formulating needs for more PV

[elesaver]

I'm gathering information on what I will need to add additional PV to my current system so I have a couple of questions.  I hope to be able to wire 4 new identical panels in 2 strings to another Classic and use the follow me option.  I currently have a MNPV6 combiner box with 2 empty slots.  Is there a way to utilize this box for the two new strings or would I have to get a whole new box?

I haven't found anything on Midnite's site with info on how to set up a second system.  I gather that I only need to run the PV from a combiner box (either the current one or a separate one) the a disconnect or baby box with appropriate breakers and then have a battery breaker there, too.  If I'm using the follow me, does the Master Classic and Whizbang take over from there or would I have to have a Whizbang in the new box, too?  Plus, does the inverter operate from the Master Classic or do I have to have something more there?

As you can tell, my mind hasn't firmly grasped this.  It seems that I all I need to do is to bring the additional PV power to the #2 Classic and to the same battery but all else remains the same with the follow me enabled with the 4-pin connectors, etc.

Thanks for the patience.  I know this is basic for most of you but for me...well, not so much.  If you only knew how not so much!  But, I'm getting there.

[ClassicCrazy]

You can use a hack saw to cut the common buss bar in your combiner box . I did that to mine . I think there was a connector on both ends of the bar where you will connect the second system wire that comes from your new Classic. So just cut it so you have enough  of the tabs to go in the two additional breakers. You want to shave a little bit off of each of the bars so there is a bit of a gap between them. I wrapped a bunch of electrical tape on the ends as well so that there was no chance of them hitting each other.  You will also need to run new wires from your second Classic to the combiner box to hook them up. 

Larry

[elesaver]

Thanks, Larry!  I was actually thinking of doing that and to make sure there was no arching between them.  Sounds like a plan.  And, yes, I'm in the process of calculating how much new wire I'll need. 

[Vic]

I'm gathering information on what I will need to add additional PV to my current system so I have a couple of questions.  I hope to be able to wire 4 new identical panels in 2 strings to another Classic and use the follow me option.  I currently have a MNPV6 combiner box with 2 empty slots   ...

  ... I gather that I only need to run the PV from a combiner box (either the current one or a separate one) the a disconnect or baby box with appropriate breakers and then have a battery breaker there, too.  If I'm using the follow me, does the Master Classic and Whizbang take over from there or would I have to have a Whizbang in the new box, too?  Plus, does the inverter operate from the Master Classic or do I have to have something more there?

Thanks for the patience.  I know this is basic for most of you but for me...well, not so much.  If you only knew how not so much!  But, I'm getting there.

Hello elesaver,

In the Manual for the smaller Combiners,  up to the MNPV6,  it does show cutting the single busbar into two pieces for your very purpose,  as Larry mentioned.  The manual does recommend cutting out a small section of the busbar,  by making two cuts (the slit).   See Page 4,  at the bottom of the page:
http://www.midnitesolar.com/pdfs/MNPV2-3-4-6_manual.pdf

This will work fine with Classics,  as there is one PV Negative buss,  and the Classics do not need to have PV Negatives isolated,  if several CCs are being used on the same battery.

Yes you will need to add  PV in,  and Battery breakers,  in some box.  As you said,  perhaps a Big Baby,  or perhaps the Baby box,  which use the DIN-Rail breakers  --  MNEPVs.

Think that you have a MiniDC for this system ...   and the Shunt belongs in this,  or whatever you are actually using.  One WBjr on one Classis is all  that is needed.  Works great with Follow Me,  and the WBjr will see ALL of the charge and discharge currents for all Classics in the system.

Since the battery connections from each Classic will be connected to a battery busbar,  or a lug on the Inverter breaker,   all of the DC output currents  are summed (combined),  and the Inverter does not care from where the current comes,  it just uses it,  as needed.

Have fun with the new design process.   Vic

[Powerplay]

My system has been running on two classic 150s since April.  You'll love this set up once you get it going.  My original Classic acts like the Master and owns the Battery temp sensor and Wzbjr.  The second one owns larger strings and kicks in when some extra juice is needed.  I split into two redundant chargers long before I had to.  I found a grounding diagram on this site that was very helpful.

This set up seems to share out heat in the system and improve expandability.  I did add a second MNPV6 and both combiners have 3 30-Amp breakers in there + each has an SPD.  There are lots of slots left.  I'm adding a new 1 Kw string this fall & building the frame now.

