Panel Grounding

Re: Panel Grounding

I am not sure I understand your question...

With inverters and generators as backup power for Grid/Utility power--You cannot guess as to the correct method of grounding. You are limited by code and by the physical design and construction of the backup power equipment.

For example, most MSW inverters cannot have neutral (white wire) tied to any sort of safety/earth ground--Especially if the battery bank (typically battery negative bus) is ground referenced too--It creates a dead short thought the inverter and will let out the magic smoke.

With most TSW inverters, they have floating (or galvanic isolated) outputs (i.e., a isolation transformer) which can have one of its outputs safely tied to earth (and battery) ground. However, some TSW inverter appear to tie the case ground and neutral output together inside the inverter. This can cause "ground loop" problems with inverter ground bond and the ground bond inside the typical main service panel.

Then through a generator in--and you have smaller gensets (under ~3.5 kW) that float their electrical outputs... And >~3.5kW which tie neutral to earth bond in the generator (to generator frame which then is connected to system/earth ground).

So--You end up with different grounds (safety/green wire/conduit, AC, DC, inverter, generator, main panel, ground rod/water pipe, even RF/HAM grounds, etc.)... And you either have to use a 2 or 3 pole (120 or 120/240 split phase power) transfer switch to "transfer" the earth to white wire/neutral bond point (or even float the neutral for MSW type inverters)--Or you have to go into the devices and verify/lift earth to neutral bonding before connecting to the home's wiring.

In a nutshell--Those are the questions... So, now what is your basic system block diagram you wish to implement?

It is not a simple question/answer type thing.

-Bill

Re: Panel Grounding

Joe J wrote: »

Than from inside the house tie in a ground to a transfer switch to the inverter to the controller to the breaker for the panels and out to that same ground rod. That's what I am thinking. Or should I tie the transfer switch to the main A/C box instead. I'm only talking about the ground from metal box to metal box. Make sense??

Can anybody shed some light on the above statement? Thinking about this a little more maybe the better way to do this is to tie everything to one common buss bar than out to the ground so if one ground is broken the other equipment would not lose their ground.

More or less--We are looking to tie the ground in "one place" If that is a "ground window" (term used in telephone central offices--basically from what I can tell, a big bus bar/group of bus bars that are all defined as telecom "ground" for the building.

If all grounds are home run back to this one (i.e., no parallel ground paths such as a ground wire from the battery bank negative, and another ground wire from a car radio where DC return/chassis ground are the same thing).

Then run a single cable from that ground window to a near by ground rod/earth ground would be fine.

The one caution is a question of safety vs lightning grounds. Lightning is RF energy (~7.5kHz maximum frequency from what I could find)--So any outside systems/components/metal structures should go straight down to an earth ground rod/plate. Brining a ground that may be subject to lightning inside a home is usually a "bad idea".

If you have "multiple grounds" that are both Lightning related and "safety related" (i.e., you have AC or DC power sent to equipment/lighting/etc. at the base of an antenna tower or out building). You can carry the "green wire" safety ground" from the primary power location (i.e., in your home) out to the equipment so you get ground protection against hot to metal faults--will pop fuse/breaker and isolate from local lighting ground). Or you can bring out a separate ground wire from the home ground rod out to the outbuilding ground rod. The local ground rods will provide lightning ground. And the ground rod to ground rod cable will provide the AC or DC safety ground connection.

That's what we do in the radio "ham" world. Don't see why this would be any different. Also I have a manual transfer switch in my system. Should that go to the main A/C ground in the electric panel or to the D/C? ground rod just because it's part of that system?

So--Sorry to be so dense... Are you talking about the metal box for an AC transfer switch, or the Neutral, or even talking about a transfer switch on a green wire ground?

Than from inside the house tie in a ground to a transfer switch to the inverter to the controller to the breaker for the panels and out to that same ground rod. That's what I am thinking. Or should I tie the transfer switch to the main A/C box instead. I'm only talking about the ground from metal box to metal box. Make sense??

And is the inverter a floated AC neutral or a MSW with DC bus grounded (to common ground rod or AC vs DC ground rod with a 6 awg cable between the two rods, etc.)?

What controller (battery charge controller?). What breaker panels (DC or AC, or Solar Combiner)? What "same ground rod" (AC ground rod for home panel, separate DC or AC ground rod for backup power system? Will separate ground rods be tied together with 6 awg cable?

-Bill

Re: Panel Grounding

If your transfer switch is tied to grid power--yes, just tie the metal box to the green/wire of your main power panel--You are fine. If there is a short, the energy is dumped back to the main panel (and pops the breaker).

The output of the TSW inverter is "floating"--You you have the choice of ground referencing its neutral output or even just carrying the neutral from the main panel through to the protected loads.

I believe the Xantrex floats the AC output with respect to ground(s)--But you need to read your manual and check with a meter to be sure.

A 2kW inverter is just right on the edge of needing a distribution box/breakers for its output (can exceed the 15 amp max/12 amp max continuous current rating of 14 AWG wiring).

-Bill