Jeremy Harris

When we were looking around there weren't that many suppliers offering a thin (~20mm) option, either (more do now, I believe). We ended up going with Silestone mainly because the local stockist had a good reputation and they did the colour we wanted.

The Sunamp can be topped up anytime, if needed. It's easy to just connect to a standard immersion timer so that you can control it in pretty much the same way as a normal hot water cylinder. In fact, our 9 kWh Sunamp is connected via a standard immersion timer, that is used to provide a boost top up on the E7 cheap rate if it hasn't charged up from PV during the day. Much harder to do this with Agile, as it's a continuously variable tariff, so a timer doesn't know exactly when the next 30 minute rate slot has dropped to a low rate. No reason why it couldn't work just fine with a normal off-peak cheap rate, or with one that has a fixed low rate tariff.

@Nickfromwales, this is a 60m² house, with the Sunamp just for DHW, so I'm really struggling to see how it would need a 12 kWh Sunamp, TBH. We use a LOT of hot water and just managed with a (regularly topped up) 4.5 kWh Sunamp, and now we have a 9 kW Sunamp we have more than enough hot water from a single cheap rate charge (or solar charge). What size UVC would you fit in a 60m² house? I'd have thought a 200 litre one would have been more than enough, for years I lived in a two bedroom house with a 120 litre cylinder, heated by an immersion, and that was fine.

The model we have is the eHW, but the 9 kWh version, which is OK for just the two of us. I suspect the tiny little 3 kWh version won't be anywhere near big enough for you, as it's really only suitable for supplying a low usage requirement, like just hot water to taps and basins. It won't be able to deliver enough hot water for a shower or bath (might just manage one quick shower before it runs out). Contrary to what @Nickfromwales says, we've found that the 9 kWh version is plenty big enough for the two of us, with enough spare hot water to allow an evening bath as well as two morning showers. As a rule of thumb I've found that a single shower takes about 3 kWh worth of hot water, a bath much the same (unless it's a large bath), so for normal use of two showers a day the 9 kWh version is about 50% over-sized. Given that it can be charged from the mains in about 3 hours this seems to be an adequate margin to me.

That doesn't bode well, if a Sunamp installer doesn't understand the fundamental principles of the product. It was something I picked up very early in the short, on the 'phone, "training" session I had with Sunamp, along with another related factor, which is that a part of the storage capacity of the Sunamp comes from the temperature at which the liquid phase change material is held, which is well above the phase transition temperature. In theory you should be able to buy and install an electrically heated Sunamp and then change it to a hot water heated one later, as the electrically heated unit will have the water heating heat exchanger fitted. The controller may need changing, but I suspect not, as the electrically heated version has both a power relay to switch the heating element on and off and a smaller relay that can provide a call for heat signal to a boiler. I've not looked at this in detail, but from the wiring manual, and from a look at the way the controller is internally wired, it seems possible to just connect the heating heat exchanger to the flow and return from a boiler and then use the dry contacts in the secondary relay to turn the boiler on and off as required. The only word of caution I'd express is that Sunamp have made several changes to their controller specification and configuration, so the above is based on what's actually in our controller (which is around 3 months old) and may or may not be what's available now. Having said that, I can't see any reason why a relay couldn't be connected to the heating output connections, together with a changeover switch, so that the Sunamp could then be used either with electric heating or with heating from a boiler, assuming that the input heat exchanger is plumbed to the boiler flow and return. In all probability the small signalling relay that's in our controller will be in all the new controllers, though, as I get the feeling that Sunamp have been trying to standardise on them a bit.

Unfortunately the issue with charging the hot water Sunamp from a heat pump has little to do with the controller or its software, it's a fundamental physical issue with the phase change material that it uses to store heat. This has a transition temperature of 58°C, but needs to be uniformly heated to about 65° (or a bit more) in order to ensure all the solid has melted to liquid. I suspect that your electrician probably doesn't understand how the Sunamp works, which isn't surprising, as it is a novel product. The electrically heated Sunamp is much the same as the hot water heated one, it differs by having an electric heating element in the base, in addition to the heating heat exchanger. This has two effects; it allows the PCM material to be directly heated, much like an immersion heater heats a hot water cylinder, and it allows both heat exchangers to be plumbed together in parallel, which increases the instantaneous heating power a bit.

