I have a fly back diode on the relay and it does not happen when the 220 ac is not connected. I just wanted to make sure that i have good isolation from the controller as the plan is to use pwm in future with a diac or tric to not completely turn off the power heads but to ramp them up and down from -+30% to 100%. Currently i am just turning them on and off in intervals whicths works fine for 20 to 30 min.
Thanks for the reply i will look into some more options maybe i can find 12 v Units which will make a big difference