immersion heater fault?

[andyb]

This is a thermal cut out which is fitted as standard in most thermostats now.
What can happen without one is that in the event of a thermostat failure the water in the tank can boil & expand to fill up the storage tank in the loft. If the tank is plastic this eventually collapses allowing the boiler water to run into the room below.

 

[Jabbajaws]

Thank you AndyB. I assumed that the copper tank was what had exploded, due to pressure build-up with the hot water. It had never occured to me that the water would travel up to the cold water tank above it.

My mother has an immersion heater in her home, and it looks ok but im worried about this issue. If l replaced the thermostat on it (should it be an older one) and replaced it with a brand new one, would this prevent this sceanario from happening, in the event of thermostat failure?

My mum's immersion heater is situated in a dangerous place, with regards to the lower floor, should this ever happen...

 

[andyb]

It should do jabbajaws, I'm not sure if the if all new immersion stats have a thermal cutouts so I would check.
The danger is with plastic tanks or similar, metal ones should be ok.

 

[jpmiff]

i suspect that all plastic water tanks designed for domestic water uses as expansoin tanks for open vented CH systems will be able to withstand the maximum water temp of 100 degrees c

 

[telectrix]

i would definitely recommend trying a new stat with thermal overload. it's only 2 connections and drop in. you can tell it's got the overload as there is a small recessed button, similar to on a PC router.

 

[andyb]

You're probably right jpmiff but hot water has caused a tank to rupture, look at this article.

BBC NEWS | England | Somerset | Baby death highlights fault risk

 

[Sintra]

Thank you AndyB. I assumed that the copper tank was what had exploded, due to pressure build-up with the hot water. It had never occured to me that the water would travel up to the cold water tank above it.

My mother has an immersion heater in her home, and it looks ok but im worried about this issue. If l replaced the thermostat on it (should it be an older one) and replaced it with a brand new one, would this prevent this sceanario from happening, in the event of thermostat failure?

My mum's immersion heater is situated in a dangerous place, with regards to the lower floor, should this ever happen...

All new elements must be provided with a thermal cut-out to prevent the water from boiling if the thermostat fails. 554.2.1

 

[antimatter]

Thank you for the feedback. One final concern l have regarding electrical immersion heaters.

Does anyone remember a few years ago, a fault occuring on a domestic immersion heater, in England, after which the thermostat failed, and the immersion continued to boil constantly, until it eventually exploded, with the tragic loss of a young infant, who was asleep on the floor below.

I noticed that on the news, it was announced that a simple part could have been fitted to the immersion heater to prevent this for a mere cost of approx £5.

What id like to know is What is the part that can be fitted, to prevent this from happening again? Does anybody know? Any info much appreciated...

Here's your answer;
Immersion heaters need overheat safety thermostat


17 November 2003

Following the tragic death of a young mother earlier this year, the CIBSE Domestic Building Services Panel has called for the heating industry to be increasingly vigilant regarding safety in immersion heater installations. The most important action is to ensure that any new or replacement immersion heaters fitted comply with the EN 60335-2-73:1996 standard which will be a legal requirement from April 2004.
This standard requires that the overheat thermostat cuts out with contacts open, is non-self resetting and operates independently of the water thermostat.

The recent death occurred when a faulty immersion heater thermostat failed, allowing the water in the plastic cold-water tank to eventually reach boiling point. During the night when the victim was asleep, the poorly-supported water tank bulged and flopped over. Hot water then poured through the ceiling onto the victim sleeping below.

As well as the safety of immersion heaters, the incident draws attention to the need to ensure that plastic cold-water tanks are provided with fully-supporting bases.

 

[Jabbajaws]

Thank you for the valuable feedback everybody. I'll defo look into changing the stat for one with thermal cutout protection anyway, just to be on the safeside...

 

[robsparky1975]

Tragic story about that young baby,i have a young child myself so heartbroken for the parents,all uk thermostats sold now are upto the required regulations,replacing a stat is very simple,follow the safe isloation procedure etc etc,then you can sleep soundly at night,that accident imo could have been possibly prevented,did it not say in the article that the couple had only lived there for a week,so reactive maintenance?why did that council not have a periodic inspection for a new tenant? i would not think that there are 3.5million homes out there with dangerous stats as immersions generally are changed regularly dependant on use,say every 5 years.i have only seen 1 element with no thermal cut out and it was ancient.

 

[Jabbajaws]

Thank you Robsparky1975.

I have three kids myself, one of which plays constantly underneath my mum's bathroom, where her hot water cylinder is housed.

She's just moved in and l want to check that it's running ok. Id read the story about baby Rhyianna and it's one of those things l want to check, just in case.

The story bothered me so much that im determined to help prevent this from happening again.

Where can l find out everything that l need to know about these immersion heaters, so that l can advise anyone who asks me, "Is that totally safe?".
Im very much a Newbie at present, qualified last year but need to gain that valuable experience, so l havent got alot of equipment.

Ive an approved voltage tester, £20 basic clampmeter from Screwfix, a continuity/insulation resistance tester, which isnt calibrated, l use it just to learn at mo. A home made line, neutral and cpc current tester (made from an 13A extension lead, entering the flex to separate line, neutral and cpc cores, so that l can place my clampmeter around each core to test amperage). Saw that on Learning Lounge on youtube. Pretty simple and 100% effective. A £20 stud detector which detects studs, obstructions and detects ac field voltage to a depth of 38mm.

Upon a visual check yesterday on mum's hot water cylinder. The hot water feed pipe runs directly over the access panel for the element, making it possibly inaccessible for me to get to. WTF...

Does that mean that the sparky wired up the cylinder before it was plumbed in? Isnt that a little bit to rather dangerous? Surely that should be done last with water in, for obvious insulation resistance test reasons?

 

[Marvo]

Thermostats fail every day. If the primary control thermostat fails in the closed position then the heater will just cycle on and off via the second safety thermostat......until it also fails. I'm not convinced that a house owner would ever be aware that the first thermostat had failed.

Second point, if the thermostat failure was due to a short circuit at the element perhaps due to leaking water then it doesn't matter how many thermostats or safety devices you have in series with the element, they're all going to weld and fuse in the closed position due to the fault current. A water heater is on a large cable so the fault current could easily be >3KA.

Wouldn't it be better just to put a catch tray with a 50mm drain pipe under the cylinder? If the footprint of the tray is 50% larger than the footprint of the immersion heater and it's associated header tanks etc then it would be safer.

 

[Graeme Harrold]

Thermostats fail every day. If the primary control thermostat fails in the closed position then the heater will just cycle on and off via the second safety thermostat......until it also fails. I'm not convinced that a house owner would ever be aware that the first thermostat had failed.

The secondary safety thermostat HAS to be manually reset if it trips, so if the primary fails closed, the homeowner will know when they run out of hot water.

 

[mikeelec]

Hi can an immersion thermostat cut out prematurely before setting is reached and if so how would i test the stat to confirm this. I ask this because ive replaced a bottom immersion on an economy 7 cylinder and the water only last for half a bath in the morning then it runs cold