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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'm not going to help this discussion directly, perhaps in the way you require, but the simple facts are:

    (a) BS 7671 Section 721 does not cover DC supplies above 48 V DC where the supply is PELV or SELV.

    (b) Solar PV is Section 712, not Section 721

    (c) Solar PV (on the DC side) is double or reinforced insulation (and not SELV or PELV) and therefore would never be covered by the limitation in voltage of 721.313

    I therefore am of the opinion that you need to conform to Section 721 for the protective measures addressed by the Section, and Section 7221 for what is covered by that Section, BUT there are no limitations in voltage for systems conforming to Section  on DC systems to Section 412 of BS 7671 (double or reinforced insulation ... so these are not prohibited by Section 721 of BS 7671, and the requirements of Section 721 ought to be addressed.

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    I'm not going to help this discussion directly, perhaps in the way you require, but the simple facts are:

    (a) BS 7671 Section 721 does not cover DC supplies above 48 V DC where the supply is PELV or SELV.

    (b) Solar PV is Section 712, not Section 721

    (c) Solar PV (on the DC side) is double or reinforced insulation (and not SELV or PELV) and therefore would never be covered by the limitation in voltage of 721.313

    I therefore am of the opinion that you need to conform to Section 721 for the protective measures addressed by the Section, and Section 7221 for what is covered by that Section, BUT there are no limitations in voltage for systems conforming to Section  on DC systems to Section 412 of BS 7671 (double or reinforced insulation ... so these are not prohibited by Section 721 of BS 7671, and the requirements of Section 721 ought to be addressed.

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