Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • Replies 51 replies
  • Subscribers 46 subscribers
  • Views 1503 views
  • Users 0 members are here
Options
You may also be interested in

Who from the IET is working with the government to allow <800W inverters to be 'plugged in'?

Steve Nixon76

The UK government made the following announcement at the end of March (www.gov.uk/.../government-to-make-plug-in-solar-available-within-months) regarding Balcony Solar/Plug-in Solar. The following section features in the 'Notes To Editors' at the end of the announcement.

"The government will work with the Energy Networks Association, DNOs and Ofgem to update the G98 distribution code and wiring regulations BS 7671 to allow UK households to connect <800W plug-in solar panels to domestic mains sockets, without the need for an electrician and with tailored safety standards."

So who is the government working with at the IET/JPEL64 to make these changes to BS7671? Or is the government simply going to bypass the IET and make amendments willy nilly?

Parents

  • It is an interesting debate. I find myself somewhat conflicted.

    On the one hand, installing solar PV seems to increase some risks, which may be mitigated in the fixed wiring, e.g. by fitting bi-directional RCBOs. If an installation is not prepared for solar PV because it is plugged in, the risk is intrinsically higher.

    Against this, a policy of increasing solar generation is perfectly reasonable on environmental grounds, if no other, so the marginal risk can be justified.

    In fact, we increase risks by plugging anything in. Think of just an ordinary socket-outlet. We aim to have a maximum Zs of 1.37 Ω (Table 41.3). If we plug in a 50 m extension lead, we add an extra 1.5 Ω. So instead of tripping instantly, it could take a minute (Figure 3A4) and we have to rely upon the BS 1362 fuse.

  • in reply to Chris Pearson
    Chris Pearson said:
    In fact, we increase risks by plugging anything in. Think of just an ordinary socket-outlet. We aim to have a maximum Zs of 1.37 Ω (Table 41.3). If we plug in a 50 m extension lead, we add an extra 1.5 Ω. So instead of tripping instantly, it could take a minute (Figure 3A4) and we have to rely upon the BS 1362 fuse.

    Hence one of the reasons for sockets that are likely to have 50m extension leads plugged into them (i.e. ones serving equipment outdoors) to have RCD protection.

       - Andy.

  • in reply to Chris Pearson
    Chris Pearson said:
    So instead of tripping instantly, it could take a minute (Figure 3A4) and we have to rely upon the BS 1362 fuse.

    Not a chance ... Maz Zs for 0.4 s and 13 A fuse is 2.3 ohms (Table 41.2) ... for 5 s it's 3.64 ohms.

    0.4 s therefore greater than the 1.37 + 1.5 ohms =2.85 ohms, so 0.4 s disconnection time is not possible, 5 s is.

    As   says, this is why we need RCDs for socket-outlets.

  • in reply to gkenyon
    gkenyon said:
    Not a chance ... Maz Zs for 0.4 s and 13 A fuse is 2.3 ohms (Table 41.2) ... for 5 s it's 3.64 ohms.

    So, you cannot quite rely upon a 13 A BS 1362 fuse, which reinforces my point. I do not think that anything makes the use of a 50 m extension lead conditional upon the installation of an RCD.

    Incidentally, it could be indoors during building work - you do not have to unwind all of it (subject to magnitude and duration of load).

Reply
  • in reply to gkenyon
    gkenyon said:
    Not a chance ... Maz Zs for 0.4 s and 13 A fuse is 2.3 ohms (Table 41.2) ... for 5 s it's 3.64 ohms.

    So, you cannot quite rely upon a 13 A BS 1362 fuse, which reinforces my point. I do not think that anything makes the use of a 50 m extension lead conditional upon the installation of an RCD.

    Incidentally, it could be indoors during building work - you do not have to unwind all of it (subject to magnitude and duration of load).

Children
  • in reply to Chris Pearson
    Chris Pearson said:
    So, you cannot quite rely upon a 13 A BS 1362 fuse, which reinforces my point. I do not think that anything makes the use of a 50 m extension lead conditional upon the installation of an RCD.

    Agreed as a basic truth, but since 16th Edition in 1991 (BS 7671:1992), our national wiring code has accounted for that use-case.

    Even if you discount that timescale based on the grounds that the requirements was for socket-outlets that "might reasonably be expected to supply equipment outdoors", the use-case has been accounted for since BS 7671:2008, some 18 years with requirements similar to our current 411.3.3 in the general case.

Community Rules & Guidelines