boiler sizeing

[Dan Robinson]

Christ, now I'll be walking funny all day .

 

[chantelle]

I know in this case it`s not a combi but most installers fit an oversized combi boiler because the higher the kilowatt the better the litres per minute, I know on paper to all you `breakdown` engineers,this is wrong but here in the land of reality people want hot water bursting out of their taps.

 

[D_Hailsham]

I know in this case it`s not a combi but most installers fit an oversized combi boiler because the higher the kilowatt the better the litres per minute, I know on paper to all you `breakdown` engineers,this is wrong but here in the land of reality people want hot water bursting out of their taps.

But installing an oversized boiler will not compensate for an inadequate flow rate.

 

[Agile]

Hi all, Had a rep round today regarding the green deal, he did a full energy survey on the house which had had quite a few extensions added since the boiler had been fitted. When I pointed this out to him and suggested that a bigger boiler may be required , he said " you must have the smallest boiler your property will allow so when it works it has to work flat out only then will it save money because only then will it condense, personally I thought he was talking crap, but I thought I would run it by you guys just to check. Any comments greatly appreciated. thanks mark

He, most of us pros here as well as the Energy Saving Trust all know that a boiler should not be oversized.

Probably beyond your capability to understand how a heating system operates but its the radiators which should be oversized to increase the efficiency and NOT the boiler!

Tony

 

[chantelle]

But installing an oversized boiler will not compensate for an inadequate flow rate.

Assuming the initial flow rate at the mains is good,a larger boiler will give better litres per min at hot tap.

 

[chantelle]

But installing an oversized boiler will not compensate for an inadequate flow rate.

Assuming the initial flow rate at the mains is good,a larger boiler will give better litres per min at hot tap. This isn`t good practice, but it`s what`s done.Seen it over and over again.

 

[chantelle]

He, most of us pros here as well as the Energy Saving Trust all know that a boiler should not be oversized.

Get over yourself, firms are installing oversized boilers daily including BG, have you ever been out with one of their sub-contractors? doubt it, all well and good spouting theory, this is how it works in the real world,not my fault,I don`t install anymore because i gave up trying to do it by the book,same reason I cannot be bothered servicing unless it`s a private job, any firm is only interested in one thing,how fast you can complete and how much money you can earn for them,they don`t care how you do it or how many corners you cut until something goes pear shaped,then, guess what? who`s name is on Gas safety certificate? Certainly not the firm, and after turning a blind eye to all engineers cutting corners,what do they do when the sh** hits the fan? Trot out the old `This is not Company policy` line.
Give me a break I know very well about boiler/rad sizing.Tell it to someone who gives a monkey`s. Rant over.

 

[D_Hailsham]

Assuming the initial flow rate at the mains is good,a larger boiler will give better litres per min at hot tap.

If the flow is good a larger boiler will just give hotter water.

 

[onlyfitidealboilers]

But installing an oversized boiler will not compensate for an inadequate flow rate.

Assuming the initial flow rate at the mains is good,a larger boiler will give better litres per min at hot tap. This isn`t good practice, but it`s what`s done.Seen it over and over again.

Chan, All combi boilers work on 24kw for heating rads & range from 24kw up for hot water. As long as your getting 15ltrs a min out your cold mains you can have 35kw boiler in a 1 bed flat! Is it over sized for heating yes is there anything you can do no.

 

[onlyfitidealboilers]

Assuming the initial flow rate at the mains is good,a larger boiler will give better litres per min at hot tap.

If the flow is good a larger boiler will just give hotter water.

No. It will give more hotter water☝️

 

[Dan Robinson]

Chan, All combi boilers work on 24kw for heating rads

Now, where to begin?

 

[srhawksy]

Ideal, don't 24kw combis have 19kw max heating output 24kw for dhw? the heating output is never as much as dhw. Then after the boiler figures out the output required from it it will modulate down to suit the load. So combis aren't oversized, but you need a minnimum (24kw) output on the hot water side to be able to provide acceptable hw rates. On most boilers you can set the load for the heating yourself...

That Chantelle doesn't seems very helpful, just likes to mouth off it seems.

Always remember, it takes more energy to put the heat into the water from cold. You want to heat it and keep it hot so a boiler chucking out 30kw say when all you need is 12kw will cycle which is inefficient. That's about my limit, need to learn more. Any answers to this will be appreciated, I promise not to tell you to get over yourselves or that your wrong

 

[D_Hailsham]

Assuming the initial flow rate at the mains is good,a larger boiler will give better litres per min at hot tap.

If the flow is good a larger boiler will just give hotter water.

No. It will give more hotter water

If you install a boiler which is larger than necessary to give the required temperature rise at the maximum available flow, then all you will get is hotter water. You will not get a higher flow rate.

 

[Dan Robinson]

Nearly all combi boilers are grossly oversized for heating.... all to get 9 l/min for a shower. It is personal preference whether or not that is "decent".

SR - the Combi Compact is 40kW heating, 36 for hot water - just thought i would throw that out there .

 

[srhawksy]

Well intergas maybe an exception.

Looks like I'm going to try on of these intergases everyone in the cc goes on about, but for half decent hot water I will need the 28/24?

I'm being the guinea pig if I like the one in my house I may start to give the option to customers