708.313

I suppose that the 48 Volt D.C. limit refers to the extra low Voltage normally used to supply 12 Volt equipment from a leisure battery.  Many caravans have 12 Volt wiring for lights and sockets for 12 Volt camping equipment and lighting. The dedicated E.L.V. wiring will not be suitable for a supply above say 48 Volts. (4 X 12 Volt batteries wired in series, although I have never personally seen that arrangement of batteries). But the E.L.V. limit is normally 50 Volts A.C. or 150 Volts D.C..


Z.

Is there a plan to have a photovoltaic array with the inverter inside the caravan?


Would that count as a supply above 50 Vdc?


Andy Betteridge

Interesting. A 48 volt dc limit would therefore seem to preclude having a landline telephone connected within the caravan?  The nominal voltage at the telephone socket being -50 volt dc w.r.t. earth. Some detail at http://www.ringbell.co.uk/ukwmo/Page240.htm  When does a mobile home become a caravan and vice-versa?


Clive

Surely it is Section 721 which applies. So we have 721.313.1.2, which says pretty much the same thing.


The occupants of the caravan are protected from normal AC supplies (single or three phase) by ADS and additional protection. No such measures are required for a D.C. supply, which could be from batteries, or a vehicle. Note that 48 V is the norm in hybrid and all-electric vehicles. Such a voltage should not kill you, but I am not volunteering to complete a circuit which consists of four lead-acid accumulators in series. ?

When does a mobile home become a caravan and vice-versa?

As far as section 721 is concerned, only when it meets the requirements for the construction and use of road vehicles. In campsite volcabulary section 721 applies to tourers and motor homes, but not statics.


  - Andy.

I think Chris may have the answer there, that there's all kinds of extra protection available on the AC side, but trust me, you CAN feel 48-50v DC (phoneline while standing on a concrete basement floor with bare feet, and no it wasn't ringing, that feels a LOT more exciting)... I'd imgaine being a metal framed and bodied building, the chances of you being well earthed while getting in contact with a 'live' dc supply are much higher in a caravan/motorhome than in a normal house.  I wonder if you could exceed it by centre tapping the battery to 'frame' or 'earth' ? (I don't have my copy of 7671 to hand, it's in the car and it's cold out)