Pictured: Heating Mat Lerway Heat Pad Waterproof for Seed Starter Germination Hydroponic Seedling,Greenhouse,Reptile,Plant (10″ x 20.75″ 110V 21W) – Note: This is an example of a waterproof heating mat, not the exact one I use
I’ve used a heating mat in my fermentation chest freezer for years. Most of these don’t provide a whole lot of heating capacity. Which, in my book, is great. The one I use is well under 20 watts. That has no trouble raising my fermentation chest freezer (located in my basement) by several degrees. I use this throughout the year whenever I want to push fermentation temperatures higher. I do not set my fermenter on the mat. I simply set it in the chest freezer, thereby warming up the ambient air inside the fermentation chamber.
Over the years, I’ve used this with both a single and a two stage temp controller. This has the effect of making a single stage temp controller into a dual stage controller. The heating mat continuously heats the ambient air and the temp controller/chest freezer act to correct that as it gets too warm. See Homebrew Hack: Mimicking Dual Stage Temp Control with a Single Stage Controller for additional details on that.
This process is more efficient with a two stage controller. The controller cycles on each stage, cooling or heating, as needed. If you’re in the market, check out the ITC-308
Beyond getting the appropriate wattage for your setup, I would also recommend getting a waterproof model. Not that you want to have these around water, but it’s nice to have some moisture resistance, especially when fermentation chambers can get humid.
If you’re in the market, try this search on Amazon – “waterproof heat mat”
Make sure the components you use are compatible and rated for your intended application. Contact manufacturer with questions about suitability or a specific application. Always read and follow manufacturer directions.
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