Has wrong kW rated boiler been fitted

[Littlemoney]

In November 2024 I had a Worcester Bosch Greenstar boiler installed. During discussions about my requirements when I advised that I bath rather than shower I was informed they would install the 30 kW model rather than 25 kW model.

I am disappointed with the hot water temperature. There is no indication on the outside of the boiler as to which model was fitted.

I have just been through all the paperwork that was left and there is an ERP efficiency label showing 24 kW figure. What does this figure refer to please.

Have they fitted the lower rated boiler. Is there anywhere on the boiler which will tell me if the 25 kW or 30 kW model has been fitted please.

I want to know if what was fitted is the same as agreed.
Thanks

 

[Mister Banks]

There should be a label on the boiler stating the model and GC number.

 

[Littlemoney]

There should be a label on the boiler stating the model and GC number.

What is the GC number please.

 

[Why Not Indeed]

Have you looked at the hot water temperature settings? Maybe it's just lower than you want.

 

[Littlemoney]

Have you looked at the hot water temperature settings? Maybe it's just lower than you want.

Hot water temperature set to 60

 

[Littlemoney]

There should be a label on the boiler stating the model and GC number.

Just found label attached to another document.

This states:
Greenstar 4000 30 kW Combi NG
GR4700iW 30 C NG
And then the GC number you mentioned

I assume the 30 kW on this label means the correct boiler was supplied. When I opted for combi boiler I hadn't appreciate the hot water temperature limitations even after opting for the higher kW rated

 

[ChrisJP]

If the HW temperature is set to 60C try raising it to 70C to see if this makes the HW more acceptable to you. 60c is the generally accepted minimum temp to kill legionnaires disease bacteria, so I guess that's why your installer set it at that. You may find 70C too hot and at risk of scalding you, but somewhere between 60 and 70C should be about right.

 

[Elkato531]

60c is the generally accepted minimum temp to kill legionnaires disease bacteria

For stored hot water. Irrelevant in the case of a combi.
A combi boiler can only heat up water at a certain rate and one of their disadvantages is that it will take longer to fill a bath than with stored hot water.
At this time of year, the incoming water will be very cold so the boiler could be struggling to achieve the temperature rise you are looking for. You could try turning the tap down a bit. It'll take longer to fill the bath but should be hotter when you finally get in.

 

[Mottie]

I set my mums combi hot water temperature by running a hot tap fully open and gradually increasing the temperature until I reached the desired temp.

 

[Notch7]

I wouldve thought the boiler size would affect max flow rate not temperature

a combi isnt that great for filling a bath

 

[gas112]

a 30kw combi is designed to roughly raise the incoming water temp by 35 degrees on a 12 litre per minute delivery rate so in the summer the water will be warmer due to it coming into the house at a higher temp .
If you want the water hotter then turn the tap down so its delivering less water per minute from the tap .

 

[CountryFan]

Just found label attached to another document.

This states:
Greenstar 4000 30 kW Combi NG
GR4700iW 30 C NG
And then the GC number you mentioned

I assume the 30 kW on this label means the correct boiler was supplied. When I opted for combi boiler I hadn't appreciate the hot water temperature limitations even after opting for the higher kW rated

I would say they fitted what you have asked for. What boiler/setup did you have previously?

 

[DP]

If the HW temperature is set to 60C try raising it to 70C to see if this makes the HW more acceptable to you. 60c is the generally accepted minimum temp to kill legionnaires disease bacteria, so I guess that's why your installer set it at that. You may find 70C too hot and at risk of scalding you, but somewhere between 60 and 70C should be about right.

Do you know combi boiler operation?
I would love to see a combi provide 60 degrees of hot water at stipulated flow rate let alone 70
And where does legionella come in, this is a combination boiler that heats water you drink- no stored water here

A combi will heat cold water by35 degrees a flow rate specified for the boiler. 30kw may well be 11 l per minute
If cold water is 10 degrees, then hot will be 45
Choke the tap down to reduce flow, boiler will shut down at around 60 degrees and water from tap will likely go milky

 

[Johntheo5]

The differences should have been explained clearly to the homeowner, especially one who had stated that "I bath rather than shower I was informed they would install the 30 kW model rather than 25 kW model" and who was considering changing from a system/heat only boiler to a combi.

Still, there is a great love for the combi in the UK, they are as rare as hens teeth around here.

According to the Commission on Climate Change, the UK has around 23 million gas boilers. According to the Energy Saving Trust, the average gas boiler costs (including thermostatic radiator valves) around £4,000. Around 80% of homes have a combi boiler. Around 78% of homes use a type of gas central heating.

 

[RandomGrinch]

According to the Energy Saving Trust, the average gas boiler costs (including thermostatic radiator valves) around £4,000. Around 80% of homes have a combi boiler. Around 78% of homes use a type of gas central heating.

I haven't found the definitive source, but those statistics don't make sense!
I believe it is media misinterpretation of the figures.
The reports generally quote...

But later on say...

I'm far more prepared to accept that 80% of boilers sold are combis, than 80% of UK housholds have a combi, when only 78% use gas C/H.

That would leave an awful lot of electric and oil combi's hanging around and no-one using system/heat only boilers!

EDIT:
In a 2019 .GOV survey report, 59% of dwellings used their "central heating system to provide hot water, without a separate cylinder", whereas 32% used their "central heating system to provide hot water through a separate hot water cylinder".