To connect an electronic outdoor DC solenoid valve to a timer, I am getting recommendations to use a silicone-filled wire nut OR solder and heat-shrink. I understand that wire-nuts are simpler for those without a soldering iron, but will heat-shrink technically form a more weatherproof and reliable connection?
Heat-shrink tubing does not always hermetically seal a connection. The advantage of the wire nuts is that they are filled with silicone (not silicon) grease that prevents water from corroding the connection.
What I have done is to make my solder connection and then cover it liberally with a high-quality silicone or urethane caulk. Put shrink tubing over that. When you shrink the tubing it forces the caulk into all of the little gaps and gives a better seal than shrink tubing alone.
I just repaired my rusty wet ground low voltage AWG16 solder joints with Wire Nuts and filled with Polyurethane(PU) , an excellent moisture inhibitor. Many plastics slowly allow Moisture absorption but in my experience, Polycarbonate (PC) is best but not liquid and PU is available in low VOC now which means it takes a day to cure exposed to air.
This cable drives my fence LEDS with 60W 14V
- silicone is good when applied to dry air voids ( to prevent condensation) on cleaned surfaces, but the seal has low adhesion strength , so interface moisture creepage is more likely or at least possible along the silicone interface.
I have had good luck with 3M 314 Series connectors. They are not hermetically sealed but Gel filled(EG-3 Grease). They say no underground or submersion. Can use with Solid or Stranded wires. Might be worth taking a look. Here is one of them 314-Box