Please help me figure out this electrical box...

cupcake

Hello everyone,

Im off grid - in the process of wiring 2 280watt panels to a small cabin...

I need help figuring out the AC box wiring...

here is the route planned:

2 280watt panels wired in parallel --> Morningstar MPPT tristar60 controller --> battery bank --> Samlex 1500 (PST-1500-12) inverter ---> Standard AC electrical panel (Square-D) ---> 'normal' AC wiring/lights/outlets/etc...


Now my question is how to wire *ONLY the AC box -- I am CONFUSED as to what is what. I understand where the hot wires go (on the middle bars), but...

1) where is the ground bar?

2) where is the neutral bar?

and

3) can you identify the letters in the attached photo...

Also I understand that the samlex 1500 (PST-1500-12) inverter is 'bonded to neutral' WITHIN the inverter so I should NOT 'bond neutral and ground' inside the electrical box...


The attached photo is my actual set-up so far -- obviously nothing is hooked up to any power source yet...

thank you EVERYONE for your help!


--cuppy

tons001

Re: Please help me figure out this electrical box...

Should be but I am sure someone will correct me if I am wrong.

A = Combines the neutral/ground bars.
B/C = Neutral/ground bars
D = Service neutral in.

Ground and neutral bars are combined which is why is you measure hot to neutral you get 120vac and hot to ground you get 120vac. What you don't want is voltage between neutral and ground in any circuits. The only reason their are two bars (B & C) is to help keep your electrical box tidy.

BB.

Re: Please help me figure out this electrical box...

Can you see if there is any connection between the neutral bus bar(s) and the metal box? (screw through bar to back panel or something?)

If these were "isolated"/insulated neutrals, I would would think you should have a grounded bus bar for green wire connection too (i.e., using ROMEX or hardwire green wires--like you have).

A sub panel should have a separate Neutral and ground bus bars. A main panel, the neutral and ground buses would be (electrically) the same.

-Bill

tons001

Re: Please help me figure out this electrical box...

BB. wrote: »

Can you see if there is any connection between the neutral bus bar(s) and the metal box? (screw through bar to back panel or something?)

If these were "isolated"/insulated neutrals, I would would think you should have a grounded bus bar for green wire connection too (i.e., using ROMEX or hardwire green wires--like you have).

A sub panel should have a separate Neutral and ground bus bars. A main panel, the neutral and ground buses would be (electrically) the same.

-Bill

So you are thinking his sub-panel box is missing a ground bar then? Out of curiosity, why would a sub panel have separate neutral and ground bars when in reality they are tied together anyways?

In this situation, it would seem that cupcake is treating the sub panel as his main panel. Could cupcake not just bond the case to the neutral bar?

vtmaps

Re: Please help me figure out this electrical box...

tons001 wrote: »

Out of curiosity, why would a sub panel have separate neutral and ground bars when in reality they are tied together anyways?

Very important: only ONE bond between ground and neutral in a system. Otherwise you could have ground loops and unsafe parallel current carrying paths.
--vtMaps

tons001

Re: Please help me figure out this electrical box...

vtmaps wrote: »

Very important: only ONE bond between ground and neutral in a system. Otherwise you could have ground loops and unsafe parallel current carrying paths.
--vtMaps

Thanks. That answers that. I don't have subpanels. In cupcake's situation then, is the inverter n-g bond acting as that one bond on the main service panel?

cupcake

Re: Please help me figure out this electrical box...

tons001 wrote: »

Should be but I am sure someone will correct me if I am wrong.

A = Combines the neutral/ground bars.
B/C = Neutral/ground bars
D = Service neutral in.

Ground and neutral bars are combined which is why is you measure hot to neutral you get 120vac and hot to ground you get 120vac. What you don't want is voltage between neutral and ground in any circuits. The only reason their are two bars (B & C) is to help keep your electrical box tidy.

Thanks for this...

OK I now understand that the big screw "D" is neutral in -- thank you for that one...

what gets me confused is why the NETRUAL and GROUND bars are 'the same'? or 'shared'? Shouldnt their be a ground bar and a SEPERATE neutral bar? or no? they are just always 'shared'?

Then -- theres this talk of 'bonding' neutral and ground --- which confused me because you just taught me that the neutral/ground bar is 'shared'...

thank you for your help so far

--cakes

tons001

Re: Please help me figure out this electrical box...

cupcake wrote: »

Thanks for this...

