When you were unable to tell us how and where you send your concerns to MidNite Solar, I pinged an Administrator on the MidNite Forum, where Principals and Founders of MidNite Solar are active (I am a member on the Forum).
The following is a response to the primary issues that you seem to have with the MNPV-3:
"Dear Lumisol, I am sorry you are so disappointed with our MNPV3 combiner. I can't comment on all of your concerns here. There were so many, I can't remember them all.1. This is a custom enclosure designed and manufactured by MidNite Solar, not a third party box.2. The MNPV3 is designed for MC4 connectors. Did you not notice the 1/2" diameter knockouts in the middle of the 7/8" knockouts? I can see them on the sides in your picture, so I will assume they were there on the bottom also just like the hundreds of thousands we have produced.3. the connector you used has a very long protrusion inside the box. That is not a standard MC4 connector. The real Multi Contact connectors we use fit fine with no interference with the mounting holes. Someone posted a picture of the pre-wired units we make for your review.4. Painting the insides of a knockout hole on an aluminum box is just weird. Ask any electrician. Nobody does is as it is unnecessary.5. The MNPV6 and MNPV3 are the bestselling combiner boxes in the world. We get NO complaints about anything. That is probably why we sell so many. We pretty much got it right according to others.6. I see the screws do protrude down below the mounting holes. Screws do have tolerances as well as punched mounting feet. So? This is not a real problem, just mount the box and don't worry about these small tolerances. Nothing bad happens. It is not a problem (well, not a problem for anyone who has ever purchased one of these before you). The rivets do not protrude lower than the mounting feet. I feel you are just trying to find something to complain about here. OK, you win on this one, but it is still a non issue to anyone but you.7. The knockouts are placed exactly where our customers want them. I am talking about professional installers that have been using them day in and day out for over ten years. If they had a problem with placement or size, we would look at changing them. We cannot however accommodate every do it yourselfer that has different ideas about how to do things. That just isn't possible.8. We have the best tech support in the industry. I do not know how you attempted to contact us. We do respond to issues. Unfortunately there would be little we could do about your issues since the product is fine.9. Please make your own boxes in the future. We don't mind.10. Thanks to all of you who are familiar with MidNite Solar and our products and had nice things to say about us.Thanks,Robin GudgelPresidentMidNite Solar"
Luisol, I (Vic) am not an employee of MidNite Solar, just a very happy customer.
MidNite's President has been active on this Forum, but was unable to log on, so I was asked to please post his message to you.
The Vmp of your PVs is 39.8 V -- this is good, as it is high enough for the CCs to have enough voltage to find a good MPP operating point, and with strings of two PVs, the operating voltage is low enough for more efficient operation.
For anyone wondering about the NEC Max Isc, this is 8.50 amps which is about 6% over the NEC max with strings of two PVs with six strings per FM CC.
Your genset power leads seem fine, to me ...
Most Generac gesets that have a battery maintainer, look for the AC power on that line to be interrupted, as a genset Start command. So, just a relay that interrupts this AC line for the duration of the desired run time is often all that is required.
I have assumed that the FM60 CCs are already installed, otherwise it would not be a very big deal to swap them for FM-80s which have an NEC total PV Isc of 64 Amps, vs the FM-60's max of 48 Amps ... it that really matters to anyone.
Alan, approximately where is this system located -- what state?
I assume that this large system is Grid Interactive (Grid Tied with batteries).
Gotta run to town, more later, Thanks, Vic
Actually, im happy with the pair of fm60s. 24*315W*0.77/48V = 121 amps. The only reason to upgrade would be if youre trying to max out oppurtunity loads.
Well, personally, would not like to run CCs that flat out for hour after hour ...
This is probably a Grid Interactive system.
AND, if it is Grid-connected, it will probably need to be Inspected ...
So, then, probably, the NEC Maximum Isc rating of the PVs will apply ... in which case, FM-80 might have been a bit better ....
BUT, just my opinion. Vic