Yoda's Victron MultiPlus and Solar Install - just hope I don't mess up.

[howson]

I don't have a dog in this fight (yet) and mostly am sitting back going , but this caught my eye,

"As for grounding the chassis of an MPPT charge controller to the chassis of your rig, when you are on rubber tires, I can’t imagine a scenario where that would make any sense. Maybe it gives you some protection from lightning that is close, but not too close? I don’t know what someone would gain from that."

Would the circumstances of being parked at almost anytime change that equation as you will have jacks / levelers (or at least the nose jack) in contact with the ground rather than than being insulated by the tires?

Funny, I knew that statement would draw attention but resisted the urge to edit the text. My .02: lightning will tear the crap out of our trailers if it hits it (or even close). Lightning is so powerful it can destroy everything in it's path and even cause a fire resulting in total loss of the unit. When it comes to lightning, IMO the only real protection is good insurance.

If we want to discuss lightning mitigation further, I can copy Jerry's post (and my response) to a new thread for further discussion.

Howard

[Yoda]

Yoda and openrangeowners ,

I took advantage of my customer-relationship with AMSolar and sent them the question. Garret responded quickly (to my delight and surprise). Below is the complete unedited text of my question and his response.

Keith--if this post sends your thread off on a long tangent I'll copy them to a new thread (and leave a note here in your thread).

Let me further state that my motive with sharing this exchange between myself and Garret is to clarify why there seems to be differences between various sources online regarding this subject, not to try and convince anyone of anything. Each individual installing their system should heed their supplier's advice, system design, and their own knowledge based on experience with electricity.

For the record, at some point I'll be adding a standard copper 6ga ground wire (I have lots left over from the 6/3 wire I originally purchased) and will be attaching it from the Multiplus' external chassis ground lug to the trailer's frame. It won't hurt anything to do so and adds another layer of safety, even if an incident is very unlikely to occur.

---------Howard's Text to AMSolar via their website-----------------

As a Senior Moderator on Grand Design's Technical Forum (https://gdrvowners.com) I have often pointed individuals to your drawings and services. One discussion that never seems to get resolved is the grounding of the case of a Multiplus to the trailer's frame, aka "ground". None of the AMSolar drawings show this, but the Victron manual seems to imply it is required? There is also discussion on the forum of grounding a SmartSolar MPPT's case to the trailer frame. In most references on these topics I find the individual advocating for this grounding states the largest wire used in the system must be used for this extra safety feature, thus in my case I'd need 4/0 from the Multiplus' case to the trailer's frame. My system works great as it is so I can't wrap my head around this...hoping you'll provide a succinct rationale (either way) that I can post in response on the forum. (If I need to go back and ground the case that's fine--just need to know.)

-------Garret's Response------------------------

Howard,
Thanks for reaching out. Good questions too. Victron recommends connecting the inverter chassis to the rig chassis with a cable half as thick as the DC cables suppling power to the inverter. So, for a Multiplus 3000, with 4/0 cable, you would use 2/0 cable to make that connection. But, I think a lot of these “rules” are written by attorneys, rather than people who know how electricity works. I don’t claim to know everything, but do know some things, and I have a hard time seeing the importance of this. A connection like this would only protect you from a perfect storm of very strange things happening all at the same time (pretty much never). It won’t improve performance (nor hurt it). That being said, I still don’t see why a 10ga wire wouldn’t do the trick, because the fault would be related to alternating current, not DC. So, our stance is that we don’t specifically recommend it, but if someone wants to, they can go for it.

As for grounding the chassis of an MPPT charge controller to the chassis of your rig, when you are on rubber tires, I can’t imagine a scenario where that would make any sense. Maybe it gives you some protection from lightning that is close, but not too close? I don’t know what someone would gain from that.

For background, I have worked in solar since 2009. I have been at AM Solar since 2015. I got my Electrical Engineering degree in 2003.

I hope this helps. Let me know if you need anything else.

Garret Towne,Electrical Engineer

---------END----------------

Howard
Thanks for doing this. Please leave this information here. Its is definitely not off topic or a sidetrack, but on point to the topic here. Its great to have it included in this thread. Thanks for reaching out to AM Solar. They deserve credit for responding so others can benefit. I feel good about buying supply's from them. So folks know they have the hard to find stuff like 8 awg PV wire and SOO cable.

I hope to hear back from Continuous Resources tomorrow. They are buried doing 4 installs. It will be interesting to hear what they say. Its nice to know they do the installs as I am sure they have run across this question before.

I have to say this is a great place where information is shared and discussed without harm or negative feelings toward anyone. It is amazing what I have re-learned from my schooling. Hopefully I wont haft to redo what I did today - but it was fun I must say and satisfying that I could make lug crimps like the pros. - then again its probably all automated or some kid with an hours training running the crimper

More tomorrow
Keith

[openrangeowners]

I ran a 4/0 cable from my DC negative bus bar to the camper frame ground (could have run a 2 AWG technically). This is not the same as grounding the chassis of the Multiplus - I also used a 4/0 cable from the Multiplus case screw meant for grounding to the camper frame (catastrophic grounding . Having a direct path from the Multiplus to the camper frame with adequate AWG wire is what Victron calls for.

When we added solar to our sticks and bricks home the electrician ran grounds that seemed redundant, but were required by electrical code. I believe the case grounds to the camper frame would fall into similar electrical code for grounding wrt the DC side of things. Our house was struck by lightning and besides loosing a laser printer, router and a GFCI outlet, we had the 2 bottom-most circuit breakers tripped - the grounding on the house saved us from more catastrophic issues - I literally saw blue at the kitchen outlet in my vision as we were struck …. That outlet was one of the tripped ones. I agree lightning strikes to a camper and/or truck are usually very catastrophic, the additional grounding may at times save things. I did have a friend have to total his truck and camper after they were stuck by lightning - neither were that old and he took a loss on both from insurance.

The additional ground (actually lack-of) likely won’t affect normal performance at all, but if you want to do things correctly, then follow what the manufacturers want done. This is the same reason I changed my solar panel wiring cutoff from a single 48VDC high amperage switch to a set of DC circuit breakers rated for a much higher voltage when I went from 2 panels in series to 3 panels in series raising my voltage from around 48 volts to 72 volts … again code requires breaking both connections from the solar panels. Neither connection gets grounded so in essence they are floating with a differential of 72 volts between them and no common ground.

[Yoda]

I don't have a dog in this fight (yet) and mostly am sitting back going , but this caught my eye,

"As for grounding the chassis of an MPPT charge controller to the chassis of your rig, when you are on rubber tires, I can’t imagine a scenario where that would make any sense. Maybe it gives you some protection from lightning that is close, but not too close? I don’t know what someone would gain from that."

Would the circumstances of being parked at almost anytime change that equation as you will have jacks / levelers (or at least the nose jack) in contact with the ground rather than than being insulated by the tires?

Jerry no fight going on - lets call is a bunch of puppies having fun dealing with 1 bone

That comment caught my eye too as I know when parked the trailer is grounded, or almost grounded. With my old trailer I got shocked once in wet conditions. Turned out the wet power cord provided a path to energies the frame. Still happens today. Search folks getting shocked touching the trailer. Dealer fixed it saying the ground/neutral bars were corroded together due to water following the cord in. I did not understand it at the time. This trailer had a cord that you pulled out from a cubby through an outside wall, not the outside attach we have now.

Now with the landing jack or stabilizers down you are somewhat grounded depending on the soil moisture, so having the components grounded to the frame makes sense to me as the path of lease resistance if a short occurs is through the frame to ground.

I once had a Wilderness 16" TT that was very close to a lightning strike. The aluminum slat skin protected the trailer. You could see the arc tracks over the skin and across the tires (they were wet from rain). Amazing nothing inside was hurt, but back in the late 70's there was not much in the unit that could be hurt - no microwave stereo-nothing.

So I am waiting to hear back from my vender on my install, as they do them.

More later
Thanks for your input
Keith

[gbkims]

The DC grounding part seems to have minimum info in Victron's Multiplus manuals.
I get the impression that Victron writes the manuals for only EEs or Victron distributors, dealers and installers.

I can see Garret's reasoning that the fault is probably unlikely.
I'd think the bouncing around the rigs take that might work something loose.

Some other inverter/charger manuals give some guidance and mention the NEC with it's focus on AC wiring(Table 250.122), and the ABYC that is for marine wiring; ABYC E-11 and A-25.
I just try to sift thru them to decide how to wire my equipment.

Victron Wiring Unlimited
7.7 System grounding
The DC ground cabling should have a sufficient thickness to be able to carry a fault current at least equal to the DC fuse rating.

Multiplus Service Manual
2. Installation
This product may only be installed by a qualified electrical engineer.

GROUNDING INSTRUCTIONS – This marine unit should be connected to a grounded, metal, permanent wiring system; or an equipment-grounding conductor should be run with circuit conductors and connected to equipment-grounding terminal or lead on unit.
Connections to unit should comply with all local codes and ordinances.

2.3 Connection of the AC cabling
In a mobile installation (for example, with a shore current plug), interrupting the shore connection will simultaneously disconnect the grounding connection.
In that case, the casing must be connected to the chassis (of the vehicle) or to the hull or grounding plate (of the boat).


Samlex EVO-3012 - 3000 Watt Pure Sine Inverter/Charger
3.13 DC SIDE GROUNDING (SEE FIG. 3.12)
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 or to the metal frame / “Chassis ” of the motorhome / caravan.
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.
...
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.

INFO...
It may be argued that if the metal frame / chassis of EVO is already bonded to Main Earth Ground "GE" for AC side grounding, why it is necessary to provide
additional DC side grounding wiring?...
If separate thicker grounding wire of the same size as the battery cable was not provided for the DC side grounding and there was a ground fault in the battery circuit, very large DC fault current from Battery+ would flow through the smaller size AC grounding wires to the Battery Negative through Earth Ground. These smaller size AC side grounding wires would be damaged due to very high DC side fault current.


Magnum MSH3012M - https://www.magnum-dimensions.com/pr...r-msh-m-series
2.4.2 DC Overcurrent Protection - Table 2-1, Recommended DC Wire/Overcurrent Device for Rated Use
Inverter Model Maximum Continuous Current Minimum DC Wire Size (rating) Maximum DC Fuse Size.......................DC Grounding Wire Size
MSH3012M.....400 amps.................................#4/0 AWG (107.2 mm^2 )...........405 amps 400 amps with time delay....#6 AWG (13.3 mm^2 )


Go Power! GP-IC-3000 - IC Series 3000-watt Inverter Charger
3.5.1 DC WIRE SIZING
DC Cable Size Inline Fuse/Circuit Breaker Recommended DC Grounding Cable Size
No. 2/0 AWG....300A Class T.......................No. 6 AWG
No. 4/0 AWG.....400A Class T......................No. 6 AWG

[howson]

gbkims -- great post, as always, Gene. Thank you! When the grounding side of this thread slows (or stops) I'm going to capture the different perspectives (and especially your post) for a Reference Material thread. This info is fantastic and shouldn't be "buried" here.

Yoda -- a "non-Facebook" atmosphere is what your moderators strive to maintain on GD's forum. Adults are allowed to have different perspectives on RV technical topics and communicate them openly here. Personally, I learn more when I'm wrong than when I'm right (so I learn a lot).

Howard

[Yoda]

Continuous Resources (CR) called me this morning. he made a suggestion on not using the negative buss bar (under the multiplus) and tie everything into the Lynx power in. It seemed logical, but as I already have thing installed It will still work as I have it laid out. I just need to tie the negative wires from the MPPT's in and ground the negative bus bar as installed.

However the grounding wire from the multiplus (4/0) needs to go to a separate frame ground and not tie into the negative buss bar which also needs a 4/0 frame ground. If I understood CR correctly I need to use two separate frame grounds. This confuses me as everything still goes to the frame. CR said Victron did not want the negative battery connection and cabinet ground going to the same point, which they do using the frame even with two separate grounding points. Based on this having the MultiPlus cabinet and MPPT grounds mixed on the same buss bar is not OK and need to be seperated.

Also as this is a mobile unit the MPPT controllers do not need the cabinet ground wires. I could find nothing in the instruction about this. If I install them they should go to a separate frame ground according the CR. They are actually grounded as installed (screwed to the aluminum plate which is attached to trailer frame). However I still plan to run separate wires to a frame ground. This will reduce any transient voltages through the aluminum plate. I have all the parts on hand.

gbkims does this make any sense to you on the cabinet grounds (Multiplus and MPPT units) going to separate frame locations?

Thanks folks
Keith

[Yoda]

Copper bar stock just arrived so I am going to start work on the Lynx power in to the switch and then to the fuse connections. Rain tomorrow we need it. Also get irrigation water tonight so need to adjust the gated pipe and make any repairs needed. also need to get some hay grass seed spread.

Busy Busy
Keith

[Jlawles2]

Yoda Keith, remember electricity is LAZY. It will take the path of least resistance. I bet if you get with CR and ask, they want the ground and negative as far apart as possible to help prevent back feed bu giving the system the possibility to dissipate the charge elsewhere.

[gbkims]

Continuous Resources (CR) called me this morning....

However the grounding wire from the multiplus (4/0) needs to go to a separate frame ground and not tie into the negative buss bar which also needs a 4/0 frame ground. If I understood CR correctly I need to use two separate frame grounds. This confuses me as everything still goes to the frame. CR said Victron did not want the negative battery connection and cabinet ground going to the same point, which they do using the frame even with two separate grounding points. Based on this having the MultiPlus cabinet and MPPT grounds mixed on the same buss bar is not OK and need to be seperated.

gbkims does this make any sense to you on the cabinet grounds (Multiplus and MPPT units) going to separate frame locations?

Thanks folks
Keith

Keith,

I'd say that CR, Victron must be making the distinction between normally current carrying conductors versus safety grounds that only have current under fault conditions, and keep them separate.
Similar to the Ground bar with Green wires and Neutral bar with White wires in a house's circuit breaker panel.

The inverter's chassis ground, which is connected directly to the inverter's AC In/Out Ground TBs, being wired to a separate chassis ground point may keep it from being disconnected, say if you were working on the DC bus wiring.

Victron Info:
Multiplus Service Manual
1. SAFETY INSTRUCTIONS
This product is a safety class I device (supplied with a ground terminal for safety purposes). Its AC input and/or output terminals must be provided with uninterruptible grounding for safety purposes.
An additional grounding point is located on the outside of the product.

Victron Wiring Unlimited
7.6 Isolation and grounding of Victron Equipment
This chapter explains the isolation of a variety of Victron products between AC and DC, or between DC and DC.
This information is needed so a system containing a Victron product can be grounded correctly.

Isolation of all Victron inverters and inverter/chargers:
• Between the AC circuitry and chassis: basic isolation. The chassis therefore must be grounded.
• Between AC and DC: reinforced isolation. Once the chassis has been grounded the DC is therefore considered safe to touch if the nominal voltage is 48 V or lower.
• Between the DC circuitry and chassis: basic isolation. Therefore, DC negative or positive grounding is allowed.

The AC ground terminal of all inverters and inverter/chargers is connected to the chassis.

I did see one of Victron's example diagrams that shows one main ground bar with the inverter's chassis ground running to it and then to ground, so I can see how other diagrams out there are similar.
Multiplus system example 3kW-24V-120VAC https://www.victronenergy.com/upload...4V-120V-AC.pdf

[Yoda]

Keith,

I'd say that CR, Victron must be making the distinction between normally current carrying conductors versus safety grounds that only have current under fault conditions, and keep them separate.
Similar to the Ground bar with Green wires and Neutral bar with White wires in a house's circuit breaker panel.

The inverter's chassis ground, which is connected directly to the inverter's AC In/Out Ground TBs, being wired to a separate chassis ground point may keep it from being disconnected, say if you were working on the DC bus wiring.

Victron Info:
Multiplus Service Manual
1. SAFETY INSTRUCTIONS
This product is a safety class I device (supplied with a ground terminal for safety purposes). Its AC input and/or output terminals must be provided with uninterruptible grounding for safety purposes.
An additional grounding point is located on the outside of the product.

Victron Wiring Unlimited
7.6 Isolation and grounding of Victron Equipment
This chapter explains the isolation of a variety of Victron products between AC and DC, or between DC and DC.
This information is needed so a system containing a Victron product can be grounded correctly.

Isolation of all Victron inverters and inverter/chargers:
• Between the AC circuitry and chassis: basic isolation. The chassis therefore must be grounded.
• Between AC and DC: reinforced isolation. Once the chassis has been grounded the DC is therefore considered safe to touch if the nominal voltage is 48 V or lower.
• Between the DC circuitry and chassis: basic isolation. Therefore, DC negative or positive grounding is allowed.

The AC ground terminal of all inverters and inverter/chargers is connected to the chassis.

I did see one of Victron's example diagrams that shows one main ground bar with the inverter's chassis ground running to it and then to ground, so I can see how other diagrams out there are similar.
Multiplus system example 3kW-24V-120VAC https://www.victronenergy.com/upload...4V-120V-AC.pdf

Gene talk about Great information and a new puzzle.

Thank you for finding that diagram. It's one of the ones I used in setting up my layout with the negative buss bar with all loads way back when and grounds going to it with shunt tied on one end going to the battery. Does is look similar to my layout? I had forgot about it. Well I have been planning this for a couple years and gave up on the MultiPlus when SWMBO said no. I threw it away when I moved to the Go Power separate inverter and separate charger plan until I found out that way cost more and I just went to the MultiPlus. Story is still out on if SWMBO has forgiven me. I guess it depends if everything works

The fact the diagram shows the opposite of what CR is telling me to do on the cabinet ground is the new puzzle . I just fired off a new email on this puzzle

Given what Jlawles2 has said (good information - thanks Joseph) I think I should I just go ahead and separate the Cabinet grounds from the negative buss bar ground as CR recommended and just go the safest way possible. I have the cable and lugs so its no issue.

Just heard back from CR. The electrical engineer they consult on the regular basis disagrees with the diagram. The cabinet/MPPT grounding wires need to be separated from the negative buss bar.

Thanks everyone for helping
Its fun learning or re-learning new things.

Keith

PS: It is raining today (snow in mountains) first good rain in many months - we need it. So no work on the trailer today. Ill start planning the next project on my list - now where did I put it?

[Yoda]

Yesterday was a good day.
First up - the grounding solution for the MultiPlus and the other equipment chassis ground wires.

I created a new grounding bar using one of the original screw holes the old grounding screw used. I will be adding a separate 4/0 grounding cable to the negative buss bar to the left. This will separate the frame attachment points by at least 3 feet.

Notice the hug blue wire nut on the lower right of the picture? See the next post. I need advice

[Yoda]

The Birds Nest


While installing the ground bar I move the blue nut above - just touched it - and this happened



There are 6 12V negative wires wrapped in that nut. One of the wires was attached to the original ground screw. Now as this is the return leg for the RV wiring should I not connect them to the negative buss bar so the shunt see the loads? Or just attach to the new frame ground bar above? I do plan to separate the wires out and not still use the wire nut. This may have been the cause of lights dimming, etc when something else was turned on due to all theses tying to a single (12 AWG?) wire in that mess of twisted wires.

Thoughts?

[Yoda]

I made other progress too

I made the connection from the Lynx power in, through the new master cut off switch to the GD power buss bar.

I still need to add some wire ties to hold it of the circuit breaker.
I did need to make an adjustment to the circuit breaker locations to get the 2/0 to fit. In hind sight I probably could have re used the 6 awg original wires, but I did not have lugs for it. I mover the circuit breaker for the slide controller further right to make room to fit under the cover. The original battery connection was to the left top stud. The red 6 awg wire goes to the factory disconnect switch which comes back as a black wire attached to the far right circuit breaker that feeds the slide controller. The second black 6 awg wire runs forward to the factory distribution panel and feed the 12 V circuits. I left that alone.

I have debated with removing the factory disconnect switch all together and running a jumper wire over to power the slide controller and just attaching the distribution panel feed wire to the positive bus bar.

Thoughts?

[Yoda]

Here is an overview of all of yesterdays progress.

Battery cables attach to the two center switches. I will be making the 2/0 negative cables today the same length as the positive ones through the switches. Again if you se an issue please let me know

Thanks Keith