Alan Ambrose

@billt >>> My system is off grid and AC coupled using SMA inverters. Is that totally off grid? You have generator back-up or something similar?

FSCables has been recommended on 't 'ub for Cat6. Also, I've used them for multicore e.g. for LED strips.

I wouldn’t underestimate the variable quality of these pipes (like everything else). Would you want to be making them for a retail price of £2.50? How would you bring the cost down? Reduce the thickness and quality of the bit you can’t see i.e. the rubber pipe? Make the braid out of shiny metal rather than stainless? Who fitted the ones you have and where did they come from? I would buy the best quality branded ones I could find, probably replace all you have, and see how well those work.

Some Stanford Prof, I forget his name, predicts that we'll eventually get massive over-capacity in renewables and thus cheaper power prices eventually. Don't heckle me, it's not my idea. However, if a bit of that is true then the peakers will be used less and less over time and therefore gas will eventually become less of an influence on electricity prices.

In this recent video, there's a couple of comments that I'm not sure I quite get. Here's a link to the video: Why Are The DNOs Limiting Your EXPORT And Even Your INVERTER SIZE? https://youtu.be/Bvpl9pvg8zk?si=4rLhJ-me57Pcwabu Here are the two comments (I've highlighted the relevant bits that were raising questions for me in bold): >>> One detail - only grid tie need approval. If your system isn't capable of pushing power into the grid (that's not capable as opposed to "set to 0") then you sidestep it at the cost of no export revenue. Setting up a big non grid tie inverter and putting the house on that with the grid as an input (generator basically) lets you side step all the mess in the difficult cases. It's not usually the best option but if you are getting 3.6kW and especially if you are also refused G100 with a bigger inverter it's definitely worth doing the maths on houses where you want bigger batteries and inverters, and remember it also lets you avoid the MCS costs too. I am guessing plug in solar is going to make it even more of a circus especially if they got 250,000 G98s submitted the month it goes legal 😎 Our setup actually has some grid tie with grid tie batteries and solar, and some non grid tie with other batteries/solar that runs the heatpumps and some other bits. It was the only way to make this big old building work within the allowed G99. <<< >>> The inverter size limitation is to do with failure cases with export limitation. If they calculate that the export limit fails, and the resultant voltage would exceed legal upper limits at your house, and your inverter voltage shutdown protections also fails, then they impose a choice: 1. Stipulate Inverter size limits, 2. Provide a quote to the solar installer for reinforce the DNO’s network so that it can accept the higher inverter size (often many thousands of pounds). At my house, I have an 8kw inverter with a 5kw export limit. When exporting 5kw, the voltage is about 247V. So there is some headroom between the export limit and the upper legal voltage. There are two a get out clauses though: 1. Install a 3.6kW inverter, but with 7kW Maximum Power Point Trackers. That enables you to hookup 7kw of solar, and at maximum power: 3.4kw can be fed to a dc coupled battery, even though the AC output is limited to 3.6kW. Sunsynk offers such an inverter. 2. Don’t connect your inverter to the grid. DNO’s only have jurisdiction over connections to their network. They have no jurisdiction over off grid systems. You could have an 8kw+ inverter supplying your house off grid. Then you can choose whether your house is connected to the grid, or your inverter, using a changeover switch. There’s no opportunity for export, or charge up with cheap overnight electricity though. <<< The reason I'm asking is that I'm planning on having a lot of panels and inverter power and self consuming as much as possible. I'm planning on over capacity so that I can make the shoulder seasons (i.e. spring & autumn) mostly self-consumption too. I don't really care about the export - I'm guessing the rates will continue to fall until it's a waste of time.

@Roger440 re: They could have completely de-linked it. You have a scheme for that? My understanding is that it's the gas-driven 'peakers' that provide power when everyone else is at max output (or offline) - hence it revolves around the price of gas.

One of the effects of the current mechanism BTW is that conventional generators including renewables get windfall profits every time the gas price spikes. Even with 'the levy'. I dare say they like that. As long as the gas peakers are needed then the marginal price will largely be set by gas. Peaking power plant - Wikipedia >>> New plans include long‑term fixed‑price contracts for renewables, protecting families when gas prices spike The financial markets are very quick to create new futures / forwards / options / swaps / CFDs etc if they think there's any demand - they don't need any government help to do that. All-in-all the current industry players are not unhappy with the current situation.

I've been looking at this issue and talking to my BC guy. His opinion is: Fire stopping cavity barriers are not enforceable under building regulations for individual domestic dwellings. Only enforceable in buildings with separate compartment ie flats or semi’s. Although I do think the fire stopping strip is a good idea it is your choice in this circumstance. I suggested this stainless metal strip (we already have 25mm ply around the window apertures), which would work well for us: https://www.roofingsuperstore.co.uk/product/terne-coated-stainless-steel-fixing-strip-50mm-x-20m-roll.html And his response was: I think metal is a good option although not seen it used, timber or fire socks (fibreglass) are nearly always used.

