LISUN JL-UL Water Spray Test Device is crucial to ensuring test accuracy, and focus should be placed on three aspects: nozzle status, water pressure control, and position calibration:
• Nozzle Inspection and Cleaning: Remove the nozzle protective cover and check whether there is impurity blockage inside the nozzle. If there is blockage, use compressed air to blow it clean or use a dedicated needle to clear it. Do not use sharp tools to scrape the inner wall of the nozzle to avoid damaging the water flow pattern. At the same time, verify whether the nozzle model is consistent with the requirements of the UL standard (the LISUN JL-UL device uses original UL nozzles with models RT100L/RT101B, and it is necessary to confirm that the nozzle identification is consistent with the standard).
• Water Pressure Calibration: Open the main water inlet valve of the device, adjust the control valve of each nozzle separately, observe the water pressure value through the pressure gauge, and adjust it to the range required by the test standard (such as 80kPa). After calibration, the water pressure should be kept stable for 5 minutes, and observe whether the pressure gauge reading fluctuation is ≤±5kPa. If the fluctuation is too large, check whether there is leakage in the water pipe or whether the valve is aging, and replace faulty components in a timely manner.
• Nozzle Position and Angle Calibration:
• Rain Test (Upper Nozzles): Adjust the height of the nozzle frame through the hand-cranked stainless steel wheel to make the distance between the nozzles and the top of the sample meet the standard requirements (usually 500-1000mm, with specific reference to the corresponding UL standard). At the same time, ensure that the distribution position of the 3 nozzles is aligned with the center of the sample to avoid water flow deviation.
• 45° Water Spray Test (Lower Nozzle): Loosen the nozzle angle fixing screw, adjust the nozzle to a 45° inclination angle (calibrated with a protractor, deviation ≤±1°), and then fix the screw to ensure that the angle does not change during the test.

3.3 Sample Placement and Fixing: Simulate Actual Use Scenarios
The placement method of the sample should be consistent with the actual use state of the product to avoid distorted test results due to improper placement. The specific operations are as follows:
• Determine Sample Posture: Adjust the sample posture according to the product’s use scenario. For example:
• Wall-mounted lamps: Fix them on the test bracket according to the actual installation angle to ensure that the rain-exposed surface is consistent with the rain direction during actual use;
• Floor-standing electrical cabinets: Place them upright on the test platform with the cabinet door closed (if the standard requires testing the “cabinet door open” scenario, open it to the specified angle according to the standard);
• Small electrical components: Place them on a dedicated sample rack to ensure that all surfaces of the sample can be covered by rainwater (no obstruction).
• Fix the Sample: Use the fixtures supporting the device (or a dedicated fixing bracket) to fix the sample to prevent the sample from shifting due to water flow impact during the test. When fixing, care should be taken not to block the waterproof structure of the sample (such as drainage holes and sealing strips). At the same time, ensure that there is a gap of ≥100mm between the sample and the test platform to facilitate the natural dripping of rainwater and simulate the drainage scenario in actual use.

3.4 Test Parameter Setting: Match Standard Requirements
Combine the operation panel (or supporting control software) of the LISUN JL-UL Water Spray Test Device to set test parameters, mainly including test duration, water flow intensity, and test mode:
• Test Duration: Input the test duration according to the corresponding UL standard (such as 10 minutes for UL1598 and 30 minutes for UL1703). The device supports setting accurate to the second to ensure that the duration deviation is ≤±1 second.
• Water Flow Intensity: Water flow intensity is indirectly controlled by water pressure (which has been calibrated during the equipment debugging stage) and does not require additional settings. However, the actual water pressure value should be filled in the parameter record form to facilitate subsequent tracing.
Test Mode: Select the “rain test” or “45° water spray test” mode. The device will automatically turn on the water supply of the corresponding nozzles (the upper 3 nozzles are turned on for the rain mode, and the lower 1 nozzle is turned on for the water spray mode). If it is necessary to conduct both tests at the same time (required by some standards), it is necessary to confirm whether the device supports the “combination mode” or execute them in stages (first rain test, then water spray test, with an interval of 10 minutes in between to allow the water on the sample surface to drip naturally).

3.5 Test Execution: Real-Time Monitoring and Recording
After starting the test, a dedicated person should be arranged to monitor the test process in real time to avoid unexpected situations affecting the test results. The specific operations are as follows:
• Start the Device: Press the “start” button of the device to start timing. At the same time, observe whether the water flow pattern is uniform (no uneven spraying or excessively large water droplets). If abnormal water flow is found, the test should be paused immediately, check whether the nozzle is blocked or the water pressure is stable, and restart the test after troubleshooting (the timing should be restarted, and the duration cannot be accumulated).
• Real-Time Recording: Record key data every 5 minutes, including water pressure value, test duration, and sample status (such as whether water leakage, smoke, abnormal noise, etc. occur). Fill in the “UL Rain Test Record Form” to ensure the authenticity and completeness of the records.
• Handle Unexpected Situations: If the sample malfunctions during the test (such as short circuit or smoke of electrical equipment), press the “emergency stop” button immediately, cut off the sample power supply (if it is an electrical product), record the fault occurrence time and phenomenon, stop the test, and analyze the cause of the fault. If the device has problems such as water leakage or pressure gauge damage, the test should also be paused, and the test should be restarted after repairing the device.