OK I now understand that the big screw "D" is neutral in -- thank you for that one...

what gets me confused is why the NETRUAL and GROUND bars are 'the same'? or 'shared'? Shouldnt their be a ground bar and a SEPERATE neutral bar? or no? they are just always 'shared'?

Then -- theres this talk of 'bonding' neutral and ground --- which confused me because you just taught me that the neutral/ground bar is 'shared'...

thank you for your help so far

--cakes

Hang tight ... read BB's post. I knew someone smarter would answer. LOL

BB.

Re: Please help me figure out this electrical box...

Yes, that would work fine... Although, if I had a choice, i would lift the N-G connection in the inverter and make the N-G connection in the "main AC panel". Heavier bonding (lightning, big shorts) and "standard" bonding location for the next guy that works on the system.

Cannot see the bottom of the panel, perhaps there is a ground bus bar there (no green screws/ground symbols anywhere in the back panel in the areas we can see--Would be strange if green screws/ground bus bar was not there--In my relatively limited experience).

-Bill

cupcake

Re: Please help me figure out this electrical box...

Thanks for your help so far...

the BOX came with a GREEN 'bonding screw' that screws into the 'middle top bar' and into the back of the actaul body of the electrical box....



I am just trying to conceptualize why neutral and ground are "OK" to touch each other in AC current -- I am DC minded and to me thats like touching positive and negative... a no-no...

thank you all for bearing with me here and helping me -- im just trying to get the 'concept' so it can 'click' in my mind...

-- c cups

cupcake

Re: Please help me figure out this electrical box...

tons001 wrote: »

So you are thinking his sub-panel box is missing a ground bar then? Out of curiosity, why would a sub panel have separate neutral and ground bars when in reality they are tied together anyways?

In this situation, it would seem that cupcake is treating the sub panel as his main panel. Could cupcake not just bond the case to the neutral bar?

To clear any confusion my box is a "MAIN PANEL BOX" *not a 'subpanel box' -- its just a 'standard' square-d breaker box .. the only power source to it will be from an inverter (samlex 1500)

cupcake

Re: Please help me figure out this electrical box...

the outside of the square d box packaging said to 'buy a ground bus bar' - WHICH I DID... but I have no idea where it goes... or how -- I see two bars ..one on left on on right..and someone here told me those were ground/neutral -- so do I just jam BOTH green AND white wires on that same bar??

tons001

Re: Please help me figure out this electrical box...

cupcake wrote: »

I am just trying to conceptualize why neutral and ground are "OK" to touch each other in AC current -- I am DC minded and to me thats like touching positive and negative... a no-no...
-- c cups

Safety. Without that bond, your circuit breakers would not trip.

Keep in mind with DC you will have much the same situation. You should have a DC +, DC - and in my setup ... Battery DC - is grounded. This is dependent on your components though because some setups call for DC + to be grounded.

BB.

Re: Please help me figure out this electrical box...

cupcake wrote: »

the BOX came with a GREEN 'bonding screw' that screws into the 'middle top bar' and into the back of the actaul body of the electrical box...

Ok, that makes sense... If this is your only panel or the Main Panel, you would drive in that screw to bond the metal box to the "neutral" bus bars (and lift the N-G in the AC inverter).

There should be another bus bar bolted to the metal box for your green wire connections.

I am just trying to conceptualize why neutral and ground are "OK" to touch each other in AC current -- I am DC minded and to me that's like touching positive and negative... a no-no...

The Neutral is the "center tap" of a 120/240 VAC transformer. You can pick any leg of the transformer to "ground" reference. "We" just pick the center tap for our ground references.

For DC--Think of two 12 volt batteries in series. you can bond the negative and get 0, +12, +24 volt "taps". Or you can put the ground in the middle and get -12, 0, +12. Or ground the + end and get -24, -12, 0 volt taps.

Or, just let the whole thing "float".

For a 12 volt car system... The Ground and Return are the same circuits (the metal frame of the car).

For AC house systems... We have "Hot", "Return", and "Safety Ground". The Hot and Return is where current is supposed flow. The Green Wire system is there to only dump current (enough current to pop a fuse/breaker on the Hot circuits). There are no fuses/breakers on neutral or ground leads. Neutrals are sized for the Hot wire "mate". Grounds are sized to dump enough current for a few seconds--And not for 100% rated load of the Hot/Neutral Pairs (although, many times the green wire is sized as the same as the Hot/Neutrals).

