Issue with controlling a heating element using PID vi

Hi everyone,

I'm facing a hard time to maintain a tide control of a heating element using labview pid vi. My project requires maintaining precise control over a range of temperatures (180 - 360 degC). I have tried tuning using ZN and Tyreus-Luyben methods in addition to using the PID autotuning wizard vi yet none of them gave me good results. For the set up I'm using a SSR  with the following vi.

I would appreciate your help as my  knowledge with labview is quite lacking 

Cheers 

Moha

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