Jeremy Harris

I sealed ours with a bit of chicken wire rolled so it would fit in the remaining space (as a vermin barrier) tied a bit of stiff wire to it (so I could pull the plug out if needed at any time) pushed this down the duct, with the wire hanging out, then sealed it with low expansion squirty foam. when the foam had hardened I carefully trimmed any excess away and then used Siga tape or self-amalgamating tape (depending on the size of the duct) to cap the ends neatly. For one 25mm duct with some coax cables coming through I just used self-amalgamating tape, wrapped around the cables first, then stretched and wrapped around the end of the duct and the cables.

@Sue B, Thanks for the kind words about the blog, seems a long time ago now. You're only around 40 miles away from us, and are welcome to visit if you wish. By complete coincidence I grew up in Denham, then Gerrards Cross, and a few days ago was listening to a recording of me from 1963, reading the lesson at Denham Parish Church.

I'd like to know the answer to the holiday home question, too, as we're going to inherit a half share in one (not by choice).

Do the remote monitors also include the standing charge? I have a suspicion that some may, and this may be a possible reason why they seem to be in error (and I agree, I've also heard lots of tales of them being way out).

Sounds as if you're well on the way to being sorted. I can recommend Freesat, we think it's brilliant. Better picture quality than Freeview and no interference at all.

TBH, this doesn't surprise me. I was warned (albeit with inaccurate information) about the HMRC tightening up on CGT three or four years ago. I think that there has been a general push over the last few years to try and increase the amount of tax due, but that isn't paid, and this may be a consequence of that.

Although we sort of partly lived in the new house for ages before selling the old house and moving permanently, there was a massive sense of relief when we sold the old house and moved in permanently. The burden of the old house is one that I'm very glad to be rid of - there was nothing wrong with it, but it was just so unpleasant in so many ways from the new house that we couldn't wait to get rid of it. Enjoy your new house; I'm sure the niggles that need fixing will come right one at a time. I share @ProDave's view about someone not being able to get UFH to work first time. I have no idea why we seem to have so many trades people that don't seem to know what they are doing.

If you are OK with hot water at around 55 deg C (which many people find perfectly OK) then an ASHP can deliver that sort of temperature. You can store that hot water in a hot water tank, but probably not in a Sunamp, as the Sunamp needs charging hot water that is hotter than that; typically around 70 to 75 °C I believe. So if you choose to use an ASHP then you probably can't mate that with a Sunamp for hot water storage. Using solar thermal for hot water is expensive (high capital cost relative to the power delivered) and won't provide much hot water in the winter months, so you will need something to augment it. If you don't have mains gas, then electricity is probably the easiest and cheapest (in terms of installation cost) as a way to augment hot water during winter. You could store heat from solar thermal and electric heating in either a Sunamp or a hot water cylinder, although there may be some challenges in controlling the charging temperature for a Sunamp when connected to a solar thermal system, and there will be a fairly big efficiency hit because the solar thermal system won't be able to start charging until the temperature exceeds 58°C, which means that the solar thermal collectors may sit there doing very little a fair bit of the time. Using PV as the power source will work with either a hot water tank or a Sunamp as the heat store. It's relatively cheap, maintenance free and has the benefit that it's pretty easy to augment with grid electricity when there's little PV generation. In terms of efficiency, a Sunamp is a fair bit more efficient than a hot water tank, because of the lower heat losses, but there is the issue at the moment regarding utilisation of all the heat storage capacity of the Sunamp. I would expect this to be resolved pretty quickly, and if it isn't I should have some figures next Monday that give an indication as to how big an issue this is when the recharge point is configured for 50%, rather than 90%. The solution that is the most complex and maintenance intensive would be solar thermal plus direct electric augmentation. The storage system that takes up the most space inside the house would be a hot water cylinder, no matter what you use to heat it. The simplest system in terms of installation may well be a monoblock ASHP coupled with a hot water tank, and this could also run the heating system. This could be augmented outside the heating season by using either PV running an immersion heater in the tank, or by using solar thermal, but my inclination would be to use PV, as solar thermal is a one trick pony, it will only deliver hot water, and only then when the tank is cool enough to accept it. You can use PV generated electricity to offset pretty much every other energy using bit of kit in the house, including an ASHP, so you get a fair bit more bang for your buck in terms of the useful energy you get for the investment.

