when i returned to solar in 2017, some ten years later, I had a idea of plug in solar, but there is a conflict between the regulations, the 15th edition ( generators) and the BS7671 requirements and recommendations as well as appliance laws and regulations.
What I am talking about is this:
The British Standard BS 7671, also known as the IET Wiring Regulations, sets out the requirements for electrical installations in the UK. When it comes to plug-in solar systems, there is a potential conflict with BS 7671 concerning the use of plug sockets for connecting micro-generation equipment like solar panels.
BS 7671 requires that all electrical installations, including those for micro-generation, must be safe and not present any risk of injury or fire. The use of standard plug sockets for connecting solar panels or micro-inverters is generally not recommended because these sockets are not designed for continuous use at the full rated current, which solar panels can generate under certain conditions. This could potentially lead to overheating and fire risks1.
Moreover, BS 7671:2018+A2:2022 has introduced changes in surge protection requirements, which could affect plug-in solar installations. Surge protective devices (SPDs) are now required where the consequence caused by overvoltage could result in serious injury, loss of life, failure of a safety service, or significant financial or data loss. For all other cases, SPDs should be fitted unless the installation owner declines such protection1.
Therefore, it’s crucial for plug-in solar systems to comply with these regulations to ensure safety and legality.
The IET Wiring Regulations, specifically BS 7671, cover the requirements for generators connected to final circuits in several sections. Here are some relevant parts:
- Regulation 411.3.3: This regulation discusses the use of RCDs (Residual Current Devices) and their exceptions, particularly when a generator is supplying a distribution unit that has 30 mA RCDs protecting final circuits1.
- Chapter 53: This chapter includes regulations such as 531.3.2, which highlights the use of RCBOs (Residual Current Circuit Breaker with Overcurrent protection) for individual final circuits in residential premises to minimize unwanted tripping, and 531.3.3, which states that RCD Type AC shall only be used to serve fixed equipment where it is known that the load current contains no DC components2.
- Regulation 421.1.7: This regulation has been redrafted to require the protection of final circuits supplying socket-outlets with a rated current not exceeding 32 A using arc fault detection devices (AFDD) in specific types of buildings3.
These sections ensure that the connection of generators to final circuits is done safely and in compliance with the latest safety standards, do take a read....
The next part is the connection location, which would generally apply to any generation source/s.
In electrical systems, the terms “upstream” and “downstream” refer to the flow of electricity from the source to the load. When discussing circuits with multiple sources of energy input, these terms help to identify the direction in which power flows and how it is managed.
Upstream Circuits: These are closer to the energy sources and handle the initial distribution of power. In a system with multiple sources, such as a grid-connected solar panel setup, the upstream circuit would include the connections at the utility scale or the point where the solar panels connect to the inverter. Upstream circuits must be capable of managing the combined input from all sources and ensuring stable distribution.
Downstream Circuits: These circuits are further along the power distribution path, closer to the end-use applications or loads. They receive power that has been managed and distributed by the upstream circuits. In a home with solar panels, the downstream circuit would be the internal wiring that delivers electricity to outlets and appliances.
With multiple sources of energy input, such as solar and wind combined with grid power, there are additional considerations:
- Energy Management: Systems must be in place to prioritize and manage the different energy inputs, often using smart meters and management systems.
- Safety and Protection: Proper protection mechanisms, like surge protectors and circuit breakers, are essential to handle the variable nature of renewable energy sources.
- Regulation Compliance: The system must comply with local regulations for connecting to the grid and managing multiple energy sources.
When connecting solar photovoltaic (PV) systems to an existing electrical installation, the solar system can be considered an additional power source. This means that parts of the installation that were originally downstream circuits may become upstream in relation to the solar input. This shift necessitates specific protection requirements to ensure safety and compliance with electrical codes.
Protection Requirements:
- Overcurrent Protection: The sum of 125 percent of the power source’s output circuit current and the rating of the overcurrent device protecting the busbar should not exceed the ampacity of the busbar1.
