Where you connect it into the breaker box is also important. You should balance the load on each leg of the 220. That's simple math as you look at the total sum of the breaker values on each 115v leg. Connect the new wire to the leg that has the lesser load on it. Make sure the buss bars are not aluminum or you'll need to use non-oxidizing paste to eliminate a fire hazard.
Nigel, during WWII China did the very same thing, naming a town "USA" which they stamped on many cheezy, garbage quality products primarily intended to be sold to American GIs. This stuff was the lowest of the low.