-Bill

BB.

Re: Please help me figure out this electrical box...

cupcake wrote: »

the outside of the square d box packaging said to 'buy a ground bus bar' - WHICH I DID... but I have no idea where it goes... or how -- I see two bars ..one on left on on right..and someone here told me those were ground/neutral -- so do I just jam BOTH green AND white wires on that same bar??

Put the bonding screw in your "A" metal. Put a Green Wire from "somewhere" in the box (one of the bus bars, to a clamp/screw on metal box, or similar--per code requirements) and connect the ground wire to your cold water pipe (metal) and/or 8-10 foot metal ground rod.

Remember that "Grounding" is to make sure that any major piece of metal (sink, stove, furnace, propane lines, etc.) are all connected (somehow) to your green wire ground system. If there is ever an AC Hot to metal short, that item will not become "energized" and a shock/fire hazard. Instead, current will flow through the green wire and back to the power source (through ground+neutral bond) and trip the breaker/inverter off.

-Bill

cupcake

Re: Please help me figure out this electrical box...

OK guys thanks for your help so far...

Please EXAMINE the photo below....

Is this correct for my intended setup.


1) add a ground bar
2) connect white wires to neutral bar on left
3) attach green wires to ground bar (green bar in photo)
4) leave the 'bonding screw' OUT in the box since the gound+neutral bonding will take place INSIDE the samlex 1500 inverter (as mentioned in the samlex unit specifications)
5) attach a proper gauge grounding wire leading outside to two 8 foot electrodes buried in the earth and separated by at least 6 feet


Is this all correct my friends?

Thank you ALL for your wonderful help so far - note in the photo I omitted the hotwire because I'm only concerned about how to do neutrals and grounds --

thanks again everyone

--cakes

Attachment not found.

tons001

Re: Please help me figure out this electrical box...

Looks right based on this entire thread. However, make sure your inverter is properly grounded or the whole grounding thing is pointless.

BB.

Re: Please help me figure out this electrical box...

Oh boy... This gets difficult very quickly.

How is your Samlex grounded (chassis ground to battery negative? Battery Negative to ground rod?

The issue is that your Samlex has a very heavy set of DC +/- cables coming in from the battery with something like a 200+ amp fuse.

What you don't want is a DC side + to chassis short on the Samlex going through the 14 awg wire to the main panel, then to the ground rod and then back to the DC - bus on the battery bank.

My recommendation--If you use the N-G in the AC inverter. Ground with a heavy cable from the Samlex chassis back to the Battery Negative Bus (at least 6 awg cable). And run your single ground cable (again 6 AWG) from the Battery negative bus to the ground rod.

Only do your AC Panel ground rod if you don't use the N-G in the inverter.

This stuff is complicated.

-Bill

cupcake

Re: Please help me figure out this electrical box...

BB. wrote: »

Oh boy... This gets difficult very quickly.

How is your Samlex grounded (chassis ground to battery negative? Battery Negative to ground rod?

The issue is that your Samlex has a very heavy set of DC +/- cables coming in from the battery with something like a 200+ amp fuse.

What you don't want is a DC side + to chassis short on the Samlex going through the 14 awg wire to the main panel, then to the ground rod and then back to the DC - bus on the battery bank.

My recommendation--If you use the N-G in the AC inverter. Ground with a heavy cable from the Samlex chassis back to the Battery Negative Bus (at least 6 awg cable). And run your single ground cable (again 6 AWG) from the Battery negative bus to the ground rod.

Only do your AC Panel ground rod if you don't use the N-G in the inverter.

This stuff is complicated.

-Bill

Thank you everyone so far for your help ...

OK so is THIS correct (see photo)

right click 'view image' if too large...

thanks

--kakez

BB.

Re: Please help me figure out this electrical box...

You do not want the "straw" colored connection in the AC box at all... Just run it to the battery negative bus.

You can run EITHER a green wire from the AC inverter (same gauge as your AC hot/neutral) to the AC Box Ground Bus OR Run a cable from the battery negative (or even from the ground rod "single point ground" to the AC Box Ground Bus (6 AWG).

