Grounding and Victron Questions

[VanBuild117]

Hello! I am building out a van system and have a 3 separate questions after reading the manuals for a Victron MPPT charger and a DC2DC charger:



1) SmartSolar MPPT 100/50 manual states in section 3.2 that the NEC requires a GFPD between the system negative and earth ground. Is this referring to placing a GFPD between the MPPT chassis negative terminal and my earth system ground? Using a GFPD device on your DC circuits is new to me. Can someone please explain to me practically what situations this would protect you from? Additionally, from my reading it appears that the NEC code chapter 6 has an exemption for mobile solar arrays here:
"690.41System Grounding: Exception : PV arrays with not more than two PV source circuits and with all PV system dc circuits not on or in buildings shall be permitted without ground-fault protection where solidly grounded".

I will only have a single PV-source circuit.

2) Orion-Tr Smart DC-DC Charger Non-Isolated 12/12 - 30A: I am trying to size the wires and breakers for this unit, but cannot seem to find how much current this unit will draw under max normal operating conditions. I guess this is where I lack a fundamental knowledge of how a DC-DC converter works. Simply put, how much amperage can this unit draw from the batteries on my van? It is not listed in the data sheet. Is it a function of the max output current or power listed? Max output power is listed as 430W / 12V = ~35.8A max that the unit will draw from my van battery? Or should I size my breakers to the listed output short circuit current of 60A?

3) Can you ground your DC system and your AC inverter through the same negative busbar, which is connected to the same earth ground (vehicle chassis)? I have not had to consider grounding DC and AC currents to the same spot before.

Thank you so much for the help!

 

[time2roll]

For the mobile application I would be skipping the GFPD. Especially for low 12v systems.

The 12/12 could draw 50% more than the output rating to boost voltage. I would use #6 to feed it and a 50 amp fuse near the power source.

Yes all negative power terminals will be on the negative bus to the battery and said bus will be bonded to the vehicle frame. Equipment chassis ground should have a separate #8 ground wire to the vehicle frame. I prefer to keep the 120vac and battery-dc separate. Assuming you have a small breaker panel with H-N-G buses... the ground bus should be connected to the vehicle frame directly.

 

[FilterGuy]

1) SmartSolar MPPT 100/50 manual states in section 3.2 that the NEC requires a GFPD between the system negative and earth ground. Is this referring to placing a GFPD between the MPPT chassis negative terminal and my earth system ground? Using a GFPD device on your DC circuits is new to me. Can someone please explain to me practically what situations this would protect you from? Additionally, from my reading it appears that the NEC code chapter 6 has an exemption for mobile solar arrays here:
"690.41System Grounding: Exception : PV arrays with not more than two PV source circuits and with all PV system dc circuits not on or in buildings shall be permitted without ground-fault protection where solidly grounded".

I will only have a single PV-source circuit.

First, GFCI on AC is very different than PV Ground Fault Protection. Please review this:

Ground Fault Protection On Solar Panel Arrays.

To get the paper, click on the orange button at the top of the screen. This paper provides a summary of what a PV ground fault is, what NEC requires for PV Ground Fault Protection and how PV ground Fault Protection is typically implemented...

diysolarforum.com

Second, Most people don't bother with this NEC rule in Van conversions

2) Orion-Tr Smart DC-DC Charger Non-Isolated 12/12 - 30A: I am trying to size the wires and breakers for this unit, but cannot seem to find how much current this unit will draw under max normal operating conditions. I guess this is where I lack a fundamental knowledge of how a DC-DC converter works. Simply put, how much amperage can this unit draw from the batteries on my van? It is not listed in the data sheet. Is it a function of the max output current or power listed? Max output power is listed as 430W / 12V = ~35.8A max that the unit will draw from my van battery? Or should I size my breakers to the listed output short circuit current of 60A?

