Should I HIPOT before or after other tests?

[gchoquette]

I'm trying to understand if there is a standard practice of running the insulation testing after or before other tests due to the possibility of one set of tests affecting the other set of tests. These are all AC units and we are conducting an AC HiPOT test.

Cheers.

The above answers look perfectly fine (1000V DC Insulation tester)

However, it appears that you are doing a repetitive production of some electrical cooling system. If this is to be sold in the consumer or industrial marketplace, you may need to do an electrical compliance check of some sort, with calibrated instruments.

There are instruments that specifically do compliance testing. They are intended for production manufacturing, which I assume is what you are doing.

They can also be rented, if you just doing a single temporary run of the product.

Here's one brand of those instruments:
https://www.arisafety.com/
They have both calibrated HiPots and Ground Bond testers. You can also automate the tests if you have a lot to do.
https://www.arisafety.com/products/hipot-tester-hypot/
https://www.arisafety.com/products/g...-tester-hyamp/

Another, more expensive brand is Haefley.

I am not associated with either of these companies. Just letting you know what manufacturers use for this type of work.

[NBatson]

DC insulation resistance often called megging. run it at 500VDC and you should be good you can run it at 1000VDC but I would start low and go up. A 1 minute test is kind of the standard for testing insulation. Megger has a great write up on insulation resistance if you want to take your knowledge a little further. Its short and written in plain English. Google "Megger A stitch in time," it should have a downloadable pdf of the write up.

[Sir_Stig]

The above answers look perfectly fine (1000V DC Insulation tester)

However, it appears that you are doing a repetitive production of some electrical cooling system. If this is to be sold in the consumer or industrial marketplace, you may need to do an electrical compliance check of some sort, with calibrated instruments.

There are instruments that specifically do compliance testing. They are intended for production manufacturing, which I assume is what you are doing.

They can also be rented, if you just doing a single temporary run of the product.

Here's one brand of those instruments:
https://www.arisafety.com/
They have both calibrated HiPots and Ground Bond testers. You can also automate the tests if you have a lot to do.
https://www.arisafety.com/products/hipot-tester-hypot/
https://www.arisafety.com/products/g...-tester-hyamp/

Another, more expensive brand is Haefley.

I am not associated with either of these companies. Just letting you know what manufacturers use for this type of work.

This is closer to what OP needs, but for the people saying to only megger it, factory acceptance testing of CSA/cUL/UL devices have corresponding standards that require specific test levels of the devices and cables. Not sure on the UL levels, but the CSA requirements are 1.5kV AC for 60 seconds on control components (there are reductions for certain devices, and a 1 second test voltage that is higher). Switchgear has a different table, but with similar requirements of 60Hz for 60 seconds. An insulation resistance tester is useful in most cases to do before a hipot, at least on >600V gear were the voltage applied is drastically different, but not required.

I believe the OP is wondering whether they should hipot first, then function test, or function test then hipot. Really there are pros and cons of each, but basically if you only have a hipot and a power source (and I'm assuming a multimeter) I would personally do a shorts and grounds check with the meter (and a visual on the wiring if it's at all possible at that stage), do the hipot, repeat the S&G check and then function check it. If it's as simple as a occilating fan, then the hipot should catch any insulation issues to ground, and the S&G should catch any obvious phase to phase shorts, at which point as long as you have a standardized energization procedure the insulation should not be negatively effected in a way that the hipot might catch.

If you do the hipot last, you risk sending out equipment that might have fuses or other components that might have been damages from the hipot test and would not be caught by the hipot test itself. In a perfect world you do a function test, then hipot, then a more basic function test that verifies nothing was damaged by the hipot, but that's not always possible.