Any recommendations for some simple guidance on solar PV please?
I want to get a better idea of what may (or may not) be feasible at home before I obtain quotes. So not too simple, but I think that the Code of Practice might be too detailed and technical.
A simple question, but Uncle Google does not help.
I gather that there is normally an a.c. isolator means of isolation adjacent to the inverter. What sort of cable is normally used to connect that to a CU please? T&E?
I ask simply because I want to get my installation "solar-ready" as far as possible.
Mine has standard T&E. It's no different to any other circuit. For some reason the installer decided to add isolators next to the inverter and also in the meter cupboard near the consumer unit. I don't know why, as I could isolate it by flipping a breaker.
Could be T&E but depending on your installation the volt drop (rise) requirement is likely to be more onerous in order to avoid "nuisance tripping" of the G98 overvoltage protection.
But often its run in SWA to avoid needing an RCD due to the circuit route or hazards.
Isolation by the inverter is recommended for maintenance and testing of the equipment, including functional switching, but not necessarily mandated.
I could isolate it by flipping a breaker.
Simon, Jam, thank you.
I am hoping that my inverter (and battery) will be in the same store room as the top floor's DB. I had thought of using an MCB for isolation, but shouldn't both live conductors be isolated?
I believe it is standard practice to have a proper AC isolator close to the inverter, for maintenance. If nothing else, it's sometimes necessary to reset the inverter if it gets in a mess.
but shouldn't both live conductors be isolated?
From a BS 7671 point of view, isolating just the line is fine on TN systems - N only needs isolating as well on TT systems (and even then isolating at the CU might be possible - e.g. using a DP RCD or main switch - although often less convenient).
At lot of equipment instructions seems to ask for all-pole isolation - presumably because they don't know if the installation will be TN or TT.
- Andy.
G98 / G99 and the IET CoP require a lockable main point of isolation disconnecting all poles inc. neutral, and that point of isolation to be somewhere accessible.
In principle that could be the customer's main switch (and that is in effect, what is sometimes done for large greenfield projects), but it's easier - and more in keeping with the requirement - to have one that doesn't also switch off other loads as collateral damage.
But it doesn't need to be adjacent to to the inverters, e.g. could be one big switch for all generators in the main plant room.
I thought the other aspect was being able to secure the isolation, rotary isolators can typically be secured with a pad-lock to prevent unintended switching. Plus they're highly visible and operable by unskilled people, when immediately next to the inverter, that makes them better for emergency switching.
But regarding the battery location, have you checked PAS 63100:2024 Fire Protection Battery Storage Systems, I think this is freely available from BSI but you need to register, it gives guidance on location. I've not seen the latest amendment of BS7671 but I understand that now has more requirements on battery storage, which I expect will be aligned with the PAS.
On your original topic about cabling, if you're thinking about running in cables, it's also worth thinking about the need for additional cables for current transformers, or RS485 comms to meters/monitoring at the main consumer unit.
I thought the other aspect was being able to secure the isolation, rotary isolators can typically be secured with a pad-lock to prevent unintended switching. Plus they're highly visible and operable by unskilled people, when immediately next to the inverter, that makes them better for emergency switching.
But regarding the battery location, have you checked PAS 63100:2024 Fire Protection Battery Storage Systems, I think this is freely available from BSI but you need to register, it gives guidance on location. I've not seen the latest amendment of BS7671 but I understand that now has more requirements on battery storage, which I expect will be aligned with the PAS.
On your original topic about cabling, if you're thinking about running in cables, it's also worth thinking about the need for additional cables for current transformers, or RS485 comms to meters/monitoring at the main consumer unit.
I thought the other aspect was being able to secure the isolation
CU components (MCB, RCCBs, Switch disconnectors etc.) are in theory lock-offable - otherwise we'd not be able to use them for isolation when working out of sight of the CU. Granted you usually need a suitable bit of kit, but anyone working on such systems should have that.
- Andy.
CU components (MCB, RCCBs, Switch disconnectors etc.) are in theory lock-offable
I have very little confidence in those dolly locks. I could, I think, install a 2-pole MCB, but then I'd have to shorten the busbar.
Or of course I could open the main switch, but then the lights would be off on that floor. (I can, and often do, wear a head torch.)
Plus they're highly visible and operable by unskilled people, when immediately next to the inverter, that makes them better for emergency switching.
Good point! (Even if it is hidden behind Mrs P's boxes of shoes.)
But regarding the battery location, have you checked PAS 63100:2024 Fire Protection Battery Storage Systems
Yes. "6.5.1 Where practicable, storage batteries shall be installed outdoors. Where it is not practicable to
install storage batteries outdoors, batteries shall only be installed indoors at a location: ... "
It seems to me that the ideal place is under the roof which bears the panels, or at least close by, but although the loft space is prohibited, the store room on the other side of the wall is not.
There is a small section of wall outdoors, but 2 storeys up is poorly accessible (a cherry-picker gets there nicely), even if it may be possible.
I've not seen the latest amendment of BS7671 but I understand that now has more requirements on battery storage
Less than you might have expected.
570.6.7.203 Stationary secondary batteries in dwellings shall be installed in a suitable location taking account of manufacturer's instructions and PAS 63100.
if you're thinking about running in cables, it's also worth thinking about the need for additional cables for current transformers, or RS485 comms to meters/monitoring at the main consumer unit
Yes, I have thought about that. There is no prospect of running a cable from the attic to the origin, but I think that a CT could be squeezed into the middle DB.
Many thanks for your advice, folks.
CU components (MCB, RCCBs, Switch disconnectors etc.) are in theory lock-offable - otherwise we'd not be able to use them for isolation when working out of sight of the CU. Granted you usually need a suitable bit of kit, but anyone working on such systems should have that.
It doesn't look like that would comply with G99 which stipulates there has to be lockable points of isolation, now a rotary isolator is almost certainly compliant because you can snap a pad lock through it to lock it in position. And bear in mind the person doing the isolation could be someone from the DNO who is following their safety procedures.
But an MCB is not directly lockable, as you discuss it needs another adaptor device to be fitted, which may or may not be available dependent on who is performing the isolation. As such, you'd be getting into a debate about whether it was lockable. I would suggest that it is not lockable, certainly not directly lockable.
G99 Requirements:
15. Common Compliance and Commissioning Requirements for all Power Generating Modules
...
15.3. Commissioning Tests / Checks required at all Power Generating Facilities
15.3.1. The following checks shall be carried out by the Installer at all Power Generating Facilities and on all Power Generating Modules irrespective of whether they have been Fully Type Tested or Type Tested:
(a) Inspect the Power Generating Facility to check compliance with BS7671.
Checks should consider:
Protection
Earthing and bonding
Selection and installation of equipment
(b) Check that suitable lockable points of isolation have been provided between the Power Generating Modules and the rest of the installation;
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