Solar Panels . . .

[The Natural Philosopher]

Christ on a bike.

[alan_m]

Apart from maybe Octopus, export tariffs require an MCS certified installation evidenced with an MCS certificate. Some MCS certified installers may refuse to work on a part install performed by someone else.

[alan_m]

The cowboys have moved from double glazing, conservatories and insulation to solar panels and heat pumps.

[alan_m]

That may limit repair options if a panel or two fails.

[charles]

It doesn't. My battery and inverter are mounted on a outside wall. Wiring runs down the side of the house (in conduit).The battery alone weights

110kg - not something easy to carry into a loft. The inverter is 'only' 32kg!

[AlanC]

My inverter and batteries are in the loft (yes, they struggled to get them up there). The wires from the panels are routed under a tile and upwards between the felt overlaps under the tiles.

[Andrew]

Using special tiles -

[Theo]

What I'd do in this situation is run a pair of wires from every panel to a terminal block in the loft (not necessarily a chock block, perhaps something a bit more sturdy and with a suitable rating for DC). Then configuring the panels into strings is something you can do later from the comfort of the loft, rather than having to crawl on the roof to install the connections later.

Stringing is part of the system design that needs to be matched to the inverter - if we don't know what inverter we're going to use we don't want to be a hostage to fortune as to how the panels are connected. You may also need to add optimisers to each panel or pair, or use microinverters instead of one big inverter.

You'll spend more on wire prewiring everything, and you need to watch the voltage drops in the wire (longer wires = more losses, maybe need to upgrade to fatter wires) but it will turn the rest of the install to a warm-and-dry electrician job rather than a crawl-on-the-roof roofing job.

There's one awkwardness though: to configure the DC side of things you'd need the wiring to be de-energised, which either means having isolators on each DC wire, covering up the panels, or doing it at night. I suppose you could also have some kind of connector that can have the downstream side prewired offline and then plugged together at night when the panels aren't generating. Would need to find a sparky happy with this arrangement as they might not have seen it before.

Theo

[Animal]

just short the panel, a clip-on lead can do that.

[alan_m]

Is the builder qualified to do all this non-standard wiring and safety isolation? The perceived cost saving by having the builder install just the panels while the roof is being done may not be real. If someone at a later date needs to work on the roof to connect the panels probably they will need some form of scaffolding erected and the extra cost of wiring and associated equipment may negate any possible savings.

[Theo]

TBH once the panels are up the electrical install isn't such a big deal (<1 day unless there are complicating factors). So I'm not sure why you would install the panels and not connect them, since they only have to generate enough to pay back for the invwrter and wiring before making it worth your while. You don't need a battery at this stage, that can come later.

After all, once the panels are on the roof the ~25 year life begins, so silly not to do the last bit to have them paying back.

The connections at the panels are just push in MC4 connectors so hard for a builder to mess up I'd have thought?

Theo

[RJH]

I suppose my problem is the MCS certification bit if I want to be able to export. Would an MCS qualified electrician be willing to carry out any extra work that needs doing? And if so, would there be a hefty premium?

As it happens the roofer has just got back to me with the details of an electrician he works with - not, so far as I can see, MCS listed. I'll phone him on Monday to see what's what.

[Theo]

You can only ask. See if there's an MCS installer who is willing for the builder to mount the panels - after all it's probably make it a much quicker/easier job than having to install scaffolding etc themselves.

For the record Octopus will pay export tariffs without an MCS install - other energy companies may follow suit, but for the moment MCS gives you more options.

Theo

[alan_m]

They do charge an inspection fee so if the installation is not up to an acceptable standard they may reject the installation for export tariff purposes.

[Andrew]

But an inspection might require scaffolding for access anyway and I thought the low voltage interconnects have to be plugged in from panel to panel as they are being installed. Do you want to trust a 'builder' to do this ?.

[Theo]

That's interesting, they didn't say that when the announced the change. Seems to be a £250 'admin fee' and if accepted you're limited to some tariffs:

At which point, getting the builder to mount the panels and getting an MCS person to do the rest may make sense. There are certain parts of MCS that relate to the design of the system (don't mount panels vertically on a north facing wall) but unless there is something egregious I imagine an MCS installer can work with what they have - after all you don't get to rebuild your house facing a different way. It is probably worth getting them involved before the panels go up as I think some parts of MCS relate to waterproofing, wind loads, etc.

I don't think Octopus care about how your panels are wired up, they're more interested in the grid side of things (ie do you have the number of panels/batteries you say you do, or did you sling a cable through to next door?). I doubt the £250 is going to cover roof access beyond going up a ladder.

The panels need to be organised in strings, but there's nothing to say you can't make a 'patch panel' of connections somewhere more accessible, at the cost of more wire, more wires going through the roof, and some voltage drops which you'd need to calculate (and potentially thicker wire to compensate).

I've not personally handled an MC4 connector but can imagine even a builder could put a plug in a socket.

Theo

[SteveW]

Indeed. The current system seems to me to be a daft scheme. There is no logical reason that connection to the grid should require anything but a check that the inverter is certified and its connections to the grid/earthing are correct. Anything on the house side should be either doable by any electrician or plug-and-play for DIY install.

[Andy Burns]

The £250 fee is likely to "eat" about 18 months of production from 8 panels, assuming you don't consume any yourself ...

[Theo]

Yebbut you are presumably saving more than that by going the non-MCS route. Although it's an interesting 'keep them honest' feature. If an MCS install costs substantially more than £250 on top of a non-MCS install, go with the non MCS. If everyone did that the premium for MCS would settle at about that level. In economics textbook land anyway.

Theo

[Mark Carver]

The DNO is interested to know about your system, because it could (along with all your neighbours' systems) cause them problems on a sunny summer's day.

If the system is capable of pushing out more than 3.68kW, they are very interested, and spend three months procrastinating before giving approval (or not).