electricity problem solving

[Forty_Two]

Looks like you might be getting confused with centre tapped inverters, which the Victron is not.

It is, however, possible that the inverter has been incorrectly installed. Once the fault is found, the inverter installation must be checked. Once again though, i'd want to know how/where the immersion is connected

This is what i am referring to from the manual:

The MultiPlus is provided with a ground relay (relay H, see appendix B) that automatically connects the Neutral output to the chassis if no external AC supply is available. If an external AC supply is provided, the ground relay H will open before the input safety relay closes. This ensures the correct operation of an earth leakage circuit breaker that is connected to the output."

 

[PaulRainbow]

This is what i am referring to from the manual:

The MultiPlus is provided with a ground relay (relay H, see appendix B) that automatically connects the Neutral output to the chassis if no external AC supply is available. If an external AC supply is provided, the ground relay H will open before the input safety relay closes. This ensures the correct operation of an earth leakage circuit breaker that is connected to the output."

OK, but that isn't to "create a neutral".

It is a requirement that any AC power source have the neutral and Earth bonded at source, in addition to correct Earthing. With a standard inverter the bonding is done at source, as is the shore power. Changing from shore power to inverter should be done via a two pole changeover switch. In the case of the Multiplus the shore power will, of course, be bonded as normal, but the inverter cannot have a permanent bond, because it can be used at the same time as shore power (the Multiplus will "boost" the shore power, if needed). This means that the Multiplus can only be bonded when the shore power is disconnected, hence the relay.

If the relay isn't working and there is a leak to Earth, which trips the RCD on shore power, the RCD should still trip because there will be an imbalance between live and neutral. If the inverter isn't correctly Earthed, all bets are off.

I'd still bypass the inverter, find and fix the problem, then ensure the inverter is wired correctly and the relay is working. Easy to check the RCD works with the inverter, under normal circumstances, just use an RCD tester on one of the boats power sockets.

 

[Alex_Blackwood]

OK, but that isn't to "create a neutral".

It is a requirement that any AC power source have the neutral and Earth bonded at source, in addition to correct Earthing. With a standard inverter the bonding is done at source, as is the shore power. Changing from shore power to inverter should be done via a two pole changeover switch. In the case of the Multiplus the shore power will, of course, be bonded as normal, but the inverter cannot have a permanent bond, because it can be used at the same time as shore power (the Multiplus will "boost" the shore power, if needed). This means that the Multiplus can only be bonded when the shore power is disconnected, hence the relay.

If the relay isn't working and there is a leak to Earth, which trips the RCD on shore power, the RCD should still trip because there will be an imbalance between live and neutral. If the inverter isn't correctly Earthed, all bets are off.

I'd still bypass the inverter, find and fix the problem, then ensure the inverter is wired correctly and the relay is working. Easy to check the RCD works with the inverter, under normal circumstances, just use an RCD tester on one of the boats power sockets.

Worth bearing in mind that a RCD will only trip if there is a fault on it's output side. Unless of course it is faulty in itself.

 

[PaulRainbow]

Worth bearing in mind that a RCD will only trip if there is a fault on it's output side. Unless of course it is faulty in itself.

I am, of course, aware of that Alex (i mentioned it in post #9), but i'm not sure how that relates to my explanation of the Victron relay ?

 

[sailaboutvic]

Good news I sure I found the problem, quick lunch and I'm off back to finish the job off for my mate .
Report back later what I found and maybe someone can explain why shore power with trip the rcd but the victron inverter doesn't, when both goes theought the same rcd.

 

[JOHNPEET]

Good news I sure I found the problem, quick lunch and I'm off back to finish the job off for my mate .
Report back later what I found and maybe someone can explain why shore power with trip the rcd but the victron inverter doesn't, when both goes theought the same rcd.

PaulRainbow has provided the explanation in post #22 of why the RCD doesn’t trip when running on the inverter- need to check the earthing relay/earth connections etc at the inverter. The RCD will not trip unless there is a return fault path back to the power source.

 

[Alex_Blackwood]

I am, of course, aware of that Alex (i mentioned it in post #9), but i'm not sure how that relates to my explanation of the Victron relay ?

Sorry Paul, you did indeed, I missed that. I am thinking too much on the hoof this week and not paying attention! Wasn't referring to your explanation of the relay. You know a lot more about these bits of kit than I do!