3.6 Sample Processing and Result Determination: Evaluate Performance According to Standards
After the test, the sample should be processed and the results determined according to the standard process. The specific steps are as follows:
• Sample Processing:
Turn off the device’s water inlet valve and power supply, remove the sample fixing fixtures, transfer the sample to a dry environment, and perform “recovery treatment” according to standard requirements (such as placing it in an environment with a temperature of 25℃ and a relative humidity of 50% for 30 minutes to allow the surface water to dry naturally, avoiding high-temperature drying which may cause sample structure deformation).
If the sample is an electrical device, measure its insulation resistance after recovery treatment (using an insulation resistance tester and applying voltage according to standard requirements, such as 500V DC) and record the insulation resistance value.
• Result Determination: Evaluate whether the sample is qualified from both “physical performance” and “electrical performance” aspects according to the judgment indicators of the corresponding UL standard. Examples of judgment standards are as follows (Table 2):

Judgment Category	Qualified Indicators	Unqualified Situations
Physical Performance	1. No obvious deformation, cracking, or corrosion of the sample;   2. No damage to the sealing structure (such as no falling off of sealing strips and no blockage of drainage holes);   3. Normal operation of mechanical components (such as switches and knobs)	1. Cracking or deformation of the sample shell leading to internal water ingress;   2. Falling off of sealing strips and rainwater seeping into the interior;   3. Jamming of mechanical components due to water ingress, resulting in inability to operate normally
Electrical Performance	1. Insulation resistance value ≥2MΩ (500V DC);   2. No short circuit or leakage (measured with a ground resistance tester, ground resistance ≤0.1Ω);   3. Normal operation of the sample after power-on (such as normal lighting of lamps without flickering or extinguishing)	1. Insulation resistance value <2MΩ;   2. Short circuit (fuse blowing or circuit breaker tripping);   3. Inability to operate normally after power-on (such as lamps not lighting or flickering)

If the sample meets all qualified indicators, it is judged as “qualified in UL rain test”; if there is any unqualified situation, it is judged as “unqualified”. The cause of the problem (such as defects in the sealing structure design or insufficient waterproof performance of materials) should be analyzed, and the product should be improved before retesting.

4. Advantages and Precautions of LISUN JL-UL Water Spray Test Device in UL Rain Test
4.1 Core Advantages of the Device
Compared with traditional rain test equipment, the LISUN JL-UL Water Spray Test Device demonstrates three advantages in “how to conduct UL rain test”, improving test efficiency and accuracy:
• High Standardization Level: It adopts original UL nozzles and standardized structural design, fully complying with international standards such as UL, ANSI, and CSA. This avoids unrecognized test results due to non-compliant equipment and reduces the cost of repeated tests for enterprises.
• Operational Convenience: The nozzle lifting adopts a hand-cranked wheel design, which does not require electric drive, making operation simple and maintenance costs low. Each nozzle is independently equipped with a pressure gauge and a control valve, facilitating individual calibration and reducing debugging difficulty. Even non-professional testers can quickly get started.
• High Test Repeatability: The device frame is made of formed aluminum material, with a stable structure and no deformation; the water pressure control accuracy is high (fluctuation ≤±5kPa), and the nozzle angle deviation is ≤±1°, ensuring consistent conditions for multiple tests. The repeatability error of test results is ≤5%, meeting the data tracing requirements of laboratories.

4.2 Test Precautions
To further ensure the accuracy of the UL rain test, the following precautions should be noted:
• Regular Equipment Calibration: It is recommended to conduct a comprehensive calibration of the LISUN JL-UL Water Spray Test Device every 6 months, including pressure gauge calibration (sent to a metrology institution for verification), nozzle angle calibration, and nozzle flow calibration (measuring the water output per unit time with a measuring cup to ensure compliance with standard requirements).
• Control Laboratory Environment: During the test, the laboratory temperature should be maintained at 23±5℃, and the relative humidity should be ≤85%. This avoids water pipe freezing due to excessively low ambient temperature or excessive water evaporation due to excessively high temperature, which may affect the test effect.
• Standardize Record-Keeping and Archiving: After the test is completed, data such as the “UL Rain Test Record Form”, equipment calibration report, and photos of the initial and post-test status of the sample should be archived, with a retention period of ≥3 years (in line with UL standards’ requirements for test data tracing), facilitating subsequent product certification or quality tracing.

5. Conclusion
The core of “how to conduct UL rain test” lies in “standardization” – every step from equipment selection, process execution to result determination must be in line with the requirements of UL and relevant international standards. As a dedicated device that complies with standards, the LISUN JL-UL Water Spray Test Device provides reliable hardware support for enterprises to conduct UL rain tests through its precise nozzle design, stable water pressure control, and flexible sample adaptation capabilities.

Through the six-step process of “pre-test preparation – equipment debugging – sample placement – parameter setting – test execution – result determination” described in this paper, testers can standardize the completion of the UL rain test and effectively evaluate the performance stability of electronic and electrical products, lamps, electrical cabinets, and other products under rainy conditions. At the same time, combined with regular equipment calibration and laboratory environment control, the accuracy and repeatability of test results can be further improved, providing strong data support for product design improvement, factory inspection, and international certification.

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