Staying safe

[SquirrellCook]

1. Should you or should you not ground your electrical hook up to your vehicles body?
2. Should you ground your Inverter (Inverters) to your vehicle body.
3. If you have grounded any mains devices to the vehicle body should you use an earth spike to ensure that ground is 0 volts?
4. Do RCD's work if your mains equipment is not grounded?
5. If you are using a RCD for external mains connection should you also be using one for your inverter?
6. If you have an inverter connected to your starter battery and one also connected to your leisure battery can both inverters share the same ground and if so do they both need RCD's?
7. If you were switching between mains and an inverter to power the same devices would you connect the inverter and switch before or after the RCD?

 

[wildebus]

Question ... You are saying RCD a lot. Do you actually mean RCD or do you mean MCB?

 

[SquirrellCook]

Please correct me if I'm wrong, but don't consumer units have RCD's as the initial protection?

 

[Nabsim]

In answer to Q4: yes they trip if appropriate when there is no ground from vehicle to earth apart from the ground in the ehu cable. Or at least mine have

 

[wildebus]

Please correct me if I'm wrong, but don't consumer units have RCD's as the initial protection?

Yes they do indeed. but just wanted to clarify as a couple of the points would point (in my mind anyway) to thinking Breaker rather than RCD.

1. Should you or should you not ground your electrical hook up to your vehicles body?
2. Should you ground your Inverter (Inverters) to your vehicle body.
3. If you have grounded any mains devices to the vehicle body should you use an earth spike to ensure that ground is 0 volts?
4. Do RCD's work if your mains equipment is not grounded?
5. If you are using a RCD for external mains connection should you also be using one for your inverter?
6. If you have an inverter connected to your starter battery and one also connected to your leisure battery can both inverters share the same ground and if so do they both need RCD's?
7. If you were switching between mains and an inverter to power the same devices would you connect the inverter and switch before or after the RCD?

1. There seems to be two different thoughts on this one that goes around. I am with the "connect EHU Earth to Chassis" team
2. They generally recommend it. I generally do
3. Meant to be good practice with a Generator. I generally don't as the vehicle is often moving when the 230V devices are powered by the inverter. When on EHU they are grounded via the EHU lead anyway so is there a need?
4. Should do
5. Interesting point. I would consider using an MCB on the Inverter outlet but not an RCD
6. Bit of a moot point to if they can share the same ground as the chances are the Leisure Battery and the Starter Battery use the same electrical ground, so you don't really have the option to do otherwise.
Do they both need RCDs? well if you were fitting an RCD it would be on the 230V output of the Inverter, not the 12V input, and the inverters are not going to go to the same outlets I presume? If you WERE using both inverters to the same circuit you could use the same RCD but you would have to make sure the inverter outputs were always electrically separated from each other otherwise it would likely not be pretty (unless the Inverters were designed to be paralled together, but I am guessing that won't be the case here?)
7. If talking about the main incoming RCD, then after - as the EHU would go to the RCD, and then distribute out to multiple circuits, one of which would be the Inverter/Mains switchover box. Then the answer is same as #5 I would say.
In this scenario, I would see the question of being a circuit is generally protected by an MCB and a Installation by an RCD - you want the circuit when fed by EHU to continue being protected by the MCB so do you feed the Inverter output to the MCB input and then to the sockets, or do you feed the MCB output to the Inverter/EHU switch and then to the sockets. You don't really want an RCD in the CU as an overall protection AND an RCD on a circuit as well, so I would only have one RCD in any supply chain.

Those are my thoughts anyway.
For what it is worth, in my setup I have an RCD that the EHU comes into, multiple MCBs for various circuits, of which one circuit is dedicated to the Multiplus Inverter/Charger. The output of the Multiplus goes to two more circuits, but via MCBs, this gives an extra level of control/protection over those two individual circuits - a bit like if you have a secondary garage Consumer Unit fed by the House CU through a particular breaker.

