You don't need to be an 'investor' to invest in Singletrack: 6 days left: 95% of target - Find out more
Is it possible for an immersion heater to partially fail?
In my brothers flat he complains the water now takes longer to heat then it used to. It’s a small 90l direct unvented tank that I think only has one immersion point.
I think he must be imagining it but could this happen?
If it's got 2 immersions (one top and one bottom) then it would take longer - but I doubt a 90L tank would have two immersions.
AFAIA they either work or they don't.
How long has he been there, if it is only recently then the water will be colder (at this time of year) so will take longer to heat.
He’s been there several years. I wondered that but as water main pipes are buried underground I wouldn’t expect there to be much difference in the water temperature, or at least enough to make a noticeable difference in heat up time?
Is there evidence in the turn dish of the prv blowing off? Of so there might be a regular supply of new cold water entering the tanks as it keeps blowing off.
Scale on the element could cause it to be worse, get a clamp meter on the feed and see what current it is pulling too.
Also as above, check there is not a discharge of water from safety devices.
Immersion heaters either work or they don't, there's no middle ground of them partially working. Scale build-up on the element or in the bottom of the tank could be the culprit. It might be worth him checking his incoming supply voltage with a multimeter or voltmeter in case that's fallen slightly, unlikely though. It's also worth checking the setting of the stat in case that's not working properly and causing the heater to cut out too early.
Actually, yes, it could partially fail. They are prone to corrosion in hard water areas.
If it has partially corroded through to the element, then the current could be going to earth through the water, rather than going through the neutral at the other end of the immersion heater element.
For this to happen, there cannot be a RCD in the supply. If there was a RCD, it'd trip immediately. Without a RCD, the circuit breaker or fuse is the circuit protection, and cannot tell if the current is going to earth or , correctly, through the neutral. The element will have to be damaged toward the neutral end for this to happen, as if it broke somewhere near to the live terminal, there would be more current flowing, and the fuse or circuit breaker would likely trip.
I've changed loads of immersions, some of them, when they come out, are held together by limescale.
Alan if the immersion fails partially as you suggest does it still heat the water, presumably consuming less current doing so. Since the energy has to go somewhere.
as water main pipes are buried underground I wouldn’t expect there to be much difference in the water temperature,
But the water goes ino the pipes at a lower temp in winter. Enough that our electric shower has a lower flow rate in winter.
Alan if the immersion fails partially as you suggest does it still heat the water, presumably consuming less current doing so. Since the energy has to go somewhere.
Yes. Put the Live and neutral terminals in a bucket of water, around 300mm apart, and you will have an immersion heater without the element. Industrial water heaters used to use this method of heating water, there are still a few working with that system, though I dont think you can get them new now.
Contrary to popular opinion, it will not bang or kill anyone touching the water, the current uses the quickest path back to earth/neutral (in the UK, the Neutral is usually of a similar impedance to earth. In most houses of the last 20+ years, earth and neutral are combined at the incoming cable). Someone putting their hand into this 'live' water will maybe feel a tingle, but will not get a shock, unless they are damp and have hold of a well earthed metallic object.
Yes. Put the Live and neutral terminals in a bucket of water, around 300mm apart, and you will have an immersion heater without the element. Industrial water heaters used to use this method of heating water, there are still a few working with that system, though I dont think you can get them new now.
Electric showers in many parts of Latin America work the same way.
A clamp meter won't work unless there's enough slack around the L or N to pass the clamp around. If he has a smart meter they come with an energy monitor which would do the same job.