New part L 55 degrees flow?

[John.g]

Means doubling the rad size if one runs with a dT of 10C.

What about legionella protection for DHW?, will all new boilers now have to have HW priority and increase the flow temp to 80C?.

 

[Matt0029]

You misunderstand Roy, the boiler will only be set to 55 deg C where the system has been designed for this, in which case there would be no advantage to turning the boiler up a bit.
In reality this will be all new builds and most complete system replacements, but it won’t be possible in all cases so there is no way manufacturers will restrict to 55 in the foreseeable future ……

Thanks but why are they stating a 55c flow? I usually set at around 65 if possible so should return at 54c so will condensate? Are they saying they want the full heat exchanger in condensating mode at all times?
Or is it more design your system to run at 55c flow temp. So can be swapped to a heat pump later? Heat pumps run at around 45-50c flow? Thanks

 

[John.g]

Boilers only start to condense at ~ 50/55C, see below.

 

[Matt0029]

Boilers only start to condense at ~ 50/55C, see below.

Thanks I thought the idea was to make sure the return was coming back at this temperature not the flow. But then again I've know some new system to only have a 6c difference flow and return.

 

[ShaunCorbs]

Condensing boiler 55/35 dt is 25
Heat pump 47.5/42.5 dt is 25 that’s why so systems are heat pump ready

 

[Ric2013]

What about legionella protection for DHW?, will all new boilers now have to have HW priority and increase the flow temp to 80C?.

That would be good. Had a long discussion with a customer recently about what temperature she should set her boiler flow to and I mentioned that ideally, the boiler would do just that (but hers doesn't).

 

[Matt0029]

Condensing boiler 55/35 dt is 25
Heat pump 47.5/42.5 dt is 25 that’s why so systems are heat pump ready

Is it looking more so that heat pumps may take over. I know there was talk of hydrogen blend/ hydrogen.

 

[Matt0029]

I've never managed to get a 25c delta T. Have struggled to get 15. We can't adjust the pump in the boiler. So just lockshield? I think Vokera mentioned on one of there boilers they had a pump were you could set the delta T.

 

[Matt0029]

Also does it mention anything about aluminium radiators? Which there say to install for heat pumps.

 

[snowhead]

Conservation of fuel and power: Approved Document L

Building regulation in England setting standards for the energy performance of new and existing buildings.

www.gov.uk