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DC LV Battery Power Supply for Motorhome

TrigPoint
Hi everyone!


I've been asked to install some wiring in a van conversion and I need a bit of advice. The plan is a 110Ah 12V leisure battery, a SELV system and TT earthing (earth electrode from the body of the van.) 


I'm trying to work out the PSCC and PFC so I can choose the overcurrent and fault protection.


So,


a) Is measuring the impedance of the battery and using Uo Cmax / Zs 2R1 (with the measured battery impedance as Zs) acceptable to calculate PSCC


and,


b) Is Uo/Ze (with measured the battery impedance as Ze) acceptable to calculate PFC?


Many thanks in advance for your answers.


Trig


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  • 0
    If you are using 12V Earthing is pointless and unnecessary. Use standard vehicle fuses etc rather than MCBs, easier and cheaper and less subject to problems with vibration. The PSSC will depend mainly on the wiring. Big conductors from the battery 35mm2, will probably give you 2-3 kA PSSC, a few metres of 3mm vehicle cable will have this down to 1 or 200 A. If you fit a mains invertor and basically run as a 230V installation is covered in BS7671 section 717, far too much to cover here. It is useful to be able to plug into a standard caravan pitch, but this with an inverter supply needs a change over switch along with RCCB and suitable inlet socket. Note that CPDs (MCBs) and an inverter supply which has seriously limited current available will not be much use for overload or short circuit protection, but will be needed for mains supply operation.
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  • 0
    If you are using 12V Earthing is pointless and unnecessary. Use standard vehicle fuses etc rather than MCBs, easier and cheaper and less subject to problems with vibration. The PSSC will depend mainly on the wiring. Big conductors from the battery 35mm2, will probably give you 2-3 kA PSSC, a few metres of 3mm vehicle cable will have this down to 1 or 200 A. If you fit a mains invertor and basically run as a 230V installation is covered in BS7671 section 717, far too much to cover here. It is useful to be able to plug into a standard caravan pitch, but this with an inverter supply needs a change over switch along with RCCB and suitable inlet socket. Note that CPDs (MCBs) and an inverter supply which has seriously limited current available will not be much use for overload or short circuit protection, but will be needed for mains supply operation.
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