Step-up transformer Wattage?

I bought a 110v wall-mounted AC which I plan to use overseas where (mostly) only 220-v sources are available. The box says 5200 BTU rating. It also says the eff. is 9.7 What minimum transformer wattage do I need? Please show calc. Thanks.

joromer

 

[dpc]

You need to look on the unit or its manual and find the specifications for maximum current required (amps).

Take the maximum current and mutiply by 120. Now increase that number by about 15%. That will give a rough guide to a minimum transformer size.

But as noted in some recent threads, if your A/C unit is designed for 60 Hz, don't expect it to work properly on 50 Hz, since motor speeds will be reduced.