Beelbeebub

Any idea why the Willis heater seems to be very common over there but almost never on this side of the sea? In GB an immersion in tank seems to be the norm for unvented electric setups. Is there some reason beyond "that's just how we do it"? Like some sort of odd regulation that banned electric heaters in tanks or something?

Pretty sure thermal stores are exempt from needing legionella cycles as they don't store the potable water at high temps, it's instantaneously heated on it's way through the coil

Am looking at a solar & battery setup. The panels bit is easy - as many as we can fit as they are cheap now. The harder part is the inverter and battery. We've had various quotes from different installers all recommending different brands! So far Tesla PW3 Sigenergy Sigenstor GivEnergy Solax Puredrive/Duracell TBH The powerwall has got a good rep but I can't bring myself to go for it given <gestures out of window> The Sigenstor looks good on paper (and physically) but is fairly new and towards the pricey end I've heard conflicting stuff about Givenergy and Solax but like the fact Givenergy is UK based I know nothing about Puredrive apart from they are apparently now the Duracell units and are also UK based Has anyone got any experience with any? Things like reliability, customer support etc

Slightly different environment but some trials have shown an increase in the agri output after the solar has gone up. Maybe shade helps with reducing water loss and keeps the temperatures in a more optimal range.

Can I check what the issue is with fitting the specified rads? Is it aesthetic? Cost? Space? I've had to replace the failed UFH in some of my upstairs rooms with rads, 600x1400 (or maybe 1600, can't remember) with a flow temp sub 40c (it runs same flow temp as UFH). They work really well, despite feeling only slightly warm and you can feel the heat coming off them and the room warms up nice and quick.

Am I right in thinking you are effectively having no heating in thr upstairs and relying on heat transferring from the ground floor and not having particularly warm bedrooms? I think the issue be the MCS rules state you have to have sufficient heating in each room to meet that rooms heat loss and they also set a temp for bedrooms at the design temps (migbt be 21c, can't remember) Those rads aren't that expensive (assume I assume k22's). Fit them then remove and cap off afterwards. Alternatively spec a higher flow temp to get smaller rads, then run at the lower flow temp (just make sure your UFH is spec'd to run at the lower flow temps, which it should be)

I did see a YT vid where the guy had fitted a small home battery system that was large enough to power his HP through the high periods (so maybe 5-10kwh) so that all his HP (plus a big chunk of domestic) was at the half price octopus cosy rate. That means your cop only needs to be about 2 to be as cheap as gas. Obvs need to invest in the home battery system.

9 is next to 0 so 0.3kw?

https://github.com/glynhudson/samsung-modbus-mim-b19n Any help?

Reasonable point, but does the HG thermal store provide similar hot water volumes? The HG mini stores that would replace a boiler are only 80l and the delivered hot water volume is less than that as the store can't deliver any useful heat once it gets below 40/45C I know they say you can run the HP at the same time to extend the volume but I don't think that would work in winter with defrost etc. The point abiut the bus grant is very valid though, which is why an adjustment so DHW can be via other means might be a good idea. This would make hybrid systems (which I guess this would be) and a2a systems eligible. Whilst installing a full HP system with a SCoP of 5.0 in every house would be the ideal, it's unrealistic. Heating is the majority of housing thermal demand. Electrifying that as much as possible would be a huge win and, as has been pointed out, a lot of boiler installs are "distress" installs where there isn't time for all the usual gubbins that goes with a "proper" HP install.

The HP would be for heat, the battery for DHW (in this thought experiment) So your HP would run pretty much as is on the cosy type tariff. The battery would run, pretty much as a cylinder would on the cosy tariff. The major difference would be a HP charging a cylinder draws less than a battery charging (for an equiv amount of hot water delivered) so there is a downside there. But the battery capacity could also be used to reduce the demand on normal and peak electricity. Remember this stems from the idea of speeding up and simplifying the install by not having to fit a cylinder. If you already have an appropriate cylinder then the disruption is zero anyway. But if your cylinder and piping isn't appropriate or, worse, you don't have a cylinder at all and just have a combi (say your combi breaks down and you just need a replacement ASAP). Then we get into the question of "how to replace a combi with a HP quickly and cheaply" the ultimate efficency can come later. Fitting some batteries (prob nearthe HP) and a high power boiler should be quicker and less disruptive than fitting a cylinder. Yes a 10kw inverter isn't cheap, but not super expensive either, under £1k is possible. Even £500. Fogstar sell a 15kwh pack for £2.5kish. With a £500 inverter and a £300 boiler you are talking £3.5k for the kit to replace a combi with very little disruption inside. Add another 4k for a 6kw HP and some fancy controls to utilise the existing rads as well as possible and we have £7.5k of hardware to swap out a combi boiler without doing any work inside bar replacing the existing boiler box with an electric boiler and Adia hub. The cables and pipes exit via the flue hole to the batteries and HP outside. The only other inside work might be a chunkier cable to the "boiler" from the fuse box.

The 2h window is just before midnight and then there is a 4h window just before "getup" time so most households would have 6h to charge. But regarding power draw, the situation would be no different from an unvented cylinder. That can only charge at a specific rate, usually no more than 6kw (2 elements). Often only 3kw. Except every bit of energy you put in can be transformed into whatever temp water you wish. Plus the standing losses are near zero, so even if you charge up your battery with 10kwh at 4pm, there will still be 10kwh to use at 10pm. Cylinder losses are typically 60w so about 1/3kwh in that same time. You also have the possibility of variable charging rates. So your system can monitor your overall draw and modulate it's charging rate to stay under your set limit. So if you put a kettle on, or the dishwasher kicks in, your battery can reduce it's draw.

