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]

49 minutes ago, Russell griffiths said:

What should be the hot water temperature at the tap,

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]

2 minutes ago, joe90 said:

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

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

5 minutes ago, joe90 said:

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

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

[PeterW]

4 minutes ago, 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.

That is for unvented cylinders 

 

28 minutes ago, Russell griffiths said:

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

 

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]

1 hour ago, PeterW said:

That is for unvented cylinders 

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...