Both, at least around here. We've got a lot of big new developments that have gone up around Salisbury in the past few years, and at a guess I'd say around 20 to 30% were timber frame, with rendered block or brick exteriors, some with partial timber cladding, the rest were block and brick. From just looking at them whilst passing by I'd say that the block and brick ones have the most glaring faults - most appeared to have missing insulation, poor cavity closings etc. The timber frame ones looked marginally better, but that may well be because it's not so obvious from outside when the insulation is missing or has big gaps.

They are indeed! I bought loads of stuff from eBay and just took the hit on VAT (where I couldn't get a VAT invoice), as the saving was usually more than the VAT.

Here's a direct link: Heat loss calculator - Master.txt and, whilst I'm at it, here's a link to a simple spreadsheet for calculating heat floor loss and UFH output: Floor heat loss and UFH calculator.txt Both of these are Excel spreadsheets, which the forum software won't allow, so they have been renamed to fool the system into thinking they are text files. Download them somewhere, then rename them, replacing the .txt suffix with .xls and they should open in most spreadsheet software OK.

I remember reading about a passive house (may have been in the Passive House magazine) that had a large, central, well-insulated water tank that formed the central column of a helical staircase. I can't recall the details, unfortunately, but the idea was to be able to buffer heat storage IIRC, rather than try to create a long-duration heat store. I think that heat was extracted from it for DHW using a small heat pump and heat was pumped back into it from solar thermal, the idea being that the big tank would only ever have a relatively small temperature change from day to day. I can see the logic behind this, as even in winter there are still a fair few days when the output from a reasonable sized collector array will exceed the daily heating and hot water demand by a fair bit. Right now we're exporting around 3 kW, for example (and the damned Sunamp isn't charging....).

Yes, they were pointed to it about a week ago now, I think.

No, we have the eHW, as the PV version is only suitable for small PV arrays (less than 3 kWp IIRC) and only has a small (I think 1 kW) electric heating element. Ours has a 3 kW heating element and was sold as being suitable for use with a higher capacity PV system. The label inside our Qontroller states that it is a UniQ_SBC_01_PV, implying that it should have been set up to utilise excess PV generation, however, as supplied, it was set up with Option 1 ON, which meant that it didn't start accepting any charge until it was 90% discharged. I changed that last Friday, in the light of information received during an email exchange with Sunamp, so that it now starts to accept a charge from 50% discharged, which should be better, but it's a long way from being ideal.

If anyone wants to do some reading, this paper from 2009 reviews many of the available PCMs and is written in a form that seems reasonably easy to read: Review of thermal energy storage with phase change materials - Sharma 2009.pdf

Good point. At the moment you'd have to rely on the mod I made to our unit (and which @Barney12 has made to his) which adds a neon indicator to show when the contactor that allows power from the PV diverter is on. It's a bit crude, but reasonably effective, as at least it shows when the unit has dropped to either the 90% or 50% threshold (depending on how it's been set up).

Yes, the only slight snag is that the insulation level needs to be very good, as with a small volume in the charge circuit the proportion of heat lost, versus heat retained, increases (what's often called the "elephant and mouse effect"). The key to utilising excess PV generation is in allowing a very low level of power from the PV system to be able to be transferred to the PCM as useful charge. The direct heating element will do that very well, if it can be adequately controlled. The indirect system using a small volume heated water loop offers safety advantages, in terms of not being able to overheat the PCM, but adds losses when charging, so would be a bit less efficient. Might not be a big enough loss to worry about, though, especially if it allows better utilisation of the heat capacity of the PCM store.

AFAIK, they have dropped the Sunamp and Stack model range completely, in favour of the UniQ range. I presume this was because the UniQ range is a better match to whatever has turned out to be their core market, which I'm guessing isn't people wanting to maximise the storage of excess PV energy. Yes, you could opt to waste a bit of hot water to ensure that the UniQ drops below the charge threshold, and that might well work as an interim measure, although it does waste energy, some of which may have been paid for during the winter months. Although we've discussed alternative charging methods, using temperature-controlled water derived from a highly variable electrical power source (diverted excess PV generation), it does seem probable that a change to the control system could allow the direct electric charging system to work more effectively. The key seems to be in the control system having enough data to make a reasonably good stab as to the state of charge of the PCM, and be able to ensure that local overheating never occurs. I'm not entirely convinced that three thermistors down the sensor tube can give enough data to do this, but may be wrong.

