Soldato
That's not efficient. I used to think the same. Here's an analogy we use at work - you're delivering 100 logs from London to Glasgow. You drive up and drop off 20 logs. You drive back down, get 20 more logs, and then drive back up again. You drop off 20 logs. You drive back down again and get another 20 logs. Then go back up and deliver the 20. You repeat this until all 100 logs are delivered. Would it not have been more efficient to drop off all the logs at once? That's what you want your heating system to do. You want maximum heat transfer from your heat emitters. So, the water coming out of the return pipe on your radiators should be cold. Unfortunately, radiators in the UK are particularly poorly balanced.
When it comes to boilers, this doesn't cause a massive problem although it could easily prevent a condensing boiler condensing, making it less efficient than it could be. For low carbon heat sources like CHP or heat pumps (available domestically, unlike CHPs), they will not operate if the return temperature back to them is excessively high.
In the UK, we've been mollycoddled by boilers that will run regardless of how **** your system is. It's this kind of "new" thinking we need to apply if we are to reduce energy consumption in our homes.
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so it'll completely depends on how well your TRVs are operating. You want a really slow flow through your radiators really. Unfortunately, I can't guide you much on this because radiator balancing is the most odious and thankless task - you balance for full load and as soon as you get to part load, it's ruined. But you want to drop as much heat across each rad as possible.
