Power your heat pump for less with Heat Pump Plus + Vaillant

Definitely! 

This week and until the installers are away I’m being good and resisting the temptation to push all the buttons. Once I’ve let it do its thing for a week or so then trust me, I’ll be all over it but till then I’m relying on the controller manual. It tells me that the controller displays a heat yield but not the COP.  I guess that that can be worked out by taking the yield along with the electricity usage from the meter.  The manual points out that the yield is affected by a variety of operating factors and is only accurate to 20% or so.  There are other sources of information such as the User controller which is in the house and the app.   I’ll also see what the HomeAssistant community has managed to winkle out of it.  Somewhere there’ll be an engineering screen for sure.

That is truly a work of art @dr_dongle! Please keep us updated with your findings 😁

@ChristopherS_OVO  Happy to oblige! so, before I forget it all here is what I have learned so far, misconceptions and all. Some of this I have posted before but this puts it all in one place.

I was told "your house will need to be really well insulated and you'll need bigger radiators" Also, "The biggest heat pump has a third of the output of your current boiler and will struggle". "It'll be noisy". "It'll be expensive". These seem to be mostly myths.

A conventional central heating system cuts off in the evening then comes on again first thing and has to drag your house from cold to liveable-in in a short time.  A heat pump system will constantly vary its output and pump speed but is on 24x7. You never turn it off so you never have to run it hard and so you can get away with a smaller output. There is clearly some penalty in having rooms that bit warmer when not in use so good insulation helps. There is an "away" setting and a scheduler for longer absences.

The circulation temperature is well below what a gas or oil boiler can deliver but again if you're not having to heat everything quickly then this is less of an issue. Your installer should do heat calculations which will show which radiators will struggle to heat the room and these will need to be replaced. We found radiators which were the same size as the originals and had pipe entries in the same place so they were just thicker so there was no impact on decorations. This worked since my radiators had 15mm pipes at both ends. If you have microbore then this probably won't work and you may need to replace pipes as well. 

Older houses are not designed for current levels of insulation so once you have loft insulation, cavity wall insulation, double glazing and plug draughts then it can get really hard. I have only a 50 cm void under my suspended floors and under-floor insulation would be a nightmare. There is only so much you can do.

For a big heat pump you may need a new spur from your main consumer unit and your supply should be rated at 100 amp.

If you haven't had work done on wiring or plumbing for a while then you may find that your installer will want to upgrade it to current standards. We needed some RCBs, earthing straps, a pressure relief overflow and two filters in the pipework.

My heat pump is no noisier than the oil boiler it replaces though it may get noisier with age. The main thing I notice is the blast of cold air as I walk past it. It is a thought that when a breeze blows past your house that every square metre of it contains up to 10 kW of extractable energy.

Vaillant seem determined to dumb down customer access to controls and to information about the system and I just have one number that I can change (the relationship between circulation temperature and outdoors). It is the same for a conventional central heating system but changing the temperature seems a bit more intuitive.  Your main control will be via TRVs on individual radiators - certainly with the Vaillant ASHP it has no temperature sensor in the house and apparently the algorithm monitors outside conditions and the flow and return temperatures instead.

Calculations indicated that the ASHP could struggle on the coldest days so I included the small oil boiler which the system can call on if needed. I have left my Hive system on for now but it has no connection to the boiler or pump and just manages some smart TRVs.

I have a grant but it only covers about half the cost of the project. I don't know about running costs yet though the new variable tariffs look hopeful. I did this to cut my CO2 output not my costs though I did have one eye on the eventual saleability and value of the house. I had to have an EPC done as part of the grant conditions and my house has gone from Band 'E' to band 'C', almost entirely because of the ASHP. That feels significant in that a buyer looking at 'E' might feel there could be cost issues whereas 'C' says 'OK'. Hopefully it will be MANY years before I have to sell.  

My next tasks are to see what I can get the system to tell me and to get it talking to OvO to benefit from the variable tariffs.

To be continued…   

I was in agreement with you until the bit where you’ve said your control is through the TRVs on the radiators. They will reduce the efficiency of the heat pump, which is happiest when the radiator water is flowing unrestricted around the system. If the weather curve is set correctly you don’t need any other controls. Room temperature should be steady throughout the house rather than shutting off individual radiators. The temperature of each room should be defined purely by the size and output of the radiator.

@ChristopherS_OVO  

onwards and upwards ...

​The ASHP is now networked with a MyVaillant CONNECT interface. Both the installer and I had expected this to have an RJ45 socket so it could be patched into the Gigabit switch three feet away but no, it is WiFi only and the boiler room is in a WiFi dead spot. One network extender later it is now talking to the Vaillant app on my phone but that is telling me pretty much nothing despite some useful looking graphs on the App web site. 

The App has a page for “EEBUS” and a slider which doesn't seem to do anything. EEBUS seems to have been developed by an industry consortium for "energy management devices in buildings to connect and interact with each other and with grid and market operators". It seems a prime contender for devices and apps to read information from the ASHP and for it to talk to a smart meter. I'm still researching this.  The crowd-developed HomeAssistant software has an EEBUS plug-in which I have loaded and used to interrogate the ASHP but which also tells me very little.  The plug-in developer tested the software with a heat pump and a different interface - the Vaillant Sensonet VR921 - which *does* have RJ45 and EEBUS sockets. The developer was able to get a lot more out of the ASHP than I could so it is possible that I need this other interface. Also being researched. Somehow we need to communicate the OvO cheap-rate timetable to the ASHP and then there is the electricity meter (in the picture), so far function unknown.

I filled in the on-line form at OvO indicating interest and assuring them that I had a valid setup. They have yet to get back to me except to point me at this forum.

There's a whole lot here I don't know and a lot is very new so I suspect that others are only beginning to feel their way around as well.

@juliamc I take your point about unnecessary restrictions to the point that I’ll be ripping up carpet to remove a redundant motorised valve as soon as I can :-). The sole use of a smart TRV that I have in mind is that we like a cool bedroom at night, something I can’t think of any other way of doing.

@juliamc sorry, re-reading your post .. you advise against *any* TRVs.? Without challenging your assertion about keeping the flow open it seems very inflexible and I’m struggling to see how that would work. Our use of this house is totally different in summer from winter or if we have guests. Also some rooms are weather-dependent, hot when the sun shines and cooler when up to three walls are exposed to a cold wind.  The ASHP only knows about the outside temperature and the temperature of the circulation return. I don’t see how it can compensate for the state of one or two rooms. I also realise now that the location of the outside temperature sensor is not optimal but that’s a different issue.  

I’m new to this though and happy to be talked out of old-school misconceptions :-)

Yes you’re right - I was oversimplifying. We also have solar gain as our large sitting room windows catch the sun all morning (when there is any). I have a Daikin with their Madoka controller which is set to modulate by 2 degrees C, so helps balance that out. I can see that if the Vaillant doesn’t have that you would be overheating there. Our bedroom radiator is sized to only get the room to 18 deg.

From what I’ve read though any guest rooms should be heated even if not used.

It’s a question of balancing the efficiency with comfort.

@juliamc so, deprecated but sometimes unavoidable?

There is also ideal versus reality - when I bought this house I inherited radiators where output-over-demand ranged from 0.6 to 4.3 (!) and though I replaced 8 out of 20 radiators, tuning the rest by replacing them would be just a tad expensive ...

PS thanks to whoever awarded me the little “I’ve got a heat pump” tag :-)

Looks like a Forum Moderator discovered your discussion @dr_dongle . It’ll have been one of them who awarded the Badge. :)