- Disconnect Placement: A PV system disconnect must isolate the components that convert solar energy into electric energy. The location of the disconnect is crucial to ensure that all downstream equipment operates properly without the power source2.
- Surge Protection: According to regulations, PV installations must be protected by surge protection devices (SPDs) on both the AC and DC sides to handle different degrees and types of protection3.
see attached diagram for solar protection using SPD
I was not going to write more in that intro post, but you get the idea that the connection of "plug in solar" that is grid tied is not simple. the regulations tend to go into detail and overboard and make a simple matter overly complicated; a bamboozle if you like.
Here are my selection of key points.
solar plugged in is a upstream and therefore should protect downstream devices and users from risk.
Would plug in solar present a risk outward or inward of a surge?
does the installation circumvent protection?
The last one and the upstream are basically the same, yes it does. and the surge risks could be viable, for example a lightening strike on the solar injected into the system where SPD may be attached from the other sources.
our Deye micro inverter ( Deye Micro inverter - with relay_) does not provide SPD therefore this is required meaning that the installation could not form a "plug in" type device.
installation should be carried out that would add the devices necessary if you were to look at the plug in route, which would not be consistent with a "standard" solar installation, while carrying out a "standard installation". the point of connection is the key here as the "plug in" would be attached in the final circuit. this brings the upstream and protection requirements which are often misunderstood from the direct handbook interpretations as the concept here dates back to some time in respect of generators or dual sources.
The guidance is "recommended" but the plug ( as in 13 amp standard socket) should NOT be used. but another type of plug can be used.
The key point being the protection requirement, and as we know the "intermediate box" would include a RCBO and SPD. This inclusion would protect the downstream and itself ( the inverter) from issues.
we then turn to the plug.
For example, a common type of plug used for generators is the CEE 16A (IEC 60309/commando) plug2.
here is the common UK plug
https://www.ebay.co.uk/itm/196260099736? BS4343/IEC309
helpful to understand how this is implemented to a house wall.
The issues in respect of the home owner is what they can or cannot do. for example legally they can change the plug type, but could not install a independent circuit feeding back to a Henley or to the consumer unit.... that said they can, but would need to give notice and have an inspection to do so. * building regs*
this connection could be costly and circumvents the issues of plug in as it would be more of a standard installation.
Pluginsolar.co.uk seem to have the idea ( which is in principle correct) that the micro inverter should not be attached to the circuit by a 13 amp plug, but they go to the installation of a FSU. ( this is a fused spur)
https://uk.rs-online.com/web/p/fused-spurs/2469580?
as you can see on the link the cable is not plugged but hard wired and legally a home owner can fit a FSU. but this offers no real protection. and some people may not have enough plugs to give up one for their solar.
We then comes to the appliance type...
Now appliances or sold units as a package fall under "a device with a fitted 13 amp plug". well there is the end of that simply. ( that's an estimated summary)
You also have to consider that most people cannot manage to wire a plug let alone install a socket change and there is not really a simple way in which to proceed. I would guess that most AC electrician's would be scared off carrying out this work and therefore we may only get away with the "can you install a AC isolator for a X amp load"
The whole idea of the regulations is to stop bad installations, fires and such risks. But if we went to the route of a AC isolator, then the installation would go to the isolator from this to a sub CU which would contain the protection devices and then connect to the micro inverter.
Now the in and out of this sub cu, could be a plug (not the standard 13 amp ( AKA the Type G or BS1363)) but a more industrial plug so we are not making suicide cables. this would allow for the installation to be removed, after all we don't know the mounting system and if its portable.
FIND THE SOLUTION....
I have updated https://www.renewsolar.co.uk/company-information/blog/delving-into-bs-7671-section-712-and-solar-panel-systems/
this covers some of the regs regarding solar plug in and what is required.. it does in fact provide the solution.