We've just had a new combi installed - a budget version Worcester Bosch Greenstar 1000 30kW. This replaced an old Baxi 105E 31kW that was falling apart. The WB unit is a nice boiler overall - the DHW arrives almost instantly - but I am disappointed to find it doesn't report the return temperature, which is crucial in a condensing boiler to achieve the claimed efficiency. At the moment I set the flow temp to 60C and I have a clip-on thermometer on order. There is a modulating pump but that can only be set manually from the controls to somewhere between 20% and 100% but it's not automatic so I don't expect to save much money at all.
We do need to change our radiators - we know that - and were hoping our old Baxi would hold out for a year or so when we would go all heat pump - but we had to change and the 1000 and it was far cheaper than we had feared.
So I was wondering whether anyone has tried adding a throttling (ball) valve on the CH (return or flow - water is incompressible!) that reduces the flow to keep the return temp down below 53C or so and dT <= 20C so flow temp should be ~70C, all controlled by a couple of thermistors and a SBC like a RasPi or Arduino? Obviously there would need to be minimum flow and if the flow temp was too high this would not be achievable but low return temperature is essential for condensing boilers.
We do need to change our radiators - we know that - and were hoping our old Baxi would hold out for a year or so when we would go all heat pump - but we had to change and the 1000 and it was far cheaper than we had feared.
So I was wondering whether anyone has tried adding a throttling (ball) valve on the CH (return or flow - water is incompressible!) that reduces the flow to keep the return temp down below 53C or so and dT <= 20C so flow temp should be ~70C, all controlled by a couple of thermistors and a SBC like a RasPi or Arduino? Obviously there would need to be minimum flow and if the flow temp was too high this would not be achievable but low return temperature is essential for condensing boilers.