Originally Posted by: APPNewbie 
I do have a question about the thermal breaker, BTW, I ordered it this morning. The reason for this placement as I indicated in above posts, is this simply for heat or current? Why would the breaker not be one that would automatically go back to closed position when heat dissapated? The only reason I can think of is that if this process keeps happening, the wire that supplies the current would wear out and nobody would know until a fire that there was a problem. Just my guess.
One more question: The T-stat is for controlling the temp. in the tank. I am reading 124.9 volts at the low side of the t-stat and the same at the high side of it. Does this mean that the t-stat is malfunctioning? How does the element know how hot to get if not for the T-stat? You mentioned in your earlier post that there may be a malfunction with T-stat. Should the current be less at the low side of the T-stat? Not sure how it works but the above seems to make sense. It seems that the T-stat should govern the amount of elec. going to the element. Whadya think?:confused:
Newbie,
Your thermal fuse is a predominantly voltage related fuse. However there is some heat characteristics associated with it as well.
It's purpose and the reason it becomes an open circuit, is for Safety, as you stated, no fires.
It is a "one shot" safety device.
One of the purposes (the main purpose) is to inform the repairman that something major happenned and to check the other components for failure before replacing just the thermal fuse.
As for voltages, it sounds like you're checking your voltage to a chassis ground, or line ground
(that is the way I was trained) you should have the same voltage on the back side of the switch(out), as you do on the front side(in) of the switch.
In most cases(your's in this case) a switch does not control voltage fluctuation, you will have 124.9 volts in and 124.9 volts out, until the switch cycles open, based on the setting, and stops voltage flow to the component, when the switch (reostat) cools down the switch closes and the process repeats.
I'm thinking a couple of possibilities, which was why I wanted you to check the heater element, and wires for damage, they're OK.
Another , would be that for some unknown reason the water supply did not submerge the element, and caused a run a way temp,and the fuse opened.
Your control may have stuck, also causing a run a way temperature.
As I stated previously, the thermal fuse may have just weakend from normal wear and tear, and failed.
Based on the information you supplied and the questions you've asked, I'm leaning towards a weak thermal fuse, at this point.
Good Luck,
:cool: :cool: :cool:
