MNPV6 Combiner conduit fill space

[Beyla]

Hi,
I’m new to the forum and have recently purchased a Classic 150. I’m running 6 12 volt panels at 260 Watts each. I have a total of 12 wires coming in to the MNPV6 Combiner and a ground wire. In order to stay below my 40% conduit fill space, I had to run 2 X 1 1/4 EMT conduits to the MNPV6. The new electrical code requires a shutoff of the PV feed in a visible location in order for first responders to shut it off from outside. I used a 1 1/4 step bit to achieve this. I have no plans to use the grounding bar within and grounded the box using a smaller grounding block made of aluminium, ( same material as original). I checked the electrical code for Canada relating to solar systems (ESSA) and after these modifications am wondering why it did not come with two 1 1/4 punch outs for my EMT bonding?

Also, if I may ask, seeing how this was the only means of complying with the conduit fill space, do my modifications make sense ? Thank you in advance for any response you may wish to provide.

Regards,

[Vic]

Hi Beyla,   welcome to the Forum.

Most PVs,   in the 260 watt range have 60 cells,   and are not really 12 V PVs.  Most 260 w PVs have STC Vmps of about 30 V,  or so.

I have not ever done any systems,  needing to comply with Canadian Codes.

Assume that your system is 12 V ?
Do not know the gauge wire that you are using for the runs from the PVs to the MNPV6,   but  in the US,  we customarily use THHN type cable,  inside EMT or PVC conduit.

THHN 10 AWG cable in 1"  EMT has a maximum number of conductors from a Table, of 16.

You might be using USE-2/RHH/XLP cables in your conduit,  which are not compact conductors,  in order to need such large conduit for 12 cables + a grounding conductor ...   dunno.

The more recent Codes do make things more difficult for many installations.

What is the system battery voltage?
What Charge Controller are you using?
What make and model number are the PVs?
What gauge type cable are you using for the PV,  to MNPV6 are you using?
What is the average length of the PV cables?

Are you using the MNPV6 as the disconnect for the emergency disconnect?

Thanks for the added info,   Vic

[Westbranch]

If you run 2 PV panels in series you should not have a 'fill' issue as there will be 1/2 the conductors... and let the CC do its magic down converting to 12 volts...

What gauge wire did you use?

Vic,  we (apparently) use the same code, it may vary by version, as to which version is be used in which jurisdiction... 
10 Provinces and a bunch of Territories in the far north...

[Beyla]

Hi and thanks for responding. I’m using 12 volt battery bank  and same with the panels. All 6 panels are running individually at 10 AWG (7.7 mm outside diameter) to 6 individual 15 amp midnite solar breakers. The average length of my pv wires to my combiner is roughly  on average 12 feet give or take 2 feet on any run. From my combiner, which I also use as a disconnect ; I run AWG 6 (100 amp rated) for about 4 feet to my arc fault 63 amp midnite solar breaker, then from there to the ( yet to be installed Classic 150), then from the Classic to a 100 amp (2X50 amps bridged breaker) prior to entering the 12 volt battery bank. Total panel wattage is 1530, however, I plan to cover half that panel if it exceeeds the Classic 150 maximum wattage on 12 volt bank of 1380, after derating, but not sure if the extra wattage will stress the Classic at around 1540 Watts on 12 volt. Hope that provides sufficient detail to determine my compliance. Also the panels are brand Canadian 3 x 265 Watts , 3 x 250 Watts. My battery bank consists of 4 X 6 volt  basically new, soon to be 8 x 6 volt. Each battery is 220 Ah at 6 volt , so at 12 volt it’s 110 Ah. For a total of 440 Ah at 12 volts , which is not sufficient for what panels I have. Any suggestions on my plan of action ? I want to keep the battery bank at 12 volt and also the panels for now. Thanks again Vic and WestBranch, nice of you to respond , much appreciated.

[mike90045]

I've seen tin plated copper or brass ground blocks,  but not bare aluminum ground blocks

[Beyla]

Hi Mike, thanks for your response,
The extra block that comes with the MNPV6 for splitting the breaker plate is what I used, since I did not need to split the box to accommodate two CC. It’s the extra block that would accomodate the feed to the extra CC if required, looks like aluminium to me. All the blocks in the MNPV6 look identical. There are two, one for grounding equipment and the other for the negative PV IN, each block are about 4 inches long. I grounded my equipment using the EMT conduit and a 4 AWG bare copper to grounding rod, double grounded with a ground rod and the another location with a ground plate. It is equipment grounding using brute direct path to ground with thick bonded copper strand. The MNPV6 is grounded by three EMT conduits and a separate copper ground with stainless steel washers and bolt on a copper connection and also on the extra block. Thanks for noticing that, not sure what the MNPV6 blocks are made of.