 

[SquirrellCook]

It's interesting to read others views as it's often possible to mislead oneself. (I've always done it this way it must be right)
Hunting for any serious information did not prove easy, then I remembered (Victron Wiring Unlimited) Look on the right hand side of the home page for this site.
Anita's answer was to read her electrical safety regulations books, but that could take weeks
Off topic a bit, but relating to industrial installations also. It seems a RCD must have a Neutral and Earth connection for it to work. A 3 phase electric motor does not have a Neutral connection! So many Industrial installations are not safe. You would need a consumer unit just for 3 phase motors. The RCD would then have one of it's output phases wired to the Neutral. That's ok until someone fits a 240 volt lighting transformer and introduces an neutral wire. When testing a RCD with a missing Neutral it does not show a fault. I expect the same with a missing Earth.

From my interpretation of the victron document they recommend all 240 volt sources go through a RCD, unless you never use external mains. Then a RCD is not required as long as you don't earth anything and allow the voltages to float.

 

[wildebus]

Something that is worth bearing in mind ... Many (most?) Inverters provide a Live and a Neutral Connection but the Earth output is not connected.
So this all adds a difference when comparing with a meter or tester:

1. Output of a standalone Inverter vs
2. Output of an Inverter connected via an Auto-switch (where the Earth is usually commoned between the 2 inputs and one output) vs
3. Output of an Inverter/Charger vs
4. Output from EHU fed circuit

Something that is not mentioned but I think is a good idea is the use of DP MCBs on sockets that you 'interact' with. So a mains charger that plugs in when you bought it and lives there forever more - no need as could be the same as being hardwired. but a socket that you plug a hairdryer into, or a coffee machine, or whatever - that should be fed via a DP MCB ideally. (but don't like the idea of an RCD feeding another RCD really, so I don't think I would have an RCD on the output of either 2, 3 or 4 on the list above as there will be an RCD already at the source (for 3 & 4 for sure, and for 2 depending on the switch state))

 

[linkshouse]

RCD is an abbreviation for Residual Current Device. They can and do work on three phase circuits with no neutral as well as single phase circuits with a neutral.

This is easier to grasp with a single phase circuit with just a live and a neutral.

If the current flowing in the live wire is not the same as the current flowing in neutral conductor then something is clearly awry! The RCD detects this difference and any difference of more than 20mA (typically) will cause the RCD to trip.

As for three phase circuits with no neutral the same still applies the total current going in one direction (source to load) must be the same as the total current going in the opposite direction Load to source), I know we are talking about AC circuits but here we are talking about at any instant in time.

Phew! I hope that makes sense and helps.

Phill

 

[SquirrellCook]

RCD is an abbreviation for Residual Current Device. They can and do work on three phase circuits with no neutral as well as single phase circuits with a neutral.

This is easier to grasp with a single phase circuit with just a live and a neutral.

If the current flowing in the live wire is not the same as the current flowing in neutral conductor then something is clearly awry! The RCD detects this difference and any difference of more than 20mA (typically) will cause the RCD to trip.

As for three phase circuits with no neutral the same still applies the total current going in one direction (source to load) must be the same as the total current going in the opposite direction Load to source), I know we are talking about AC circuits but here we are talking about at any instant in time.

Phew! I hope that makes sense and helps.

Phill

I'm still convinced I've discovered a horror with the 3 phase motor RCD protection. I must pluck up enough courage to spend a week or more reading Anita's books.

 

[SquirrellCook]

Something that is worth bearing in mind ... Many (most?) Inverters provide a Live and a Neutral Connection but the Earth output is not connected.
So this all adds a difference when comparing with a meter or tester:

1. Output of a standalone Inverter vs
2. Output of an Inverter connected via an Auto-switch (where the Earth is usually commoned between the 2 inputs and one output) vs
3. Output of an Inverter/Charger vs
4. Output from EHU fed circuit

Something that is not mentioned but I think is a good idea is the use of DP MCBs on sockets that you 'interact' with. So a mains charger that plugs in when you bought it and lives there forever more - no need as could be the same as being hardwired. but a socket that you plug a hairdryer into, or a coffee machine, or whatever - that should be fed via a DP MCB ideally. (but don't like the idea of an RCD feeding another RCD really, so I don't think I would have an RCD on the output of either 2, 3 or 4 on the list above as there will be an RCD already at the source (for 3 & 4 for sure, and for 2 depending on the switch state))

Victron seem to like two RCD's I wonder if that is double Dutch?