My system is wired with expansion in mind but I wish I had converted to 48V earlier since I'll be maxing out a key breaker & need to take that wire up from 2 Awg soon.

But it is set up that I can drop a 48 Volt inverter into the mix & nothing else changes at least.  (Re-group the battery bank of course.)

[ClassicCrazy]

Powerplay,
Do you have a link for the grounding diagram you saw ?
Thanks
Larry

[elesaver]

Since the battery connections from each Classic will be connected to a battery busbar,  or a lug on the Inverter breaker,   all of the DC output currents  are summed (combined),  and the Inverter does not care from where the current comes,  it just uses it,  as needed.

I'm sketchy on this, Vic.  Here's my wiring plan which apparently needs tweaking.  Yes, I have a MNDC mini disconnect with the Whizbang, jr on the shunt in there.  Since there's not enough room for enough breakers, I'm considering a Baby Box for the new strings coming from the combiner with separate wiring just like the first set up. 


PV+ through Baby Box 40A breaker to Classic #2 terminal block
PV-  directly to Classic #2 terminal block
Batt -  from same battery to Classic #2 terminal block
Batt + from same battery to Baby Box 80A breaker to Classic #2 terminal block

If you have time, would you correct the wiring?

I've looked at the combiner manual.  Who knew?!  "When all else fails, read the directions."  That's one of my faults...one of many, may I add. :-(

Thanks again.

[Vic]

elesaver,

Not much time right now,

The one thing for right now,  would suggest using the Big Baby Box.  The Baby box is nice,  but,  there is very little room to run cables around breakers,  etc,  ant the Big box is little more expensive.

If you presently have the baby box,  it is probably OK,  just a bit harder to work with.

More later,  am on a project just now.   Vic

[elesaver]

No rush, Vic.  I appreciate all that you do to help.  I had already decided on the Big Baby Box although I like the MNDC size...plus, it would allow for more changes, if desired, in the months ahead.  I don't see more changes at this point but that's what I would've said when I bought my first 12V solar panel for a gate opener years ago.  As everyone here knows, solar is addictive!

[Powerplay]

ClassicCrazy,  It is one that gave wire sizes in square mm.  I re-drew it for my own use but found it a good start.  I looked back to a thread that I thought it was in and didn't find it there.  Still looking & will post a link when I find it.

[Vic]

Hi elesaver,

First,  there is a Baby Box,  and the Big Baby Box ...  had suggested using the Big Baby:
https://www.solar-electric.com/misobigbabox.html

You mentioned being a "bit sketchy"  on some aspect of either the exact wiring of the Classic #2,  or something else ...

The MNDC Quad box accepts the Panel Mount breakers,  which are available in sizes up to 100 A,  in a single breaker.  The MNEPV breakers that fit into the Baby boxes are DIN-Rail types,  and,  up to a 63 A rating,  these breakers occupy a single slot in the box.  The MNEPV 80,  and 100 A breakers need two slots,  and these two larger breakers are more than double the cost of the MNEDC breakers.   Your choice.  The MNEDC breakers use threaded studs,  for crimped lugs,  the MNEPV breakers use screw type compression connections.   You may not need more than a 63 A breaker for CC #2,  at this point anyway.

Your wiring concept for #2 seems fine,  Just make certain that the circuit breakers are sized to protect the cable that you are using from the Combiner to the CC#2 input breaker  --  40 A,  and also for the output breaker.

For CC #2,  the output breaker can probably connect to the same place as does CC #1 ...  do not know how your MNDC is configured.  You probably have a positive battery busbar in the MNDC,  where CC #1 connects.  If there is space on that for the CC#2 output breaker's battery connection,  there,  then use that.

Perhaps CC# 1's output breaker connects to the battery at the Main DC breaker for the inverter,  if so,  connect the cable from CC# 2's output breaker there.  If you are using the inverter Main DC breaker for the CC's connection to the battery,  make certain to place the connection on the battery end of the breaker,  NOT the inverter end.

If CC#1's battery connection occurs at the battery's positive terminal,  then you would probably need to place the CC#2's battery connection there,  probably with a separate cable,  in conduit.   Personally,  prefer using the battery side of the inverter Main DC breaker for CC battery (breaker) cable connections,  as the inverter DC cables are run in conduit,  and the Main DC breaker is inside a metal box,  with all of the other DC connections,  and so on.   Some opinions will differ a bit on this ...

