Hot water temperature issue

[Chris*****]

I have a hot water cylinder and a cold water tank in the loft. We have just had a new system boiler fitted, Viessmann Vitodens 100-w and the domestic hot water is hot but not as hot as before. I can’t see how I can turn this up, the boiler manual says to press on the touch screen until a tap icon is shown but there is no such icon. For reasons I’m not going into I can’t contact the installer so wondered if I could get help here.
Thanks in advance..

 

[SimonG]

Turn up cylinder stat.

 

[Chris*****]

Does this work with the boiler?
I thought it would be for the immersion heater only.
Why would the temperature be lower with a new boiler? I know the cylinder wasn’t touched at all.

 

[king of pipes]

Check your boiler thermostat setting it needs to be set at 65 ° c or above to achieve a good hotwater temperature. Cheers kop

 

[SimonG]

Pics of boiler and cylinder cupboard?

 

[Chris*****]

Boiler is set at 75

 

[Chris*****]

Does boiler central heating temperature affect the dhw then?
I thought they were separate but is that not true in this case?

 

[Riley]

I suspect your installer has set it back correctly between 55-60°c

 

[Chris*****]

Boiler is set at 75. Does this affect both ch and dhw?

 

[Riley]

Same water heats both

 

[Chris*****]

So how does a stat on the cylinder affect any of this?

 

[chris watkins]

It would normally close a zone valve to stop the flow of heating water when the cylinder (domestic) water reached temperature (60-65degC)

 

[Riley]

It tells the boiler how long to heat for until it’s up to temperature. I think you’re focusing on the temp on the boiler too much. For example if the boiler were only heating to 40°c you’d never get your hot water up to 55°c you have to allow for some heat loss during transfer of heat to the water in the cylinder so the water circulating round the boiler must get to a higher temp in order to satisfy the heat requirement

 

[snowhead]

It opens and closes the valve that allows the boiler flow to heat the water in the cylinder.

Just to be clear, the stat mentioned is NOT the one inside the Immersion heater, it should be strapped to the side of the cylinder.

 

[townfanjon]

A 100 compact will not give you a tap symbol, only the combi does , have you got the correct manual

 

[fixitflav]

So how does a stat on the cylinder affect any of this?

The boiler just heats water. The hot water is a closed circuit and goes to the rads, or to a coil inside the HW cylinder, or both at the same time, depending on the system, controlled by a 3-port or 2 off 2-port valves. The coil in the HW cylinder heats the water which comes out of the taps. The cylinder stat determines when the boiler fires (and stops firing).
The boiler manual sounds like one for a combi boiler, which provides HW direct, and has tap and rad icons to show you what it's doing. As you have a separate HW cylinder the absence of those icons is correct.

 

[chris watkins]

The Tap symbol only applies if you have a combination boiler or a special probe which allows the boiler to control the cylinder but this is rarely used in this country.

 

[Chris*****]

Well now I understand the way it works everything becomes clearer. Many thanks for a great answer.

 

[townfanjon]

a special probe which allows the boiler to control the cylinder but this is rarely used in this country.

It does in my humble abode lol

 

[Welder]

It does in my humble abode lol

Surly you mean on your "YorkyShiire Estate" Sir?
We don't have humble abodes in Yorkshire - aka God's Own County!

 

[townfanjon]

Surly you mean on your "YorkyShiire Estate" Sir?
We don't have humble abodes in Yorkshire - aka God's Own County!

Lol , you maybe right , when we moved in here my pal called it “ southfork “

 

[Welder]

Lol , you maybe right , when we moved in here my pal called it “ southfork “

So, Yorkshire's version of JR? Or is it Sue Ellen?

 

[fronty]

Any chance you can post a pic of your front panel - there are various different versions of the Vitodens 100, including a 4 pipe version that heats the hot water on a separate circuit (and doesn't need a cylinder stat).

I have a Vitodens 100 too but it's a heat only boiler with 2 pipes, a cyclinder stat (set at 65) and 3 port valve, and no touch screen - I'm just interested in how you have yours set up as I have to run mine at near max to get decent heating and hot water. Boiler temp runs at a steady 72 degrees when it's modulating so all's good, but just feels weird having to have the temp dial on max (it's actually off the scale!).