Do you have lightning in your area? Using the 6 AWG from the battery bus negative or the ground rod negative and Lightning arrestors would probably be a better idea.

Whether you call the battery bus negative as your single point ground or the "Master Ground Rod" is sort of semantics. Ideally, you want to make sure that the ground rod to battery negative bus is never "lifted" during normal servicing of the battery bank (i.e., if the battery bus negative is always solidly connected hunk of metal/copper--Vs just tying a grounding wire to the battery negative post which not a good plan).

White neutrals can go to either left or right neutral bus.

Depending on how "D" is attached, you may move it to the right for the inverter AC connection, or have to wrap the inverter neutral to the left with the large lug is, or simply use the small neutral bus hole(s) if the inverter cable it something that will fit (10, 12, or 14 AWG).

-Bill

cupcake

Re: Please help me figure out this electrical box...

BB. wrote: »

You do not want the "straw" colored connection in the AC box at all... Just run it to the battery negative bus.

You can run EITHER a green wire from the AC inverter (same gauge as your AC hot/neutral) to the AC Box Ground Bus OR Run a cable from the battery negative (or even from the ground rod "single point ground" to the AC Box Ground Bus (6 AWG).

Do you have lightning in your area? Using the 6 AWG from the battery bus negative or the ground rod negative and Lightning arrestors would probably be a better idea.

Whether you call the battery bus negative as your single point ground or the "Master Ground Rod" is sort of semantics. Ideally, you want to make sure that the ground rod to battery negative bus is never "lifted" during normal servicing of the battery bank (i.e., if the battery bus negative is always solidly connected hunk of metal/copper--Vs just tying a grounding wire to the battery negative post which not a good plan).

White neutrals can go to either left or right neutral bus.

Depending on how "D" is attached, you may move it to the right for the inverter AC connection, or have to wrap the inverter neutral to the left with the large lug is, or simply use the small neutral bus hole(s) if the inverter cable it something that will fit (10, 12, or 14 AWG).

-Bill

OK - thanks - I understand alot so far - the only area I need clarification is with the grounding -- I get neutral now, I get to install a seperate ground bar...

..but then you are saying to make the grounding rod connection - ie the 'master ground' from the batter negative AND the chassis of the inverter

right?


So it should look like this:

INVERTER CHASSIS ----> GROUNDING ROD BURIED IN EARTH

AND

NEGATIVE BATTERY TERMINAL

---

> GROUNDING ROD BURIED IN EARTH


Do I finally have it 100% correct???

Thank you again

--sweetcakes

BB.

Re: Please help me figure out this electrical box...

Yes--The current path for any short circuit 12 VDC power should be heavy cable (like 6 AWG minimum). Pretend that you get a short from 12v+ to inverter chassis. Trace the "return current" path and make sure that it goes through 6 awg wire (minimum).

-Bill

cupcake

Re: Please help me figure out this electrical box...

BB. wrote: »

Yes--The current path for any short circuit 12 VDC power should be heavy cable (like 6 AWG minimum). Pretend that you get a short from 12v+ to inverter chassis. Trace the "return current" path and make sure that it goes through 6 awg wire (minimum).

-Bill

Thank you Mr. Bill....


So one last clarification:

So basically Im attaching 2 6 guage bare copper leads to the grounding rod:

INVERTER >---(6 awg bare copper wire)---> grounding rods
Battery negative terminal >---(6 awg bare copper wire)---> [same] grounding rods

^ IS that it? The whole set up is safely grounded now?



thank you --

--caxxx

BB.

Re: Please help me figure out this electrical box...

And a Green Wire from the Inverter AC ground (gnd+neutral bond) to the green wire ground block in the AC panel (all AC green wires should go to the green wire ground block in the AC panel).

No ground bonding screw from "A" to the Panel metal.

-Bill

mike95490

Re: Please help me figure out this electrical box...

one more thing, your box is designed for a "Split Phase" feed. The breakers plug into the 2 silvery interleaved buss bars in the middle. Phase A, and Phase B. Your inverter is single phase. So you will either have to only use half the breakers, or jumper the 2 buss bars together. (or maybe there is something I'm not seeing in the photos)

Jumpering the 2 buss bars together, will make a bizarre nightmare for the next person - use a weird color wire for the jumper

BB.

Re: Please help me figure out this electrical box...

