Sorry if this is silly, but I'm not that familiar with conventions of doing electrical work on a vehicle that uses the chassis as the negative conductive path.So, I'm installing an inverter in my 5th wheel. Directions say to run pos and neg wires to the inverter from the battery (2 wires makes sense, given the current they might be handling). Then they say to run a ground wire from the inverter ground connection to the chassis of the vehicle. Now it just so happens that the only negative lead for the battery grounds to the frame. So, electrically, rather than ground the inverter to the frame, could I either a) connect the ground wire to the negative terminal of the battery, or b) just tap off of the main neg. going to the inverter, and use the tap to go to the inverters ground?On the 120v side, it has a GFCI outlet - would either of the variations above mess with how that works?

I would run a separate ground. It is only a little bit of #12 wire anyway. Fred.

Golden_HVAC wrote:I would run a separate ground. It is only a little bit of #12 wire anyway. Fred.Well, if I follow directions, it's supposed to be about about 3 feet of at least #0 wire to get to the nearest frame member.....better if 1/0 or 2/0. With terminals. So it gets to be a pain in the behind to source, crimp and route....Granted, for 120v AC, it would only be #12.....

I have often wondered about this myself. As near as I can tell connecting the Ground to the Negative isn't going to affect the operation of any inverter.-

Flapper wrote:Golden_HVAC wrote:I would run a separate ground. It is only a little bit of #12 wire anyway. Fred.Well, if I follow directions, it's supposed to be about about 3 feet of at least #0 wire to get to the nearest frame member.....better if 1/0 or 2/0. With terminals. So it gets to be a pain in the behind to source, crimp and route....Granted, for 120v AC, it would only be #12.....What inverter calls for that size wire for the chassis ground? Xantrex calls for #8 on their 3kw models (minimum of 4/0 for battery cables).

I would run the two wires back to the battery (of the recommended size) and then ground the inverter chassis to your frame with something like 12 gauge. Grounding the inverter chassis to your frame keeps the Inverter box (a Faraday shield) at the same potential as the chassis which minimizes noise from the inverter. The positive and negative inputs carry a lot of current so their respective inputs at the imverter are really moving with respect to chassis ground

Grounding an Inverter? | Good Sam Community

Calkidd
Explorer
Jul 17, 2014
Glad you go it going. I also got mine installed with the DPDT. I also install an indicator light to tell me when the inverter is on since it is mounted in the storage compartment.
Flapper
Explorer
Jul 11, 2014
Thanks to wwest who gave the most concise reason as to why jumpering the neg to the ground on the inverter may not be the best idea. FYI, I completed my install yesterday, as per the manuals instructions, and all is well. Still not completely clear on the theory of grounding, but it is more of an academic issue than an implementation issue for me now.
As far as conflicts between the inverter/converter...I got around that the easy way - there is one dedicated line coming from the inverter. If there is anything I need to run, I'll plug it into that outlet. 600w is too small for the AC, microwave, toaster, coffee maker, etc. We've got workarounds for all those from our tent camping days, anyway. All of the systems seem to be happy running at 12v, except the TV, so that will be the primary use. Now I just have to manage the amps for best battery life....
KJINTF
Explorer
Jul 10, 2014
enblethen

Agreed
This little inverter does not have an integrated transfer switch (which typically takes care of the neutral / ground switching) nor a charging function as the larger Inverter/Chargers do. Not sure when but the flexibility this little guy offers without that fixed internal connection could be of some use.
enblethen
Nomad
Jul 10, 2014
JJINTF:
Drawing is correct. Of course it is; that is how it is designed and tested by a testing laboratory such as UL or CSA. It grounds the neutral establishing a service point. Normally this connection is within the inverter and does not require an external jumper.
KJINTF
Explorer
Jul 10, 2014
It does indeed
Check out the Morningstar Solar web site
The Sure Sine 300 product manual clearly shows the installation requirements
Carb_Cleaner
Explorer
Jul 10, 2014
This is the max size allowed by the forum:

It appears to show the inverter's chassis ground tied to the A/C neutral wire (white wire) and an Earth ground (which I would assume is the RV's frame). That's the first time I've come across that layout for an inverter.
wwest
Explorer
Jul 10, 2014
Flapper wrote:
Sorry if this is silly, but I'm not that familiar with conventions of doing electrical work on a vehicle that uses the chassis as the negative conductive path.
So, I'm installing an inverter in my 5th wheel. Directions say to run pos and neg wires to the inverter from the battery (2 wires makes sense, given the current they might be handling). Then they say to run a ground wire from the inverter ground connection to the chassis of the vehicle. Now it just so happens that the only negative lead for the battery grounds to the frame. So, electrically, rather than ground the inverter to the frame, could I either a) connect the ground wire to the negative terminal of the battery, or b) just tap off of the main neg. going to the inverter, and use the tap to go to the inverters ground?
On the 120v side, it has a GFCI outlet - would either of the variations above mess with how that works?

Internal to the inverter the battery negative connect, also chassis ground, is often NOT carried over, connected to the inverter output side. GFI may not (cannot?) work unless the inverter case is connected to the RV chassis ground.

ALL 120 VAC current, amps, flowing in the HOT side (black wire) of the 120 VAC source MUST return on the neutral (white) wire. If ANY current is detected flowing in the 120 VAC ground return (green) wire the GFI will trip, open the circuit.
KJINTF
Explorer
Jul 10, 2014
The inverter install is as above
Check Morningstar web site for specifics

The Transfer switch aka DPDT 30amp relay came from a defective 50amp transfer switch out of a old inverter / charger - Darn thing had 12 of these very nice heavy duty DPDT relays in it.

Obtained the relay coil power from a plug in brick 115ac to 12VDC. The AC input to the brick comes directly from inverter. The DPDT connections open both White aka neutral and Black aka hot lines after the breaker and before the recp. Really very simple install and does for us exactly what it was inteneded to do.
Calkidd
Explorer
Jul 10, 2014
KJINTF wrote:
I agree the Breaker is part of the standard wiring and might not be needed on the inverter source leg if the inverter has a dedicated fuse or breaker.

There are hundreds of ways to properly install an inverter. I used a 30amp DPDT relay with a 12Vdc coil to isolate a single AC circuit, one of the two recp circuits. When the inverter is "on" the circuit is always inverter powered when "off" and I have shore or gen power the circuit is powered normally.

Grounding is indeed confusing because we really do not have a ground in the RV's. This is from the Morningstar Sure Sine 300 manual - wired mine this way except the AC output with it's 3amp fuse drives the 30amp DPDT relay.

I can't really see the diagram, but do you think you could post a diagram of how you have your's wired? It sounds like you have a homemade transfer switch.
KJINTF
Explorer
Jul 10, 2014
I agree the Breaker is part of the standard wiring and might not be needed on the inverter source leg if the inverter has a dedicated fuse or breaker.

There are hundreds of ways to properly install an inverter. I used a 30amp DPDT relay with a 12Vdc coil to isolate a single AC circuit, one of the two recp circuits. When the inverter is "on" the circuit is always inverter powered when "off" and I have shore or gen power the circuit is powered normally.

Grounding is indeed confusing because we really do not have a ground in the RV's. This is from the Morningstar Sure Sine 300 manual - wired mine this way except the AC output with it's 3amp fuse drives the 30amp DPDT relay.

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