Hot Water Cylinder - Water Too Hot (Ed.)

[adzyp]

Hi all, just moved into our first property with a water tank and conventional boiler.

Boiler has a temp dial (Main 24) annoyingly that has no indication of what the temp values actually are!

Tank has its own temp setting which I have set at just under 60.

But if tap is turned to the hot side the water comes out way too hot especially when we have children in the house.

Its pumped and has all this kit in the airing cupboard.

Any suggestions?

 

[Exedon]

The cylinder stat controls your hot water temperature
Turn it down a bit more if hot water higher temperature than you want.
Check hot motorised valve is working with hot water powered up turn down cylinder stat you should hear valve closing.
If boiler continues to run could be faulty motorised valve.

 

[adzyp]

The cylinder stat controls your hot water temperature
Turn it down a bit more if hot water higher temperature than you want.
Check hot motorised valve is working with hot water powered up turn down cylinder stat you should hear valve closing.
If boiler continues to run could be faulty motorised valve.

Ok, does the cylinder not need to stay around 60 though to kill bacteria?

 

[Exedon]

It needs to be raised to 60c to kill legionella ideally get a thermometer and check temperature at taps.

 

[adzyp]

It needs to be raised to 60c to kill legionella ideally get a thermometer and check temperature at taps.

Yeah thats why ive got it set to 60, ill give a thermometer a go if i can find one.

Pump seems ok. Heard it kick in when water turned on, albeit whirring a bit to start, then turned temp down and it stopped

 

[JohnD]

Ok, does the cylinder not need to stay around 60 though to kill bacteria?

50C will kill legionella, and it will not grow above 45C or below 20C. So it will not reproduce in the cold incoming water nor in the hot stored water.

50C kills it more slowly than 60C, but stored water in a cylinder is usually kept hot.

It is more of a risk in stored warm water in a dirty tank, so look at your cold water storage cistern and ensure it has a cover and an insulating jacket. Clean out any dirt or drowned wildlife that provides nutrients for bacteria.

"The bacteria multiply where temperatures are between 20-45°C and nutrients are available. The bacteria are dormant below 20°C and do not survive above 60°C." https://www.hse.gov.uk/healthservices/legionella.htm

 

[JohnD]

But if tap is turned to the hot side the water comes out way too hot especially when we have children in the house.

If the motorised valve controlling the supply from the boiler to the cylinder coil is worn out, it may allow the cylinder to be heated whenever the radiators are on, even if the cylinder is already hot. You can detect this by feeling the pipe coming out of the valve. The valves commonly last 10 to 20 years. The water part of the valve can be worn out even if the electric motor part is working or renewed.

 

[Rodders53]

Measure HW temperature at the taps when running... Those tank stats will probably be inaccurate and the water at top of the tank is likely to in excess of the set temp lower down...
I use a digital meat thermometer held in the HW stream.

Building Regs now require thermostatic mixer valves set to and absolute max of 48C. So thermostatic bath mixers are wise. One can also get / fit TMVs for basins or even fit them to the whole house HW supply... {with some caveats around Legionella... Google will find you the full lowdown if interested}.

NB most such mixer taps and shower mixers have a 'stop' around the 38C mark -- human blood temperature -- that is used for comfort.

 

[dilalio]

But if tap is turned to the hot side the water comes out way too hot especially when we have children in the house.

If water is at 50-60° then it's being heated to around what it can be, with the controls present.

Point of use blending required if you want to get it below that.

New builds now have tmvs installed for this purpose. Trouble is, many owners don't know they're there!

 

[grahamderek]

turn off the immersion heater

 

[Notch7]

Ok, does the cylinder not need to stay around 60 though to kill bacteria?

No

“At 50˚C 90% of legionella dies in between 80 and 124 minutes depending on the strain, let’s call it a worse of 2 call it 2 hours”

Legionella and Water Temperature: What You Need To Know

Stay informed about Legionella water temperature management! Learn about the risks in water systems and how water temperature can prevent Legionnaires' disease

www.heatgeek.com

The hot water cylinder will have stratification, ie there will be a temperature gradient, if you feel the underside of the tank it will be cold or lukewarm, whereas the pipe at the top will be scolding.

Your cylinder stat is about 1/3 of the way up, so if it’s 60 deg there the water at the pipe at the top will be higher.

My cylinder stat is set to 50 and the water at the tap comes out at about 60

 

[Notch7]

Boiler has a temp dial (Main 24) annoyingly that has no indication of what the temp values actually are

The temperature of the flow temp from the boiler doesn’t influence hot water cylinder temp as such, if you have a high boiler flow temp it will heat the hot water up faster until the cylinder stat stops calling for heat.

 

[JohnD]

There are various pipe thermometers and infra- red scanners, but this type us very cheap and handy.

Digital LCD Thermometer Temperature Meter Gauge with Waterproof Sensor Probe UK | eBay

Temperature range: -50~ 110°C. Temperature display resolution: 0.1. Weight: 22g.

www.ebay.co.uk

You can tape the sensor end to a pipe or something and preferably put some insulating lagging over it.

 

[adzyp]

Just put a meat thermometer under the kitchen tap and was recording 63 degrees c.

Ive knocked the cylinder down to 50 now so will see if that brings the temp down any

 

[andy_nufc]

turn off the immersion heater

Bingo. Why has no one else spotted this?