Just reading another thread and saw that my long held belief that rads should be balanced to achieve an 11C temp drop may not be correct? It's stated that as long as the same temp drop exists across all rads then this is fine, whether it be 2C or 11C.
I had always assumed that the 11C drop value was based on maximising boiler efficiency and/or most efficient transfer of heat from the rads to the environment but now I'm totally confused.
Could someone kindly post a big dummy's explanation for me. TIA
Yes, but for a conventional boiler the effect is tiny. If the return is 10C hotter than ideal, the flue gasses would be, say, 10C hotter (which is optimistic), so if we assumed a burner temperature of 1000C dropping to a flue temperature of 150C instead of 140C, that's only a
1% difference in boiler efficiency.
If the temperature drop is low, you might be running the pump faster than is necessary, although the heat from that adds to the house anyway.
Well you'd have to define what you mean by the efficiency of a radiator. Having a smaller drop at the same flow temperaturte would cause the radiator to give off more power as it's average temperature would be higher.
For a condensing boiler, the drop is more important, not for the sake of the drop itself, but to keep the return temperature down to give the efficiency benefits one hopes to achieve from condensing operation, whilst having the flow temperature high enough to give a reasonable average radiator temperature. 70/50 is a common design critera. Mine runs mostly at 45/41 which is a tiny drop for a condensing boiler, but because the return temperature is lower than the 70/50 case, I'm running more efficiently.
Yes. And also remember that the whole point of balancing is to make sure that some rads are not hogging all the flow and starving the others - so if
*all* your rads have a low drop, they obviously all have adequate flow.
Your drops *are* very low low though (assuming you're measuring them properly). I think I would be inclined to reduce the pump speed if its not already on its lowest setting.
Bovvered hasn't post his temperature drops so I guess you're referring to mine. The pump here has been set speed 3 until now so I've just reduced it to 2. I'll see about measuring the temp' drops again in a few days.
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