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Maximum DC voltage for caravan and motorhome PV systems/supplies

Oliver Goode

What is the maximum permitted DC voltage (supply voltage) for PV solar systems that are attached to campervans and motorhomes? Many motor caravans (including caravans and motorhomes) now have solar panels as a means of charging the leisure batteries, with most exceeding the 48V 'nominal DC supply voltage' as stated in Section 721 - Electrical Installations in Caravans and Motor Caravans. 

A PV power supply system is defined as a supply in section A721, Sources of supply - A721.313.4 (v)

This seems straightforward. However, when looking at section 712 (PV) it seems that PV is treated as a separate generating circuit. It treats PV up to 1500 V DC as permissible with double or reinforced insulation, and SELV or PELV.  So, it is accepted practice that a PV array on a caravan may operate anywhere within that envelope, so long as the output to the installation (battery side) respects ≤ 48 V DC nominal. 
For example: The solar generation (panels) to the charge controller (MPPT) can be > 48V (with required protection), but the battery supply (MPPT to battery) MUST be < 48V. 

A lot of campervan installations I work with have a max voltage (Voc) higher than 48V. Do these installations comply or not?

Any help or guidance is greatly appreciated.


 

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    I'd add that looking at 721.1 the scope of section 721 (as stated in 721.1) is limited to "the electrical installation of caravans and motor caravans at nominal voltage not exceeding 230/400V AC or 48V DC" - thus it seems to me that a >48V DC system would be out of scope of section 721 thus the voltage limits of 721.313.1.2 wouldn't apply (although the general parts of BS 7671 and any the sections for any other relevant special locations and installations would).

       - Andy.

  • 0 in reply to AJJewsbury
    AJJewsbury said:
    I'd add that looking at 721.1 the scope of section 721 (as stated in 721.1) is limited to "the electrical installation of caravans and motor caravans at nominal voltage not exceeding 230/400V AC or 48V DC" - thus it seems to me that a >48V DC system would be out of scope of section 721 thus the voltage limits of 721.313.1.2 wouldn't apply (although the general parts of BS 7671 and any the sections for any other relevant special locations and installations would).

    But there is nothing in BS 7671 that says anything other than SELV and PELV systems in caravans is limited to 48 V DC, which means that the PV installation might simply be considered out of scope for that Section ... I did say it might not be helpful, at least in the way that provides a simple "yes/no" answer.

  • 0 in reply to gkenyon
    gkenyon said:
    But there is nothing in BS 7671 that says anything other than SELV and PELV systems in caravans is limited to 48 V DC,

    Maybe crossing wires here, but as I read 721.313.1.2 (very last sentence) the 48V limit applies to all DC supplies to a caravan installation - without any regard to the method of protection from shock (if it's outside the ELV range 721.414 wouldn't come into play anyway).

      - Andy.

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  • 0 in reply to gkenyon
    gkenyon said:
    But there is nothing in BS 7671 that says anything other than SELV and PELV systems in caravans is limited to 48 V DC,

    Maybe crossing wires here, but as I read 721.313.1.2 (very last sentence) the 48V limit applies to all DC supplies to a caravan installation - without any regard to the method of protection from shock (if it's outside the ELV range 721.414 wouldn't come into play anyway).

      - Andy.

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