jimseng

That PV ultra cable seems to solve many problems. Good tip!

@Nickfromwales PVC trunking? Does that fit with: PVC would be cheaper but it is only a 3m run straight down into the posi joists and then on to the inverter wall.

So according to the latest guidance, don't fit DC isolators as they are a fire risk, except do fit them because the fire brigade like to isolate the PV when tackling a fire. What fun! Having climbed back up the scaff and looked at it again it is a really easy vertical run down from the roof to the plant room posi joists so fitting trunking should be easy.

For the DC and solar side, me. The electrical contractor is doing everything up to the inverter and the load output side. I'm getting my ducks in a row.

This may be a stupid question but can anyone guide me to where I can find these regs?

I was referring to the whole house having a 45mm battened service void behind the plasterboard for all electrics and plumbing. I'm asking what would be the correct method for getting two runs down to the plant room once it exits the loft space. Is it adequate to follow safe zones in the service void down two floors or am I expected to afford extra mechanical protection for the solar cable.

Hello. I am planning on bringing the 2 strings +/- cabling through the roof into my loft space. It is an in roof system and I believe there is room to bring the cables in via two cable entry housings mounted underneath the last panels in the strings. I am planning on using PV cabling with MC4 connections to the last solar panels in the strings, through the roof via the entry housing into a connection box. I think it would be sensible to put the SPDs for the solar in the connection box, two breakers and then on to the ground floor plant room to the inverter. In the loft space the cable run will be in conduit. Does it need to be metal or can I use plastic? My house, which is still in build has a 45mm service void on top of the insulation membrane. Are there any specific rules about running the cabling through that, i.e. further mechanical protection? I am probably going to be running this cable in way before the ac first fix happens.

Great. Thanks. I really wasn't expecting that.

Hello. Solfit recommend Staubli MC4 connectors for their in roof system. I'm going to need to only a small amount of connectors just to install the system and then hopefully not touch it for a long time. Midummer Wholesale have an MC4 crimp tool for £83.00 + vat This is what they say on the web site: "This tool is the official Staubli tool so is designed to make reliable, long-lasting connections. This crimping tool can be used to crimp wires of size 2.5, 4 & 6mm." £83.00 seems reasonable for something that will hopefully end up in a draw after a few days, the £350.00+ price tag I have seen elsewhere seems a lot. Does anybody have an opinion as to whether the Midsummer ones could make 10 or so good connections for a DIY install or should I definitely go for a pricier set and perhaps sell on ebay afterwards? Any recommendations? I don't think pre made cables will work because of glands etc.

I was of the understanding that if one has more than one earth point you have a potential for a path for stray current (e.g. lighting) from one point, through the equipment to another. That's good enough for me. Thanks for all the responses. I'll stop worrying about it, get the electrician to fit a ground rod and get on with it.

This is the last piece of the puzzle for me and the bit I have been obsessing over, perhaps unnecessarily, but obsessing I am. I believe that when the house goes off grid the inverter disconnects the live and neutral but not the earth. That is certainly what the it shows in the Sunsynk and Growatt manual. Which means installing an earth rod gives two earthing points and therefore a permanent ground loop except when there is a specific DNO cable fault and you lose the DNO earth. And it isn't discussed anywhere as if it has been completely overlooked. Indeed! But I'm thinking about it. And I can deal with it by installing a relay with an extra NO contact to swap the earth from DNO to ground spike. That means whatever the fault is that caused the grid failure, there is a bonded earth in the islanded house but never a ground loop. But since I have never seen this mentioned then either I'm fussing about nothing, nobody has noticed, which they should have, or I have got it completely wrong. I'll move on from this subject once somebody convinces me that I am an idiot or that everyone else except me is an idiot. It won't be the first time. (I'm not saying which way round either)😀

@JohnMoI get that. I think I am being really pedantic, and I am considering the long term. Again, probably over thinking it but there are a couple of scenarios. And I am talking about where I am on grid and there is a power cut: 1. Power cut downstream of local earth point. DNO earth still remains so local ground spike creates and earth loop. -Bad 2. Power cut due to cable fault. No DNO earth. Local ground spike is necessary, no earth loop. -Good It seems a simple thing to fit a double pole relay to create the local E/N bond and at the same time swap from the DNO earth to local earth rod. But I haven't seen a single mention of this being done anywhere, which, in my experience, doesn't mean it shouldn't be done, just that it is a detail that is ignored/ nobody cares/ hasn't been discussed.

