marshian

I think it's a bit more nuanced and people give advice based on their own set up (I'm just as guilty of that which is why I try to ref my current set up when responding) If we look at the process and what we are trying to do when batch heating water there is some sound reasons for controlling flow rate via a gate valve and or pump speed Slower the pump speed the gate needs to be more open - speed the pump up and you'll need to close the gate valve more We want the HW supplied by the boiler to spend as long as possible in contact with the cooler water in the tank to allow as much heat transfer as possible We want the water to flow in at the top of the coil and out at the bottom so at every point in the coil the HW from the boiler is able to transfer heat because the water outside the coil and in the tank is cooler as you go down the tank Pump speed can have an effect - if you have a boiler that doesn't control the speed of the pump then you need to establish the lowest pump speed possible to maximise the time in the coil However - there is absolutely no point screwing the flow down to a point where the flow rate in the circuit is insufficient for the boiler resulting in repeated short cycling as this a massive waste of gas. So the target is to heat the water in the tank in preferably one burn so initial start up losses are minimised.

PS mine is now set up on X plan (DHWP) so can’t do both at sane time but the gate valve still is in use just slowing the flow down to keep the boiler from throwing full power at the re-heat (viessman 16kW boiler with 4kW min output - vented 115 litre HW tank with stupid 0.3 m coil - although I have new unvented 180 litre tank to fit with 2.7m2 coil that will initially be set up as vented)

it would probably be worth a little experiment to optimise the gate valve setting ready for winter mine is set to 1 3/4 turns out from fully closed in all year round. Easy to find the optimum - fire up on HW only let the boiler stabilise at target flow temp then slowly shut the gate valve 1/8 of a turn at a time until the boiler trips out due to temp rising above set point (too little flow) back out again 1/4 turn and thats your setting for summer and winter (open enough for HW heating in summer to keep boiler happy and closed enough that in winter when running both CH and HW together for a period of tome that the route thro the coil isn’t stealing all the flow and starving the CH circuit

I thought S Plan was either HW or CH but I guess it can be configured to do both CH and HW at same time in which case yes running both together over a longer period would work (I used to have Y plan set up and did similar but I did have a gate valve on the HW coil return to stop the HW tank stealing all the flow

Your 30 yr old HW water tank will have a very small coil (0.3 m) designed for a non condensing boiler set up running much higher flow temps. Your Boiler has a min output of 7 kWh - it can't go below that so instead if the Tank stat is still calling for heat the hysterisis of the boiler means it will have to see a temperature lower than the set point in order to fire again and with little of no heat transfer that could take some time. Half way thro the HW heating cycle (when the boiler is coasting after a burn) run a hot tap for 5 mins - this should introduce enough cold water into the tank to drop the return temp and the boiler should fire again much sooner - this will tell you that the coil in the tank is way too small for the boiler min KW If you want a quick fix turn the flow temp up to max for HW and cut the time down - do the water heating in one burn and rely on the tankstat to say satisfied to end the HW reheat cycle PS if you are running low flow temps to improve efficiency you really are wasting your time - You aren't going to get much condensing efficiency doing HW recharge with a tiny coil in a 30 year old tank anyway so you might as well hit it hard and just get it done

Sorry but that's the wrong order Try to remove the immersion heater with the tank still full first (Obviously don't remove it but crack off the joint) then once it's cracked you can drain down knowing that the immersion has been loosened If you try to remove an immersion heater that's been in a copper tank for a while with the tank drained down - you will need a new tank anyway as the soft copper will ruck up around the immersion boss and then fracture

Any brand recommendations that are current - some of the 50 for £20 Amazon ones have shocking reviews and there is a proliferation of brands on Amazon - probably all made in same place but to different stds

That is a lovely tip and one I would never have thought of - Thanks for sharing New Kitchen being delivered in Oct so very useful and timely

I'm so disappointed he didn't buy one of these for each room I loved the advertised claims, then the test and finally the deconstruction of the unit The old adage is "if it looks too good to be true then it probably is" has never been more apt

Lovely european feel to that - Bravo

^ This 100% When I applied for planning permission for a 2 storey house extension and a single storey garage extension I had 5 objections to planning from neighbours - all were over-ruled (3 because the extensions wouldn't be visible so them) and 2 other the reason for objections were already covered by the plans (obscured glass in one window for one side and no window on another wall for the other) Having gained planning I then had to put up with further complaints from the two all thro the build - people can just be knobs about the pettiest things. Final complaint was related to the boundary fence which I was re-instating to 6ft as per original and planning were advising that it could only be 3ft and I ended up telling the planning officer to take me to court if they wanted (in the meantime I made the 6ft fence into a 6ft gate ) which really pissed the neighbour off

If I got an EPC done it would state that with a gas boiler the heat energy required is 18,000 kWh for CH and 3500 kWh for HW We heat 24/7 with a weather compensated flow temp that peaks at 35 at -2.5 Deg C outside and actual kWh is 8000 for CH and 2000 kWh for HW Just as bonkers - EPC's aren't worth a toss IMO if I was looking to buy a house I'd want to see the last years worth of energy statements - far better guide than an EPC

Interesting topic - Heat Geek have just released a video on the subject and there was one thing that got my attention bearing in mind I am all rads (no UFH) and they are almost all converted to TBOE from a flow perspective - I will one day convert to heat pump but when the boiler dies or Gas v Electricity cost perspective drives the change. Anyway here it is

Perfect solution - glad I could help

Put another concrete block in a non visible area so you can test it there?