 

[PaulRainbow]

Sorry Paul, you did indeed, I missed that. I am thinking too much on the hoof this week and not paying attention! Wasn't referring to your explanation of the relay. You know a lot more about these bits of kit than I do!

No problem Alex, we all do it at times.

 

[PaulRainbow]

Good news I sure I found the problem, quick lunch and I'm off back to finish the job off for my mate .
Report back later what I found and maybe someone can explain why shore power with trip the rcd but the victron inverter doesn't, when both goes theought the same rcd.

Vic, can you check if the inverter case is Earthed ?

 

[sailaboutvic]

thanks everyone for all the suggestions
the boat Najad 44CC

just a quick run down how the boat wired .
shore power travel throught a transformer , then the victron charger/inverter , into a switching box and end up at the RCD .
so which ever is used ,shore power or inverter both go through the RCD .
from there was two breakers an 6A which was disconnected and a 16A .
the 16A wires LNE then entered a junction box where all the wires from the domestic supply where all twisted to gather (see photo ) .

this morning as my best mate here ? Paul suggested I disconnected the hot water immersion heater , RCD still trip when the shore power came on .
ended up opening the J box and stripping all the twisted wired and start joining one at a time to the RCD ,
it turned out it was the front power sockets ,
water have found its way into then .

I wasn't happy twisting all the wires to gather again , plus if there was another problem one day it made the job harder to trace a problem so persuade my mate to put in more breakers ( it didn't take much persuading )

another full day cramp in a locker but at less the problem sorted .

I'm sure someone like Paul would had found the problem in a fraction of the time it took me .

some photo to be getting on with.
old RCD , J box , new breakers .

BUT I still confuse why the RCD tripped the RCD when the shore power was used only , (no problem with the inverter.)
when both shore and inverter power both used the same RCD .
any one explain ?.
again thanks everyone .

 

[PaulRainbow]

BUT I still confuse why the RCD tripped the RCD when the shore power was used only , (no problem with the inverter.)
when both shore and inverter power both used the same RCD .
any one explain ?.
again thanks everyone .

Glad to hear you found it Vic

I'd have the inverter installation checked. Make sure the Earth relay is working and that the inverter case is Earthed to the water. Your make should get an RCD tester to make sure the RCD trips when using the inverter.

 

[Boater Sam]

Neutral to earth fault, on inverter the relay connects the neutral to the earth so the rcd does not see the fault until the link is off and the land line is connected.

It is always odd thinking that the neutral to earth causes a trip, we get used to tracing line to earth too much.

 

[sailaboutvic]

Glad to hear you found it Vic

I'd have the inverter installation checked. Make sure the Earth relay is working and that the inverter case is Earthed to the water. Your make should get an RCD tester to make sure the RCD trips when using the inverter.

Sure Paul I pass that on to him .
I'm just glad I found the problem , it's when you at it for hours and still don't find a problem that gets me .
Any way they very happy .

 

[PaulRainbow]

Neutral to earth fault, on inverter the relay connects the neutral to the earth so the rcd does not see the fault until the link is off and the land line is connected.

Neutral and Earth are bonded at source on the shore power and they need to be on a normal inverter. Because the Victron Multiplus can be on at the same time as shore power the inverter neutral and Earth cannot be permanently bonded, they can only be bonded when the shore power is off, hence the relay.

So, if the inverter is installed correctly the RCD should behave in exactly the same way. It's possible to deactivate the relay or for the relay (or it's switching circuitry) to be faulty. It's also possible (more likely IMO) that the inverter case Earth is not connected to Earth (via the water).

It's a misconception that the RCD will trip if there is a leak even if the Earth is not connected. We know in this case that some water has got into a socket, that could be causing some minor continuity between live and neutral, but not enough to trip the MCB. With shore power connected and the shore side Earth working some of that current will go to Earth, the RCD will detect the imbalance and trip. When the inverter is on it should be the same, but if the relay isn't closed or the Earth connection isn't properly made, the leaking current has no fault path and the RCD will not trip.

 

[sailaboutvic]

@ Paul Rainbow
Paul thanks for that I pass it on ,
Some new I leaned too .
Never having a victron inverter/charger it's not some thing I looked into .

Vic