A piece of kit can't be defined as having no, medium or even high legionella risk. Its about the possibility of contamination, amplification etc. which might bear no relevance to the plant. Its a bit like asking, I've got a cooling tower...what's the risk? The answer is - it depends. Having said that; if you're using fresh mains supplied water (i.e. not reusing the same water post spray) and are confident in the pipework leading to the cabinet having no deadlegs and getting regular use then I would suggest that the chances of getting legionella proliferating are almost as minimal as they can be. The raising of temp to 65 is good but still would need to be held there a few minutes to ensure a kill. 5% salt unlikely to have massive short term effect on Lp either - can still be viable at 30% salinity. But the biggie is fresh, clean water...that's your best control measure.

and there should be a maintenance programme for cleaning the cabinet, to prevent any 'nutrients' growing.