The solar PV installation - how it all fits together.
Part 1 - The AC electrical installation.
The solar PV installation can be split up into a few different areas. The mounting of the panels, the DC electrical work and the AC electrical work. This is how the AC installation is fitted. The AC is the mains electricity that is supplied to you house and is normally around 230-240v. So, working from the inverter, this is how the energy travels from the PV array and how the AC system is installed. First of all we have the Inverter, there will be more about this when we talk about the DC installation but this converts the power from your array from DC to AC.
A Solar PV Inverter, this one is an SMA Sunnyboy.
A welding cable (flex) goes from the inverter into an electrical isolator. This is just a switch to turn the AC supply on and off.
a rotary isolator
The inverter and the isolator are often mounted in the loft but can also be in the garage, cellar or in a cupboard. This part of the installation can be pretty much ignored once installed and working. The only requirements for the inverter location is that it needs to have some ventilation- ie, not be completely enclosed and not be completely inaccessible, though its not something that needs looking at often.
From the isolator the power then needs to get to your consumer unit or fuse box. This means a cable that's run through the inside of your house, which is the preferable way. The cable will not be visible and is hidden by running it inside cupboards, under floorboards or sometimes in wall cavities. Ideally this would be the way we like to run cables in the same way a standard electrician would run a supply cable for a shower or a new socket circuit.
This would generally be done using flat twin and earth cable such as this, which is the same as that used in most houses for lights, sockets etc..
Flat grey twin and earth cable
Sometimes it is not possible to run the cable internally, this could be because to do so may cause damage to the house decor or there might be barriers along the cable run such as steel beams or concrete. In this situation we may have to run the battery cable externally down the outside of your house. If we do this we will hide the cable as best we can. As electricians we don't like to do this and always aim for our work to be invisible, however we do it. Some installers like to install the cable externally as a matter of course because it is often easier, make sure you ask how the cable will be fitted when getting quotes form installers, after all, if you employed an electrician to put a socket in you loft you would'nt expect them to have the cable down your outside wall without good reason. The external cable would be armoured- so protected from any damage and look like this:
A steel wired armoured cable
The cable would reach your mains location, where your fuse-box or consumer unit is. The cable will first go to a generation meter, this measures all the electricity that is produced by your system. You will need to take a reading from this to give to your energy supplier to receive your feed in tariff payment. Its basically the same as the meter that you already have from your energy supplier but this one you get paid for whats on the meter rather than the other way round!
A generation meter
The power then goes into another isolator similar to the one next to the inverter. The isolator is lockable in the off position so anyone working on the system can safely isolate it. From the isolator the cable then goes into your consumer unit. The circuit is wired exactly the same as any other in your house and is protected by a circuit breaker, the difference is that the electricity flows the other way.
A consumer unit
From the consumer unit the power generated by your PV system will either be used by the appliances in your house or, if you are generating more than you are using, be exported back into the national grid through your electricity meter and your main incoming cable.
A meter and main solar cable, this an older type disc meter
Well, that's the basics of the of the AC electrical installation, the next part of the Solar PV installation is the DC electricity system- this covers the inverter and the wiring to the Solar PV modules.
Northern Sunlight is a solar PV company based in Sowerby Bridge near Halifax, West Yorkshire. We design and install Photovoltaic Solar energy systems for commercial and domestic customers and provide design and consultancy services for large renewable suppliers and house builders. We offer a one to one service for householders wishing to take advantage of the Feed in Tariff and offer bespoke PV systems designed to meet your needs, with a choice of components and manufacturers.