I did do a check on the frame company and its directors before placing the order. This showed that the company seemed to have had some tough times during the recession but had kept going. It's a judgement call in the end, with any company, but I took the view that a company that had managed to keep trading, despite a significant downturn in new builds, was probably going to be a reasonable bet. The history of the directors is also a useful guide, as some companies come and go with the same directors just starting a new company from the ashes of the last one. This shows up on checks, reasonably well.

It varies. The system I've been looking at can deliver 3.6 kW, but that can be increased by adding additional inverters (they can be paralleled up). For us, 3.6 kW is more than enough, as we want to use the battery pack to offset peak rate electricity use in winter (so charging the pack overnight from E7, when there's little PV generation) and offset the import of electricity around the clock in the months when we generate a fair bit from PV. The peak loads are a very small part of the energy usage, and not really worth sizing the inverter for. The heating runs from E7, so would be on in parallel with battery charging in winter and the cooling runs from excess PV generation, so would just slightly reduce the amount by which the battery could be charged in summer. In summer, we need a steady 200 to 300 W overnight to offset grid import, which should be no more than about half the battery pack capacity of 9.6 kW at most. In winter we need roughly the same to offset peak rate import during the day, perhaps a little more.

Not sure there is any servicing to do, though. The battery pack in my car doesn't get serviced, neither does the inverter on the PV system, so really all servicing can ever be is a check that the system is still working. As for peak current, certainly a house system places a much lower demand on the battery than a car, but cars don't really place a high peak current demand on their battery packs either. My car draws a maximum of under 5C from the pack under hard acceleration, which is about the rating that cheap lithium cells from 20 years ago could tolerate. Getting cells to deliver 20C to 25C is now commonplace, with some cells being well able to deliver around 40C, so even a Tesla isn't really placing much of a demand on its battery pack (a dual motor Model S Performance with its 100 kWh pack, in Ludicrous mode, only draws about 6C from its pack at maximum acceleration).

Changes to the lighting have near-zero impact on the overall maximum demand, as a 6 A lighting circuit can run nearly 1,400 W of lighting, which is way more than most houses need (the total lighting demand for our 130m² house, with all internal lights turned on, is about 300 W). Running a 6m length of insulated pipe should be fairly easy, and not too costly, especially if it's just a single insulated pipe. Perhaps cheapest to just insulated a length of 22mm plastic pipe yourselves, rather than buy the pre-insulated stuff. This isn't hard to do, I slid insulation over a length of around 4m of 25mm MDPE outside pipe, taped it up then slid it inside a duct to protect the insulation.

I've been watching prices for a year or two now and they are steadily reducing, but not by enough to make them viable, in terms of paying back the investment through lifetime cost savings. Not far off, though, the 9.6 kWh system I recently had a quote for is within about 10% of break-even, and with the added benefit of providing a backup power supply (for us, we get lots of power cuts) it seems worth investing in. I've no doubt that prices will continue to fall, though, as most of the price is in the battery packs, and the prices of those seems to be falling as a consequence of the increased popularity of electric vehicles. I'm not yet convinced that electric vehicle cells are best suited to home storage, though, because of potential cycle life issues. Redox flow batteries seem to be a promising home storage technology, as they potentially have a long life, if the capacity loss issues that have been seen with electrode degradation can be resolved . The snag is that they aren't suitable for electric vehicles, which seems to be the mass market driver for battery development, and so not a lot of development cash is being spent on them. Redox flow batteries are about at the same stage of development as lithium ion chemistry was around 15 years ago, when they were also suffering from problems related to electrode composition.

As far as the electrical work is concerned, the Sunamp is near-identical to fitting a tank with an immersion. The only difference is that a FCU, fused at 3A, has to be connected in parallel with the feed that supplies the heating element, so that there's a fused low current supply for the Sunamp control box. That's about 15 minutes work and less than £10 in materials, so nowhere near £100. I still cannot see how the installation can be made compliant with the regs with an 11 kW instant water heater. If your electrician is prepared to ignore the regs and sign off the installation with this fitted, then I'd be inclined to make sure he knows that you will hold him responsible if there are any future overheating or other problems relating to the potentially overloaded incoming supply.

