So I have an existing thermostat cable on my 2nd floor that only has 4 wires, and I need a 5th wire to use as the common wire.
Can I use the existing cable to fish or guide a new 6 wire cable through down to the basement? If so, what kind of tie or connection should I use between the two wires so that it doesn't come loose as I pull the cable through, and to keep it streamlined so that it can slide through holes or whatever it's going through? Is it better to pull the cable from the top floor or from the bottom floor? Is there a chance I'll get stuck or lose the cable in the wall - and thus should I just leave it to the professional?
Any tips in general for this? Is this recommended?