Boiler design flow temperature

markin

I believe any modern boiler not in condensing mode should still be 87%, Like for like height and length but with fins could be double the efficacy, or so i read.

Buy a thermometer with a probe you can stick on the pipe, or an IR thermometer to workout the actual return temp, But i think leaving all rads open and getting it well into condensing mode would get the higher efficacy with the system as it is Vs using tvrs.

BUFF

Sterlingtimes said:

What would have been the design flow temperature (leaving the boiler) for a central heating for a detached house built in 1996? 

The system is a vented s-plan with small radiators using 10 mm microbore. If the temperature outside is in the order of 10 degrees, then a boiler setting of 65 degrees is nearly adequate. If the temperature outside is in the order of 0 degrees, then a boiler setting of 60 degrees is nearly adequate. But 70 degrees is better for the coldest room when the outside temperature is low.

very probably 80/60

Sterlingtimes

markin said:

I believe any modern boiler not in condensing mode should still be 87%, Like for like height and length but with fins could be double the efficacy, or so i read.

Buy a thermometer with a probe you can stick on the pipe, or an IR thermometer to workout the actual return temp, But i think leaving all rads open and getting it well into condensing mode would get the higher efficacy with the system as it is Vs using tvrs.

Thank you. This view on efficiency is interesting. The winter efficiency of my boiler is 90.7%, so the savings to be achieved through lowering the flow temperature may be relatively small.

I have a thermometer with clamps, but I am not confident it is sufficiently accurate. However, there is a "secret code" to obtain the measurements from the boiler: I will look this up and conduct some tests.

matelodave

Have you tried running it for longer but at a lower temperature.

Consider that driving at 80 up the motorway with slowing, braking and accelerating to maintain your speed, compared with cruising along at around 55. You'll still get there, it will take a bit longer but you'll save about 20% in fuel consumption.

Its much the same with a boiler, having it cycle away to maintain a high flow temp is going to use a lot more energy than having it run for longer at a lower flow temperature as not only wont it go into condensing mode, every time the boiler restarts it roars away at full blast until the return temp caused the boiler stat to shut it off.

Much, like roaring up the motorway at full throttle and stopping every few minutes and then thrashing up again for another short burst.

Sterlingtimes

matelodave said:

Have you tried running it for longer but at a lower temperature.

Consider that driving at 80 up the motorway with slowing, 

This is the crux of the matter.

I had manual TRVs, and the family always turned them up to the maximum, judging the room temperature by the warmth of the radiators. The system worked superbly in this mode but not economically.

I have recently fitted intelligent TRVs to 14 radiators. The dynamics of the system are quite changed. Now typically, only zero, one or two radiators are on at any time. It is very much an on-off affair.

Measurably my gas usage for heating, excluding hot water, is moving from an eight-year annual average of 18,215 kWh to 12,260 kWh, a saving of 33% or £615. The economics speak for themselves.

But one large bedroom is not heating satisfactorily. I can correct this by pre-heating, but the better approach (as suggested by correspondents here) would be to size the radiator up. With you help, I am starting to get my head around the issues. Thank you.