For those of you with a wood stove - I am really impressed and happy with my US Stove Miracle Heat Reclaimer.
It was an easy install, and simply goes in after the first joint of pipe. It works on a thermo disc, which when hot enough it opens, and runs the fan. I am seeing anywhere from 50 -80F degree differential across the piping!
Well worth the install if you have a wood stove as a heat source in a shop as it seems to work wonders in reclaiming heat that would otherwise go up the flue.
You can check the miracle heat reclaimer out here: Amazon.ca