 

[wildebus]

Interesting.
Good protection but if an RCD trips when on hookup, which one will it be? as they are next to each other in that example, will it matter? not really. But will you know why it tripped? not necessarily.
I could change my MP Outlet CU from a 2 way 2-MCB one to a 4 way 2-MCB + RCD like in that example.

I've been thinking of tidying up all my wiring as it has got all kind of bits and pieces from the various testing I do anyway

 

[wildebus]

This is an interesting discussion

I was checking out the Victron community for discussions on this subject and came across this point which is relevant to the Multiplus.
from https://community.victronenergy.com/questions/25706/victron-multi-rcd.html
You need to leave the "Ground Relay" box ticked.
The Ground relay will close when mains is not present and the bypass relay is open.
The ground relay connects the earth wire and neutral wire together. This is what defines the Neutral. Fault current can then flow from Live via the Earth wire to get back to the transformer in the MultiPlus which will result in an imbalance of current flowing through the RCD causing it to trip.
Similarly, fault current can flow through your body, through the soil, through the earth rod and reach the MultiPlus' transformer via the earth wire connected to the earth rod - which will cause an imbalance of current in the RCD and it will trip.

When on mains, the bypass relay closes and the Ground Relay will open. The Earth-Neutral bond is made at the incoming supply to the house. When on mains, the RCD operation will work like above, but using the house's incoming Neutral - Earth bond instead.

I checked my settings and the ground relay box is checked by default.
This was a reply to a question from someone using the unit in their shed, so a ground spike/earth rod is doable. bit harder in a van.

 

[SquirrellCook]

The only thing you are doing with an earth spike is holding ground at zero volts. Even if ground floats above zero volts the RCD can still work as the voltages and currents float too. Just don’t pass a data cable though the window to another computer or you could blow the comms ports. I guess this is why on a three pin plug the earth pin is longer.

 

[Nabsim]

I must say it’s all beyond me but I thought I had seen that having more than one RCD for the same thing was not good. I believe it may have been in relation to say adding wiring for a shed taking power from a plu inside the house.

I will also say I did exactly that on advice from sparky sat work years ago. Ran an armoured cable to a separate consumer unit in the shed that had a 3 pin plug on the end.

 

[wildebus]

It can be a pain that is true.
If you think about it, most people here will be running 2 RCDs in series. One in their van and one on the EHU Source (house or campsite) that is supplying power to the van RCD.
It doesnt stop anything working but when you don't what RCD will trip .... Annoying.

 

[Nabsim]

I never run an earth when I use my generator. I connect it to the EHU point on the van once running. Usually it just runs the 2 battery chargers and the Dyson is always plugged in so that gets a top up. I don’t think I actually use anything more than chargers at any time genny has been used so no device has an earth connected in the plug.
I presume this isn’t a problem as I have been doing it getting on for a year now?

 

[SquirrellCook]

Have a read of Victron Wiring Unlimited page 56 to page 65 it shows quite clearly why some installations don't require grounding and some become dangerous if inadvertently grounded. Like plugging into domestic mains. It's nice to know your safe and others too.

 

[wildebus]

Interesting.
Good protection but if an RCD trips when on hookup, which one will it be? as they are next to each other in that example, will it matter? not really. But will you know why it tripped? not necessarily.
I could change my MP Outlet CU from a 2 way 2-MCB one to a 4 way 2-MCB + RCD like in that example.

