To get fuel from right tank, turn off left tank boost pumps and open cross feed. Right system will then supply fuel to both motors and APU. The only time the DC pump fires up is when the DC pump presssure switch senses no fuel ( less than 3or4 psi) pressure in the left engine fuel feed manifold. Pulling CB,s on the left boost pumps, all three, will allow the DC pump to operate as long as the cross feed valve remains closed. If my memory serves the APU uses around 150-200 kg per hour.
Hope this helps