Jetta03
Alberta Canada
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Hi all. So I've recently added a 230 watt solar panel, twin grp 27 12 volt batteries, mppt controller to my 2009 Forest River Shamrock 21ss trailer. Works great, and I'm now in the process of hooking up a 1000watt pure sine wave inverter and have a question about grounding.
Should I connect the ground screw on the inverter to the trailer chassis? Not sure if it makes a difference but I plan to plug the trailer shore power directly into the inverter (with a/c, microwave, converter, electric hot water breakers all OFF). Would it ground through the ac connection?
Thx in advance
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2oldman
Winchester WA
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Sure. Does the installation manual say anything?
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smkettner
Southern California
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I would only bother with the case ground if inverter was permanently mounted.
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Jetta03
Alberta Canada
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Unfortunately I don't have the installation manual, it didn't come with one. The inverter is going to be permanently mounted.
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BFL13
Victoria, BC
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Yes, the ground lug on the outside casing of the inverter is to be wired to the trailer frame using the wire gauge stated in the inverter's manual. or just use #10 or #8 that is plenty fat enough for the likely length
What happens is on the inside of that casing (chassis) the 120v receptacle's ground prong hole may or may not be linked to that same chassis inside. If it is, then when you plug your shore power cable into a receptacle, that 120v ground prong will also reach the trailer frame at the other end of the shore power cord where it goes to the power centre and is grounded to the frame. Never mind that, it doesn't matter.
What does matter is that the neg DC input terminal to the inverter from the battery should not be linked directly to the inverter's chassis ground. Go to the frame from the chassis ground lug, not back around to its own neg input.
But! you say, the battery neg is grounded to the frame and that goes to the inverter neg. So why isn't that a Bad Thing? Answer is I don't know, but it seems to make everything happy to have that indirect connection, so just ignore that little detail and don't worry. 
Deck mounted converters have the same thing sort of. Their outside chassis ground goes to the rig's frame. Inside the chassis that ground lug is wired over to the 120v input cord's ground wire. But that is separate from the converter's neg output
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donn0128
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I did not ground mine. Manual did not say anything about it. I suspect that the 120V side is grounded internally thru the DC side.
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2oldman
Winchester WA
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Jetta03 wrote: installation manual, it didn't come with one.. What is the make/model?
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OnaQuest
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The case of your inverter should be grounded to your rig's chassis/frame.
The only reason most/some of the inverter manufacturers state that you should not hook the inverter case ground to the negative battery cable connection is because many inverter installations use a dedicated battery bank only for the inverter, and it may not have the negative battery terminal hooked to frame ground. This is quite common.
I suspect your battery bank is also serving as your house batteries, and therefore has it's negative side grounded to the frame. In this case, hooking the case ground to the battery negative would be electrically sound, but is not advisable, since unhooking the battery for any reason (maintenance, etc...)would also remove the case ground.
It's best to follow suggested practice and ground directly to frame ground.
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smkettner
Southern California
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Jetta03 wrote:The inverter is going to be permanently mounted. Definately use the chassis ground. This is a separate connection from inverter direct to the RV frame. I recommend #8 green.
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