Our portable immersion water heaters will need testing periodically and many churches either have their own kit or bring in an electrician.
There are two things that need to be understood as they may lead to false fails.
When seeking for an earth, the usual thing to do would be to touch the heating elements with the earth probe. We are advised by the coil manufacturers (in the UK) that a contact should be sought at the base of the coil (see the photograph).
When it comes to plugging in the appliance for its Portable Appliance Test, the 2.4kW heaters are straight-forward as they only have one plug. The 4.8kW water heater has two plugs and it is important to get the right one. With the 4.8kW heater, one element is the master and the other the slave. The latter will not work unless the master is plugged in and switched on. On our 4.8kW heater we mark the flex for the master element with a piece of black tape so you get the correct plug. Then one needs to make a test on both elements (at the base of the element).
As a final point, any scale on the elements can give a false fail, I know a trained spark will know this but it does get forgotten. There is an article on cleaning away scale, other than just scraping and chipping a bit off.