Does a 30 kw gas condensing boiler use much more gas than a 24 kw

Par1

As above guys

scudo2

Par1 wrote: »

As above guys

Yes and No
Boiler size has to be calculated correctly for maximum efficency, espicaly to achive maximum condensing mode.
To big, and it will use more fuel.
To small and it will use more fuel.

Modulaton boilers are best to componsate for this aspect, to small and it can never cope efficentaly

Par1

Par1 wrote: »

As above guys

Yep, as a guess a 30 kW boiler will use about 6kw more worth of gas than a 24kw.

Dtp1979

gary71 wrote: »

Yep, as a guess a 30 kW boiler will use about 6kw more worth of gas than a 24kw.

Unless the system needs 30kw
It depends how big your system is op
If this boiler is for a standard 3 bed semi detached that needs maybe 16kw to heat it the yes 30 will use more. The boiler initially fires at 30 before it modulates, even if it's only heating a small system. That's why I like Ariston. You can turn down from 24kw to 16 if needs be so the boilers max output is 16

Dtp1979

Dtp1979 wrote: »

Unless the system needs 30kw
It depends how big your system is op
If this boiler is for a standard 3 bed semi detached that needs maybe 16kw to heat it the yes 30 will use more. The boiler initially fires at 30 before it modulates, even if it's only heating a small system. That's why I like Ariston. You can turn down from 24kw to 16 if needs be so the boilers max output is 16

I answered the OPs question.

The real answer is get someone qualified and competent to fit a boiler which will prevent a home owner from ever having to get their head round heat load requirements and basic system design.

kirving

Still, no harm in a homeowner knowing a bit about the system in their house rather.

Dtp1979

Kevin Irving wrote: »

Still, no harm in a homeowner knowing a bit about the system in their house rather.

As l

Dtp1979

As long as that's how far it goes. Gary's right

Kevin Irving

Kevin Irving wrote: »

Still, no harm in a homeowner knowing a bit about the system in their house rather.

I wish they would but not the areas they can be easily confused with.

I have fitted lots of heating systems and replacement boilers and it's my responsibility to calculate the heat load and then by taking in to account the system characteristics i'd then commission the boiler to match my findings, it's not a part of the install I would expect a homeowner to be involved in.

To look at the output only is meaningless without knowing the whole picture and can lead to confusion.

Due to a different system design boilers in the UK are often 18kw or below which wouldn't fly in a environment like this where there is such confusion over boiler sizing and bigger is better.

What a home owner should be asking is what is the KW requirement for my home and how will that requirement be met in the most economic and controllable way.

Par1

gary71 wrote: »

I answered the OPs question.

The real answer is get someone qualified and competent to fit a boiler which will prevent a home owner from ever having to get their head round heat load requirements and basic system design.

No you did not answer the question you merely stated the obvious difference of 6Kw. Furthermore i do not need to' get someone qualified and competent to fit a boiler which will prevent a home owner from ever having to get their head round heat load requirements and basic system design' as i do not need that requirement you have just assumed i do. I merely asked a question to which people (excluding yourself) were very helpful

Par1

Kevin Irving wrote: »

Still, no harm in a homeowner knowing a bit about the system in their house rather.

Totally agree...cheers for reply

Par1

gary71 wrote: »

I wish they would but not the areas they can be easily confused with.

I have fitted lots of heating systems and replacement boilers and it's my responsibility to calculate the heat load and then by taking in to account the system characteristics i'd then commission the boiler to match my findings, it's not a part of the install I would expect a homeowner to be involved in.

To look at the output only is meaningless without knowing the whole picture and can lead to confusion.

Due to a different system design boilers in the UK are often 18kw or below which wouldn't fly in a environment like this where there is such confusion over boiler sizing and bigger is better.

What a home owner should be asking is what is the KW requirement for my home and how will that requirement be met in the most economic and controllable way.

Yes i agree if that were the original question but again you are taking the question out of context..i asked the original question to see if the actual boilers burned more gas than each other. I did not ask for a system design or any of the above non relevant info you a putting into your replies.

Finally from your post 'it's not a part of the install I would expect a homeowner to be involved in.....does that mean you degign a boiler/system installation then come in and just tell the home owner that they have no say in the matter so dont talk and just pay over the money?.....oh yea thats a great business attitude

Wearb

I know you got a bit peeved by the answer, but even if it sounded flippant, it was an answer to your question. The reason was the way the question was asked. It didn't give enough information. It was akin to asking how far is it from Africa to USA. Well it depends on which part of each place and if one person said 6,000Km and another said 7,000Km, they would both be correct.

So back to your question; as most boilers rarely run at full capacity, your boiler would be chosen by calculating the maximum demand. With modern high efficiency boilers, you would rarely oversize, unless a building extension or similar was planned for. Even then a boiler with a large firing range would be chosen.
With the simple way that your question was asked (is 10 greater than 8) you shouldn't take offence to simple answers.

OP your question was a yes or no question, why should I have to guess the context of your simplistic question?

Why also do you not ask why it is homeowners shouldn't get involved in sizing boilers or is it easier to assume it's because I'm bad at my job?

DGOBS

Question

Does a 30 kw gas condensing boiler use much more gas than a 24 kw

Answer

Yep, as a guess a 30 kW boiler will use about 6kw more worth of gas than a 24kw.

Is the correct answer, to be honest. To the question being asked.

Calculating house size and heat load requirements and matching that to the modulation of the appliance is somewhat a more complicated answer, and would also have to factor in the appliance modulation range, the different efficiencies at the different modulation rates, as heat exchangers get better efficiency at different heat loads, the minimum household requirement against the minimum fire range on both sizes off appliances if different. And to be honest a number of other factors also.

The simple answer is, if a 30kw gas boiler fires at full load for an hour, against a 24kw boiler at full load for an hour, it will burn 6kw more gas heat energy. With no part load calculations.

corkgsxr

gary71 wrote: »

Yep, as a guess a 30 kW boiler will use about 6kw more worth of gas than a 24kw.

That's why I love the Worcester. They start small and work up to demand. And the 28kw can run at 7 kw

corkgsxr

corkgsxr wrote: »

That's why I love the Worcester. They start small and work up to demand. And the 28kw can run at 7 kw

It works better on other boilers if you tell the boiler what the load is or does the Worcester not require range rating?

corkgsxr

gary71 wrote: »

It works better on other boilers if you tell the boiler what the load is or does the Worcester not require range rating?

It never runs full unless needed.

Like the vokera s ( don't fit them so anecdotal) fire on full and cut down to suit. Worcester does the opposite. It fires low and rises to meet demand. So theoretically never fires too much