New OffGrid Victron - Possible Ground Loop ?

[Snapperhead]

Hi AC Power guru’s…..

I know this topic has been done to death, and I have been reading posts till my eyes are bleeding… But I can’t find a definitive answer to my specific question. Most posts relate to boating with shore power anomaly’s, RV Vans with their chassis dilemmas or complicated multi-phase setups with GFCI issues….

There appears to be conflicting opinions on this diverse topic, so here is my question to make my newly installed off-grid back-up circuits safe and get my head around Earth / Neutral bonding once and for all

From looking at the attached pics and sexy diagram, this is how my newly installed and fully compliant system is right now, prior to the connection of any domestic mains supply or AC generator input. Due to my very limited solar array and allusive Winter sunshine here in the Mountains of South Eastern Australia…. I’m wanting to supplement this stand-alone system with some power from my existing domestic supply to charge my battery’s when they are critically low. This new stand-alone system supply’s my fridge, two water pumps and my home lighting only. (see below for system specs)

My questions are as follows:

1. Should the Earth/Neutral bond strap in DB-2 Sub Board (see pic #3) be connected at all ? Or should the E/N bond be controlled by, and within the Quattro only ?

2. When my domestic supply power (DB-1 Main Board) is connected to the Quattro (AC in 2), should the loads on DB-2 Sub Board obtain their E/N bond from the power source (i.e. DB-1 Main Board) and NOT locally from DB-1 Sub Board via it’s E/N bond strap ? (assuming the Quattro’s Earth Relay opens as it should whilst it is connected to AC power on it’s AC input, and it’s own E/N bond is disconnected also)

3. Should I include the Earth wire at all from my domestic supply (DB-1 main Board) when supplying the Quattro with power (AC-in 2) due to the fact that both DB-1 Main Board and DB-2 Sub Board both have separate Earthing Rods (approx. 15 metres apart) ? (my instincts say ‘absolutely YES’ but I need this confirmed)

4. Should the earth wire on the output of the Generator be connected to the Quattro AC-in 1 also ? Or left as it is now with it’s output Earth and Neutral and Active connected to DB-2 Sub Board first (via circuit breaker) and then only Active & Neutral cables going into Quattro AC-in 1 ? (see pic #2) i.e. When system is running on Generator AC, shouldn’t the Power Source (Generator) dictate the E/N bond and NOT the DB-2 Sub Board ? (assuming again the Quattro’s Earth Relay opens between it’s Earth & Neutral whilst the Generator AC is present on AC in 1) and (assuming the Generator does in fact have it’s own internal earth neutral bond)

5. Finally, from looking at my beautiful diagram, where would you expect to see RCB units installed ? At present, the only RCB’s within DB-2 Sub Board are on the output loads. Am I right in assuming there should be an RCB (RCD / GFCI / RCCB) between the output of the Inverter and DB-2 Sub Panel ?

Much thanks in anticipation of any light you could shed on this, and avoid my sleepless nights laying awake pondering earths, neutrals and electrified things…..

 

[Snapperhead]

System Specs: (see pic #1)

Quattro II 230v 48v/5K/70

2.64kW PV 3S2P

2x BSL LiFePo4 48v Connected via CAN-Bus)

Cerbo GX

Victron MPPT 150/60 (connected via V.E Direct)

 

[Snapperhead]

Testing has shown my Generator is in fact NOT Earth/Neutral tied as suspected… Still no advice re above sub board bonding and safe way to use shore power for charging ???

 

[mikefitz]

any light you could shed on this

My thoughts on your system.

Picture 1 shows the generator outout connected to the Quatro and DB2 , is this a requirement?

The Quattro provides a neutral to PE when stand alone. If AC is present on either of the AC inputs it releases the stand alone ground and relies on the neutral to PE bond to be provided by the AC source.

The usual application of the Quattro is either inverter or pass through, AC grid or generator

Normally the AC main board has the neutral to PE bond, not the sub board . When on generator AC , the neutral to PE bond is at the generator .

