Unable To Remove Thermostat From Immersion Heated Cylinder

[PugSky]

Firstly hello, and thanks for ready my question/thread.

I believe my thermostat is faulty as the water is far too hot. There in not enough room to remove the thermostat as it hits the roof of the airing cupboard. Only idea I’ve had (other than removing the tank) is to cut the thermostat tube with a hacksaw and then re-fit a shorter unit. Is this a viable solution or am I mad (Computer Engineer by day).

Thanks

Kenan

 

[batty]

I assume you have tried turning it down? You could go for a shorter stat but you may not get totally correct temperature. Welcome to the forum by the way.

 

[PugSky]

Hi Snoopy,

   Thanks for the quick reply and the welcome. I have tried changing the temprature, which was set to 50 when I first checked it (new house) so assume the seller knew about the fault. I can hear it click at 55 but the water temprature is much hotter hense my assumption its faulty. Not worried if the temprature is not 100% as the heating system will need chaning in the next few years just wanted to check there was no other option than getting the hacksaw out (I'm also great with a hammer).

 

[batty]

You say the heating system needs changing so water is only electrically heated at present?

 

[PugSky]

The heating system has been in the house since it was built 40 odds years ago, so is a little on the old side and we are assuming it will need replacing at some point in the future. From what I can work out the water is only heated by the electricity/immersion system.

The boiler looks like it will only heat the water for the heating, stick labels put on by previous owner also indicate heating only. And we have tried to warm the water in the tank but it won’t trigger/fire for anything other than turning up the heating thermostat. There is a heating timer connected to the emersion system which seems to be the only way to heat the water in the tank.

 

[Marvo]

I can hear it click at 55 but the water temperature is much hotter hense my assumption its faulty.

Analogue/mechanical thermostats in cylinders are rarely accurate to better that 10%. Several factors including heating over-run, t/stat differential and water temperature gradient within the cylinder can make for compounded inaccuracies.

Not worried if the temprature is not 100% as the heating system will need chaning in the next few years just wanted to check there was no other option than getting the hacksaw out (I'm also great with a hammer).

The sensing tube of the thermostat is often surprisingly flexible and can often be bent at a radius without damage occuring. Rather leave the cylinder set a little too hot than end up with it being too cool and introducing a legionella infection risk. Never run below 50 Celsius unless the system has a periodic cleansing cycle built in.

 

[batty]

You may have a gravity hot water system and possibly this is why water is getting so hot. How high is the boiler temperature set, maybe reduce this a bit to bring hot water temperature down. As a newbie you can't post pics but maybe this could be sorted so we could see if hot water tank is actually on the central heating system.

 

[NozSpark]

Assuming that you have a loft or a void above the cylinder then you could always make some more headroom by cutting a hole

 

[PugSky]

Thanks again for the replys.

The tank is gravety feed from what I can work out as there is one cold pipe feed in the bottom of the tank and one hot feed out the top. I haven't had the heating on and the boiler hasen't fired so I know it's not heating the water by the gas. There is only 1 boiler temp dial, has settings from 1-5 and is set to 2.

Cutting a hole in the roof is not an option, unless I don't want my wife to speak to me for a while. Thinking about it where the downside

 

[Technician]

 Never run below 50 Celsius unless the system has a periodic cleansing cycle built in.

That is a fair point and I have heard that 60 Cel is preferred.  In a conversation

with a Legionella specialist I trotted this one out. 

His reply?

"Not necessarilly........."   "depends upon the strain."

 

[PugSky]

That is a fair point and I have heard that 60 Cel is preferred.  In a conversation

with a Legionella specialist I trotted this one out. 

His reply?

"Not necessarilly........."   "depends upon the strain."

Just to clarify, the thermostat is set to 50, but the water temperature is scalding.

 

[Marvo]

Scalding is somewhat a loose term, water temperatures above 55 degrees Celsius are too hot for comfort and above 60 degrees can easily cause burns. Can you get access to a temperature tester? Many of the cheap multmeters available from supermarkets can check temperatures as well as voltage etc.

I can't remember off hand the exact legionella temperature ranges, under a certain temperature is an absolute no-no and there's another threshold where it doesn't kill it but it won't multiply then there's a range where it kills it over a certain length of time. I'm sure the UK will have it's own set of guidelines or regulations in one of the health and safety requirement documents. It's certainly a worthwhile consideration if you're looking to reduce cylinder temperature especially if there's a shower being supplied.

 

[Technician]

The problem with stored hot water in any form was and is

the incubation of the legionella.  As Marvo states, there

is a threshold and the holding temperature should be

above this.  The beasties are there in the water; no doubt

but the INTENT is to limit the potential for multiplication.

35 deg Cel (approx) appears to be the optimum for this event.

 

[NozSpark]

I didn't think that legionella needed to be considered in a domestic setting due to the relatively low quantities of stored hot water and the proportionally high levels of drawn off water.

And also the fact that it isn't drinking water

I could easily be wrong though

 

[Technician]

Noz; a perfectly valid observation. Once released in a domestic

environment, it can be infectious.  That, as I have had it explained

to me, is the problem.

 

[SLIPSHOD & SLAPDASH]

Can you electrically  test the stat before destroying it, do you have a multimeter  ?

 

[PugSky]

Thermostat destroyed and replacement fitted. Water temprature issue now resolved.

Thanks for the advise guys.

 

[a3]

Thanks for reporting back to us  :Salute

 

[Bruspark]

Re water temperatures HSE and IPHE say

70 - 80c disinfects

66c kills in 2 minutes

60c kills in 32 minutes

55c  kills in 5 - 6 hours

20 - 45 c legionella multiply

20c dormant below 20

45c is the most dangerous level for Legionella in stored water yet it is also the highest level that would not cause immediate critical burns from a tap/bath/shower

The answer for 'at risk populations' is apparently to fit thermostatic limiters at each outlet and NOT to store the water at 45 c

 

[septiclecky]

On a gravity typ

Thanks again for the replys.

The tank is gravety feed from what I can work out as there is one cold pipe feed in the bottom of the tank and one hot feed out the top. I haven't had the heating on and the boiler hasen't fired so I know it's not heating the water by the gas. There is only 1 boiler temp dial, has settings from 1-5 and is set to 2.

Cutting a hole in the roof is not an option, unless I don't want my wife to speak to me for a while. Thinking about it where the downside

You have said it is gravity fed system doesn't matter what you have the thermostat set at it will have no control over the temperature of the hot water as long as you have the boiler on. The thermostat will only switch on and off the immersion heater.