Kettle sour temperature control

[Ciaran]

Been planning a first kettle soured berliner weisse and i think i know the process/recipe i want to follow. The only issue is I'm not sure how to keep the temperature at 41c for the lactobacillus over 2-3 days. As far as equipment goes i have a fermentation larder fridge which I normally run with a brewferm heat belt to control normal  saccharomyces/ale fermentations. I'm worries about trying to use this for higher souring temperatures over long periods.  Would I be better getting a tube heater or a fan heater of some sort or would anyone have any suggestions on how they do kettle souring temperature control?  Cheers.

[Pheeel]

You'll need a tube heater or wrap it in an electric blanket.