Need to calibrate a cylinder thermostat?

[Agile]

You do seem to have some fixed ideas and to ignore our advice.

Its usual to lose just 1-2 degrees between cylinder and tap!

Now you want to risk killing her from legionella!

 

[Hamslay]

You do seem to have some fixed ideas and to ignore our advice.

Now you want to risk killing her from legionella!

Not sure what you mean there! I've not messed with the thermostat, as recommended, and have adjusted it to a point that I figure is around 60C in the tank. What advice did I ignore?

 

[warmadmax]

Well, having left the thermostat set to 45C thinking it might bring the tap temperature down nearer 60C, I measured the water today at 47C. It's possible to wash your hands under the running hot water alone now, so Mum is happy!

I don't know what temperature the water is being stored at, as there's obviously a heat loss in the pipework, but I'm guessing it can't be far below the recommended 60C if it comes out of a kitchen tap at 47C?

I think I'll tweak the cylinder thermostat up to 50C and work on the basis that the water is probably stored at a safe temperature, but cool enough that Mum's guest will stop scalding themselves when they wash their hands!

Thanks everyone for your help!

you've said you've moved the stat to 45C and 50C, leave it at 60C

you need the stored water to be below the stat to be 55C to kill legionella in the hot water tank, the stat is a third of the way up to ensure all the water above it is at least that temp.

have a look at this
wikipedia - legionella

a ubiquitous aquatic organism that thrives in temperatures between 25 and 45 °C


and
[code:1]
Temperature affects the survival of Legionella as follows:[21]
70 to 80 °C (158 to 176 °F): Disinfection range
At 66 °C (151 °F): Legionellae die within 2 minutes
At 60 °C (140 °F): They die within 32 minutes
At 55 °C (131 °F): They die within 5 to 6 hours
Above 50 °C (122 °F): They can survive but do not multiply
35 to 46 °C (95 to 115 °F): Ideal growth range
20 to 50 °C (68 to 122 °F): Growth range
Below 20 °C (68 °F): They can survive but are dormant
[/code:1]


if the hot water is 47oC coming out the tap, and as stated, it only loses a few degrees in transmission, your in the legionella growth range

keep the stat at 60oC on the tank,
if scalding is a problem, get a thermostatic mixer valve (TMV) for the hot tap, that reduces the temp right at the tap, not in the pipework / stored water.

 

[D_Hailsham]

You need the stored water to be below the stat to be 55C to kill legionella in the hot water tank, the stat is a third of the way up to ensure all the water above it is at least that temp.

I thought the water temperature had to be above 55C and preferably 60C to kill legionella bacteria.

 

[Agile]

The stat is 1/3 of the way up as that best measures when the tank is mostly warm on a standard size tank.

Tony

 

[elcaro]

Hi all, can I post to this after all these months?
Our boiler is not a combi. The CH programming control seems to allow CH+HW or HW only but not CH only. From reading on here I thought about turning the setting down on the sensor stuck onto the side of the cylinder. Then legionella got mentioned. Not sure abut this. OK a certain temp kills legionella so we don't want to go below that. But what about all the times when the heating system is switched off? Surely then the cylinder temp will go back to ambient?
I'd be grateful for any advice. TIA, Terry.

 

[D_Hailsham]

But what about all the times when the heating system is switched off? Surely then the cylinder temp will go back to ambient?

If the cylinder is well insulated the drop in temperature will be very small.

 

[CBF]

........

 

[elcaro]

Thanks D_Hailsham. Yes the cylinder is well-insulated. I would have thought that if the CH/HW is used intermittently the temp. would still spend a certain amount of time is the bad temp. zone, either on its way or on its way down, whatever the setting was. Not so much in winter, but in summer the heating / HW could be off for days; only switched on, in fact, when I want some hot water!
Thanks - Terry.