I've been thinking of tidying up all my wiring as it has got all kind of bits and pieces from the various testing I do anyway

I'm tidying up some wiring in the van today and I forgot that I DO actually have an RCD fitted on the Multiplus Output!
On one output I have just an MCB on one set of sockets; but on the others that include a socket near the sink and an external socket that I use for power tools I had added an RCD between the Multiplus and the Sockets for additional safety.

As an aside, if people are reading this thread and thinking maybe they want to add an RCD or MCBs to their inverter outlet, these are a couple of handy little Consumer units types that I think are useful.

2020-07-02_12-45-34 by David, on Flickr
The 5-way one is actually setup for an Incoming RCD, a DP MCB for Circuits and a SP MCB for the Battery Charger, but could easily be a left as a 4-way with a RCD and a Single DP MCB for an inverter outlet
The 2-way one would be the ideal one I think for an Inverter where you want to add RCD Protection. Nice and small so easy to find a place for usually and in this case fitted in fact with an RCBO, which is essentially a combination RCD and MCB and perfect for a single circuit protection from a supply.
Available from all the usual sources.

 

[SquirrellCook]

Just a thought Dave.
You have power coming in on your hookup. Live and Neutral have been reversed.
This is feeding your Multiplus and all your domestic sockets are powered from the multiplus.
I guess being an inverter the multiplus isn't that fussy about what it's being fed?
Would the multiplus correct the live and neutral fault?

 

[wildebus]

Just a thought Dave.
You have power coming in on your hookup. Live and Neutral have been reversed.
This is feeding your Multiplus and all your domestic sockets are powered from the multiplus.
I guess being an inverter the multiplus isn't that fussy about what it's being fed?
Would the multiplus correct the live and neutral fault?

I don't think it would correct it. I am pretty sure that it absolutely would not in fact.
The reason is (This is my logic - it might be wrong) that one of the great features is that it can provide Power Assist to the EHU.
So say you had a campsite with a 6A hookup and you turn on your 2kW water heater (which wants around 9A of power). The EHU will give it 6A but the Inverter within the Multiplus will top up the remaining 3A.
If the Multiplus did switch over L & N, then ALL the power would have to go through the inverter, some from the battery and some from the EHU?
possible, but .... with the Power Assist, you can get much more than the Inverter is rated at. If I had a 10A hookup for arguments sake, I could with the Multiplus run the 2kW inverter AND a 2kW Induction hob at the same time without anything tripping - 2,400W would come from the EHU, and 1,600W assistance from the Battery via the Inverter in Power Assist mode. The inverter could not deliver 4000W on its own.

I remembered there is an interesting video on the Multiplus and how it works posted by Victron. Well worth a watch (I just did to see where it discusses Power Assist .. around 7 minutes in)

There is the same question raised on the Victron community - https://community.victronenergy.com/questions/9224/l-and-n-inverted-input.html
The 'accepted' answer is actually from the lady who authored the Victron 'Wiring Unlimited' PDF



Your question does raise an intriging question actually ...
Let's just say the L & N on the EHU are not 'corrected' so you are feeding the Multiplus the wrong way round on a dodgy French campsite with the paltry 6A hookup.
In off-grid mode, the Interter supplies AC Power - and the Live and Neutral are correct
In Power Assist mode, the power comes from both Mains AND Inverter. Does the Inverter part swap its internal L & N round to suit the incoming? or is there not really a defined true L & N output from the inverter anyway?
And how will the RCD act?


I think once I get my setup back in place (just relocated my Consumer Units a bit) I will swap the L & N on the incomer to the MP and see what the tester tells me for those scenarios (I'll post what I find here).
But when you consider the features of a Multiplus, I think it maybe makes it even more important to check the EHU polarity is right?

(I think the comments on the Victron community site are very Euro-centric where they don't really take that much notice of L & N reversing and so their consumer units and sockets are often 'better' than ours, where we have more expectation that the source is correct and don't accomodate for the reverse. Hence why DP MCBs are a good idea!)