As a first level approximation, for a 12V-12V charger, the current in will be the same as the current out. However, the conversion is not 100% efficient so the current in will be slightly larger than current out. I would use a 90% efficiency so call it ~35.8A/.9 = 39.8A. The fuse at the starter battery needs a 25% buffer so it should be sized at 39.8A x 1.25 =49.7A. Round that up to 50A.

Your wire should be able to handle 50A.

One common problem with AC charging is the voltage drop on the long run from the inverter to the charger. Make sure you have a large enough wire to minimize the voltage drop. You are likely to find you need something in the 2AWG range.

Also... I gave up trying to only count on Victron's voltage-based engine detection. I run an ACC from the engine to the vehicle to the on-off input of the TR Smart.

3) Can you ground your DC system and your AC inverter through the same negative busbar, which is connected to the same earth ground (vehicle chassis)? I have not had to consider grounding DC and AC currents to the same spot before.

For a 12V system, grounding the DC is optional, but grounding to the same point as AC is the right way to do it.



.

 

[vbadov]

For the mobile application I would be skipping the GFPD. Especially for low 12v systems.

The 12/12 could draw 50% more than the output rating to boost voltage. I would use #6 to feed it and a 50 amp fuse near the power source.

Yes all negative power terminals will be on the negative bus to the battery and said bus will be bonded to the vehicle frame. Equipment chassis ground should have a separate #8 ground wire to the vehicle frame. I prefer to keep the 120vac and battery-dc separate. Assuming you have a small breaker panel with H-N-G buses... the ground bus should be connected to the vehicle frame directly.

Thanks for your input I don't even know what gfpd means haha

 

[FilterGuy]

Thanks for your input I don't even know what gfpd means haha

Ground Fault Protection Device

 

[mikefitz]

AWG 6 in the maximum the Orion can accommodate, the manual recommends this cable size with 60 amp fuses at each battery.
Expect 35 to 40 amps input from the starter battery.
Regarding 'earthing' in the van, house battery negative connects to van metal. Also a from Inverter case connection point-to-point van metal, one size down on high current feed cables to inverter.
If the inverter AC output is distributed within the van then consider neutral bonding to protective earth ( that is connected to van metal) and earth leakage protection.

 

[vbadov]

For the mobile application I would be skipping the GFPD. Especially for low 12v systems.

The 12/12 could draw 50% more than the output rating to boost voltage. I would use #6 to feed it and a 50 amp fuse near the power source.

Yes all negative power terminals will be on the negative bus to the battery and said bus will be bonded to the vehicle frame. Equipment chassis ground should have a separate #8 ground wire to the vehicle frame. I prefer to keep the 120vac and battery-dc separate. Assuming you have a small breaker panel with H-N-G buses... the ground bus should be connected to the vehicle frame directly.

I think I I figured it out thanks for your great reply to the question

 

[time2roll]

If the inverter AC output is distributed within the van then consider neutral bonding to protective earth ( that is connected to van metal) and earth leakage protection.

Any N-G bond should not be present if panel is connected to utility power. The N-G bond can be isolated with the transfer switch.

 

[vbadov]

Ground Fault Protection Device

Thank you. I ended up Googling it and found out also.. what a dummy I am sometimes. Should have just done that in the first place. thank you for your help.. I've done that before I should know better?

 

[vbadov]

I have read all this communication a couple of times. And I read the link about grounding. I still can't figure it out at all. I'm going to be putting in a
48 volt system.. in my work trailer and I have an existing system in the motorhome I live in and I don't have stuff grounded. Everything seems to be working.. my battery's in the motorhome are grounded. But I don't get all the other grounding information I've been reading on this timeline . I can't seem to understand it..
I'm going to have to really get it broke down in super simpleton terms.

The only thing I did ground to the frame was an Aimes battery charger that I'm using when it's cloudy for a couple days.

