Author Topic: MNPV6 Combiner conduit fill space  (Read 509 times)

Vic

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Re: MNPV6 Combiner conduit fill space
« Reply #15 on: April 12, 2018, 06:15:50 PM »
OK Thanks,  Beyla,   the new link to 265W PVs  is much easier to predict compatibility.

The standard rule-of-thumb for paralleling PVs is ideally they should have Vmps within 5% (10% difference maximum).

And the rule for adding PVs in a series string,  it that the Imps should be within 5% (10% max).

So between your two different PVs  the Vmps are within about 1.7%,   and the Imps are within about 4.3%,   so you should be fine,   IMO.

FWIW,   Thanks for getting rid of the Optimizer!   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Beyla

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Re: MNPV6 Combiner conduit fill space
« Reply #16 on: April 13, 2018, 08:37:55 PM »
Thank you again for the continued support and advice. I have a couple more questions to solidify or correct my understanding of what my best options are.

1. 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?

2. Would I be better off with 2 strings of 3 or or 3 strings of 2, given my existing and planned expansion of another three or four panels?  My next battery purchases will be 12 volt 220ah to mitigate the number of parallel runs in the battery bank. I am not concerned about the cost of pv wire, I have more than I need. Also have 6 breakers @15 amp.

3. This will give me the available breaker space to put in a 63 amp disconnect breaker in the outside combiner box, which is at eye level and for additional safety , an additional 63 amp Arc Fault breaker going into the Classic 150 fed from the aforementioned 63 amp breaker/disconnect.I already have these breakers and this would give me the flexibility of shutting of the pv power from inside or outside. Does this make sense ?

4. Since my combiner box is not on the roof, I must install a PVC electrical box with two 1.25 inch holes at the bottom, over the two ends of the EMT conduits piercing the roof, then fasten the box to it with a PVC screw-on to prevent pv cable fraying. This PVC box is big enough to pass the Pv cables into the PVC box using waterproof cable entry and then straight down the two EMT conduits ends inside the PVC box then to the combiner box. There are no connectors at all inside the PVC box, it is simply a way to achieve watertight IP65 rated entry into the EMT. I was informed that I require a ground in that box even though it goes nowhere from there and all the metal is already grounded with EMT conduit with clamped on grounding lugs right up to that PVC box. The only thing it is, is a protector for the wires and a waterproofing to prevent wires getting wet as well as the inside of the EMT. Introducing a grounded block in that PVC box is just asking for trouble IMO. What is your assessment of my long an winded concern,  :-\


Classic 150, MNPV6, Canadian Solar 1540 Watts panels, Aims 1200W Pure Sine, 6 X12 volt panels, 4X Crown 6 volt batteries in 12V bank.

Vic

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Re: MNPV6 Combiner conduit fill space
« Reply #17 on: April 14, 2018, 12:46:58 AM »
Hi Beyla,

 1 & 2:On a 12 V system,  with an MPPT CC,  you will need more input voltage to the CC than will be provided by real 12 V PVs (with a Vmp of around 18 V or so).   Single 60 cell PVs (with Vmp around 30 - 33 V)  would be fine.   But on a 24 V system single 60 cell PVs will not have sufficient voltage into the CC.

So,  would suggest that you use three strings of two PVs.   This should be fine for 12 or 24 V battery systems  (at least strings of two when you move to 24 V).

Let's think more about your batteries and their configuration for now,   and for the change to 24 V.   6V batteries may well be better than 12 V batteries.   Please do not buy any more things,  right now.

3.  The Classic has Arc Fault built in.   So my may not need an AF breaker.
Sounds like this system will need to be inspected ... so the AHJ (Inspection Authority)  may be able to advise you on what they want to see.

You have noted the need for Responders to be able to shut down your system.  There are Codes that will probably apply to your situation.

You definitely will want a PV in Disconnect close to the Classic (as well as one on the Classic output to the battery,  of course).

4.  Generally the Code provisions that did permit EMT conduit to be Equipment Grounding Conductor,  have been eliminated in recent Code revisions.   Generally,  now,   there needs to be such a conductor inside the conduit,   that is Bonded to all metal boxes/equipment,  etc.   Again check with the AHJ for the Code revision in use for your installation and/or any requirements that they will have for your installation.   The proposed PVC box for the conduit roof transition should now require a Bonding lug,  as the box is not conductive.

I am not a Code expert,   and do not the Code revision that applies to your situation.  It is always best to check with the AHJ regarding the Code revision and any other requirements they expect to see.

Just my opinions,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Robin

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Re: MNPV6 Combiner conduit fill space
« Reply #18 on: May 20, 2018, 03:05:53 PM »
I am not familiar with any DC arc fault breakers. What do you have?
Robin Gudgel