Re: Immersion Heater Fuse Blowing

Then to prove that the immersion is faulty, rewire it from a plug and see if that blows the fuse too. The thermostat will not cause fuse blowing in my experience, while the element will.

I have changed lots of elements over many years and only once has the cylinder started to twist and buckle because of tightness, although the element still undid ok and a new one went in ok. Always start the undoing process with the cylinder full, even if the element is at the bottom, the weight of water keeps everything stable, also use a socket with crossbar if possible. MrCheerful

The element could have shorted to the casing, causing it to draw more current. This will make the fuse carrier very hot (and the cable quite likely warm too). If it's an intermittent short such as a cable fault, then the fuse carrier won't have time to heat up (although it might be slightly warm just from normal operation of the immersion heater).

This is a handy technique to diagnose an overload current blowing a fuse verses a fault current (short circuit) blowing a fuse, but you have to get there immediately after it happens.

When removing an immersion element from a cylinder, always heat the copper around the immersion with a blowlamp. This expands the copper and makes it easier to screw out.