Interesting. I've just been looking up the phase transition temperature for paraffin waxes and it seems that they can be very finely tuned, with one form of paraffin wax having a phase transition temperature of 21.7 °C , which looks to be a good match to a room temperature stabilisation system like this. The effect would be to increase the thermal time constant of the house a fair bit, I would imagine, with the panels absorbing heat when the room temperature is over 21.7 °C and then releasing it when it drops below that temperature.

Yes, or you could try and build a hydronic unit similar to the one that sat in the top of the old Sunamp PV. That used an immersion heater in a tube, with a variable speed Grundfos pump and a flow sensor, to take whatever excess PV was available and use it to run a charging loop at a high enough temperature to cause the PCM to change phase. The earlier discussions around using a Willis heater and pump, plus a control system, in order to replicate this set up seemed to have merit. One advantage of the UniQ is that these unit already have a separate charging heat exchanger circuit, so it would be possible to make a small add-on box that just used excess PV to heat a small volume of water to above the PCM phase transition temperature and pump it through the unit to charge it. The main heat exchanger could still be used to provide DHW as normal. I think there's an advantage it trying to keep the charging circuit water volume as low as possible, as that way there's less initial energy needed in order to get the temperature high enough to effectively start to charge the PCM. A Willis heater only has a low volume, so if well insulated would heat up to the temperature needed relatively quickly, even if there was only a few tens of watts of excess PV - the lower limit would be set by the heat losses from the charging circuit when sat at required temperature (probably around 75 °C or so, I think). Turning the pump on when the temperature was at the set point, and varying the pump speed to try and maintain that temperature, seems a viable way to try to run the control system, just allowing the variable PV power level to go directly to the heating element.

I suspect it may well just be penny-pinching, by using more sand in the mix. One report mentioned the mix having 15 parts of sand in it, which would tend to support this view. Could also be building in very cold weather, though, or not protecting the brick/blockwork from overnight frost, maybe.

AFAIK it only effects the electrically heated eHW models, not the water heated models. I believe the issue is only related to the turn on point for the electric heating element, but have nothing other than guesswork and a bit of crude reverse engineering to support that view

Whether or not the 50%/90% issue impacts on charging from E7 depends on how much usable capacity you need from the Sunamp. For example, if your use case was like ours, where we draw off around 4 kWh of hot water first think in the morning, but then use very little during the day, then there's a chance that a 9 kWh Sunamp may not have discharged down to the 50% level before the E7 period starts. Under those conditions it wouldn't charge that night, so next morning would have around 50% charge remaining. If the usage the following day was such that, say, 7 kWh of hot water was needed, then the Sunamp would run out of charge part way through. If it was set for 90% discharge before accepting charge then it could be far worse, in that there could be a very high probability that it wouldn't charge overnight during the E7 period for the first night after a day of using some hot water and so run out of hot water the following day. If you had a Sunamp set for 50% before accepting a charge and used most of the capacity during the day, every day, then the unit would always charge every night during the E7 period, so there wouldn't be a problem. The main issue seems to be mainly for those who have opted to have a bit of "spare" capacity when ordering a unit, not realising that this "spare" capacity is really a liability that can leave them with no hot water (as has already happened to us once).

Might a binary rotary switch be an option? I have a feeling that I may have one or two around somewhere, goodness knows where they are though!

The pot of pipe lube kept being given the youngest lad on our ground works team towards the end of each day - along with suitable comments as to the use he might have for it that evening. Trouble was the lad was a bit shy and used to go bright crimson every time the other lads did it, which made them take the mickey out of him even more... You can DIY the pipe lube easily enough if you want loads of it and don't want to pay for the ready made stuff. It's usually just water mixed with about 20% glycerine and thickened to a gel with methyl cellulose.