Heating elements - do they NEED to be fully immersed while running?

[goatus]

I'm planning on slapping together a herms tube with a stick-type heating element slips between the coils of the herms coil. It will be a lot easier to build with both the element and the coil mounted through the lid of the tube as depicted in my highly artistic sketch below:


Red = element, Grey = herms coil, Blue = water level

But as you can see, this kind of design will leave an air gap at the base of the heating element where it will not be immersed in water (the actual gap will be less than depicted here, but you get the point). Will this damage the element? Or as long as there is some water to absorb the energy the element wont burn out? I'm thinking of the over the side immersion heating elements not being fully immersed, but perhaps they work differently. Thoughts?

 

[fraser_john]

The elements commonly bought often have 3cm or so that do not heat, so you might be ok.... but you would have to monitor it because if it does not cover it, it will over heat.

 

[Camo6]

Good questions. I guess it depends on your element and where the resistive load begins. I think most elements have a dead space close to the flange but this may differ by design. If you do leave a hot spot of the element out of the liquid then that part of the element will be unable to disperse heat effectively and failure will likely result.
I have a HEX design just like yours but I've mounted the element through the base. The herms coil just clears the element so it must be mounted straight to avoid contact but it is completely immersed so no worries about hot spots.

 

[fraser_john]

Just to show what I am on about, this is the five star 2400w job, you can see the unheated part as it has not changed colour


Brewing right now, so convenient post

 

[goatus]

Hmmm.. guess i should stop being lazy and mount it from the bottom then. No doubt i would blow the element one day and have to do it anyway.

 

[Grainer]

Put it at the bottom and save yourself an explosion of some type

 

[Camo6]

I used a 5star stick type element with stainless guard in mine. Sealed with silicone o rings and silicone it has been leak free for a couple of trial runs and a few simple brews so far but in the event of a leak I left the cable gland out of the guard so it could be detected quickly.

 

[dicko]

I agree with fitting it from the bottom.

To be sure...to be sure