Question
Everytime we PAT test any of our 3 phase 415v motors with the Primetest 100, it shows up as Failed Test even on a new motor.
We are using a short lead with a 32 amp 4 pin, socket and a 3 pin 13amp plug other end. The screen display shows:
- RPE = OK
- RISO = OK
- I Leak = FAIL
Here is what we get: We have tested 3 different electric motors.
- 1. I Leak = 1.98 ma Motor has a lead length of 4.4 metres
- 2. I Leak = 2.34 ma Motor has a lead length of 4.7 metres
- 3. I Leak = 2.35 ma Motor has a lead length of 2.3 metres
Answer
The reason for the fails here is due to the type of PAT Tester and the test settings. The Primetest 100 is a basic unit, primarily designed for carrying out tests on standard 240V appliances.
The “one-button” style operation means that the tester must have pre-programmed Pass thresholds in order to determine a pass or fail. These thresholds are as follows:
Class I Tests
- Earth Continuity: 0.2ohm
- Insulation Resistance: 1Mohm
- Substitute Leakage: 0.75mA
Class II Tests
- Insulation Resistance: 2Mohm
- Substitute Leakage: 0.25mA
The problem with this type of tester is that you have no control over these Pass limits. For Class I equipment, there are several Pass limits:
Portable or hand-held Class I Equipment
0.75mA
Class I Heating Appliances
0.75mA or 0.75mA per kW, whichever is greater, with a maximum of 5mA.
Other Class I Equipment
3.5mA
The three phase motors in this case would come under the “Other Class I Equipment” classification, with a maximum limit of 3.5mA. Whilst the Primetest 100 is indicating a fail, it is basing this on the lower of the two Pass limits, therefore you must take the reading into account instead. All your results are within the 3.5mA limit, therefore all your motors have actually passed.
There are PAT testers that allow you to adjust the Pass limits, therefore ensuring you get consistent results. In addition the Seaward Primetest 250 can carry out a powered 3 phase leakage test, with the use of a special adaptor.
It is also worth noting that the leakage test is not a required test when it comes to PAT.