Does the above add more confusion that clarity?   Have Fun,   Vic

[elesaver]

In order to clear up some of this, it is best to begin thinking like a rock! :-)  I'm pretty dense on things sometimes.  Here's where my original thinking was:  The second classic (Classic #2) has the primary responsibility of allowing more PV without causing problems for the first class (Master).  Bring in the PV, battery re-charges more quickly and therefore, can handle a larger load. 

All that is good.  Getting the wiring from the combiner to the Big Baby Box and then to Classic #2 is a snap.  It'll go to a 63A breaker in the Big Baby and then to the PV+ connection at the cc terminal block.  If this is not correct, please let me know.

Now, It's getting the battery wiring right that is throwing me.  In the original Master set up with the Midnite mini-dc disconnect, the battery positive comes into the disconnect and to the bottom terminal of the 125A main inverter breaker of the disconnect.  Another battery positive wire runs from the bottom of that main 125A breaker to an 80A DIN rail breaker then on to the Battery + connection at the cc terminal block.  The battery negative is attached to the right side of the shunt for the Whizbang and another battery negative is attached to the left side of the shunt with an additional wire at that location to the inverter negative.  If this is not correct, of course you'll let me know. :-)

Now, see if I have this right:  I will need to wire the Classic #2 battery positive output from the cc terminal block to the bottom of the main 125A breaker and then out to the battery so that there will be two cables instead of one.    I am not sure if the battery negative cable goes directly from the battery to the cc or if it needs to be wired somewhere else?

Hopefully, I've explained well enough to validate if this plan is right or not.  Thank you for taking time!

[Powerplay]

Classic Crazy said:

Powerplay,
Do you have a link for the grounding diagram you saw ?
Thanks
Larry

Got it.  Look in 'System Design & Layout' and the thread titled: 'Grounding Question'

Reply # 12 in that thread from back in February is by Zoneblue and he has a link with a general grounding discussion and one of the drawings I liked is toward the bottom of the drawing at that link.  Shows wire sizes in mm squared.

[CDN-VT]

Links to help
http://zoneblue.org/cms/page.php?view=system-earthing
http://kb1uas.com/mnsforum/index.php?topic=2641.msg25016#msg25016

[Vic]

   ...    Getting the wiring from the combiner to the Big Baby Box and then to Classic #2 is a snap.  It'll go to a 63A breaker in the Big Baby and then to the PV+ connection at the cc terminal block.  If this is not correct, please let me know.

Now, It's getting the battery wiring right that is throwing me.  In the original Master set up with the Midnite mini-dc disconnect, the battery positive comes into the disconnect and to the bottom terminal of the 125A main inverter breaker of the disconnect.  Another battery positive wire runs from the bottom of that main 125A breaker to an 80A DIN rail breaker then on to the Battery + connection at the cc terminal block.  The battery negative is attached to the right side of the shunt for the Whizbang and another battery negative is attached to the left side of the shunt with an additional wire at that location to the inverter negative.  If this is not correct, of course you'll let me know. :-)

Now, see if I have this right:  I will need to wire the Classic #2 battery positive output from the cc terminal block to the bottom of the main 125A breaker and then out to the battery so that there will be two cables instead of one.    I am not sure if the battery negative cable goes directly from the battery to the cc or if it needs to be wired somewhere else?

Hopefully, I've explained well enough to validate if this plan is right or not.  Thank you for taking time!

elesaver,

Your plan for wiring the new PV positive to and from the Pig Baby box,   and to Cl #2 sounds fine.

The negative cable from the Combiner for the new PVs should connect to Cl #2 in the same manner as was done for Cl #1.  The MNDC can accept an Optional insulated negative busbar,  that has a cable connecting this busbar to the Shunt;
QUESTION:  Does your MNDC have the Optional insulated negative busbar,  for the PV negative connections?   If you do not have this PV negative busbar,  you will need to connect  CC #2's negative cable from the Combiner to the side of the Shunt,  where the inverter negative cable is connected (this is where the PV negative from the Combiner for CC #1 should also be connected.

Your description of the battery positive sounds fine,  and the positive cable to CC #1's 80 A breaker.  Do the same thing for CC #2,   connecting to its 63 A output breaker.

Essentially,  all you need to do for wiring CC #2,  is to copy what you have done for CC #!,  as CC 1 appears to be working well,  and the WBjr appears to have correct connections,  as it appears to keep track of current into and out of the battery bank correctly.

I do not have the facility to make acceptable diagrams ...   unfortunate.
Good Luck,    Vic

Connect the cable for CC #2's battery negative in the same manner as was done for CC #1.