Hot water temperature

[Russell griffiths]

Morning two part question, I have a vented cylinder that is heated just with an immersion heater, a couple of days ago the cylinder boiled and expanded into the loft tank, so I fitted a new immersion thermostat. 

 

What should be the hot water temperature at the tap, I think there is a set temp to stop nasty bugs breeding, it was previously bloody hot, so it’s a bit more user friendly now, however it’s affecting our mixer shower, so I want to start at one point and work out where to go from. 

 

Cheers. 

[ToughButterCup]

40 is the safe temperature set in our Hansgrohe iBox.

That's the German setting so the UK one must be higher... ?

 

[scottishjohn]

  On 14/09/2020 at 06:27, Russell griffiths said:

What should be the hot water temperature at the tap,

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that will depend on size of your tank -if you have to add cold water to it--then maybe its too hot ,but if tank is small then will need to set hotter and add cold at point of use

 I set my hot water form my solar tank to exit at 45c - I did this fitting a mixer at tank exit  so i could get best temp gain from my panels when available

most normal days water in tank would be 80c+  at top where dhw was pulled from

lower down where UFH coil was30-40c

due to size of tank   300litres

If there is a next time then much bigger tank and store at lower temp .but still with mixer at  outlet.

 I still hope I can use solar thermal for allm ywater heating needs  inc UFH --but canot do any more planning untill I have a  fixed house design and heat loss calcs 

I have a 5000litre tank i made up 10years ago with input +out put colis fitted --a GRP ex chemcial pressure tank 

 

my guess is that sunk in a  dry hole surrounded with concrete and PIr might be big enough --time and costings  will tell

 

 

Edited September 14, 2020 by scottishjohn

[SteamyTea]

I had my cylinder set at 50°C, but have recently lowered it to reduce losses.

It needs to be as low as possible, but still needs to deliver enough hot water.  In a way, only you can answer that.  If you feel it is too hot, turn it down.

I don't have a thermostatically controlled shower, it is just a basic valve that blends the hot and cold, worked well for the last 15 years.

 

 

[Russell griffiths]

Is there not a temperature setting that it needs to be to kill of legionnaires disease. 

[ma9mwah]

I think the thought is that for anti-legionnaire then a vented system is should be >=60c. For unvented then the risk is much smaller that you can run to 45c (good for ASHP people) 

[joe90]

The consensus over the years on this forum is that legionnaires occurrence in domestic circumstances are almost zero So many of us only heat to about 45-48’. I would set as low as possible and slowly increase it if it’s needed. The lower the tank temp the lower the standing losses.

[SteamyTea]

  On 14/09/2020 at 09:54, joe90 said:

consensus over the years on this forum is that legionnaires occurrence in domestic circumstances are almost zero

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Yes, it is a rather specific, and unique set of circumstances. Why it generally a problem with old cooling systems, and not DHW.

  On 14/09/2020 at 09:54, joe90 said:

set as low as possible and slowly increase it if it’s needed

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What I do when I have guests. 20 seconds with a small screwdriver.

[PeterW]

  On 14/09/2020 at 09:54, joe90 said:

The consensus over the years on this forum is that legionnaires occurrence in domestic circumstances are almost zero So many of us only heat to about 45-48’. I would set as low as possible and slowly increase it if it’s needed. The lower the tank temp the lower the standing losses.

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That is for unvented cylinders 

 

  On 14/09/2020 at 09:31, Russell griffiths said:

Is there not a temperature setting that it needs to be to kill of legionnaires disease. 

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For a vented cylinder it is 65c periodically but ideally you should have some sort of blending with cold prior to stop scalding. I run a vented tank at 53c on gas and occasionally push the immersion to take it to 65c

[joe90]

  On 14/09/2020 at 10:02, PeterW said:

That is for unvented cylinders 

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Ah, didn’t read post properly ?

[ProDave]

Yes it was agreed for an unvented cylinder fed with treated mains water there was no legionairs risk, but you cannot say that for a vented tank fed cylinder so it would be wise to regularly heat it to 60 degees or more.

[Russell griffiths]

Ok back to my water problems. 

I decided to go and get a thermometer so we can get some figures to work from. 

The temperature at the hot tap is 56 so knowing the risk of legionaries is low in a domestic situation then that is probably fine. 

However this is lower than the scalding temperature it was previously and that has had a knock on effect on the thermostatic mixer shower. 

The temperature at the shower head is 37 which we find too cold. 

So a couple of things

 

Anybody know what sort of temperature these mixer valves are set too it’s a reasonable expensive  MIRA one as recommended by @Nickfromwales 3 years ago. 

 

If the input from the tank is 59 why is the mixer mixing it down to 37 when previously it was hotter. 

 

Are these mixers adjustable, I remember when it came there was a funny blue spanner thing with it for some sort of maintenance. 

 

I will need to dig out the manual and have a look, but it’s easier asking you lot from the comfort of the sofa than having to deal with the mess I call an office. 

 

Cheers russ. 

[ToughButterCup]

I've used Hansgrohe iBox. It has a 'settable ' default temperature (40).

[dpmiller]

Is the cold water tankfed too or is it at a different pressure to the hot? Might be the valve is a little unbalanced at the lower temp...