What confuses the situation is that it appears you will have three seperate supplies via DB2 in the dwelling, the grid powering stuff, the Quatro powering other stuff from grid/ inverter/ generator, and generator powered stuff

If the Quattro powered stuff is in seperate building with no grid powered stuff, then don't export the PE from main board to Quattro, only L and N, use the local earth rod for PE.
If the Quatro power and grid power are running in the same building, only use the main panel PE earth rod and ignore the sub panel PE rod.
I would expect RCBO protection on outputs of the Quattro.

I may have not fully understood your system and have assumed Incorrectly what's required. Hopefully my ramblings will prompt input from others.

 

[Snapperhead]

My thoughts on your system.

Picture 1 shows the generator outout connected to the Quatro and DB2 , is this a requirement?

The Quattro provides a neutral to PE when stand alone. If AC is present on either of the AC inputs it releases the stand alone ground and relies on the neutral to PE bond to be provided by the AC source.

The usual application of the Quattro is either inverter or pass through, AC grid or generator

Normally the AC main board has the neutral to PE bond, not the sub board . When on generator AC , the neutral to PE bond is at the generator .

What confuses the situation is that it appears you will have three seperate supplies via DB2 in the dwelling, the grid powering stuff, the Quatro powering other stuff from grid/ inverter/ generator, and generator powered stuff

If the Quattro powered stuff is in seperate building with no grid powered stuff, then don't export the PE from main board to Quattro, only L and N, use the local earth rod for PE.
If the Quatro power and grid power are running in the same building, only use the main panel PE earth rod and ignore the sub panel PE rod.
I would expect RCBO protection on outputs of the Quattro.

I may have not fully understood your system and have assumed Incorrectly what's required. Hopefully my ramblings will prompt input from others.

Thanks heaps for your input Mike . . . This is a newly installed system (and supposedly compliant) for separate and dedicated circuits within my home. It only runs my house lighting, water pumps and fridge. These circuits are all separate from the main DB-1 and consist of hard wired outlets into DB-2, which as you can see has it's own E/N Bond which I'm confused about.... as I've learned that stand-alone systems such as mine should get thier E/N bonding from the source (i.e Quattro Ground Relay)

The system wasn't wired or configured for any AC Input or generator, however the installer has stated any generators here in Victoria must be hard wired and not connected by any removable plug/socket.

What I'm wanting to do it simply have the option of charging my battery's from my house mains and/or generator when the battery's become critically low, or as a redundant (pass through) power source should the Quattro fail etc. (my existing home grid connected power system has lots of excess solar during the day)

The basic wiring was left as per pics by the installer, so I could include a generator socket after after it was certified and inspected etc. My first question is the best way to wire the generator..... through DB-2 (into it's E/N bond) as it has been prepared to do, or directly into the AC-In 1 of the Quattro (which I feel is the better way to go), keeping in mind the generator doesn't appear to have it's own E/N bond (which is weird - it's a BlackDiamond Gen7S - 6.5kVa - I've measured 3.5 M Ohms between Earth / Neutral) I'm assuming I'd have to bond this generator at it's output ?

Secondly, I have a dedicated 15A outlet (4mm cable) next to the Quattro that is wired into my main DB-1 with it's own dedicated Circuit Breaker within DB-1 and nothing else on that circuit. This is what I'm intending to use to charge the battery's once I'm sure I've understood the grounding requirments. I'm feeling that the E/N bond located in DB-2 should not be there, as when the Quattro is inverting, it is providing the necessary bond. Likewise, when I'd have the Quattro AC-in 2 plugged into the house system (DB-1), the Quattro will open it's Grounding Relay and the system should then obtain it's bond from DB-1 as it's new souce (and point of disconnect) right ? Am I on the right path ?

I have setup the relevant Assistants within Ve-Config using the CerboGX Relay and the Quattro Aux relay (using AC-Ignore general flag) etc for using the AC-In 2 when it's connected...... So that's all good to go. I'll be controlling the charge from this 'Shore Power' setup manually to start with, then play with S.O.C. and load parameters down the track.

I'm just wanting to avoid any current moving between my earthing systems or creating any sort of ground loop...... So far all my RCB's are triggering as per normal when tested (25mA - So that's good I am also somewhat confused about having both earth rods 15 metres apart and how they will interact with each other / or not ?

Really appreciate any input before I begin testing the AC Inputs.