Heat pump question.

16 Apr 2008
Reaction score
United Kingdom
With a combi we are told that there should be an ideal temperature drop across a radiator of 20C. On my system I can achieve 12C using the lockshields with my boiler set at 50C. This keeps the efficiency of my boiler sitting at around 96%, as the flow from the return is well below the condensing threshold of 55C sitting at around 33C due to the boiler modulating.

As heat pumps seem to require a flow temperature no higher than 50C but the lower the temperature the better, I am in heat pump territory if I ever changed. As heat pumps don’t condense can the lockshields be set to pass more water so producing more heat accross the surface of the radiator with more of the radiator being hot while maintaining balancing? This would result in the return temperature to the heat pump being higher than it would with a condensing boiler. With a higher return temperature would this aid the efficiency of the heat pump as it would have to work less hard, which is the opposite to how a combi works?
Last edited:
Sponsored Links
And the lower the flow temp the better, which is why they're well suited to UFH; the size of the emitter is huge. When I mention I have UFH most people say "oh, it must be lovely to feel the floor warm"- not really; my flow temp is about 25 degrees so it's more like it's "not cold" than "obviously warm".

Your house being warmed by 50C rads might need those rads changing out for much larger ones at much lower temps than ask an HP to do 50C

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links