I'm sorry to keep banging on about this but it is a complex subject without a definitive answer and easy to get wrong (and I bet many professionals get it wrong despite their qualifications). @kelvin. When you added your earth rod, did you leave the SSEN earthing permanently in place? It seems to me that inverters in islanding mode probably leave the existing earth in place, which potentially is fine until there is a local cabling fault. However an additional earth rod would surely introduce a ground loop if the DNO earth isn't disconnected in islanding mode. Maybe I am over thinking it but it seems this isn't a settled subject yet, and it should be simple to get right with the correct information.

@Kelvin. Just to be clear, were you happy to use the earth provided by SSEN or are you talking more generally about running off grid for a while. Sorry to keep banging on about it but I am obsessing about getting my install right and the earth neutral bonding is niggling me.

It does occur to me that due to the ground works required generally on site it makes sense to get the DNO to hook up the supply but hold off on the meter installation until I am closer to building regs sign off. National grid have specified a PME. I guess I can use the earth connection from that rather than a ground spike and provide my own local N/E bond? Unless this statement affects that?

I had forgotten that, and had a quick look and remembered that they don't show up on the ENA database as G100 compliant. I think that is why I had forgotten. Shame because the pricing seems better than Sunsynk, with better availability.

I'm actually struggling to get to the truth! It seems from what I have read that professional installers don't get this right either. In the Sunsynk manual I read this to mean that the Sunsynk inverter internally bonds the earth and neutral on the load side when the gird fails as the DNO bond is lost. Although in the same manual it states (as Mattg4321 has pointed out) that the inverter provides a 240v connection to drive an external relay to achieve this...So which is it Sunsyk? Growatt do the same but the 240v signal is present when on grid and goes to zero on grid failure. (So one has to choose a NO or NC contactor accordingly.) It seems that one can link the grid DB and backup load DB neutral together and use the permanent DNO bond. This is fine until the DNO earth neutral bond fails and any local bonding inadvertently serves as the bond for the entire local infrastructure. Although it seems this is only a problem in countries where people steal the cabling. I'm still working through it but it seems I will likely go with the Growatt due to budget and fit an external contactor to provide the E/N bond in the event of grid power failure.

@Mattg4321 The Sunsynk has an internal relay, that was why I asked this question and you have confirmed what I was thinking, that many inverters don't, and I do need to fit my own system for this, probably if I go for the Growatt. I'll investigate.

@Dillsue I think I need to be a bit more specific when forming my questions. I just assume everybody telepathically knows what I am asking.

I haven't chosen an inverter yet and I am still specifically inquiring about the earth neutral bond requirements in the uk. And more specifically that one make (Sunsynk) mentions there is an earth neutral bond relay internally and the Growatt doesn't mention this so I thought I would ask what people do on this forum. As for the grid connection, I don't see the point in hooking it up and paying the standing charge months before I actually move into the house but if there is all that solar on the roof and the batteries are in I might as well at least use it to make the tea, just to curry favor with the builders. I should get enough for that at least, and possibly a cupcake.

What I am asking is what is needed in terms of earth neutral bonding as the Sunsynk manual states there is an internal relay to bond the earth and neutral when the grid shuts off in event of a power cut and the Growatt doesn't specifically mention this. There is a lot of talk about earth / neutral bonding but it is hard to distinguish what is for the American market and other countries and what is required for the UK. I'm not sure I understand how my first post suggests I don't have a plan. I think I am mis-understanding something. Can you explain?

I do have a plan! I am just holding off on the grid for a while until I am closer to building regs sign off but the solar is going up much earlier. It would be a shame not to use it. I am going to by a hybrid and run it off grid until the DNO turn up. So I won't need to change anything when I hook into the grid?

Hello. I think I will have my inverter up and running way before I get round to getting the grid hook up on my new build. I assume this means I need an earth neutral bond and a ground spike to start with. Is this correct? In the long term I see that Sunsynk inverters have an internal relay to achieve this but I can't find one mentioned in the Growatt manual. I just thought I would ask for any pointers when I get round to installing this. Once I have the grid connected how would I go about setting this up for grid power failure? Thanks

Hello. By budget says Growatt 10k or Sunsynk 8.8k. The Growatt on paper seems to be the right choice, the numbers are a bit better generally. The Growatt is a significantly cheaper brand. Given that either unit will do what I need is there anything I should be worried about with the Growatt brand? Thanks

So it seems I have a choice of getting close to the max PV ISC with 3 strings of 8 or close to the max PV input voltage with 2 x 12. Even at the never attained -10 degrees I am still 3 volts below the stated max input voltage with 2 strings of 12. Unless I go for a Growatt which, on paper gives me +25v of max voltage headroom. There must be a reason why the Growatt is cheaper though. I still can't make up my mind!