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One of the reasons why it may be worth skipping all these to start with and just set to manual. Come back to more complicated stuff once it's shown that the building can indeed be warmed. I'm not familiar with Valliant so can't really help zoot with specifics on the controller.

Firstly, using the timer is not wrong as such, it comes down to HOW you use it. In your particular building, using the timer to stop the heatpump working for long periods is the issue. It's ok to use the timer to set a modest setback, ie, 2C. So most of the time you run at say 18C but overnight set it to 16C. But using the timer to say you want 20C for 2 hours and then 10C for the rest of the time just won't deliver the result you expect. This partly due to the way the heatpump works and partly due to your building. I would guess that most people with heatpumps do use the timer. I can't tell you how to do it but it will be possible through the menus. You want to have a setback to setting the timer makes sense. In my mind, first step is to get your warmer, second step is to optimise things so your system works in the most efficient and comfortable way for you. First step can be done by just setting to ON*, second step might need the timer to do but in a way theres no point learning to use the timer if you can't get warmer with the thing just set to ON. * I do think the thermostat needs sorting first.

Let me have a run at this. If this doesn't click try to expand on what aspect isn't clicking. Your system has three different ways of running. Heating always available (ON if the room temp is below the setpoint temperature) - we are refering to this as 'ON' Heating is not available, 'OFF' Auto/Timer In Timer mode, the system is always in the ON state BUT the setpoint temperature changes according to the timer. You can make this really complex if you want. You could say at 9am you want it to be 25C, 12pm 20C, 8pm 25C, 12am 10C, etc Most people use the timer to set a daytime/'at home' temperature 'setpoint' and a nighttime/'not at home' temperature 'setback', but you don't have to do that. Right now your system is likely set up to have one temperature during the 2 hours each morning and evening and a 'setback' temperature that is much lower the rest of the time. So it's never really off, just that the temperature outside those 2 hour periods is set low enough that the system never turns on. The minimum temperature setting is usually 'Frost Protection' which means the only time it comes on is if it gets so cold the heatpump might freeze which would damage it.

Before looking for boosters, try out the other networks. Theres only 3 physical networks now so not a huge task.

Can't remember where the £60 comes from but I know I assumed £60 was pure heatpump cost, with the other £12 being other costs + standing charge, a guestimate of course. (likely a little off as my Octopus standing charge is about £12)

I've been thinking about this and wanted to put some numbers on it. Taking a hypothetical two storey 120m2 building with 2ft stone walls. 6x10x5 footprint. Assume worst case U-value of walls (from scottish gvt doc) of 2. Relatively poor double glazed windows, also 2 (makes calc easy). Wall area 10x5x2 + 6x5x2 = 100 + 60 = 160 m2 of wall Heatloss through wall per C of difference between inside and outside = 160 * 2 = 320W Heat input requried (Watts) Average Outside Temp Inside temp 0 3 6 9 12 15 4800 3840 2880 1920 960 16 5120 4160 3200 2240 1280 17 5440 4480 3520 2560 1600 18 5760 4800 3840 2880 1920 19 6080 5120 4160 3200 2240 20 6400 5440 4480 3520 2560 Approximate cost for 1 month/30days at 25p/kwh Average Outside Temp Inside temp 0 3 6 9 12 15 288 230.4 172.8 115.2 57.6 16 307.2 249.6 192 134.4 76.8 17 326.4 268.8 211.2 153.6 96 18 345.6 288 230.4 172.8 115.2 19 364.8 307.2 249.6 192 134.4 20 384 326.4 268.8 211.2 153.6 So if we assume that for the year the outside temp averages 0 for one month, 3 for 1 month, 6 for two months and 12 for two months. (6 month heating season) and a SCOP of 3. Annual spend on energy would be (ignoring DHW): Inside temp 15 979.2 16 1094.4 17 1209.6 18 1324.8 19 1440 20 1555.2 Obviously a lot of assumptions here (ignoring losses through roof and drafts, ignoring modern extension, taking likely worst case U value for walls and COP). As a sanity check Nick said his similar property cost him £450 for a month to maintain at 19.5C. I'm assuming that's not averaged over the year but what it costs mid winter in which case it's not far off these approximations. The difference by degree C is lower than I was expecting but I think these are still useful numbers and I think shows zoot could likely maintain an internal temp of about 16 without spending significantly more. If with our help he can get to a COP of 4.5 on his heatpump then he could do better. If there are significant drafts then all bets are off, but drafts can be fixed.

