Beelbeebub

If you aren't bothered about claiming the grant then you could install a muktisplit A2A heatpump This would give you cooling in the summer and leave the gas boiler for water and backup heating in winter. (summer water could be immersion heater from PV?) You haven't mentioned if you have a gas hob - factor that cost in if you want to get rid of gas altogether.

JohnMo's solution sounds nice and simple. If you do decide to go for mechanical ventilation, I have used the ventaxia sentinel kentic series a few times now and been happy with the price/performance. Build quality seems pretty good and (hopefully) spares & support should be OK given they are a UK company. 🤞 I use the radial 75mm smoothbore ducting with manifolds for ease of installation and reduced noise between rooms. For some properties I have put a supply and extract in opposite corners of the room to get around the issue of undercutting doors etc.

That's good, thought they ought to include that in the main table figures rather than as an extra. That way they could include the cop. I have seen various ways of showing the performance of HPs but the best (IMHO) is to have a outside temp / flow temp table with each "cell" giving power, input power and cop. It then had 3 tables giving those figures at the maximum, most efficient and lowest outputs. There was some shading on the cells where output was being affected by defrost. That would seem to give all the info needed.

You'd be surprised. If the leak was in thr 1st floor or loft, I would expect you to see something. But if it's the ground floor, depending on location and construction you might not. A property had a persistent leak. Half a bar a week. No sign of water. Clue cam in autumn when kitchen windows had bad condensation. Check with humidity monitors showed high humidity in kitchen. Eventually found a failed joint leaking to under the kitchen floor. The construction was a oncrete slab, with 2" timber battens, then floorboards, a 5mm ply layer and then lino. When we lifted the floor there was about an inch of water. If you have a suspended floor or even a slab, water could be leaking and you not know. Get hold of a couple of humidity meter (these are good https://amzn.eu/d/bMbXgA2) Stick them in varouhs rooms for a few days and see if you can find one that has higher humidity than the others. That may give you a clue.

I'm not sure "all dc" would include low voltage stuff like door bells. I think (and am happy to be corrected) that under 50v DC is low voltage and different regs apply - so single insulated is fine. This would prob apply to the single panel type "camping" systems people stick on vans and the like. But for the high voltage DC you get with large arrays a different set of regs apply and they say DC must be double insulated. Hence using special solar cable rather than regular 4 or 6mm 2 core. I imagine you would need similar if you had another high voltage DC application eg some sort of machine tool or something.

That's a serious volume of water being lost. If you don't know where it's going (eg a leaky prv is dumping it down the tundish) I'd be really concerned about damage to the fabric of the building. Something somewhere is going to be soaked and that is never a good thing.

The cables have a DC rating because you can stick DC down any conductor. But the UK regs say that cables that carry DC must meet certain requirements around insulation etc. Specifically the conductors need to be double insulated whilst they can be single insulated for AC. Here is an armoured AC cable. Notice you have: Copper conductors Layer of insulation (the coloured bit) Packing material (beige bit) Armour Outer sheath. Here is an armoured DC cable Copper conductors Layer of insulation (white) Layer of insulation (the red/white bit) Packing material (beige bit) Armour Outer sheath. Notice the two layers of insulation around each conductor You could use the top cable, it would physically work, in the same way you could just bury an extension flex in your garden to power your garage. But it wouldn't meet the regulations. For that you need the specialist cable.

