Even if you don’t move to heat pump for a long time a triple radiator or multi-finned one will enable you to lower the flow temperature and get better performance from your boiler.
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Re my q re control, Jaga says
“The fans will modulate down when the room temperature is met – the room temperature is measured by a sensor at the base of the radiator – the water temperature is measured by a different sensor and is independent of the room temperature.”
How do you find the radiator’s own sensor works in conjunction with the room-thermostat, which shuts down the boiler itself? Should they both be set to the same desired room-temp?
(The water-temp that Jaga refers to is of course the flow-temp, which is set separately.)
Thanks!
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Hi Mike,
I don’t remember anything that you could alter in terms of that - so maybe that is a new refinement.
We have a general thermostat and TRVs on the radiators. The fans simply turn off when the room is up to temperature so the radiators are not drawing heat. It all works fine.
Yours,
Alan
I am told that the relatively flat, wholly finless, cast-iron radiators and one-and-a-half-inch (main circuit) galvanised steel pipework in our 1950s house are probably a pre-loved hospital system which the builder found at that time (so I am pleased that at least the upfront carbon in that is low. The subsidiary pipes to the radiators are three-quarter-inch galvanised steel). My hope, from what I have read of water volumes and heat pumps, is that this ancient system will be good for a heat pump, in that it has a high volume of water in the system, so might be fine without a buffer tank. I wonder if I am correct.
My understanding for many years has been that if you can install large enough finless radiators (which emit their heat largely as radiative heat), such as ours, then the comfort you derive from them will be greater than that from convector (finned) radiators with the same nominal heat output. Is that still the received wisdom? This I have understood is due to the difference between the two types of heat output from a radiator, namely radiative and convective. While the radiative heat warms all the surfaces of the room and its occupants, much of the convective heat rises as warm air, providing less comfort.
But given that the radiative heat output is proportional to the fourth power of the absolute temperature, maybe the lower flow temperature at which a heat pump is most efficient means that this benefit of radiative heat does not apply to a heat pump system. Of course, in a passivehouse there is relatively little heat requirement and relatively little temperature variation with height. But not many of us are destined to be living in those.
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You are quite correct that and old heating system in a Passivhaus would be perfectly fine, though one designed for the house would probably have the desired effect with less energy input.
Radiative heat is the effect you feel when standing by a heat source and is utilised in infrared heating.
Convective heat involves circulation of the air and therefore has an inbuilt draught effect. The opposite is the “cold draught” felt in front of a perfectly airtight but single pane window. Once the temperature has stabilised the draught effect disappears. The body feels any draught that is not positively hot as cooler than it really is. This is why airtight homes don’t need such a high temperature to feel comfortable.
Returning to your old radiators, if you can upgrade the fabric of the house to the extent that the radiators are seriously oversized then they should work with a heat pump giving off mainly radiative heat. Experiment with lowering your boiler flow temperature to find out how much more airtightness and insulation you need.
You will probably have a job convincing a heat pump company of the above.