They have an overheat safety cut-out to stop the thing burning out if it runs out of water.
My guess is that the safety cut-out is defective and triggering too soon.
Performance Power is a B&Q brand - I doubt that you will ever get it repaired - if it has unexpired warranty and you have proof of purchase take it back to the shop for a replacement - otherwise throw it away.
Good Luck...
May 2016
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