Yes, that's fine. It"s what my set up uses. If my panels were on the garage and my inverter in the house, then I woikd need the specialist DC SWA to carry the DC between garage and inverter. My understanding is the issue with carrying DC along standard SWA, it that DC needs double insulated conductors and standard SWA is single insulated.

https://www.doncastercables.com/cables/20/89/PV-Ultra--/PV-Ultra-----Double-Insulated-Multicore-DC-Cable/ The do 4 core so you can have 2 strings if required. Regarding upgrades it depends a bit on which panels you're putting in. Current "mid range" panels are in the 450w range with some premium panels going over 500w, a few years go the 450w panels were premium and most were 400w or lower In 10 years time the cheapest panels might be 550w and the premium ones 650w So if you reolwce/upgrade your current will go up even if your array stays nominally the same. Also we don't know what planning will do in the future, it may be they change the permitted development allowance and you could add more panels. Be nice if the cables were already sized for that, especially if relaying them would be a faff - if the route would be a doddle to add an extra cable don't worry too much. But if it"s a sod, just do it once

I think it's that the regs require the conductors to be double insulated within the armour. Ie you take double insulated conductors, then pack them into an armoured sheath, then wrap that in insulation (which is mainly to protect the armour) Most SWA is single insulated inside the armour ie each cable is single insulated, Ie you take single insulated conductors (like you woikd find in a twin and earth) then wrap those in the armour. I think it's because DC shorts between conductors are much worse than AC for the same voltage and current. So the individual conductors need that extra level of protection.

Chunkier DC cables gives you headroom should you upgrade to more/better panels in the future. The resistance of 6mm cables, about 2/3 that of 4mm2 (and 1/4 of the 1.5mm cable) is lower which will reduce your i2r losses (not as much as lowering your current but there isn't much you can do about that) There are DC specific armoured cables now (the common AC ones are not suitible for DC) which makes doing the runs much neater and easier.

So £60 each or about £200 per kw? Roughly halved in price and doubled in output. The same money now buys you 2x the output vs 2 years ago, in the same footprint! Wow!

Sorry, I meant the old panels. As you say we are nearly at £100/kw before vat now. I was wondering what the ratio was when you put the orginal panels in.

Given Wikipedia is one of the training data sets, any "AI" answer will almost certainly be less trustworthy. "AI" is, at it's heart, very fancy auto complete. You give it an input and it creates a statistically likely response. You ask for a picture of a dog on a unicycle in the style of Rembrant and it spits out it's best guess but it doesn't actually know what a dog, unicycle or Rembrant are. Similarly, if you ask it a technical question it will reply with an answer that sounds right, has some formulas and technical words in etc. It's.a bit like that game "would I lie to you". Except it just picks the answer based on who sounds right rather than knowing what is right. Sometimes they are the same thing. A large proportion of the time they are not.

Can I ask, how much those panels cost and how old they were? Just trying to get a handle on how much things have moved on in the past few years.

Yes, that's the point. The minimum output often quoted by manufacturers is often achieved at the coldest temps when it is irrelevant. The relevant figure is minimum at the higher outdoor and that is a lot higher for the reasons you mention. I can't remember which brand it was (it might have been a mitsubishi or maybe a york) that I looked at but the minimum "spring" output was something like 5kw whilst the depths of winter max output was 10kw. So the effective modulation was 2:1.even though it could output 12kw max (in spring) and as little as 3kw in winter. (4:1)

One of the things about heatpump modulation is that, unlike boiler modulation, it's very dependent on air and flow temperature A HP might have a max of 12kw at 7C outside air and 35C flow. And a minimum output of 3kw at - 5C outside and 65C inside. But that doesn't really mean it has a 4:1 modulation We really need the opposite, the minimum at 7C/35C (or better yet 15C/30C) and the maximum at - 5C/65C Often that figure is closer to 2:1 Which is why sizing for just being able to do the job on the coldest days is prob best as you will. Have many more days where you are bumping into to lower modulation limit.

This is exactly the point. The exact performance of any unit will vary by location even for nominally identical properties. Each manufacturer will optimise for slightly different conditions. Model Y from brand X might be slightly better paper than Model A from Brand B, but in the exact conditions (even down to how thr occupier uses it) of a given install the latter might perform slightly better I think chasing the last few % of efficency by looking at the scant data given by most manufacturers is a bit of a losing battle.

