advice on how to optimize system
I'm looking for some advice on how to optimize my system.
I presently have a s-plan heating system with 25kw regular Glow worm boiler and a hot water cylinder. This is connected to a simple 2-channel programmer for timed control of the hot water and left on constant for the heating with a connection to a wired tado wall thermostat (on-off relay format). I also tado smart TRVs in all my rooms.
The difficulty/ challenge I'm facing is how to best manage the hot water control without negatively impacting the efficiency of the heating. Ideally I want to use 80C flow temp for quickly and efficiently heating the hot water cylinder (to around 55c) and a much lower flow temperature of 55C for the heating circuit.
I have several choices that I am considering but am not sure which makes most sense.
1) MANUAL APPROACH. run the system at flow rate of 55C for heating but then once a day manually turn off the heating circuit and heat the hot water at 80C for 20mins and then re-engage the heating with hot water program turned off. This approach works but is not the most convenient and requires daily manual intervention.
2) AUTOMATIC BUT COMPROMISE. compromise and run the boiler at 65c with timed hot water program and just accept that the heating circuit as a higher temp than is most efficient. This approach has the benefit of no changes in the system and being the simplist, but may not deliver the best performance.
3) WEATHER SENSOR add a weather sensor to the boiler (I believe there's a connection for it) to bring lower flow temps for heating but make the connection to the boiler via a relay that turns disconnects the weather sensor when the hot water is called for so that the boiler defaults to a higher flow temp of 75-80C for the hot water cylinder. Not sure how the boiler will like this approach or whether it invalidates the warranty.
4) SMART WIRING. add a glow worm smart wiring centre (same as valiant vr65) and make all connections using that instead of dumb connections so that the tado uses a digital ebus connection and the boiler will use lower flow temps for small heat loads but knows to use higher temperature for the hot water cylinder when hot water is activated. Not sure if this will truly work and the tado and the boiler will actually properly talk to each other.
can I ask, what would you suggest and why?
Thanks.
Oliver
Answers
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The solution for me would be 2). Set the boiler to 65 deg C. That is the minimum temperature to ensure your hot water is protected from Legionella. No faffing around either. The potential ££ savings at lower flow temperatures and fixed HW schedule should be more than offset by smart use of your Tado controls. Depending on your lifestyle, you may have better control of the HW schedule with Tado, using an add-on-wireless receiver.
The green line in the chart below are actual monthly savings from learning to adjust the 'smart' controls for our use. That's minimising the heating schedule to our lifestyle by adapting/tweaking room temperatures/times and geo-location 'away'. Occasionally we get the early morning HW schedule awry and 10 minutes HW heating is enough to get hot water for a shower. The blue line is our result from daily 'faffing around' with the dumb controls.
If you're interested, Cambridge Architectural Research have a report of potential energy savings from different behaviours: https://www.cambridgeenergy.org.uk/wp-content/uploads/2013/11/CAR-Behaviours-Final-Report-Revision-3-060812.pdf In the grand scheme of their ranked savings, our 45% is quite feasible.
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That's most useful and interesting -- many thanks.
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