How To Properly Ground System

[Ulmo]

I am considering setting up a system around the MPP Solar unit. How do you ground the system to protect against ground faults or accidental stray charge on an appliance chassis?
Electrical code says that Neutral (White Wire) and Earth ground (Green Wire )can only be bonded at the main breaker panel. How is the earth ground connection made when the transfer switch switches over to battery or Solar from utility?

I just want to throw in my 4 cents here: once you have proper grounding, look into surge protection, too, to make all that compliance actually financially beneficial to you in the probable long run by leveraging your grounding to save money: I have heard good recommendations for surge protection from these folks, plus they have their own test vid to show theirs works, so I will refer them, and made in USA makes them much better, too:

MidNite Solar Inc. Renewable Energy System Electrical Components and E-Panels

MidNite Solar is the industry leader and manufacture of quality Renewable Energy System electrical components and E-Panels.

www.midnitesolar.com

also at

Check out their videos at http://www.midnitesolar.com/videoDisplay.php under "SPD (Surge Protection Devices)".

If you want quantities other than a dozen of each model, then you have to order their product from their distributers since they only sell in boxes of a dozen.

From everything I've seen reviewed about them and the specs they show, they are the best in class for this product, and maybe one of the only ones. (Before I looked into them, I installed some Littelfuse products myself, but only in one spot, and I know I need three more spots covered for full protection, so that's on my to-do list, and I'm going to use Midnite Solar SPDs to finish that.)

 

[erik.calco]

MidNite Solar Inc. Renewable Energy System Electrical Components and E-Panels

MidNite Solar is the industry leader and manufacture of quality Renewable Energy System electrical components and E-Panels.

www.midnitesolar.com

also at

Let's ask ElectroBOOM to review one of those.

EDIT: I just pinged him a request. This is right up his alley.

 

[Hedges]

Solar Panels (frames & rails) need to be grounded separately as their grounding is to protect from lightning etc. This is a separate grounding aside from the actual "electrical system" as such.

Are you saying solar panel frames should have a copper wire to a ground rod, but do NOT connect by copper wire to the AC ground system?

I think they should tie in to AC ground.

Often, one side of the PV DC wiring has an electrical path to AC ground system. My Sunny Island battery inverters have chassis grounded on AC side. They also have a lug for a 3rd wire to the battery, connecting battery ( - ) to inverter chassis and presumably another ground rod. (this smaller wire is sufficient to clear the battery fuse if battery ( + ) shorts to chassis.) So now PV panels in a DC charging system have a path to AC grounding system.

With ( + ) side of PV at perhaps +140V DC, if a panel gets cracked and gets wet, the panel frame is now at 140 VDC. I want a ground wire to pull that to zero.

I'm using grid-tie inverters. The old SWR2500U had a 1A "GFCI" fuse tying ( - ) to chassis. Broken panel could bring PV frame to almost +600V.
My latest 10000TLUS transformerless inverters buck the DC directly to two AC hots, so ( + ) and ( - ) are nominally +/-300 VDC or less on my split-phase system. If used across two legs of 3 phase, the solar cells themselves will actually orbit around ground potential at 60 Hz, and a short to PV frame would deliver AC line voltage to the frame.

So I think PV frames, besides having a nice ground for lightning, should have a copper ground wire tied back to the AC ground system.

What do you think?

 

[offgriddle]

Are you saying solar panel frames should have a copper wire to a ground rod, but do NOT connect by copper wire to the AC ground system?

I think they should tie in to AC ground.

Often, one side of the PV DC wiring has an electrical path to AC ground system. My Sunny Island battery inverters have chassis grounded on AC side. They also have a lug for a 3rd wire to the battery, connecting battery ( - ) to inverter chassis and presumably another ground rod. (this smaller wire is sufficient to clear the battery fuse if battery ( + ) shorts to chassis.) So now PV panels in a DC charging system have a path to AC grounding system.

With ( + ) side of PV at perhaps +140V DC, if a panel gets cracked and gets wet, the panel frame is now at 140 VDC. I want a ground wire to pull that to zero.

I'm using grid-tie inverters. The old SWR2500U had a 1A "GFCI" fuse tying ( - ) to chassis. Broken panel could bring PV frame to almost +600V.
My latest 10000TLUS transformerless inverters buck the DC directly to two AC hots, so ( + ) and ( - ) are nominally +/-300 VDC or less on my split-phase system. If used across two legs of 3 phase, the solar cells themselves will actually orbit around ground potential at 60 Hz, and a short to PV frame would deliver AC line voltage to the frame.

So I think PV frames, besides having a nice ground for lightning, should have a copper ground wire tied back to the AC ground system.

What do you think?

Bond all grounds together to earth ground but remember, DC negative is not to be confused with or connected to earth ground.

