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.
 

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.
 

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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DaveInDenver

Expedition Leader
Provided its not damaged, been overheated, etc. nothing wrong with ’Knobbin wiring. Dissapates heat better than jacketed cable too !! But no grounding typically...Better use a cotton pullstring on that old bathroom luminaire.

Most AHJs require its removal if its exposed during some kind of building renovation.

Btw,
Those tubes work great to keep your knife sharp.
Indeed. Current code (Article 394) allows existing knob and tube to remain in residential and can be extended in hollow spaces and unfinished attics. Otherwise can't be installed or repaired, has to be replaced completely if you're touching it.

Bathrooms and kitchens would have to get GFI and 3 conductors. At least if you like your spouse and guests or you're getting permits and inspections anyway.
 

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