PaulRainbow
Well-Known Member
ooooh look how high up the wall i can wee.
Generator question for elec electronic engineers
- Thread starter Rocksteadee
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Gumpy
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At my age I am lucky if I can avoid weeing on my shoes.
Alex_Blackwood
Well-Known Member
Nice when you have isolated the supply and put your hand on the busbar to show the "Competent Person" that the system is dead and safe to work on!
Also Think Lodden has his centre taps mixed up If his lamp lights up 50% on L/E, N/E then I suggest there are actually two Lines i.e. between phases, not phase - neutral.
Any way back to the Original post. His inverter is designed with a dedicated N/E jumper connection. According to the hand book!
Gumpy
Well-Known Member
Not confused here at all! I have seen quite a few systems (inverters and generator inverters) where it is not possible to put a N-E link in despite what the manual has said and its a simple matter to do the test to confirm that it is OK.
Solent sailer
Well-Known Member
Inverters sometimes use a capacitor to link the neutral to earth, this can give odd readings and generally you are able to fit a n-e link in the consumer unit as suggested by the supplier, I would get them to confirm this in writing then link the n-e yourself, I have had to do this with old inverters in the past.
VicS
Well-Known Member
If you fit the link in the consumer unit It will be between earth and neutral when switched to shore power... there should not be a local link between earth and neutral. If the shorepower supply "polarity" happened to be reversed the link would then short the shorepower supply live to earth as already explained.
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Lon nan Gruagach
Well-Known Member
Also a N-PE link in the consumer unit will trip the RCD in the pontoon box even if everything is correct polarity.
PaulRainbow
Well-Known Member
That'll never happen, the shoreside RCD will trip as soon as the power is turned on. That's why the PE-N connection has to be made at the supply, in the OPs case the genset inverter.
Lon nan Gruagach
Well-Known Member
'Lectrickery is fast, very fast, speed of light fast even. Its all well and good to say "ohh the trip will go" but in the 30mS they have to scratch their arse and decide if its really worth doing its thang you will get some very nasty fault currents flowing. Especially if the last part of the circuit to close is a switch designed to make a good connection immediately as opposed to a loose wire that brushes against sommat it oughtnt to do.
Rocksteadee
Well-Known Member
And there was me thinking it was an easy answer
VicS
Well-Known Member
At least it should do, but RCDs are electronic devices and can fail . However if the RCD fails to trip the overcurrent protection device will trip
PaulRainbow
Well-Known Member
If a local PE-N connection is made at the onboard consumer unit it will trip the shore power RCD.
In an installation without an RCD (rather than using your unlikely scenario of the RCD failing to trip), if there was a PE-N connection, that would not cause an MCB to trip, there is no overcurrent event.
There is no possibility of the scenario you described ;
because the PE-N cannot exist after an RCD.
matthewriches
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superheat6k
Well-Known Member
The switch controlling the power from the generator should also control the shore power to the onboard consumer unit. It should be a two pole three position switch switching Live, Neutral from both the generator and the shore power, with the Off position in the middle.
The Earth to neutral connection from the generator neutral can be made on the back of the switch on the generator side, or anywhere along the supply cable back to the generator, but ideally as close to the generator as is feasible, and without any further switch or break point provided.
Such a switch makes it impossible to have both shore and generator connections live to the consumer unit at the same time. Thus the idea of earth connected to neutral in more than one place cannot arise.
PaulRainbow
Well-Known Member
Why are you telling me this ? I'm not the one who suggested a PE-N connection at the consumer unit.
PaulRainbow
Well-Known Member
Surely you know how to turn the power back on ?
matthewriches
Well-Known Member
If you were to short neutral to earth downstream of an RCD, it would not trip as soon as the power is turned on, assuming no load. This is because no fault current would exist.
You would find however that once you start to put a load downstream of the RCD, that it would disconnect, once the RCD senses a fault (imbalance between sum total of L and N respectively).
You would find however that once you start to put a load downstream of the RCD, that it would disconnect, once the RCD senses a fault (imbalance between sum total of L and N respectively).
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VicS
Well-Known Member
I tried it once with a plug in RCD. No load just a deliberate neutral to earth short .... it tripped !
superheat6k
Well-Known Member
Because you are rattling on a about a situation in which with correct wiring and switching cannot arise.
However, this is not an answer for you personally, it is a response to your (digressed) thread response for all interested to read.
And I am trying to remind the readers and the OP of the key thing they should be thinking about in order to avoid electrocuting themselves.
Lon nan Gruagach
Well-Known Member
For the RCD to not trip there would have to be no (significant) load by any consumer on the same supply right back to the sub-station or other transformer isolator (which ever is nearest){unless you are in the amazingly unlikely situation of a fully balanced 3 phase supply]
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