That's a nice setup, but I ran my air intake outside as I have 2 classic bikes in garage and I was thinking of petrol fumes being drawn in.This is my setup. 5kw Diesel heater warms the place up the fastest but I maintain the temp with this cheep heat pump I got from Electriq. The claim 2.35 kW Heating using just 0.75kW power but I have no way of confirming that. On really cold days I use both. It is half way up the wall as my garage is dug into a slope and that is ground level.
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John.