Yes they do. I reread my post and the units were correct (aside from capitalisation - which is an artifact of using a touch keyboard making capitalisation time consuming)

Isn't the point that a UVC stays relatively well stratified when discharging so if you have 150l of 65C water you get most of that at 65C before the last little bit drops off due to mixing? This was one of the arguments against thermal stores for HPs. Yes, a good chunk of batteries only output 0.5C ie a 10kwh battery only puts out 5kw, which would mean having to install (and pay for) a larger capacity. This does make the economics a bit worse. But a larger battery of 20-30kwh would give enough storage to run a HP through the peak periods meaning it would be plausible to install a 20kwh battery, 12kw HP and 10kw instant boilers. That may be alot quicker to install and every day is £750 in labour minimum. 3 days saved coukd be £2k plus saved on the install which is a good chunk of the materials difference

The sunamp is an option though that would have be installed inside and they are super heavy. Cost wise they are about half way between a cylinder and a battery. The batteries can be installed outside or anywhere really and can provide more functions than any pure thermal storage solution eg uninterrupted power supply, time shifting all electrical demand, solar input. As has been mentioned it could also get around the "cold leg" issue for large/awkward properties. It also offers the possibility of easy increace in hot water storage by simply adding another battery The key thing would be to get the BUS grant to apply in cases where the HP isn't the sole hot water source and/or to reduce the price of batteries.

One of the big issues with HPs is hot water. Specifically the tank needed as they cannot provide instantaneous hot water so require a cylinder. If there isn't an existing cylinder, fitting one requires extra cost (around 1k for a 150l cylinder plus labour ), space (at least 150l!), disruption and time. Say £1500 in materials plus labour. I had a look at battery storage as an alternative though experiment. (stop me if I've corked up the maths) A 150l cylinder stores about 10kwh of energy (4.2kj x {65-10} x 150 /3600) So a 10kwh battery would have roughly the same DHW capacity. A 10kwh battery is around £2500 (a fox ess home battery) A 13kw stiebel eltron instantaneous water heater is around £400. So say £3k for a battery DHW solution equivilent to a 150l cylinder. A 300l equivilent woukd cost about £5,500 (vs maybe £1,500) So the batteries cost more.... But you could combine it with a small inverter it could provide home electricity storage to help lower bills by time shifting cheap electricity so your HP (and house) could use more cheap rate electricity from a tariff like Octopus Cosy. Given the cheap HP rates are about half normal ie about 2x gas prices it should make being cheaper than gas very easy whilst making the install much easier and quicker We just need batteries to come down a tiny bit more.

Yes, though this would very much depend on the UFH system itself. If it was a close spaced spiral in a slab, it would probably be fine. But if it was the up/down pattern in a thin overlay system it woukd be a problem. I do wonder how quick HPs can ramp temps up and down. If the temp ramped up to rad target and the UFH loops shut down, then the temp ramps down and the ufh opens up whilst the rads remain open all the time. That would be a possible solution.

This would be interesting. I can see a few possibilities. You could just rely on the standard mixer and pump setup and accept the loss of efficency. The actuators would fit on the standard ufh manifold actuators so it could flow modulate each loop as if it were a radiator. They could junk the pump and mixer and run directly and either modulate the flow to each loop so the power is appropriate - conceptually there isn't any difference between a UFH loop and a big, high mass radiator. The only caveat would be if the flow temp for radiators is too high to safely use in the UFH loop. The other option would be to run the ufh as a separate zone from the rads, ie the UFH is open loop at 35C for 30 mins (potentially the rads could also run at that) , then you shut that off and run the rads at 45C for 30 mins and repeat.

They seem to have given a series of recent (last few weeks) interviews on YT and have snagged some more funding.

With an outside temp of 3 you have a 17C temp difference to inside. You said your design temp was - 3.4C so design temp diff wouod be 24C So at 3C your power should be roughly 17/24 x11 which is close to 8kw. I'll assume your UFH isnt under powered, so are your rads too small? Do you need to up your flow temps a bit? What are your bills like? (as an aside, how is your UFH plumbed in? Is it direct or does it mix down to a lower temp? Can you get a reading of the floor temperature?)

How are the other houses getting on? So you have any monitoring hardware eg heat meter, elec consumption for HP only? Is it possible your HP isn't going flat out? I know some have "eco" modes that restrict output to the most efficient range at the cost of absolute power output. If your HP is set in that regime you might be getting less than 11kw

You also mention the performance is worse on windy days This would point to a potential air tightness issue. If your airtightness is less than designed/estimated then your heat demand will be higher due to more airchanges per hour than expected. Do you have any drafts in windy weather?ie around windows or light fittings?

Feels a bit steep.

Supposedly British designed and built (I assume with a far eastern compressor). https://ebac.com/heatpumps At least they come in grey and black which will probably look better, or at least less obvious. Interesting slant to the top of the casing which presumably helps shed water in our climate. The only other interesting thing is thry claim a different defrost strategy that reduces the energy lost. It seems (reading between the lines) that at temperatures above 3C but below the critical temp when frost starts to form they simoky don't bother with heating the coil using the compressor in reverse. They (I assume) just run the fan and rely on the fact the frost will melt away naturally in the above freezing air. They also mention that when they do use the reverse cycle they do so at the minimum temperature to melt the ice to water but not to vapourise it. Although the clouds of steam some brands give off during defrost look impressive I don't think they are heating rhe cool up very much, in those conditions it doesn't take very warm water to produce visible steam. But is suppose every little helps. The only downside to this strategy (which tbh I assumed every manufacturer did anyway) is it must be slower than using active heating - so your proportion of heating time to defrost time will be worse and your effective power output lowered.

As you say, there are loads of options. But the point is they all require work (and thus time and cost) to fit. By using the almost universally fitted TRV interface, the time to fit becomes negligible. We aren't after perfect, linear flow control. Just flow control that is "good enough"