Dreadnaught

To be fair to Ovo Energy, they are now fixing the problems I reported with the "Heat Pump Plus" addon. And it appears that the underlying issue was not their fault (a component of my system had been swapped by Vaillant under warranty, which interrupted the connection to them). I will likely stay with Ovo Energy now as I think its the best tariff for my circumstance (no battery, no PV), at least until Octopus or someone else launches a tariff that integrates similarly with my Vaillant heat pump as rumours suggest they will.

Based on my past experience of Octopus Energy, I'd much rather swap back to them from Ovo Energy. Perhaps in due course I will.

Ovo Energy sent me an invitation to be part of their "Heat Pump Plus trial", where they will indeed control one's heat pump, aiming to heat the home when the grid is greenest. They don't control your heat pump with the vanilla 15p/kWh heat-pump add-on.

I moved to Ovo from Octopus in October and am having problems with the "Heat Pump Plus" addon. I am giving them the benefit of the doubt for now but am not very impressed so far. I hope they will fix things soon. My baseline tariff with Ovo is just their basic variable-rate one. No tie-ins. Given the problems thus far I am keen to be ready to depart at short notice.

Interestingly Ovo is also offering a trial* of an add-on that incentives users to shift consumption away from the peak period (4pm to 7pm). It's a monthly refund for such usage shifting and can be taken along with the "heat pump add on". I wonder if the "Heat Pump add on" might be eventually replaced by a new version that has the same low rate but excludes the peak period. A combination of the two. * called "Power Move" and it runs to at least December as an experiment.

Very interesting @scottishjohn.

That would be me then. Do you have any LVT at yours? I cannot imagine you would give the job to anyone else.

Oh, because I am not going to do the whole house in one go. I am thinking two rooms at a time. Usually it will be the same thickness on each side of the threshold. The only possible exception is the Plant Room to Utility Room threshold. I might use floor paint in the Plant Room, but LVT (3mm) on top of self-levelling compound (3mm) in the neighbouring Utility Room.

A related question … When applying a self-levelling compound across a floor, what do you use at the door threshold as a barrier to limit the flow?

Fabulous, thanks guys. I am not sure I can match the high-levels of workmanship on display in both those, but I will do my best!

In my Plant Room around the UFH manifold I have a big hole through the concrete floor (filled with PIR insulation). See photo. I would now like to pour a 3mm self-levelling compound across the whole floor and add LVT (stick-down), including across the area of the hole. What to do about that hole - and give a stable base for the self-levelling compound and LVT?! I am unsure.

Trying to decide on basin wastes: "Flip" vs "click-clack" vs "pop up". Has anyone got one of these? I wonder what they are like in reality. Looks quite nice. (It's a McAlpine BW60SPH-CB). It's a McAlpine BW60SPH-CB.

Just to clarify… the Energy Integral for the "Vaillant Arotherm Plus" heat pump is the name given to a way that the heat pump's microprocessor controller decides when to turn off the compressor pump, and hence stop heating. And the same Energy Integral also then informs the controller when to subsequently to turn it back on again. (There is also another way the compressor turns on and off unrelated to the Energy Integral, but that's by-the-by). The Energy Integral in this case has the units of "º minutes" ("degree minutes"); note this is not degrees "per" minute. Simplified and only dealing with heating … the controller calculates the number of degrees that the "flow temperature" deviates from the "targeted flow temperature" each minute. This is then summed cumulatively each minute to keep a running total. For example… if the flow temperature in the pipe leaving the heat pump is 42º and the controller is targeting a 38º flow temperature then (42-38) = "4" is added to the Energy Integral at the end of that minute. If in the next minute the figures are 45 and 38 then "7" is added at the end of the subsequent minute. And so on minute by minute. This cumulative sum is the "Energy Integral". Then… when that cumulative sum of these figures reaches zero (from its negative starting point; default is "-60" but this can be changed in the settings) the controller turns the compressor pump off and heating stops. There are more subtleties than I have mentioned above … such as overrun of the sum and the control of the separate building-circulation pump … but that's the essence of it. It's simple and elegant. I suspect that cumulative counters are used commonly in electronic control-systems. Perhaps an engineer here could confirm this.

Persuasion: happy to discuss offline. (Vaillant after-sales had mentioned a cost of £490 to replace the board.) Yes the new board is now installed and, as you say, I took care not to forget the cooling resistor (I even wrote a reminder note in big-black-pen and stuck it on the appliance ahead of time 😄). Firmware versions now … Heat pump: 351.09.02 HP controller: 351.09.01 Interestingly, the Vaillant engineer also modified the opening on the other side of the appliance, the opening for the power connections. As you may know, there have been some reports of water ingress there causing a short-circuit and I believe that newer models have been modified as a result. In my case, he removed that panel and put a clear sheet of thin self-adhesive acrylic over the entire opening before refitting the panel. This gives an extra layer of protection for the underlying circuit board. He said it was Vaillant's chosen mitigation method and was done for me as a precaution. I have read online that others have solved the issue with a line of sealant along the top of that panel, which I was considering adding but it is now no longer needed.

