Hi,
I'm not understanding your 2n paragraph. If you ground the inverter case to the RV chassis, how is this creating two places where the AC neutral is bonded to ground? It seems to me that the AC neutral is bonded to ground in the inverter (and only there), and the inverter case is grounded to the chassis - how does that create two neutral to ground bonding points?
But, the DC side of the inverter also has grounding requirements.
If you think about the DC side of the inverter grounding requirements, the inverter case needs to be grounded to the chassis for the case of the 12 volt DC faulting to the inverter case - this has to be done no matter what is happening on the AC side. According to the Samlex inverter manual, the wire used to bond the inverter case to the chassis should be large enough to blow the inverter fuse - quite a large conductor for most inverters.
From the Samlex manual - note that they also provide links to two white papers on grounding, which should make for some great bedtime reading.
The excerpt just below is from the Samplex 1212F inverter/charger manual:
https://samlexamerica.com/wp-content/uploads/2021/01/11027-EVO-1212F-1224F-0220_Hrez.pdf
See the sentence I bolded ...
"
3.11 GROUNDING TO EARTH OR TO OTHER DESIGNATED GROUND
i
INFO
Please read following on-line White Papers for complete understanding of Grounding at www.
samlexamerica.com (Home > Support > White Papers):
• “Grounded Electrical Power Distribution"
• “Grounding System and Lightning / Ground Fault Protection”
SECTION 3 | Installation
SAMLEX AMERICA INC. | 57
Grounding means connecting (bonding) to Earth Ground or to the other designated Ground. For example, in a
motorhome / caravan, the metal frame of the motorhome / caravan is normally designated as the Negative DC Ground
/ RV Ground. Similarly, all metal portions of boats and marine craft are bonded together and called Boat Ground.
Grounding is required for (i) protection against damage due to lightning strike and (ii) protection against electric shock
due to “Ground Fault”. In case of EVO™, “Ground Fault” may occur due to inadvertent contact between an energized
ungrounded current carrying conductor and exposed metal surface resulting in voltage getting fed to (i) the metal
chassis of the EVO™ or (ii) to the metal chassis of the devices connected to EVO™ or (iii) to the metal frame/ chassis
in an RV / motorhome / caravan. When this energized exposed surface is touched, the voltage will drive current
through the body to Earth Ground producing electric shock. When properly grounded to Earth Ground (or Frame /
Chassis Ground in motorhome or caravan), the Leakage Current Protection Device (like RCD, GFCI etc.) or Over Current
Protection Device (like Circuit Breaker or Fuse) will trip and interrupt the circuit feeding power from the AC source
(EVO™ / AC Input) or the DC source (12V / 24V battery). Proper grounding will ensure that all exposed metal surfaces
will have equal potential and will be bonded to (i) a single common Earth Ground point i.e. the Ground Rod / buried
metallic water / gas pipe at the premises or (ii) the Frame / Chassis Ground in a motorhome / caravan.
3.12 GROUNDING ARRANGEMENT
Internally, EVO™ consists of DC and AC Section that are isolated through a transformer (See these sections in Figs 3.12
and 3.13). Both these sections are required to be grounded appropriately.
For wiring details for appropriate grounding, refer to Figs 3.12 and 3.13, and associated explanation under Section 3.13
and 3.14.
When using a generator instead of Grid, please ensure that the Neutral of the generator is bonded to the metal frame
of the generator and the metal frame of the generator is bonded to Earth Ground through the Grounding Electrode
(GE) i.e. the Ground Rod. Refer to Section 3.14.1 for additional details.
3.13 DC SIDE GROUNDING
Please refer to Figs 3.12 and 3.13.
DC side grounding involves bonding of the metal frame/chassis of EVO™, the metal chassis of the DC Electrical Panel
and the Battery Negative Terminal to Earth Ground in shore based installation (Fig 3.12) or to the metal frame / “Chassis
” of the motorhome / caravan (Fig 3.13).
This ensures that in case of a ground fault in the +12V / +24V circuit, the
fuse in the +Battery line blows to clear the fault. This fuse in the +Battery line has Ampere capacity matching the rated
DC input current of the EVO™ in Inverter Mode. The wire size used for DC side grounding should be minimum AWG
#6 or of the same size as the battery cable, whichever is thicker (Battery cable size should have minimum Ampacity ≥
the Ampere rating of this battery fuse depending upon the model of the EVO™ being used). This recommendation
on sizing of the DC Side Grounding Wire will be superseded by the National / Local Electrical Codes."
It goes on after this to talk about grounding the AC side of the inverter.
I do agree its a very confusing subject.
Gary