£60 worth of heat should be enough to keep the inside warmer than the outside if applied correctly. That there are times when this is not the case strongly suggests the current energy use is not being used optimally. We have asked him to try and his recent posts suggests he is considering it. The proof is in the pudding. If he tries it and it works then he can decide what to do with that knowledge. If he doesn't try he never knows. In this house I agree. Well insulated houses it could work, just wouldnt be very efficient. I think recent posts suggests Zoot is willing to try and see what happens so long as his bedroom can be kept reasonable for him to sleep in. Using the heatpump to just heat the water and turning off the rads, may indeed work out better if the budget is strictly set, using the immersion seems like an unnecessary waste given he has a heatpump can do the same job at 2.5x the efficiency (depending on the length of pipes see JohnMo's example). If he decides to go ahead part of my suggestion is to monitor the meter closely (stated much earlier and would do again if we get to that point). It is certainly the case that running the experiment for a couple of weeks will add cost, but I suspect averaged over the year it won't make much difference for the experiment. Long term is different, after the experiement Zoot will have information needed to make decisions. What is enough? It depends what temperature you want the inside. Every 1C costs a lot, lowering the thermostat gives zoot flexibility. I think it's realistic for not much more money to get zoot to the point where he still needs a blanket in his sitting room but while sitting there with his blanket he feels comfortable rather than still cold. I suspect £250 per month over the year gets the place to approximately cozy. I've said before my mums place costs about £2000 a year to heat. Thats with uninsulated solid brick walls (some only single skin). That's £160 per month averaged. Zoots walls being super thick likely have a higher U value than my mums.

That is up to zoot. We have said repeatedly that if he wants to be warmer he will have to spend more, but it is also clear that a lot of what he already spends is wasted. My goal in helping is to get the system to the point where zoot has a choice. How much to spend is variable. Every 1C of internal temperature will cost money. For his current £60 per month if applied wisely his internal temp could be maintained at a level where his breath is not visible. Warm and cosy no, but its still an improvement. Spending more can raise the temperature and once the system is functioning correctly what temperature and how much to spend is completely down to zoot.

Ah I am sorry. I'm using 'setpoint' to mean the temperature you set the system to deliver. 'setback' is used to mean a lower temperature than the one you normally want. So you might set 'setpoint' to 20C for daytime and 'setback' to 18C for nighttime. No problem.

When you buy it you get two boxes. 1. The thermostat that you can put wherever 2. A reciever box that is wired into the heatpump controller.

Ah this is confusing isn't it! Let me try again: The thing we want to avoid is where the heating is full blast for a few hours a day and then entirely off for the rest of the time. We want the system to be on and able to provide heat at any time day or night (if the thermostat says it needs heat). However, it is ok to have the temperature set point vary by time as long as by a small amount. ie it's ok to have the setpoint be 20C in the daytime and 18C at nighttime and use the timer to do this It would not be ok to have 20C in the day and 10C at night as that is too big a difference and it is effectively the same as just turning the system off overnight. Given you have struggled with the system it seems best to keep things as easy as possible. The easiest possible way is to keep the system on 24x7 and use a TRV in your bedroom to lower the temp in your bedroom vs other rooms. Setting up the timer with two different temperatures is the other option but more complicated to do. Edit: You may well need a TRV in the bedroom anyway even if you use the timer for setback because it is better insulated than the rest of the property it is likely to warm up first and end up hotter than the others spaces without a TRV

I think @Nickfromwales's suggestion to get a wireless one, that has a reciever that is wired in to your existing may be the easier option. I do think either way though it would be better done by someone else. But I don't know Valliant specifically or whats involved there so will leave this to others.