Shouldn't the sizing include defrost and DHW as well though? If you heat demand on your coldest day is 7kw continuous, because you will spend some time defrosting (say 15% of the time) you need to up you actual output, then you'll be 2 or 3 hours heating hot water. So up again. So your 7kw house might need a 9kw or 10kw at -5C hear pump. But it will only need that for a day or two a year. The rest of the time it'll be running at maybe 75% "full throttle" until you get to late spring or early autumn when your lower modulation limit becomes more important. The choice of HP will constrained by other factors like local availability and expertise, physical size, price, warranty, aesthetics etc.

The rating of a Heatpumps is a bit subjective anyway. Indint think you can generalise. Manufacturers make a series of differently sized machines, but the actual "rating" varies from manufacturer to manufacturer and market to market (due to climate variations) So a 6.5kw machine in the UK might only be 5kw in Sweden and 8kw in southern France. Some manufacturers quote the max power at 7C outside and others at -5C. So the way manufacturer A's range falls might make the smaller units more efficent, whilst manufacturer B's range has the larger units more efficent. As a rule of thumb the bigger the evaporator is, in relation to the load, the more efficent a HP can be and the physics of the rotary, scroll and swing compressors makes efficencies drop off markedly in low load regions.

I think the evaporator coil size to power output makes a difference too. You quite often see the smaller of the two outputs using the same "frame" size is more efficient.

There is a whole shutdown sequence including shutting down the bms etc etc. My point being it's fairly easy as all the isolators (AC and DC) switches and buttons are in one place. If there is a loft isolator, before it can be turned the operator has to go down stairs do the various operations before coming back up. There is, unless the isolator is locked on, a fair chance someone will just turn the knob possibly under full load. Much less likely if the isolation requires opening a box (with a tool) and then using another tool to disconnect the MC4s

The end panels of each string will generally (but not always) come with factory MC4 connectors. The "tail" is not normally very long, depending on your positioning and roof construction you might have to join on to those outside on the roof. If you were desperate to have a "disconnection" point on the loft, might the solution be to have a fairly large enclosure with the DC cables coming in from the roof (having connected with the tails on the roof via MC4), through a gland and then terminate with MC4 connectors. Those then fit to mating connectors on thr DC cables running through the house (either in ducts or as wire armoured) to the inverter. That enclosure could then be closed or even locked and a warning label stuck on it. That would seem to be allowed by the table I posted. That would allow for the through house run to be isolated and use crimped, approved and maintainance free connections all around. Assuming your inverter has the correct DC isolator built in. My inverter has instructions to turn the inverter off (shutdown) before using the isolator ie the isolator and connectors should never be operated under load. If there is no current flowing there won't be an arc.

Yes, you are correct - normal SWA won't do. You do need to be able to isolate the DC supply from the inverter but you *don't* need a separate DC isolator *if* your inverter has a suitible one built in (which most modern ones do) (The Institution of Engineering and Technology - Code of Practice for Grid-connected Solar Photovoltaic Systems) Statistically speaking, DC isolators have been the biggest cause of fires. And as such the latest guidence says to avoid them (as long as you have a built in one). https://www.thefpa.co.uk/advice-and-guidance/free-documents?q=RC62 Recommendations for fire safety with PV panel installations

I was sold on the need to shift as much from fossil fuels to renewables as possible because of the climate arguments but the real clincher was the declining production. I had thought that it was a straight pick between 2 options: A) continue a fossil fuel economy (and co2 emissions) dependant on UK sourced fuels B) transition away from fossil fuels (and lower co2) towards electricity that we get from wind and solar (which are also UK sourced) And you can argue back and forth about the choice between A and B depending on your views on CO2, the costs, the effect on the economy. But actually because of declining production, option A doesn't really exist Option A) is actually "to continue a fossil fuel economy (and co2 emissions) dependant on foreign sourced fuels" - in a Union Jack coat. And B) is your only option if you really care about the UK's energy security.