WATER HEATER CASE STUDY
Applications Consulting / 1 Day
May 2019
A large company, manufacturing water heaters for residential and industrial applications, required consulting on properly performing and understanding the hipot test. They are testing to UL173 and their Process Engineers, Quality Department, and Operations Managers wanted to ensure all requirements were being met. Most of their Device(s) Under Test (DUT) come down a conveyor belt with exposed cables accessible for testing. Operators are given a certain amount of time (seconds) to complete testing. A thorough review of this process and best practice recommendations were requested. The manufacturer tests with UL and gets audited every 6 months. Currently, they’re using Hypot IIIs on their 5 lines but have purchased one of the new Hypot Series testers.
Consulting Visit
First observation was the use of a third-party Calibration Lab. It appears the Cal Lab is performing improper calibration methods since the ‘Cal. Date’ on all units still read 2016. Proper calibration is an integral part of having reliable test results. Operator safety was another main topic. During the testing process, it was observed that operators’ hands were resting on the water heater. Also, operators’ legs were, at times, contacting DUTs while sitting in the chairs used during testing. Additionally, with no ‘Lo-limit’ set and the use of probes for quick contact in a conveyor setting, it was very easy for operators to attempt to tap the mains cable, miss, yet still pass. On that basis, understanding test results and parameters were a focus of the training. An assembly line was found using a frayed cable which was passing every product. The duration of this situation was unknown; therefore, a large inventory may have been shipped without getting tested. A lack of a verification method was also discovered. This is required for those who test with UL, thus, recommendations were made to integrate a TVB-2 within their testing processes.
KEY POINTS
- Basics of Electrical Safety 101/102
- Safe workstation practices and testing methods
- Setup and Programming of Hypot Series
- Daily verification method
- Train Operators and Staff with Safe Workstation Practices
- What to Avoid When Testing
- Testing procedure review
Consulting Notes
Classroom style training was performed covering Hipot test theory. This was most valuable for those responsible for compliance, as they emphasized the need to understand the “what & why” of hipot testing. A test was administered as a group to confirm retention of information and specifications. The major issue was finding an optimal way to hipot test a unit with loose cables and within the allotted time limit, since an adapter box wasn’t an option. Customer noted many changes will be implemented and processes reviewed for safety after this training.