Electronic – Is it okay to connect a European 240V transformer to a US 240V outlet


I've an old Bosch German made automotive charger transformer with ratings 14V/9V, 220-250V @ 50/60Hz 132VA. Can I use it on the 220 to 240V outlet here in the US which uses a split – phase system as the transformer was intent to be used on Europe style 240V with a Live and Neutral system?
Will there be any difference in its performance?

Note: I'd initially asked this question in the comments section of "How is the 220V line in US different from other parts of world? Does a US 220V line need two switches for each wire?". But has been removed by moderators and was asked to make separate thread so this info is seen by everyone.Thanks.

Best Answer

Yes, you can connect that to a US 220-240 V outlet. Just connect to the two hot lines and connect nothing to the neutral. However, there are normally only 30 to 60 amp 240 volt outlets available in US residences. They are dedicated to clothes dryer cooktop and oven use. To add a 240 volt circuit requires two adjacent 120 volt circuit breaker spaces in the distribution box. You will need a 15 or 20 amp double breaker whichever is the smallest available. You can connect additional 120 volt circuits to the same breaker, but they must not be circuits like bathroom and kitchen outlets that can not be mixed with outlets elsewhere.

It is not a good idea to connect to a higher current circuit because the higher rated circuit breaker might not prevent a fire if you have a short-circuit in the charger or in the charger cord. If you want to do that you should have smaller fuses near the outlet. I don't know if that is permitted by code.

You should use a US receptacle and plug rated for 240 volts and the fuse or circuit breaker current rating. You probably will not find a suitable converter for a 240 volt US receptacle.

There could be a difference in performance related to the actual voltage in the previous vs. present locations. However the transformer will be operating within the specified voltage and frequency range, so that is nothing to be concerned about. If the new voltage is higher, the charging current may be a little higher and the charging time a little quicker and the opposite if the voltage is lower. I assume an old charger may not have any voltage regulation. The operating temperature may be lower or higher.

A 15 or 20 amp 240 volt receptacle installed for a window air conditioner is an excellent choice for this application.