 

[mapguy525]

AC must be grounded following Electrical Codes relative to your jurisdiction (the rules do vary a bit, make no assumptions). Grounding Plates, Rods are commonly used for such, in some cases it is allowed to use metal water pipes coming into a home (due to extensive use of PEX and others, most are eliminating this option). Main electrical panel is grounded and all plugs, switches, sub-panels etc are all bonded together with the bare copper / green wire and share the one common ground circuit for the structure. Think of it like a Daisy Chain, all linked together. Some codes allow for multiple grounding points (rods, plates etc) while others do not, your codes are your guide. (note, if you want insurance coverage, follow codes and get inspected as required)

It is very important to consider the requirements of the Local Authority with Jurisdiction in regards to grounding and bonding as local soil conditions can require differing strategies to get a well functioning grounding/bonding system. Permits or not -getting it right/well functioning is the ultimate goal for most(assumption).
In my jurisdiction -the electrical inspectors want a one piece run of bare copper, properly sized bonding the plumbing and mechanical (gas) piping to the primary AC panel. They also push for a length of the potable water service piping to be buried copper starting about 10' from foundation to a point inside structure where a transition to PEX is expected. The ground rod(s) connection likewise must be one continuous length of properly sized copper from primary AC panel to the last ground rod. UFER trenches are also popular in place of ground rod(s) even in the mostly wet conditions of the Puget Sound region.

A well thought out plumbing and mechanical system are integral with a well functioning AC grounding and or bonding system.

 

[TinyQualityHomes]

EDIT - ADDITION :
I forgot to mention, Lightning Protection ! Something which I have noticed is rarely brought up. In fixed systems on the ground (cabin's, homes etc) lightning protection is important, one surge and all your goodies can go POOF with big clouds of Magic Smoke. Everything is an equal opportunity victim to lighting, so Never Underestimate what it can do to you & your gear.
A good reference article here: https://www.wholesalesolar.com/solar-information/grounding-lightning-protection

I went to this site. Thanks for sharing it! It contained lots of valuable information.

 

[offgriddle]

It is very important to consider the requirements of the Local Authority with Jurisdiction in regards to grounding and bonding as local soil conditions can require differing strategies to get a well functioning grounding/bonding system. Permits or not -getting it right/well functioning is the ultimate goal for most(assumption).
In my jurisdiction -the electrical inspectors want a one piece run of bare copper, properly sized bonding the plumbing and mechanical (gas) piping to the primary AC panel. They also push for a length of the potable water service piping to be buried copper starting about 10' from foundation to a point inside structure where a transition to PEX is expected. The ground rod(s) connection likewise must be one continuous length of properly sized copper from primary AC panel to the last ground rod. UFER trenches are also popular in place of ground rod(s) even in the mostly wet conditions of the Puget Sound region.

A well thought out plumbing and mechanical system are integral with a well functioning AC grounding and or bonding system.

Well said clear and concise thanks.

 

[CascadeOffGrid]

Grounding and Bonding seems to be the most confusing and most commonly messed up part of installations. What I am saying applies to the National Electrical Code in the US but may be applicable in other places as well. Small local changes in code though can change some of these rules.

Neutral - Ground Bonding
1. If you have an inverter with a built in transfer switch for shore power or a generator connection, there will more than likely be a neutral to ground relay inside the inverter. When you are inverter mode, the neutral and ground are bonded together via this relay and should not be tied together downstream in the RV or electrical distribution panel. When you plug into shore power, the relay disconnects the neutral-to-ground bond because the neutral-to-ground bond should be made at the first means of disconnect to the utility power. This relay is programmable normally to accommodate other situations where the neutral-ground bond is made in the distribution system.
2. If you do not have an inverter with a built-in transfer switch, the the neutral-ground bond will most likely need to be made up in the distribution system. If you add an external transfer switch to a system like this, you will have to make sure that the neutral-ground bond is switched if necessary to prevent double bonding of the neutral-ground.

Equipment Grounding
1. This is a complicated subject and there is a lot to know here to create safe and code compliant systems. Everyone needs to learn the terminology and the differences between EGC (equipment grounding conductors) and the GEC (grounding electrode conductor). Only then can you begin to understand how to properly create a grounding system.

The ground off of your solar panel frames and racking is an equipment grounding conductor.

In a grid tie inverter system, this ground normally connects to the inverter and may be internally connected to the AC EGC. The grid tied inverter should have internal ground fault protection and the solar panel frame EGC is necessary for that to function correctly.

When connecting solar panels to a charge controller, the solar panel frame EGC should be run to an external ground fault breaker (for non-mobile applications). Outback and Midnite solar both have good resources on this setup.

There is a lot more to discuss on this system but that's all I have time for at the moment.

 

[mapguy525]

You are correct. Grounding and bonding is not understood by a large number of participants on the forum.

Neutral - Ground Bonding
1. If you have an inverter with a built in transfer switch for shore power or a generator connection, there will more than likely be a neutral to ground relay inside the inverter. When you are inverter mode, the neutral and ground are bonded together via this relay and should not be tied together downstream in the RV or electrical distribution panel. When you plug into shore power, the relay disconnects the neutral-to-ground bond because the neutral-to-ground bond should be made at the first means of disconnect to the utility power. This relay is programmable normally to accommodate other situations where the neutral-ground bond is made in the distribution system.

UL 458 listed devices help overcome this issue in mobile application such as RV's. Problem is people are looking at cost first then actual function without having a basis of how electricity functions in theory and actuality. Cost is a valid selection criteria but function/compatibility/code compliance(safety)/installation requirements are really more important to a safe well functioning system than the price of one component.

 

[Zil]

I operated industrial systems. The power went out, the transfer switch opened the white and three black wires. It did not open the green, or bare, earth wire. The generator started and came up to speed. The transfer switch went to generator side and connected those white and black wires to the generator wires. Never interrupting the earth ground wire. On my small stuff I don't have any connection with mains electric so have no need of transfer.