How to keep power trips isolated and not trip the whole place when testing faulty appliances?

[Qwe7410]

Having some 1400W 230V heaters to test and repair that have a power trip problem. I've unplugged all the connections and open them up one by one to identify the part that is causing the trips.

Everytime it trips, it trips the whole place through the main circuit breaker. How can I do it safely and not trip the entire office? I've used some of those masterplug rcd adaptors and they don't work, still tripping the entire place but I've plugged them to an extension though if that matters.

Other than that, I usually I test the heating element first because they are usually the cause. What should be the other tests that should be done?

 

[littlespark]

We have specific appliance testers in the UK, maybe you can get one of them.

Mainly checks the safety of an appliance, rather than it’s operation… as you can have something that works perfectly, but for example, isn’t earthed properly. Short circuit to the metal casing and you have a big block of metal at potentially mains voltage.

Heating elements can be tested using an insulation resistance tester or a top range multimeter. If you know what to look for with the results you can determine a good or bad element.

 

[Qwe7410]

This time I've a problem with a torn wire rather than the heating element.

Usually for the heating element I will measure the resistance between the two terminals, its usually around 40ohms. Also measure if there's continuity between the terminal and the chassis.

In the machine there's a regulator, solenoid, a main switch, a microswitch to activate the pump, a vibration pump, 2 less, a mechanical power relay that traffics power to the heating element if I'm not wrong, a pressure sensor, a safety switch against over heating and a few water probes.

I traced that by measuring continuity between all the terminals and then wires to the metal chassis, I got a positive in one of the wires. I examined the wire and found a tear in the insulation and the copper were exposed.

I also traced a problem with the main rocker switch, it has some continuity even when it's off.

It's the British 3 pin plug and I turned my meter to measuring resistance 2k measured the live and neutral on the plug and got a reading of 0.46 when the switch is not powered but on "on" position.
I compared to a new machine and they gave a reading of 2.3.

The machine no longer tripped after getting the exposed wire patched with electrical tape and the main switch replaced. But there's something unusual with the operation of the machine, the sensors were haywire. I replaced the regulator and things seem to work as how it should be. I measured the live and neutral at the plug and it now reads 3.1 which I'm not sure if it's acceptable. Not sure if it's a satisfactory repair or there's something else that has to be addressed.

Is there anything else I should do to make it safer for repairing such electrical issues with power trip?