Yes, good point. You are quite right. My new-build house has huge thermal inertia. The concrete raft foundation for my bungalow acts as a 55-tonne heat store. The UFH pipes are embedded deep inside it. The internal temperature for the dwelling changes on a time scale of days (sometimes even weeks). This means that it is far less important when I add heat to the dwelling. Day or night makes no real difference. This all means that I can control the heat pump somewhat differently from most homes and I can try to maximise efficiency … to save money (and the planet). Hence the unusual slant of my questions here.

Update. After a bit of "persuasion", Vaillant swapped the board in my Arotherm Plus free-of-charge. All good. Many thanks for everyone's help and suggestions.

Good advice.

Ah, I see. Well done. I have emailed them. Let's see how they reply.

Ah I see, that's unfortunate news. I will have to see how much Vaillant will charge to swap mine out in the heat pump itself. Did you ask Vaillant to change yours?

@Dan F, turning to these settings … "Room temp. mod." "Set-back mode" "Set-back temperature" I am in two minds about these. The best way to run a heat pump is "low and slow", which would suggest running it 24/7 at the lowest temperature commensurate with a comfortable internal temperature. But the CoP at night will be worse. So turning the compressor off at night could lead to better CoP overall. These settings above could allow a half-way house. Leave the heating on at night but lower the "target flow temperature" overnight to minimise the impact of the lower temperatures during that period. Any thoughts, @Dan F?

Good question. Short answer "not any more, I think". Long answer: when I bought the UniTower it had the bug in the controller yes. Then my installer got in to a bit of a pickle and called in the Vaillant flying squad to help (the problem turned out to be installer-error 😄 but that's another story). In problem solving, the Vaillant engineer (with a little bit of encouragement from me) swapped out the controller board inside the controller, which, as you would imagine, I was very pleased to see him do! I now have "351.09.01" on the controller in my UniTower but the version in the heat pump itself is still with the bugged "351.06.07", hence "I think" above.

Reflecting on what you've told me, for my system … "Compressor hyster. Heat." could easily be set at 15º (its highest possible value). Nothing bad will happen to the UFH pipes or my 55-tonne concrete-raft foundation-slab if the water circulating is 15º hotter than the "target flow temperature" and it will mean that, in the circumstances where "Energy Integral" is not shutting the compressor down, that the compressor will run for longer – good for CoP. "Compr.start heat. from": similarly I can set this at -120 ºmin (the lowest possible value, a reduction from the default at -60 ºmin) for similar reasons, so that the "Energy Integral" takes longer to shut the compressor down, again helping CoP.

This all now presents another question: what are the best settings for a well-insulated house with a simple heating system* for … "Compressor hyster. Heat." "Compr.start heat. from" "Room temp. mod." "Set-back mode" "Set-back temperature" Are there any other settings that are relevant for heating that I have missed? * Mine, unlike yours, is, hydraulically, a very simple system: flow is to the UFH manifold without a secondary pump and without buffer or low-loss header. Single zone, no controllable zones; no wiring centre; all manifold valves are fully open. Low system resistance (big fat pipes throughout). Basic system diagram code "8". As simple as can be. I calculated that my total system volume is about 100 litres.

@Dan F, thank you. That makes full sense now. It's effectively a double limit for when the compressor is turned off: (i) the energy integral; (ii) and a ΔT between the "target flow temperature" and the "actual flow temperature" (not the return temperature) . Local and system conditions will define which limit is hit first, as you say. An example: if the "target flow temperature" is set at 25º, the compressor will operate until the flow temperature reaches (25+7) = 32º (the return temperature is irrelevant), OR if the "Energy Integral" has reached "0" (from its user-selectable starting value, with default -60 ºmin). Is that correct? Regarding when the compressor restarts after being shut down, do you happen to know whether it is only the "Energy Integral" that does so, or whether "Compressor hyster. Heat." also does so at the other extreme (in my example above 25-7 = 18º)?

Thanks @Dan F. Very interesting. With the Arotherm Plus, do you happen to know how the user-selectable setting of "Compressor hyster. Heat.", which seems to define a ΔT, is relevant? Its default is 7℃ and the range of possible settings is 0 to 15 ℃. (The setting is not accessible via the VRC 720 but only via the heat-pump controller - which in my case is part of the UniTower). In operation, my guess has been that the controller targets a ΔT according to the value set for this setting and uses the "target flow temperature" only for the "Energy Integral" calculation, to define when the heat pump turns off (or on), but I might be over-simplifying. With a constant flow rate (which we know is an idiosyncrasy of the Arotherm Plus), one might think that targeting both "ΔT" and "Target flow temperature" at the same time would more often than not be contradictory when the only parameter subject to control is the compressor speed, hence my enquiry.