In the simple diagram below showing grounding arrangements within a motorhome, do i need to run a extra grounding cable from the consumer unit earthing bar to the grounding busbar. I don't understand how the RCD in the consumer unit will trip (when there is a fault) when there is no true earth connection, only chassis grounding? Thanks for any help offered.
Hi Maximoney1,
An RCD measures the difference between the live wire current and neutral wire current if there is a difference of more than the RCD device's rated trip value (30mA is the allowed maximum (for human safety) in our region). So if you have an earth fault (meaning there is power leaking to any "source" except your main DB (or inverter) the RCD should trip. )
I would not connect chassis earth to consumer unit earth (lightning etc). However, PV and plant standards vary by region i would check your local PV wiring standards for mobile homes and follow that.
As for grounding I would carry an earth rod and hammer around with you, when you park your mobile home stick the rod into the ground and wet the ground around the rod. I guess in the first world mobile home "sites" would have earth terminals you can connect to. You would need to check with your local wiring standards/requirements on where and how you are allowed to do this and how to connect it to your DB. Typically Inverters require TN-CS grounding.
Thanks kenyon, but where/when I am parked up overnight on tarmacadam, i cannot hammer a spike into the ground etc. From reading your answer, i'm thinking that even without a ground spike connection, the RCD will still trip on any live/neutral wiring making contact with a metal surface which conducts some of the electricity. Is this sufficiently safe in the 'mobile' setting? I will rarely(if ever) use campsite connections, but will make use of restuarants which allow you to park overnight in their car park if you buy a meal.
If i've read your answer wrongly, please highlight this, as this is a major concern of mine. Thanks for your help.
