Flow temperature for a combi boiler

Bendy_House

BUFF said:

For a condensing boiler the lower the return temperature the better for efficiency.The next set of Building Standards Part L 2022 will make the maximum designed flow temperature of new/retrofit installation to be 55°C or lower.

...almost certainly when designed with an appropriate CH system, such as UFH or oversized rads.

Apodemus

Bendy_House said:

BUFF said:

For a condensing boiler the lower the return temperature the better for efficiency.The next set of Building Standards Part L 2022 will make the maximum designed flow temperature of new/retrofit installation to be 55°C or lower.

...almost certainly when designed with an appropriate CH system, such as UFH or oversized rads.

...and to coincide with the phasing out of gas boilers!

BUFF

Apodemus said:

Bendy_House said:

BUFF said:

For a condensing boiler the lower the return temperature the better for efficiency.The next set of Building Standards Part L 2022 will make the maximum designed flow temperature of new/retrofit installation to be 55°C or lower.

...almost certainly when designed with an appropriate CH system, such as UFH or oversized rads.

...and to coincide with the phasing out of gas boilers!

No, it will come in in England from 15th June, 2022 - well before the phasing out of gas boilers.
There are get outs for listed buildings/conservation areas where meeting it would cause unacceptable changes in character & also for buildings where plans are submitted before the change date.

https://www.gov.uk/government/publications/conservation-of-fuel-and-power-approved-document-l

Apodemus

Buff,  Thanks for this - it is an interesting document.  Am I correct, though, that the sections you quote are in the Non-Domestic Buildings part of the document?

EDIT:  Found it! Covered for domestic premises in s5.8 of the original consultation draft.  There is a let-out "where it is not feasible..." clause for existing dwellings.

It's going to be tricky to limit heating output to 55C, yet ensure hot water tanks get to 60C for Legionella control!

BUFF

Apodemus said:

Buff,  Thanks for this - it is an interesting document.  Am I correct, though, that the sections you quote are in the Non-Domestic Buildings part of the document?

EDIT:  Found it! Covered for domestic premises in s5.8 of the original consultation draft.  There is a let-out "where it is not feasible..." clause for existing dwellings.

It's going to be tricky to limit heating output to 55C, yet ensure hot water tanks get to 60C for Legionella control!

The intent, though, is clearly that if it is possible then it should be done.

Most boilers have separate controls for DHW & CH, most boilers sold currently are combis so no tank & for those who do have a tank but can't set DHW output separately, an immerser ...?

I live in a 1905 sandstone terrace in a Conservation Area (so no solid wall insulation& no double glazing to the front elevation) in Glasgow ( so quite far north in UK terms) & I was already running my condensing combi at 55C flow under normal usage before I learnt of this. 

JohnB47

My new CH system was set to  65 degrees. On suggestions from this site I dropped it to 60 but the house didn't get warm quickly enough in the morning, so I raised it to 62, then 64. Feels good for now. Seems like folks just need to adjust things to suit themselves, bearing in mind the need to adjust things to suit the seasons/weather/house insulation. There is no formula here, adjust things to suit your circumstances gradually over time. As for boiler efficiency, fair enough, we can talk about that forever. But if you're cold, perhaps we just to need to turn it up.

BUFF

or turn it on earlier (programmer) ...
Does your new system have Optimum Start (or similar)?

Dedekind

Thanks everyone, all comments are very helpful.

The controls I have are via one Nest thermostat and the temperature controls in the boiler itself. 

At the moment it only heats our radiators but a manifold will be added soon for an UFH in an extension, which will have its own separate thermostat as well.

I find that the house has been warm enough the past few days, and in the morning it heats ip fairly quickly. The only issue? Is that it doesn't go above 22 on the Nest -- but 22 is already a bit hot so I have it set up a bit lower.

BUFF

The Nest should learn how your house heats but unfortunately it is not capable of talking to the WB's (proprietary) EMS bus to achieve ultimate efficiency.