I guess I better I ground my inverter
Body to the frame of the vehicle where the other ground is

At the moment I have a 3000 watt renergy. It is working good.. today I looked at it and did see a grounding place. I guess I thought everything was just grounded through the battery cables.

I'm running two different solar arrays with two different solar chargers. Do I need to ground those to the frame of the vehicle also.

Well if anybody has any quick input on my comment it would be appreciated. I don't even know if this comment is very understandable. Thanks in advance Vince

 

[FilterGuy]

And I read the link about grounding.

Is this the link you are talking about?

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

The best way to get specifics is to give specifics on what you are doing. Do you have a diagram of a system you have questions about?

 

[vbadov]

Is this the link you are talking about?

Grounding Made simpler - Part 1: AC/houshold grounding

To get the paper, click on the orange button at the top of the screen. The subject of grounding is a complex, multifaceted subject, that is often treated as an after-thought but needs to be considered from the beginning of the design and build...

diysolarforum.com

The best way to get specifics is to give specifics on what you are doing. Do you have a diagram of a system you have questions about?

I don't have the diagram yet.
I'm just using a sungold 6500 48 volt all in one staying at 120 volts output for now I'm going to have six 450 watt solar panels Up on the Roof of a bekins moving trailer.. I'm going to wire a Predator generator into the AC input more than likely. And it's completely off grid. I am going to power my living area with it quite often even though I have a 12-volt system up...

I was looking at another one of Will's video. And I think he said it might not even need to be grounded.
I have to look at that video again. I've got to see them so many times before it sinks in. Well I'm off to work I'm late I better go I'll get back to you thank you very much

 

[FilterGuy]

Technically, the NEC makes grounding on 12V, 24V, and 36V DC optional but requires grounding for 48V. In a trailer that would be chassis.
On the AC side there are floating systems, but I do not recommend it. I recommend tieing AC ground to the chassis.

I believe the Sungold 6500 is the same as the EG4 and MPP equivalent and does dynamic bonding. Consequently, you will not need to worry about the neutral-ground bonding...... until you add the Predator Generator. I would recommend that when the preditor is plugged into the system, you have a bonding plug in an extra socket of the Generator.

Amazon.com : portable generator bonding plug

 

[vbadov]

Technically, the NEC makes grounding on 12V, 24V, and 36V DC optional but requires grounding for 48V. In a trailer that would be chassis.
On the AC side there are floating systems, but I do not recommend it. I recommend tieing AC ground to the chassis.

I believe the Sungold 6500 is the same as the EG4 and MPP equivalent and does dynamic bonding. Consequently, you will not need to worry about the neutral-ground bonding...... until you add the Predator Generator. I would recommend that when the preditor is plugged into the system, you have a bonding plug in an extra socket of the Generator.

Amazon.com : portable generator bonding plug

Thank you very much sorry it took so long to get back to you I don't really get any notifications anywhere so I didn't know I had a reply I appreciate that so much all my stuff is almost coming in. It won't be too long I'll be trying to make this happen

Can you be so kind to tell me what NEC means LOL I'm so bad with abbreviations. I did pretty much understand your reply and thank you again

 

[time2roll]

National
Electric
Code

 

[FilterGuy]

Thank you very much sorry it took so long to get back to you I don't really get any notifications anywhere so I didn't know I had a reply I appreciate that so much all my stuff is almost coming in. It won't be too long I'll be trying to make this happen

Can you be so kind to tell me what NEC means LOL I'm so bad with abbreviations. I did pretty much understand your reply and thank you again

NEC is the National Electric Code. This is an electrical rule book that is updated every 3 years and used by local governments throughout the US for the local Electrical requirements for building codes.

The NEC is developed by the National Fire Prevention Association (NFPA) which is a nonprofit that creates various standards relating to fire and building safety.


BTW: I am bad with TLAs too.

 

[vbadov]

Thank you I didn't notice your comment till now. I don't seem to get any notifications. I just happened to come over here for something else and then saw that I had notifications