Jumpering the Red and Black phases together is very common with 120 VAC systems.

The only thing to be careful about in wiring your house is that you always use Hot+Return for your 120 VAC circuits. If you use a Black+Read+White (plus ground), the Neutral on a 120 VAC only system will have the black+red currents add on the White Wire (and over current it--15a+10a=25 amp on white wire for 120 VAC only system).

With Black+Red+White on a 120/240 split phase system, the black+red currents subtract on the white wire (15a-10a=5 amp on white wire for split phase systems).

-Bill

cupcake

Re: Please help me figure out this electrical box...

mike95490 wrote: »

one more thing, your box is designed for a "Split Phase" feed. The breakers plug into the 2 silvery interleaved buss bars in the middle. Phase A, and Phase B. Your inverter is single phase. So you will either have to only use half the breakers, or jumper the 2 buss bars together. (or maybe there is something I'm not seeing in the photos)

Jumpering the 2 buss bars together, will make a bizarre nightmare for the next person - use a weird color wire for the jumper

Sounds great...

..I appreciate your tip..truly....

I think I'll just use one phase for now and add a jumper when I expand...

Thanks everyone for the tips so far..great forum... and I will be sure to buy from this site as well...

Mike can you post a photo of your setup?... I am curioe...

--cup

cupcake

Re: Please help me figure out this electrical box...

BB. wrote: »

Jumpering the Red and Black phases together is very common with 120 VAC systems.

The only thing to be careful about in wiring your house is that you always use Hot+Return for your 120 VAC circuits. If you use a Black+Read+White (plus ground), the Neutral on a 120 VAC only system will have the black+red currents add on the White Wire (and over current it--15a+10a=25 amp on white wire for 120 VAC only system).

With Black+Red+White on a 120/240 split phase system, the black+red currents subtract on the white wire (15a-10a=5 amp on white wire for split phase systems).

-Bill

Right now I have 2 circuits as you can see from the photo.of my box...

Hot..return..and green are the only wires involved...

Each circuit is a switch powering a overhead light...

You are saying make no circuits with red wires right??

--cake

mike95490

Re: Please help me figure out this electrical box...

cupcake wrote: »

...Mike can you post a photo of your setup?... I am curioe....

The 3 links in my .sig below, have many photos

BB.

Re: Please help me figure out this electrical box...

With a split phase system (120/240 VAC) as in North America... The Black and Red wires are 120 VAC and 180 degrees out of phase. So you can have 2 "full power" 120 VAC branch circuits with just 3 wires plus ground (black+red+white+green). You can get (for example) 15 amps from black+white and 15 amps red+white--Or 15 amps of 240 VAC with Black+Red (or combination thereof).

With 120 VAC--You would run 120 VAC Black+White+Green for one 15 amp circuit. And a second Black+White+Green for a second 120 VAC circuit. So it takes 5-6 wires (2x black+white + 1-2 green grounds) for two 120 VAC circuits vs 4 wires (Red+Black+White+Green) for 2x120 VAC circuits on a split phase circuit.

So, you have to use a bit more copper wire, and, obviously, you cannot get "native" 240 VAC from a 120 VAC setup.

-Bill

cupcake

Re: Please help me figure out this electrical box...

BB. wrote: »

With a split phase system (120/240 VAC) as in North America... The Black and Red wires are 120 VAC and 180 degrees out of phase. So you can have 2 "full power" 120 VAC branch circuits with just 3 wires plus ground (black+red+white+green). You can get (for example) 15 amps from black+white and 15 amps red+white--Or 15 amps of 240 VAC with Black+Red (or combination thereof).

With 120 VAC--You would run 120 VAC Black+White+Green for one 15 amp circuit. And a second Black+White+Green for a second 120 VAC circuit. So it takes 5-6 wires (2x black+white + 1-2 green grounds) for two 120 VAC circuits vs 4 wires (Red+Black+White+Green) for 2x120 VAC circuits on a split phase circuit.

So, you have to use a bit more copper wire, and, obviously, you cannot get "native" 240 VAC from a 120 VAC setup.

-Bill

Thank you Mr.Bill...


...getting back to grounding all of this...
....is a large sized grounding wire necesarry for the box to inverter to battery negative to inverter chassis grounds which will all lead to the burried rods...

Isint the idea that copper wire offers less resistance than the human body?

--cuppie