This is a question I would like clarified. I have a very good isolation transformer which I use all the time.I would just like to get a concise description off you guys.

They are simple devices. There's a ton of stuff on the internet on this subject, such as:

http://www.allaboutcircuits.com/technical-articles/transformer-isolation/

Google is your friend.

I do use google quite a bit. But really I would like to know how techs on this page use them i.e alongside dim bulb testers and variacs and what not to use with them.

The main use for mine is when firing up radios I am suspicious of & sometimes for a first power up since refit. I have a 'kill switch' mounted on mine (in a box) and if something does not go according to plan. I can kill the circuit swiftly.

I do not use a dim bulb.

Variac I have & use to adjust the stepdown transformer so I get 110, or 115V. They are not isolation transformers they are "variable auto transformers" and at I suspect on the out put side an RCD will not save you.

I can't see a reason why an RCD wouldn't work with a transformer that doesn't isolate the secondary from the primary windings. One simple way to test this is to wire a pair of electrician's test lamps from the active side of the variac to earth. If your RCD trips then its protection is available.

Most of our RCD's trip at 30mA I have deliberately put one on the OP side and it will not trip below around 130 something volts from memory.

My isolation transformer was originally for lighting (3A). The fuse was internal, that got shifted to an external one, on the basis that it was less likely to blow if was easy to get at and there were spares.

"Kill switch" was an add on, as well as a switch containing a light, to show when it was on, plus a pilot to show if the transformer was still alive (fuse fail indicator).

Because of the power here, MOV's & RF filtering capacitors were also added.

Marc

Agreed, they won't work on lower voltages although due to the non-isolation properties of a variac one should work on the line side of one. I haven't tried either way so I am only considering the theory. When I get some time to spare I might test a few scenarios.

A kill switch is a good idea, especially if it is a mushroom button. I worked at a school for seven years once and they had mushroom buttons at each piece of machinery in every industrial arts workshop. It was wired up as a bit of overkill though - the pressing of any of these buttons killed all machinery in every workshop rather than just where danger was present, presenting the possibility of creating other problems - cutting edges such as saw blades and drill bits have to move at a specific speed and be as sharp as possible to prevent catching of the material being worked and this isn't possible if the user has no control over the speed and gets surprised by a blackout situation. This isn't an issue when there is only one worker though or where each button only isolates its own piece of machinery.

plus a pilot to show if the transformer was still alive (fuse fail indicator).

Fuse blocks with a neon wired in parallel with the fuse cartridge are available.

Because of the power here, MOV's & RF filtering capacitors were also added.

Dirty power is a big problem and not easy or cheap to overcome. I currently work at a private hospital and with the several thousand switch-mode power supplies inside the building plus wired networks for computers and telephones plus wireless networks for WiFi, DECT phones, all three mobile phone networks and ECG telemetry I am surprised that we aren't microwaving ourselves in there.

I tend to replace more than our fair share of RCDs too - they are probably affected by the dirty power and certainly aren't built with longevity in mind, like most things these days and the RCDs are the leading brand too.