Kettle?

It depends a bit on which version of the user interface you have.
For my Vitodens 200, the second screen has the 'energy display' where all connected devices are shown, which in my case has the hot water cylinder in there as well. There is a button at the bottom with a battery-like symbol. That is the button that starts a one-off heating cycle for the cylinder, or, presumably, the bathtub.

Thanks for your thoughts.

I did call the Viessmann helpline and seems that my boiler (Vitoden 200W) does not have a boost option. His suggest is to have only one DHW heating time set, from early in the morning to late at night. Then, if the systems calls for more DHW, the boiler fires up to ensure the cylinder is always up to speed.

I used to have that but found that the boiler was spending quite a lot of time with things running, using electricity but not actually needing to heat the DHW or UFH. Don't know the actual electricity usage but when one hears the boiler making 'working' noises, it must be using electricity.

So now I have it set for two heating periods.

However, more extensive Googling and an in-depth read of the User Manual and I found a section entitled "DHW for a Few Hours Only." Not exactly a chapter title I would have looked up!

Seems that the best way is to go into Party Mode, which will heat the DHW first (before UFH), crank up the temp. and after 15-30 mins, turn Party Mode off. Alternatively, apparently, open Party Mode, do not change the temperature but do press OK to accept whatever is displayed; wait 10 or more seconds then turn PM off.

An alternative method is to install a simpler to use immersion timer switch. The current one will do what it says on the box with a one hour boost, but with all the available heating options, it uses a back-up rechargeable battery to remember those settings. Since there is no need to have the switch powered up 24/7 for no reason, it has been off for X years, resulting in the battery loosing its charge. Turning it on kinda achieves nothing until the battery has a residual charge, then have to figure out how to set the time, date, etc, before the boost will work.

I may be misjudging my wife, but if I find it difficult to figure out, don't think she will be able to do so.

All the stuff I've seen recently says that standby losses on modern devices really are irrelevant - the regulation is sub 1W but the reality is nearly all are much much less than that.

Posted By: RexThanks for your thoughts.
An alternative method is to install a simpler to use immersion timer switch.

I fitted something like this for my (demented) mother who had started leaving the immersion on all the time (after a fused spur/switch)
https://www.tlc-direct.co.uk/Products/SMTGBT4N.html?

But again you're into cost-benefit. It's costing you c3x as much to use the immersion to heat the water than it would to use your gas boiler and you've spent c£25+ installing a timeswitch.

Posted By: RexThanks for your thoughts.
I used to have that but found that the boiler was spending quite a lot of time with things running, using electricity but not actually needing to heat the DHW or UFH. Don't know the actual electricity usage but when one hears the boiler making 'working' noises, it must be using electricity.

Do you have Weather Compensation installed on your boiler? what sort of flow and return temps are you using for the UFH? I think I posted something a few weeks back about the savings these offer - most UK condensing boilers rarely if ever work in condensing mode so are c85% efficient vs c95%.

My UFH runs super cool (currently 0C outside, flow temp (solid/wood floor coverings) 26.5C/29.5C) and modulates the burner down (currently running at 21%) so it runs for long periods and doesn't cycle with the pumps running constantly but at low speed. I get the impression that cycling (ie firing up/down) is both inefficient and hard on the boiler - the app gives those stats in the diagnostics and mine runs at about twice the number of running hours as 'boilers starts' which the engineer was really happy about.

the cost of running the electronics and pumps is pretty much insignificant compared to the energy of heating water - a few 10's of watts of electricity (this typical Grundfos pump maxes out at 34w https://www.screwfix.com/p/grundfos-alpha-1-15-50-60-domestic-heating-circulator-230v/483fj) whereas your boiler ). The smallest Vitodens 200 system boiler I can find is 11kW ie 11000watts.
And of course all that electrical use generates a bit of heat anyway which isn't wasted.

Yes, FST17A is what I have got. Computers and routers and even LED lights use a whole lot more than a timeswitch. Switching off the router overnight is supposedly bad for your connection speed, IIRC. In a year or so it will also kill your landline phones as well as whatsapp etc on the mobiles.

From a more recent page on the same site:
"Consumers with modern full fibre connections don’t need to worry about this, but frequently switching-off the router on a copper based broadband line (i.e. ADSL, FTTC / VDSL2 or G.fast) could cause the Dynamic Line Management (DLM) system to assume your connection is unstable and drop the speed to compensate.

"As a side note, a lot of network operators tend to automatically push firmware (software) updates down to their broadband routers in homes during the early hours of the morning. Completely turning off the router during this period would disrupt that and might cause you to miss vital security or feature additions."
(from https://www.ispreview.co.uk/index.php/2022/10/clarifying-the-confusion-over-turning-off-wifi-vs-broadband-at-night.html )

I'm on a copper connection, so don't want to turn it off. Apparently the "average" power consumption of my router is 6 W. So turning it off overnight would save me 6*7*365 => 15 kWh @ 15p = £2.25 per year

My £2.15 doesn't seem to match Simon's £10-15?

Yes, when I said copper, I meant fibre to the cabinet and then copper. I get 80 Mbps down/20 up; I'm quite close to the cabinet and use VDSL.

The turning off thing is certainly not a scam. The modem in your router has to train itself to your copper wire every time it powers up. I'm impressed by your lack of wi-fi devices

My vitodens, even if it has no heat to generate, runs the pumps once a day to keep the impellers lubricated ('pump creep'). The few Wh that consumes is well worth it if it extends the lifetime of the internal pump and the UFH one.