sharpener

This is bc the volume of water in a rad is approx proportional to its surface area, and so is its output (assuming all have same construction i.e. 1 set of convector fins per heated element, or not). So you need a flow rate proportional to volume which gives you both constant dT and a constant warmup time. AFAIR @JamesPadidn't like this method <g> when I first proposed it so good to see it come up again!

I think none of the above, quite. Heat loss from rad is proportional to (mean rad temp - room temp) x (rad area) Heat supplied by heating circuit is proportional to (flow rate) x (delta T) In the steady state these must balance. Most HPs will modulate their output in an attempt to maintain the delta T, so typically the flow will emerge 5 deg hotter than the water returns to it (assuming the HP has enough power to meet the total load). If you have an oversize rad in yr system then it is always possible to turn its flow rate down until the heat input to it matches the loss to the room with the specified 5 deg delta T. Then the return temp will be the same as the other (correctly sized) rads. Yes if you overdo this the return water will be colder than that and dilute the return from the other rads, in theory the flow temp will fall slightly as a result and the whole system will reach a new equilibrium at fractionally lower output. But I don't think this will be enough to worrry about, in the limit of course the rad will be off and will then not affect the return temp at all.

Just read a feature in the Economist predictions for 2025. To the foregoing list we can add: Chinese firm HiNa to start industrial production of grid-scale sodium battery technology in 2025. (I remember sodium-sulphur being the great hope for electric cars >30 years ago.) US co Form Energy are developing iron-air batteries and Italy's Energy Dome uses CO2 under pressure instead of air, both to start construction of US plants next year. Over-capacity in Chinese EV battery manufacutre means capital cost of solar + batteries now less than new coal plant in China or new gas-fired in US.

Having three times moved away from Scottish Power and twice been moved back again under SoLR I am not keen, their pricing looks suicidal. From the first email on 19 June It has taken me until yesterday to get Octopus to install smart meter in place of Radio Teleswitch E7 switch me to Cosy tariff transfer me from deemed export with Good Energy to Outgoing Fixed get the various databases updated correctly start monthly billing with correct meter readings Everything seemed to involve my prodding or intervention at every stage but they have finally offered a reasonable amount of compensation for the hassle. Am not anxious to start this all over again with a supplier that may turn out to be flaky.

If there are coliform bacteria present I would also worry about possible cryptosporidium from animal faeces, this has cost SWW a shed load of money this summer in an area near me.

I am having difficult reconciling this statement with the following Expect to pay three figures p.a. It cost me ~£150 to get a full analysis done, they found high Fe concentration but couldn't advise why it might be there or what to do about it. Also paid a specialist firm who supplied bone char filters and pH correction media, they weren't very impressive either. Simplex Health have a range of DIY tests (but their pH strips are no good with low conductivity water, use the drops from Water for Health instead). Companies like Wrekin Water can advise on a complete system and supply the bits, they were quite helpful in advising on pH correction. It looks as though you could get the Daro steriliser with voltage-free output and use that to control yr pump, would at most require a relay or small contactor. Possibly with a solenoid valve as well to ensure positive shut-off if lamp fails. Try them, IME talking to the equipment suppliers is more useful that trying to find specialist services.

Worth getting it tested e.g. Adey or Fernox tests. Your HP installer/servicer should be able to do this. Possibly you would be better to fill the primary system with the softened water, provided the pH is not too low. Vaillant specify quite a narrow range, and definitely on the alkaline side of neutral "If the value is below 8.2 or above 10.0, clean the installation and treat the heating water.".

They certainly can, it's built into the smart meters they are so keen for us to have. Pumped storage. Air under pressure in underground caverns/salt mines/depleted oil fields. They have even tried falling weights in disused mine shafts and trains on inclined planes, but the value of the gravitational constant g in <m*g*h> is so small you need truly massive weights.

I think your original post sums it up exactly! However there are some tests you could still do to help diagnose the problem. This will save some electrician time on site as the tests are a bit time-consuming: Identify which valve is which. Check which valve moves under what circumstances. As upthread, the manual lever will go floppy when the valve is actuated. You cannot normally hear the valve opening but when the power is removed it whizzes shut with a very distinctive sound (which can be transmitted down the pipework over long distances, I can hear a valve in the loft shutting from the plant room). In heating mode does the weather compensation work i.e. does the pipe to the heating circuit get hotter as the weather gets colder? This is the important thing to verify as it will affect the running costs. In HW mode is the flow to the cylinder properly hot (hotter than in heating mode) and does the heating pipe also get hot? If so it is wasting energy.

If it is rock hard I would use a chemical cleaner e.g. citric acid based descaler that you leave in for 3 days while the system is running, then flush and neutralise. Better chance of getting it clean than just short term mechanical flushing even with a cleaning agent.

Clark brand jet pump from Machine Mart then. With our whole-house RW supply I have had several failures with Stuart Turner and would buy a DAB next time.

Does it just have an integral web server which you can see via your wifi, or does the signal also go through the Shelley servers as well? Am trying to minimise my use of such things though of course have to use the Vaillant servers for their app. Have not had any big problems with this but many ppl report significant outages and incompatibilities. How is yr install going @JamesPa?

AIUI the regen flow to waste might be able to withstand some back pressure. There is a washing machine waste standpipe fitting which is designed as a clamp-on tee connection to an existing 50mm kitchen waste, and incorporates a non-return valve. That might work for the regen waste. Otherwise used a U-bend trap or take it to a trapped drain then there will be no smell. The overflow by the sound of it will not tolerate any back pressure so should go out through the wall to a safe but visible overflow location e.g. above a porous surface or a surface water drain. IME the "Hotun" combined tundish and waterless trap is NBG, it requires quite some flow to open the valve (even though the spring is so light it does not shut the valve reliably) and overflows onto the floor at only slightly more flow. Hep2O type of waterless bladder trap not much better, a lot of back pressure is required to open the bladder, to the extent it backs up to my UVC tundish.

