jimseng

I don't think it is really about having a disconnection point in the loft. I started this thread wondering if there was any point in having the SPD/Fuse/MCB box in my first post. I have concluded that it isn't as @Dillsue pointed out, what is the point of a fuse given the short circuit current of the panels? So I think I will stick with MC4s and buy a cheap crimper for the 8 terminations or so I will have to do. This seems the safest way to make the connections over any period of time, day or night when I come to it.

Thanks. Lower risk is the important phrase there!

I'm actually thinking of buying a pair of MC4 cables and cutting them in half. This would give me 4 MC4 connectors outside the roof to connect to the ends of the two strings and I would bring the cut ends through a cable entry and through the internal membrane inside the loft. (I don't have roof felt, it is OSB and a breathable membrane under the panels.) So really I either choose MC4 connections and buy a crimper or terminate them in something like an Isolator or a termination box, whatever the term for that is. Personally I think the isolator fire risk is slightly overblown, especially as I will be able to easily inspect it. It's not like it is tucked away in a crawl space. I'm going to have to make a decision.

@Dillsue Really the only reason I am thinking of putting any termination in the loft is to avoid MC4 connections in the run from the last panels to the inverter. It is not a living space from the building inspector's perspective but I will be using it for some purpose other than spider accommodation and it will have a fixed stair case. (a 10m Scalextric track and guitars perhaps?) An isolator seems like a neat way of terminating the feed through the roof to the cable run to the ground floor. I guess that means it is quickly and easily accessible (and therefore inspectable on a regular basis).

The thing that confuses me over the SWA discussion is that I plan to use PV ultra cable, which now comes in an SWA version. I was planning on running it from the loft to the ground floor and to the inverter inside the service voids/posi joists using safe zones. This is only a 3m drop. This is from Doncaster Cables: This strongly suggests I don't need to use SWA which adds about £3.00/ metre. I'll use SWA if I have to but unless "without the need for conduit installations" means "must be run in conduit" then I'll go for the cheaper option.

@ProDave Can you remember if this has to be fitted to the flue pipe first (I suspect it needs tightening but I can't tell from the image) or can the flue pipe be inserted through it once it is in place in the wall. It makes a difference to me in planing the date for the insulation. Thanks

I think I have found it:

Indeed, but it's the regs I have to follow!

@ProDave. That looks like the sort of thing. Do you have a supply reference for that? I assume, being described as a sleeve that the 125mm twin wall sits inside it? Or is it actually an insulated twin wall flue in itself?

Hello. I have had a flue designed and I now have all the bits on site. The issue is the installer is now not available for some time and I really want to fit the flue through the wall to the outside before the insulation goes in. I haven't been able to get hold of the installer so I thought I would ask here. I have a timber frame building with 350mm Warmcell insulation. The installer has specified 2 45 degree bends and twin wall flue to pass through the bedroom wall to the outside of the house and then up. This means passing through plasterboard, intello membrane, Warmcell then through larch wood cladding. I have been supplied an expandable wall sleeve to surround the twin wall flue where it passes through the wall: This wall sleeve is barely wider internally to the twin wall flue which specifies a 50mm minimum distance to combustibles so I am confused as to how I maintain the minimum distance, unless I have mis-understood, or been supplied the wrong thing. Can someone advise? I'm trying to get all parts that pass through the wall installed before I seal up for the insulation.

Thanks for the replies. I'll fit an isolator. That's another one ticked off the list.

So do people see the need for fusing/spd/MCB between the panels and inverter, or as @JohnMo says, nothing between panels and inverter. If it is nothing then I am either going to have to fit MC4 connections to the PV coming through the roof or find some suitable method of terminating them safely, giving me a method of continuing the cable run at a later date. The panels are going on the roof sooner than the rest of the build. Edit: I should say MC4 connections to the ends of the PV cables that have come through the roof into the loft space.

I also have two 16k batteries which won't be going up there.

Hi All When I come to install my panels on my roof I was thinking of installing one of these in my loft (or something similar). I will have two strings: Much of my thinking is that it would give me a way of terminating the solar cables and allowing me to fully connect up the array before I continue to do the rest of the cabling to the inverter on the ground floor. (Eliminating un-terminated high voltage cables seems like a good thing). I just want to check that this is a sensible thing to do. I have some nagging doubts: The inverter already has class II surge protection. Is the current protection and fusing necessary given that the arrays are inherently current limiting in their output? If anybody wants to suggest putting in a DC islolator how does that square with the current advise not to fit isolators and rely on the inverter DC isolator? Is there any alternative I should consider if any of this is unnecessary such as a simple termination bus bar. (Does such a thing exist?) I am considering that I could probably do away with having to crimp my own MC4 connectors given that the Growatt PV input seems to be gland and screw terminal, not MC4 for the PV input. Comments?

Thanks @Peaklander That is an interesting IET article

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.