[Vic]

   ...   Vic,  we (apparently) use the same code, it may vary by version, as to which version is be used in which jurisdiction... 
10 Provinces and a bunch of Territories in the far north...

Yea,   but often your cables are not what we us in the US.
Most cables in conduit here,   are THHN/THWN/THW-2/MTW.   This cable is compact,   with thin insulation,   allowing more conductors in trade sizes of conduit verses some of the cables used in Canada  ...

Wanted the specs on the PVs and the battery voltage to be able to understand more about ideal string configuration.

Most often,  with MPPT CCs,  PVs are arranged in strings of two or three PVs.   This minimizes the number of cable runs to the Combiner,   and Combiner breakers.

In some larger installations,   have drilled out the Combiner conduit knock-outs,   but this was in situations of needing 30 PVs (strings of three),   etc.

All of the buss bars that are in common use in electrical systems/panels/boxes look like AL,   but they are Tin-plated Al,   and are suitable for use with Cu/Al  cable.   These look like plain Al,   but are not.

Many times,  for systems that need to be Inspected,  changing bussbars and ground lugs,   etc from what was the Listed for a box/panel  will (technically) be outside of the Listed use/rating.

Beyla,  if you could supply the info on the exact cable type,  specs on PVs,   and perhaps info on the coldest temperatures for the site of this system,   we could help more.

Thanks,   Vic

[Vic]

And,   here is a Link to the Classic String Sizer:
http://midnitesolar.com/sizingTool/displaySizing.php

This will help you decide the best PV string configuration,  given your PVs,  temperatures,   battery voltage,   etc.

Vic

[Beyla]

Yes, I have used the tool, but the wattage says excessive wattage , no matter which way you toss the dice on 12 volt battery bank, however I can cover half a panel for now and bring it within the wattage specification. I used  -40 degrees for both temperatures. I currently have some 12v appliances and my inverter is a modest 1200 watt pure sine Aims.. not th greatest but serves my purpose and has auto transfer switch in case battery drops below set point, which is why I want it all on 12 V for max amps.

Next year I plan to go in series and change my inverter and battery bank  to 24 volt to increase wattage.

PV Cable specifications :
Here is what I have, thanks.

Specifications:
• length: 20 feet (One pair)
• Wire Gauge: 10AWG
• Rating Voltage: -DC :1.8KV -AC: 0.6~1KV
• Degree of Protection: IP65
• Fire Rated: IEC60332-1
• Temperature: -40~ï¹¢90â,,ƒ
• Normal Cross Sectional Area of the Conductor (mm2): 6.0
• Service life: ＞25 years（ -40~ï¹¢90â,,ƒï¼‰

Solar Panel  specifications:

265 Watts
Optimum Operating Voltage 30.6 V
Optimum Operating Current 8.66 A
Open Circuit Voltage  37.7 V
Short Circuit Current  ISC  9.23 A
Maximum Sytem Voltage  IEC 1000 and  UL 100O V

Maximum Series Fuse 15 A

Maximum Temp 85 C

Class A

Regards and thanks,

[Ron Swanson]

Someone help me if I missed something here.

Beyla, you keep saying these are 12V panels but they are not.  They are more like 24V panels with a Mpp of 30V.  But it does not really matter.

What prevents you from hooking them up in series in 2 strings of 3?  Then the combiner will only have 4 wires, 2 positive and 2 negative.  Your charge controller will be working with 91 volts Mpp and your combined array current will only be 17 amps.

The charge controller will work with 1 x 6, 2 x 3 and 3 x 2 strings but 3 x 2 is better for several reasons.  The calculated power is the same any way but the combined array current is much higher at lower voltages which could be an issue depending on how long the wire is. 

The 1.2 excessive wattage still fits within their guidelines.  If it was any higher you want to upsize but that little bit of excess is OK per the specs.

[Vic]

Thanks Beyla,  for all of the added info.

