Connecting a 300W Inverter

Pilotamis

Observer
I was given a 300W inverter and I’m not entirely certain how to wire it up. The DC side has an earth ground terminal that that is bonded to the chassis of the inverter. The AC side has only 2 terminals, no ground. My plan is to use a GFCI receptacle to charge laptops and camera batteries. Does the ground on the DC side of the inverter need to be bonded to the battery negative? Does the ground wire for the 120V line get used? If I grounded the GFCI to the inverter would that protect both chassis? Both the GFCI and inverter chassis are isolated if I don’t. I didn’t know if bonding them, the GFCI would protect both, but I don’t think so.

 

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RandyP

Adventurer
In your case it is simpler, read the "Note" in the instructions and complete item #4 in the wiring description. done.. <edit> the complete wiring diagram is figure 6, including all grounding.
 
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RandyP

Adventurer
Note that in the Sure Sine Install & Op manual, last page lists GFCI devices by mfgr/part number that work with your inverter. Make sure to use one of the recommended devices.
 

dreadlocks

Well-known member
Most code calls for Neutral and Ground to be bonded at Mains, and only at mains.. Is the wiring to this ONLY hooked up to the inverter or is it also hooked up to shore power? transfer switch?

If outlets are ONLY wired to Inverter, bond Neutral and Ground at Inverter.. if outlets are wired to Shore/Upstream Mains also, then do NOT bond Neutral and Ground at the inverter unless you have a transfer switch that transfers neutral.

for the most part anyhow, gets a lil complicated to stay in code once you throw a generator w/floating neutral.. usually easiest to modify generator to bond neutral if you want to stay in code.
 

Verkstad

Raggarkung
It looks very simple and straight forward if reading that instructions manual. Its all on page 10...
As far as bonding battery negative to earth ground, its not shown that way in instructions. At least as a dedicated negative to ground jumper. But if installed in a car, negative and earthground will be at same potential anyway.

GFCIs, obviously use one of the models shown.
I dunno specifics of those GFCIs. Perhaps they are listed for portable equipment, which you will quickly learn to hate...
I was given a 300W inverter and I’m not entirely certain how to wire it up. The DC side has an earth ground terminal that that is bonded to the chassis of the inverter. The AC side has only 2 terminals, no ground. My plan is to use a GFCI receptacle to charge laptops and camera batteries. Does the ground on the DC side of the inverter need to be bonded to the battery negative? Does the ground wire for the 120V line get used? If I grounded the GFCI to the inverter would that protect both chassis? Both the GFCI and inverter chassis are isolated if I don’t. I didn’t know if bonding them, the GFCI would protect both, but I don’t think so.

 

DaveInDenver

Expedition Leader
There is quite a bit of code compliance and safety items when grounding an inverter. I just read thru the grounding section of the Magnum MSH3012 M smart inverter pages 23-27. Answered all my questions. You might look at it.
Note that this particular Magnum device is assumed to connect to shore power (e.g. the electrical grid) and has a transfer switch built in. It'll also reverse in stand-by and charge the battery. The rules and ABYC & NEC codes it follows are not universal for every generator or inverter nor every installation.

It's usually best to read the manual for the actual device.

Screen Shot 2019-11-08 at 7.02.22 AM.png
 
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DaveInDenver

Expedition Leader
Morningstar doesn't give direction other than to say these GFCI are the only ones approved for using with this inverter. Morningstar doesn't clarify grounding, floating or NEC adherence any further other than the diagram nor do they mention shore power.

Screen Shot 2019-11-08 at 7.32.49 AM.png

Either way, grounded or ungrounded, a GFCI is going to work. GFCI compares hot to neutral and if there's a current imbalance they open. The assumption is that if current is delivered on hot but not present in the same magnitude returning on neutral it must by default be shorted to ground.

To work GFCI does rely on the fact that neutral is well connected. When the neutral/return has a spotty connection they trip, so they can be a real nuisance. I assume Morningstar has tested the ones they list to make sure they'll actually work acceptably.
 
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RandyP

Adventurer
I used this same inverter in a popup camper for years. ac went to one GFCI duplex receptacle. Plugged in a power strip there with multiple outlets. Charged many different DC batteries from the plug strip. Worked flawlessly.
 

DaveInDenver

Expedition Leader
FWIW, just a data point I suppose. Toyota offered a factory installed inverter and I have one in my truck. It appears in the wiring diagram that the 120V outlet ground is tied to chassis and thus battery negative, which I verified is truly the case. The wiring diagram doesn't show a neutral-ground connection and it measures open, so there's nothing in the circuit that seems to bonds neutral to ground. Nothing indicates there's GFI but it's possible it does internal to the inverter, that I couldn't say.
 

RandyP

Adventurer
There should be a ac Neutral to ground (on the device) jumper and the ground should be bonded to the grounding electrode (vehicle chassis). If the ac neutral is not bonded to the chassis ground and the ac hot goes (shorts) to chassis ground, any ac over current device in the schem will not clear the fault, and the neutral conductor will be an elevated voltage compared to chassis ground. You could get shocked if you touch both the chassis ground and the neutral circuit wiring conductor.
 

Verkstad

Raggarkung
To work GFCI does rely on the fact that neutral is well connected. When the neutral/return has a spotty connection they trip, so they can be a real nuisance.
Further, Most GFCI receptacles wont work if its supply neutral is disconnected.
That situation is hazardous because its ungrounded output conductor can remain energised. Without a connected supply side neutral, the GFCI does not have internal power to operate.

This is remedied by using a listed for portable equipment GFCI.
That type needs constant power to remain "on". If either supply conductor fails, Its output relay falls open and will not manually reset until power is applied again.

Dunno offhand how AHJ applies that to campers.
If it can plug into mains, Basically a camper is portable cord connected equipment.
One could plug their dodgy shorepower cord into a dodgy campground receptacle and not have GFCI protection on its ungrounded conductors.
 
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DaveInDenver

Expedition Leader
Is open neutral part of the 2015 revision to UL 943 for GFCI that now must self test and lock out? The list of recommended outlets Morningstar includes appears to be those newer style GFCI that you would find at Home Depot.
 
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Verkstad

Raggarkung
Does an open neutral protecting GFCI require an earth ground? Would one function floating?
Dunno...
At least with portable GFCIs of a few years ago. Those require no ground. Using electrically latched relay to remain on. Dropping its supply power, dropped out its relay so it needed a manual reset after its supply was switched back on.
But nowdays there are "self resetting" portable GFCIs. Upon re-power, they will turn back on. Never played around with that type, But I suspect they dont need ground either.
I think the Morningstar recommended outlets are the improved 2015 UL 943 types that constantly self test. They come out of the box tripped and won't reset if wired incorrectly.
Same dunno thing there. I installed a few since they were introduced, But not examined them in detail.
Said that, Since GFCIs may be used to retrofit old work, (2 wire receptacles). One might safely conclude the newer GFCIs dont need a grounding conductor to operate.
 
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