You are not allowed to do this as the spring water could conceivably contaminate the mains supply. Yr second idea is better, there are rainwater systems cos that do proprietary versions of that kind of thing e.g. this.

Too right. I usually put a single drop of 3-in-1 oil on the threads, it means more of the torque you apply gets transformed into axial force on the nut/olive/pipe interface which is the bit that matters.

I have looked into the requirements for this a bit as we have a rainwater harvesting system. I would not let water with known e. coli contamination enter the house. We have UV as a belt-and-braces thing even though (i) there is not routinely any bacterial contamination and (ii) we have a separate mains drinking water supply to the kitchen and wash basins. However in a case like yours IIRC you would be required to have not one but two UV sterilisers with lamp fail detection and automatic changeover on the first failure and shut-off on the second. The water regs are very stringent for a reason and I don't think you would get away with anything less than an air break between the systems as well. If you keep the mains supply you will have to pay standing charges anyway. As @JohnMo says you also need filters upstream of the UV to prevent bacteria hiding behind silt particles. Coupled with UV lamp replacements I would think the consumables and standing charges would make it an uneconomic proposition.

I have been studying some music on youtube recently and getting increasingly annoyed by the masses of intrusive ads selling small electric heaters that claim to heat your house for fraction of the usual cost. Mostly they have some "magic" heating element based on ceramics or precious metals etc. We all know they are a physical impossibility but presumably they would not exist if ppl did not buy them. The level of technical education of the general public is truly shocking and some of the heating industry not a lot better. So I fear @JamesPa is correct, and cannot see any justification for using public money to pursue the concept of hybrid systems in the UK environment. The scope for fiddling the results is so vast and the potential returns so poor. While writing, I need a 13A adaptor linked to my wifi so I can switch off my Honeywell Evohome zone controller remotely. Is this thing from Shelley any good or do ppl recommend sthg else? The controller has an annoying bug that after a power cut it does not come back on in the same state it went off. But I can use this to my advantage. If it is set to Away, then when I am planning to return if I turn it off remotely for 3 hours the standby battery will go flat and it will the come back in Normal mode so re-enabling the heating.

35W/sq m should be quite achievable for a new build. Difficult to say any more without detailed knowledge of type of building & its construction. You might think about installing the 12kW first, configured for adding the 7kW later, but wait until you build the extension. Depending on the usage pattern and as-built thermal performance it might turn out you do not need it.

I would imagine that the behaviour in the time domain could reasonably be modelled by RC delay circuits. I can't think what the analogue for inductance might be so probably not any second order differential equations. But still room for oscillatory behaviour depending what is in the control systems. I don't think you would have much joy trying to prise that out of the mfrs. Presumably they have some theoretical models of house behavious to refine the control systems against. You must be all agog @JamesPa. Look forward to reading the write-up, are you going to start a thread on this? PM me on the side if I can help. Was new to me when loft conversion ppl suggested it for my bathroom ceiling. No idea if it works, a better suggestion would have been to line the window wall with insulated plasterboard, there was just an inch to play with which would have made a significant difference. Main objection is the blasted stuff is impossible to fix through bc it binds the drill bit.

I took it to mean the Octopus Cosy cheap period 2200 - 2359. Like you and me the OP is on Cosy.

That is only 7 degrees change for 12 deg change in OAT so a slope of 0.6, maybe you should up it a bit. The time constants involved in UFH are so long that you cannot realistically expect an immediate response after an off period. If your HP size was well matched to the heat loss then it would need to run nearly the entire time in cold weather. That seems very cold for Northamption even in the recent cold snap. Either your WC settings are still wrong or you should not be trying to run the HP intermittently or it is simply not big enough. What does your installer's Heat Loss Calculation say and how does yr HP capacity compare with this?

My first thought. But it might be better to increase the slope of the WC (Water Law) instead of adding an offset - if that's what the +5 deg setting is, I am not too familiar with Samsung terminology. If in doubt RTM.

No, it was physically impossible to do short of a substantial amount of building work. Hence the quest for a workaround. The new tank is a heat store so I can heat with cheap rate electricity during peak hours. As upthread I would suggest you pursue the HX option, hence my interest in the price they quote. I don't think a secondary destratification pump will be enough on its own. Well depending on the cost of the HX I would think that might work out cheaper in the long run. Need to do a proper cost-benefit analysis. Octopus Cosy is good bc of the afternoon cheap period just before the evening peak so better than E7 for a HP. Using your own PV is now suboptimal when you can sell everything you generate to Octopus at 15p and substitute it with cheap rate bought from them at 12p or Eon at 6.7 or Tomato at 5.

For example by default Vaillant HPs modulate the compressor, fan and pump to maintain a dT of 5C. This requires a flow rate of 170 l/hr per kW of output. It is possible to define the building circulation rate separately for both HW and CH but I don't know of anyone who has done this or why they would. I recommend reading the detailed analysis by Michael Podesta of how their weather compensation works. It is complicated, and spread over this and the three succeeding articles. Not helped by some errors in the Vaillant manuals in particular the basic graph illustrating how WC works(!).

No, unless it is completely choked just clean it out, reassemble and re-open the service valves. Do the same all over again after a day, a week, a month depending on the rate it collects grot until it eventually slows down. This doesn't sound like a blocked filter though. You may have an entirely different problem, like the HW diverter valve which seem very prone to fail.