Weird things I found when fixing my water heater - please tell me this is okay

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Boise, Idaho
Hi all, I am new to this forum, so please let me know if I need to restructure this post.

A few days ago my 17 year old water heater stopped working after the power tripped. The heater runs on gas so this was probably a coincidence – but I add it in case somebody thinks it’s relevant. After some time on Google and YouTube I decided that it’s probably the thermocouple that was dead (the pilot light would come on but die as soon as I tried to turn the system to normal function). I replaced the thermocouple and this did the trick - the water heater is now working again… But I had to do to some weird things along the way that I would appreciate some feedback on.

Weird thing number one – the water heater’s original thermocouple is 15 inches long. I couldn’t find a 15 inch so I bought an 18 inch, however the diameter of the 18 inch thermocouple was bigger than the mounting bracket, so that didn’t work. I found a 24 inch thermocouple with a narrower diameter. I installed that, and it is working fine. I would really appreciate it if somebody that knows more than we can tell me that the length of the thermocouple doesn’t matter beyond it looking weird that I have a few inches of copper wire in a mess at the base of the water heater.

Weird thing number two –
this is the more concerning issue. Instead of the Thermocouple plugging right into the gas valve assembly it was plugging into the female-end of a sub-assembly. The sub-assembly had one end plugged into the socket where the thermocouple would normally go, but it also had two wires connected to a resistor and then going up to the top of the tank where it connected to a “therm-o-disc”, which in turn was connected to a wire that runs around the top of the tank where the exhaust is. I assume that this is a safety mechanism that disconnects the thermocouple if the temperature at the top of the tank gets too high – causing the gas to be cut off and preventing the system from over-heating. Ideally, I would like to have this safety mechanism in place, BUT… the female end of the sub-assembly is totally stripped and I couldn’t plug the thermocouple into it. So, I circumvented the sub-assembly and plugged the thermocouple directly into the gas valve assembly where the sub-assembly was previously plugging into. I believe that the “therm-o-disc” cut off was an excessive safety measure as a plumber that was here this morning said that he didn’t know what it does and that if he services the tank he would probably remove it. I have attached a bunch of photos. It would be great to hear somebody that knows more than me say “what you did is fine and that therm-o-disc sub assembly is unnecessary". Or “you should fix that stripped part and make sure that the sub-assembly is working, and here is why, and here is how”.

Any insights into either of the weird things would be much appreciated!


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