Stage 1 was to work out how to just set the thing on all the time. That was the easiest. Stage 2 was to work out how to set the timer. Setting the timer is better but more complicated. Edit: Short term, as a trial just turning it on can be tried. Long term you likely want to adjust the timer.

Yes, on is on at a fixed set point. The timer mode allows you to vary the setpoint over time. The next point on my list was to find out how to adjust the timer. Did you do that? If not, then maybe theres a video on youtube on how to do it, or someone here who knows Valliant can help you through it. Did you have a conversation about the thermostat? What was the answer there? It's not something you would want to be fiddling regularly. In the ideal world you would set this up once and then not touch it again. A lot of people will set it up at when things start turning cold and then turn it off when it's warm (but with the right set temperature, even this is not really necessary). This is a common understanding but it's not exactly correct. In houses with thick stone walls like yours to be comfortable you need to warm up the structure. I know this seems wrong to you, all we can ask is for you to give it a try and see if it works. In my case, I was originally only heating the space I was in, I was warmish, but had very cold feet. Then I switched to trying to heat the whole place up in the morning and letting it cool overnight. It would take hours to get up to temperature and then lose all the heat overnight and have to start again in the morning. This was very expensive. Now I have switched to keeping the place at a relatively constant temperature (with a setback) it's much more comfortable and burns less gas than heating from cold every morning.

In a normal house maybe. But not so sure in this particular one, especially during the warm up phase. The 2ft thick walls downstairs will still be emitting coolth, long after the modern upstairs bedroom has warmed up.

@Nickfromwales's suggestion of just wiring in an external wireless one is the easy solution to that. TBH I think that's likely the better option in anycase. But doesn't seem like something that will be ready for Monday.

The important thing is the thermostat is moved into the cold, old, part of the building, not close a raditor or other heat source. It doesn't strictly have to be the coldest room as long as its generally cold in the area. Putting it in the hallway or the bottom of the stairs is common. If you moved it into your warm bedroom/warm workshop that would be bad and might make things worse.

@zoothorn I think I was the one who saw you saying you were still cold and suggested you try again at making changes to things so you could get warm. I know you didn't come back here asking for that, but since you have a new system it does seem worth trying. I agree with @Nickfromwales that this thread could do with a timeout until after the engineer visit. We are all trying to help. I know some of the suggestions seem wrong to you. The go against your experience. All I can say is that people aren't making these things up, they are the result of real-life experience in their own and friends homes. We are passing on what has worked for us and many others. Once the engineer has visited then you have a choice, you can come back here and work with us to try new things (even things that seem wrong to you) to see if it works, or you can not. As a group I think we all think its possible for you to be much more comfortable than you are now (not perfect, but better). To be clear though, it will cost you more in bills. If you can't stand any higher bills (at least double what you pay now) then that puts a blocker on things.

Setback is the minimum temp you want the house to be kept at, ie, overnight if you are running a timer schedule. Rad temperature. 46C is lower than I was guessing based on your description of the rads being hot. Your system should be relatively efficient with rad temp of 46C. So a COP of >4 rather than the 2.5-3 I'd previously guessed. This is good. Though rad temperature and setback temperature are two different things so maybe he was talking about multiple things and the two got jumbled? Different to HW temp. Ideally HW temp should be a bit hotter. 55C maybe 46C is a fine temperature for your situation, I wouldn't worry about changing it but if you want to then ask the engineer on Monday.

The £700 is an approximate maximum amount of energy your heatpump could use in 1 month if running flat out 24x7. It is not what you need to spend to warm your house. That your bills are so low is a sign that your heatpump has been working much below it's maximum capacity and with some changes could provide much more heat. @Big Jimbo's question is a good one. Would appreciate your thoughts on that.