I’ve a bunch of these, most of which have been there for 30 years. No problems except for one within one of those shower-hose-like kitchen taps. I wonder whether some are much better quality than others? Real stainless shouldn’t rust much with standard water. Agree that relying on the rubber hose isn’t the smartest.

Thanks, that's interesting. I also just found that 21 degrees offer the open/close sensors too, but no more detail than that right now.

Yeah, I'm not convinced. I've spent not too much of my life (5 man days maybe) putting cables in routes that didn't exist before - but enough to know that it's an absolute major PITA. Europe does the duct thing often in concrete. And I've run quite a bit of stuff in conduit in my Larsen-truss style roof (actually made with Posi Joists but you get the picture). Some of those cables we will be able to replace if we need to - some of the longer runs probably won't. Too much friction. I think that either 50mm trays on their side or the equivalent with 50mm battens in our 50mm service cavity should work fine - as @-rick- suggests. If there's strategic access where the 'trays' do 90 degree corners, so much the better. As @ProDave points out - put some kind of socket / switch / sensor point (PIR or temperature/humidity maybe) at the positions you want and you can force 'safe zone' lines anywhere you like. At least you should be able to do 95% of the run without resorting to cutting plasterboard. For internal walls, maybe there's a 50mm zone in the middle of the wall somehow - that might make a good acoustic break too. Our geometry is very simple and rectangular so maybe that makes it a much easier prospect for us.

We used 3x 100 flexi ducts - one for water, one for 230V, one for data / other stuff. Most heads off to the front of the plot where all the services come in, but a few will go elsewhere. We'll see how well this works later 😉.

@dpmiller Ah interesting, these ones (below)? Did you consider the ceiling roses too? Pity there's not some kind of all encompassing standard for 230V / LED / USB C.

I found another one: BRIGi Foam 1.2 MPa @ 2% / 0.040 W/mK Comes in a lot of sizes. p.s. I figure my triple glazed double doors @ 180Kg, 2m wide exert ~0.01MPa

>>> I don't really want to have to plan where every device cable goes ... for the next 50 years...yeah, exactly. I figure I have a good chance of using a fish tape or electricians rods to run a new cable assuming the runs are fairly straight and there's access at any corners. Maybe it helps that our room layout is fairly simple & rectangular.

In our present place, built about 30 years ago - in the sitting room we have a bunch of small round pin sockets for wall lights - they're all controlled by a single switch. This kind of thing below. Is there a more modern version? Anyone doing this?

Why? To give a fighting chance of running a new cable or replacing an old one. The current model when we hide the cables and assume they will be OK for the life of the building seems to me a bit flawed 😉.

Reporting back: Rationel has these as an option, but not, it seems for tilt-and-turn e.g.

p.s. maybe this is the explanation, but does it not then leave the building industry up the creek? Inside Housing - News - UK certification body for construction products has accreditation suspended

In my search for longer lasting battens, I called the guys above, who say those are no longer available. I also called Kedel re their plastic battens: 50 x 25 Roofing Battens, Recycled Plastic Battens ... to ask whether there's any BS5534 adherence/ certification. They'll get back to me. In the process, I looked at the BBA site. Oddly, there's this weird note (below). WTF does that mean, and who are UKAS - I mistakenly thought that BBA were the authority. To add a little spice I see on the 'myBBA' search that only Marley has a current BBA cert for their battens. ?

OK lovely, thanks for all the feedback - looks like that scheme will work fine then. Like @JohnMo, I'm thinking of shoulder months / winter performance and also as @Nickfromwales mentioned UPS-style backup. In the Sigenergy line-up this seems to require the 'Gateway HomeMax' and apparently will take a connection to a max of 3 inverters. It looks like I need to do some wading through manuals. FYI I discovered these DC contactors & arc protectors recently: Fire Safety Devices ArcBox - Solar Connector Enclosure

I'm particularly looking at the Sigenergy SigenStor Energy Controller 6.0 SP 6.0kW 1-Phase... But a general question - if you're planning more panels than the inverter will handle for max DC voltage reasons - can you simply parallel them? I imagine the software has to be smart enough to do that. For instance, with strings of 11 panels each giving, say, 380 VDC max / 5.4 kWp and an inverter which will accept 550 VDC max, would I be able to run several strings with several inverters 'in parallel'?

>>> Do you mean a whole house ducted system with a main unit in the loft Yeah, that one. I'm leaning towards 180mm foam ducts atm, which sounds like it would work.

@ProDave So, I just need to put a dummy 'point, accessory or switchgear' to establish a zone / cable tray anywhere I like? 😄 I'm sure I need some temperature/humidity sensors up at 2.4m 😉

While we've still got the roof open, I would like to put in some ducts for potential ducted AC into the bedrooms. Anyone seen a good duct size calculator? Or just some simple rules of thumb?