First,  do not know the cable type that you are using  (the standard designator used to convey its insulation type and/or probable use).

But,  at 7.7 MM,  this must have heavy insulation,  or perhaps two layers of insulation,   like USE or USE-2,  or RHH,   RHW  etc.   These designators are used in the USA,  but   IIRC,   Canada has some of its own cable designators ...   In any case  the 10 gauge cable that you appear to be using for the PV-to Combiner runs appears to be almost twice the OD of what most of use for these cable runs,  that are in conduit  --  THHN.  10 AWG THHN has an OD  of 0.161"  nominal.   Believe your cable  --  7.7 MM  --  is about 0.303"  nominal IIRC.

Often  many of us make the transition from PV cable that is rated for Exposure (to the elements) to THHN,   inside a small conduit box (one per PV,  or PV string).  Mostly these boxes are cast Al,   and waterproof(when installed correctly).   These boxes have threaded ports (NPT) that accept common conduit fittings.   Am sure that you have seen and used these before.   This approach  would have increased the number of conductors permitted in the conduit before the max fill number was reached.

For your 12 V system,   or the planned change to 24 V,   strings of two of your PVs  should do fine.  "Strings"  of one of your 60 cell PVs  would generally be a poor fit for almost any 24 V Lead Acid battery system,  because of the relatively low Vmp rating of these PVs (even with a PWM type CC).  When using Flooded Lead Acid (FLA)  24 V battery with single 60 cell PVs  and an MPPT CC,  would be a particularly poor fit.

Seems that you are considering trying to run four parallel battery strings on your 12 V system.  Parallel battery strings can be difficult to manage,   particularly when there are more than two strings.

Just some random thoughts,   IMO.    Some of the above is probably covering things of which you are well aware,   etc.   Vic

[Westbranch]

Beyla said : Also the panels are brand Canadian 3 x 265 Watts , 3 x 250 Watts.

can you post the specs of these 6 PV's as you would have 2 x 265W, 2 x 250W an a set of 1- 265W plus 1 at 250W  and those 2 may not be a good fit

[Beyla]

Thank you for responding, yes they are 60 cell.

250 Watt panels:
http://www.solarelectricsupply.com/fileuploader/download/download/?d=0&file=custom%2Fupload%2FCSI-CS6P-220-250.pdf

265 Watt panels :
https://www.canadiansolar.com/downloads/datasheets/na/Canadian_Solar-Datasheet-CS6PP_Quartech-v5.3_na.pdf


I believe I can run them in series of 2 for a 24 volt array of 3 strings. This will reduce the pv wire runs to the combiner. I want to be sure I can run the two different panels in a string. Are these two panels compatible?

Also, I am quite sure I ordered 12 Volt panels, even though the specs says 30+ volts. I think the 24 volt panels are more expensive and I paid $200 CDN for these panels. Can someone enlighten me as to wether they are indeed 12 or 24 volt panels? 

Also, I was under the impression that the Classic would be less stressed running a 12 volt pv array than a 24 volt array,  going to a 12V battery bank, am I mistaken?

Thanks again for your help and continued support,by now you might be getting annoyed at my continued ignorance. 

[Vic]

Hey Beyla,

60-cell PVs are neither 12,  nor 24 V  PVs.   They might be called something like a 20 V nominal PV.   These PVs were initially thought of as Grid Tie panels,   and not for battery based systems (in general).

Are you certain that the Link to the 265 W PVs is correct?   That link shows these PVs as having built-in power Optimizers.   I have no experience with these.   It is possible that they might be used as strings of two,   but only with another of the same type.

Will l look at this more ...   AND,   your questions are not tedious or ignorant.   We all are learning,   and have asked many,   many questions of our own.   So,  welcome aboard.   I sure do not know about these Optimizer PVs.

There has been a Warning from MidNite about Tigo (sp?)  Optimizers doing possible damage to MN Classics,   IIRC.    Later,   Thanks for the info.   Vic

[Beyla]

Thanks Vic, for making me feel at home.

I corrected the above link to the 265 Watt panel data sheet, here it is :

https://www.canadiansolar.com/downloads/datasheets/na/Canadian_Solar-Datasheet-CS6PP_Quartech-v5.3_na.pdf

Hope that gets rid of that optimizer thingy... 

...look like it did, no Solar Edge optimizer on mine.


Regards and appreciation,