Couple of things to add: 1. The only time a 9kw heatpump would need to work flat out continuously in zoots property is during the few super cold days of the year, if that. The rest of the time it would work a lot less. 2. The electricity bill is averaged over the year, so even if you spend £600 in the worst month, the amount you pay monthly will be a lot less than that. 3. @S2D2's calcs assume a COP of 3. That's the measure of efficiency of the install. A COP of 3 is a good guess for zoot's current setup (maybe less) but with some changes the COP of 4.5 or even higher is possible. If that was done the amount of electricity used to produce the heat goes down a lot. Instead of needing 3kw of electricity it needs 2kw. So £446 running flat out vs £669.

As you said yourself the rads were coming on and off. They weren't on continuously. We have talked about how the thermostat is in the wrong place. The system may have been set to run, but the thermostat was stopping it running most of the time. Your bill would have been very much higher had it been actually producing heat constantly. Both @Dillsue and I have done some rough calcs for your place. The results are that your heatpump is likely not able to maintain 20C internally during the coldest days of the year. No company would want to install something that can't maintain 20C during the coldest days. In fact I suspect that most companies would want to make sure the heatpump could maintain 23C. That doesn't mean that the heatpump flat out wont work. Just that for 2-3weeks a year it will be colder than 20C inside. Given right now you are much colder than that I'm suggesting changes that could allow you to be warmer than you are now. @Big Jimbo is right though, if you want to be warm in your house you will have to be able to afford bigger bills. How much bigger is unclear, but his estimate of £250 is a good starting point. Some things are not as obvious as they seem. Because the old rooms have very thick walls, once they are cold they are difficult to warm up. So if you really want to prove your theory you need to run the house for at least a week, probably more with the heating on and rads warm continuously. If after 2 weeks of doing that, it's still cold then you will have proved your point (at as the house is now). If it's warmer but not toasty then we can have a conversation about making it better. Edit to add: if after two weeks of constant heating it's still deathly cold then its still not game over, just that improvements need to be made to the place and I'm not talking insulation. It's more likely plasterboard tent type issues or drafts (despite your best efforts).

The physics is the same, to get a comfortable house you will undoubtably have to spend more on bills than I do but the same principles apply. My mums house does not and she is able to heat that perfectly fine. Yes it costs her approx £2000 a year but its not cold (so long as the heating is on) Medium warm rads on 24x7 will output much more heat than hot rads on for short periods of time. 12 rads designed for heatpump temps should be able to output the full capacity of your heatpump without issue. The fact your energy bill is only £70 shows that this hasn't been tried yet. For you to get a warm house it will cost substantially more than £70 per month. If my mums leaky, mostly uninsulated house can be kept warm then so can yours. Take @Nickfromwales up on his offer. TRY to run your house in a different way. Physics and experience from people on this forum says it's possible. Unfortunately you've had a bad experience with previous installers putting a system in that wasn't set up right and gave the impression that your house is unfixable. Try to set that experience aside and start with a blank sheet of paper.

I'm saying the rads should be hot whenever the room is colder than your set temperature, including overnight. This is how I run my system, how @Nickfromwales runs his, ditto @JohnMo@marshian and many many more. With a TRV you can set the temperature in your bedroom lower, but the heat is required in the rest of the house to prevent the stone walls getting cold. Once they are cold then warming them up again is super difficult. Once your house is warm, the radiators will only be on as needed to maintain the warmth, but to get the house warm they need to be on continously, likely for many many days because your house is so cold right now. As I said many posts ago, I've found running my system 24x7 seems to be using less energy than running my system on a timer. The reason is that it takes a lot more energy to heat a cold space up than it does to maintain a constant temperature.

Maybe this helps: The Thermostat/controller is there to put heat into the system whenever the coldest room needs heat (to do this it needs to be located in the coldest room) The TRVs are there to set the hottest temperature you want the individual rooms to reach. There are ways to make systems work without TRVs but your house is a long way away from that. So you need TRVs in rooms that would otherwise get too hot as the system is heating up the cold rooms. You don't really need TRVs in the cold rooms. In my flat I have removed the TRVs from everywhere but the bedrooms and it works fine, but if I remove the TRVs from the bedrooms then the bedrooms overheat as the system is trying to warm up the cold other rooms. (My bedrooms have much better thermal properties - like your new bedroom in the old house)