Can I use a 110v transformer in reverse?

[51m0nb]

I am an experienced DIYer (build my own house etc) and I’ve offered to help a friend in France. However, all my power tools are 230v. Could I use a safety transformer in reverse to convert the local 110v to 240v?

 

[Julie.]

Sort of.

Though are you sure it's 110v there - may be 220v

The real issue may be the wiring of the transformer, often the 240v side has a fuse or overload, whilst the 55-0-55 v side may have split windings, one fused at say 32A for the 32A outlet, and the other at 16A for the 16A outlet, - in this case using it in reverse may limit the capacity as you aren't using all the windings, or limited by the size of fuse. (Smaller transformers have the single secondary, but may still have fuse size issues).

In using the transformer though you would have to re-wire it, a socket outlet on the 240v side, and socket inlets for the 110V side, it would be dangerous to use the plug/sockets the wrong way round - exposed pins must never be live.

In addition you will have to re-arrange the earths (the 0 in the 55-0-55 must not be earthed, and the neutral side of the outlet should be earthed) and it must have a proper rcd on the 240v side after the split of neutral and cpc.

So technically a transformer may be used either way round, but there are practical safety issues in configuring a 240v supply correctly.

 

[brianmoooore]

I've connected to the mains electricity supply in every corner of France, and never come across anything other than 230V.

 

[Lucien Nunes]

France used to have some 110V and 127V, but I thought it was all replaced with 220/380 decades ago, officially now 230/400. I have never encountered any other voltages either, but most of my work in France has been in cities. Is this a remote rural site? How sure are you that it's 110V?

 

[LukeD]

Never seen 110v in france !

 

[Vortigern]

Neither have I ever seen 110v in France, largely because I have never been there.

 

[brianmoooore]

France used to have some 110V and 127V, but I thought it was all replaced with 220/380 decades ago, officially now 230/400.

Most places were like this originally, will all manner of different voltages and frequencies used, plus DC.
IIRC, the first time I visited Germany I came across 120V AC supplies, and I can just remember 110V lamps stocked alongside 240V lamps in some shops local to me, to service an area not far from me that had a 110V DC supply which must have survived up until around the late fifties or early sixties.
All long gone now.