Interesting offer. EDF are claiming that the price includes a discount, but over £7k for 8.2 kWh is nearly £3k more than I've been quoted for a 9.6 kWh system, so it's not fantastic value. The 9.6 kWh system I've been quoted has a 10 year warranty, the same as the Powervault.

Ours was, five stage payments, with something like a 10% deposit and then payments at completion of each erected stage that were roughly equal to the value. The final payment was 20%, paid only after the house was complete and had been insulated and air tested and shown to meet the passive house criteria.

I've got a feeling that someone from one of the security/anti-virus firms did an experiment a bit like this. A surprisingly large number of people just clicked straight through, even when there were prominent warnings.

One of mine broadcasts the SSID "GCHQ"...

Would a dry verge look better? We have the Kytun stuff and it makes for a neat edge to slates: http://www.kytun.com/

Yes, the shared wall will be treated as being to an unheated space, as it probably will be most of the time.

100mm of PIR laid over the concrete, with a floating timber floor on top, and a perimeter/area ratio of 1 gives a total U value, allowing for surface resistance, of about 0.18 W/m.K.

Do you know the area and the depth of the concrete garage floor? To work out the U value all the layers need to be taken into account, together with the surface resistance both sides and the perimeter/area ratio. The timber floating floor will improve things slightly, as will the surface resistance effects, and the thickness of the underlying concrete. The insulation manufacturers tend to be a bit optimistic in the general examples they quote, so the best way to get a reasonably accurate answer is to use the λ value for the insulation material, and the λ value for all the other layers that make up the floor, together with thicknesses of those layers, the perimeter/area ratio and the surface resistances. That way everything is accounted for and the result is likely to be fairly realistic.

Not sure how you can get the same U value with 100mm PIR or 50mm PIR and 50mm screed. Ignoring perimeter effects (just because I don't know the perimeter for your floor) I make the basic U value of 100mm of PIR about 0.22 W/m.K (not great, and will be worse when the perimeter losses are taken into account) and for 50mm PIR plus 50mm screed the basic U value increases to about 0.432 W/m.K, which is far too high to meet building regs. The true U values will be slightly different, depending on the concrete floor thickness, the floor build up above the insulation and the insulation level, if any, around the perimeter.

The yacht I was working on was a one-off, custom built boat, that was being built by a company set up by the owner specifically to build his own yacht. It's fair to say the owner had more money than sense, but he certainly didn't "under fund" the project. Anything we wanted we could have, and the chap in charge of the lay-up was the one I learned pretty much everything about laminating from. He'd been hired in from up-country specifically because of his skills and knowledge in custom yacht construction. No, @SteamyTea and I have a fair level of knowledge of some of the pitfalls that can arise when doing GRP work in general, not specifically related to GRP yacht production. One of those pitfalls, directly relevant to this thread, is the very well-understood need to keep everything bone dry, because of resin cure inhibition caused by moisture. Most of my composite work has been on aircraft components, rather than boats, although I did make one small boat from epoxy foam sandwich a few years ago.

Me too. We bought a house in Scotland that had inward opening tilt and turn windows. They were so impractical to open that we kept them closed all the time. Having to pull curtains right to the sides and remove everything from the window cills just to open a window is just bonkers.

Given the slow state of the market where you are, then if they were sitting on plots of land that weren't selling they could well have just run out of time/money. Might be just down to them being caught by the relatively local house sales recession in your area.

The Salus actuators don't care about the direction, they just try to establish a temperature differential between the two (unmarked) sensors. The temperature differential they aim for depends on the flow temperature, so if this is less than 30°C the valve will aim to get a 4°C differential, if the flow temperature is over 30°C then the actuator will try to maintain a 7°C differential. So, when in cooling mode the actuator tries to maintain a 4°C temperature differential between flow and return, which seems to be OK (it's the same differential as it tries to maintain in heating mode for us). The manifold TMV just fully opens, as it tries to get the manifold temperature up to the set value and can't, so it stays wide open. The manifold temperature in cooling mode is then determined by the ASHP set temperature.