I'm planning to install several temperature sensors in my hot-air furnace's ductwork, specifically in the return duct and in the supply plenum of each of our two furnaces. The sensors I plan to use are 7mm in diameter; I'm looking for a way to get them into the ducts without a) leaking air and b) looking crappy.
So far, my best thought is a 5/16" or 3/8" hole drilled and sealed up with foil ("real") duct tape; are there other ways that might be cleaner-looking?
This is mostly a "because it seems cool" project; planning to use a Raspberry Pi to capture the data and add it to a small home status dashboard I have set up. It will also give some insight into how the furnaces and A/C are performing.
Best Answer
If you can't get to both sides, you could drill a 1/2" hole (which may be tricky) and then use a knock out plug that is designed to snap in from one side.
You could then use something like the strain relief described in gregmac's answer to mount the thermo couple on the plug and then snap it in and seal the edge with foil tape.