Boiler Temp

[planemad]

I have a Vaillant 418 heat only boiler and the Vaillant group service engineer who does the yearly service says best to leave at 60c on the rotary dial.
The hot water thermostat is also set to 60c so I get a lot of short cycling on the boiler.

What is the best boiler temp?

Shall I increase boiler by 5 or 10 c or reduce hot water thermostat to 55c?

Thanks all

 

[Dan Robinson]

Faillant at its best....

Boiler stat to 65 or 70, cylinder stat to 55.

You need a good 10 degrees difference between the two.

 

[planemad]

Thanks

 

[Agile]

In the ideal world you will have the hot water set at about 55 C and the boiler at least 65 C and for the CH the lowest temperature that will make the place warm enough.

But in that ideal world the CH would be controlled according to the outside temperature. Most boilers can have a cheap sensor added but not on the Vaillants where an expensive propriety controller is required. Hardly worth the expense for many people.

 

[dilalio]

Eh! I thought it was a Vaillant, not an Ideal!!!

 

[Dan Robinson]

Same schit - different box

 

[planemad]

In the ideal world you will have the hot water set at about 55 C and the boiler at least 65 C and for the CH the lowest temperature that will make the place warm enough.

But in that ideal world the CH would be controlled according to the outside temperature. Most boilers can have a cheap sensor added but not on the Vaillants where an expensive propriety controller is required. Hardly worth the expense for many people.

On the boiler I only have control of one temp knob which does both heating and hot water. I have just set it to 67c and the water thermostat to 55c. I tend to leave it on the constant setting so I alway have hot water.

Incidentally I have a large 4 bed with 2 bathrooms and the water tank is only 140litre which is 1050 x 450 Seems a bit small to me. What do you experts think?

 

[Dan Robinson]

I only have 150 litres in our 4 bed house. Am about to change it fro a 170, but not because the 150 is too small.

 

[Agile]

Its not the volume of the cylinder that matters.

Its the number of users that is important. Also how much they use.

I use the rule of thumb of 50 li plus 50 li per person. So three people would be 200 li. Five people 300 li etc. But 300 li usually manages 6 or 7 quite well. The faster the reheat the better of course. As well as the time distribution of usage.

A friend who teaches HVAC could not remember the figure but thought it was 37 li/person. But some of those taught figures are based on a rather meagre social housing expectation rather than an affluent owner occupier.

Tony