here is a dirty solution. Heat shrink each wire separately. Thoroughly superglue them together. Then cut a longer piece of heat shrink the will cover both together. Heatshrink everything again. You can add a dab of superglue into the ends of the heat shrink just to be sure.
Silicone sealer is inappropriate for this purpose.
There is an easier way. I have done this before. I got it at Builders warehouse. It is a cable Joint kit. You join your cables, place the plastic tube over the cables, mix some resin, and pour ino the container. Wait an hour or so, and it is ready for underwater use.They are usually used with fountain pumps.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
Is the cable that needs extending before or after the transformer? If it's 220v I'd strongly advise against a joint that will be near or in the water.
You do get heat shrink sleeve that comes with a heat activated adhesive on the inside but whether or not it would make a waterproof joint would depend very much on the profile of the cable.
Those little tiny resin joint kits they make for extending flex/trailing cables are very difficult to use because of their miniature size, again it could be hit and miss whether the end result would be waterproof.
If you try to use silicone sealant inside heatshrink sleeve then it won't shrink properly when you apply heat. Not sure about superglue, I've never tried it but it sounds like it would also be hit and miss.
Self amalgamating tape might be waterproof if it's correctly stretched as it's wrapped but I still think you be far better and safer to have any joints outside of the tank in a dry area.
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I have used these kits on a number of occasions and they worked every time. I also clean the cables with benzine to remove any residue of oils from handling before placing it into the plastic holder. I do tape the ends of the plastic tube before pouring in the resin, to prevent run out and a shortage of resin with in the chamber. Another point is to not touch the joint once you have poured for a few hours, so that there is absolutely no movement of the cable in the setting resin.
The majority of borehole installations use this type of joint kit to join the motor cable to the supply cable.
There is a heat shrink kit with glue that is activated when heated, which speeds up the installation, but with anything in life, you must have the correct heat controlled gun for the application. The paint remover heat gun does not qualify as it may burn the heat shrink, or push the temperature beyond the specifications of the heat shrink, and damaging its characteristics.
Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
We use the bigger resin filled cable joints regularly and they take me about 1/2 an hour to complete one on a steel wire armoured cable. I've only once fitted one of those miniature type on an appliance flex and it took me an hour and a couple of attempts because everything is small and fiddly and compact. If I remember correctly there was also a sachet of powder you had to mix with the resin. I just found it a pain in the ass, maybe it's because my fingers are too big, I'm not sure.
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Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
Solar pumping, Solar Geyser & Solar Security lighting solutions - www.microsolve.co.za
AndyD (16-Sep-16)
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