Repairing rust on a panel.

And the output was quoted in BTU?

Thats stating the obvous

Its rare now in domestic works to fit boilers that cant do both

No it wasnt .

The obvious seems to be needed with you.

Only for low cost installations, or where space is limited. Stored hot water gets round the limitations of flow imposed by a combi. Stating the obvious again.

and with non condensing 'new install' boilers precisely how do you intend to comply with Part L1?

Part L1/L2 are complied with because the primary heating source is ground pump / solar panel heat recovery units which give a low TER All been calculated to meet sbem

The non condensing boilers are redundant backup units placed in critical areas

It's hardly an common installation.

BTW, who did the calculations?

Not me although i can do them , the system designers provided all the calculations all the figures went to the architects office and he had an independant engineer varify them as they had to be taken into contex with other services

And yet you insist a condensing boiler runs hotter than a non condensing one?

One of the reasons heat exchangers are now made of SS or ally rather than cast iron etc is because of corrosion. A problem if a non condensing boiler is run at a low temperature.

A decent modern condensing boiler modulates the burn. And is equally as efficient at low output.

What you say was true of older boilers that simply switched on and off.

Combi boilers need to be about 30 kW to give a reasonable flow. Even in a small house or flat.

It would be a problem if any boiler was run at a low temperature all the time

The main reason they now use Ali is its ability to transfer heat rapidly and its ease of machining .

Another reason is weight , also helps to meet the recycling targets , ali is the most common metal in the world but its an expensive product to refine , once refined however its relatively cheap to recycle

Can you not read and understand? Have you ever even heard of dew point?

Better units use stainless steel.

Yes i have heard of dew point , its a variable point within a temperature scale were gases become liquid , the dew point itself can be varied further by the presence of other materials close by that have a higher or lower temperature .Different gas's have different dew points

With water the dew point is not only effected by temperature extremes but also the amount of water held within the atmosphere (humidity) and the relative temperature of the surrounding surface

(thats a simple explanation )

Im aware of that ,