What if a 240v/12v transformer is wired wrongly?

[alan333]

Hi,
I have a Thorn TQPSXD60/240V transformer supplying 12v to three 20w lights. Simple wiring, one end takes 240v in, the other gives 12v out. However there are no obvious markings for which of the two 'in' terminals are live or neutral (there's no earth). There's a minuscule 'N' and an equally minuscule 'D' on the fitted connector strip points (so minuscule that glasses, a magnifying glass and perfect lighting was needed to make them out). Neutral is connected to N and live to D, and it works fine and doesn't heat up or anything. What would happen if the wiring is the wrong way round? And what does D denote?
Thanks

 

[securespark]

Don't know. I suspect not a lot would happen if you got the connection on the primary (ie L&N coming in) the wrong way round, but if you got the primary and secondary mixed up, there would be a large bang.

 

[mattylad]

For AC mains it does not matter which terminal you use as long as you use the correct pair (called the "primary" or 240v in).

As Securespark says - there would be a bit of a bang if you connected the mains to the output.

 

[333rocky333]

Could it be a "P", some use "p" or "Ph" to denote PHASE, some even only mark "N" for Neutral and leave the other Blank.
Sometimes its evident by the schematic on the unit rather than at the terminals

 

[alan333]

Thanks for the replies guys
It’s definitely a D. Either way it’s safe to use.