Combiner/Breaker for Panels for eG4 6000xp

[hogback]

Hi All,

Helping a friend install panels to run into an eg4 6000. We have 16 420W commercial modules, and will do 4 strings of 4. 2 strings will combine on the roof, and each 8 module group will go into their own mppt on the eg4. The specs of the panels are as follows:

vmp 72.9
imp 5.77
voc 85.6
isc 6.2

The first thing I need is a set of breakers/disconnects and a box at the eg4 unit that is rated for over 342V and 15A. I've only ever used 150V midnite stuff before. Any suggestions? I know I don't need current interrupting capability rigorously, but the eg4 calls out for it. I think I've seen some breaker configurations that stack lower V breakers to bring the V rating up - does that make any sense?

Also, my friend is interested in being able to disconnect the 4-module strings on the roof from each other. I myself wouldn't bother. What might I say to convince him otherwise? I any case, I do need some sort of box on the roof to connect emt so I can bring the home runs down off the roof. I was also planning on ditching the mc4s and crimping/sealing to pv wire.

All help/suggestions much appreciates!

 

[DIYrich]

The midnight solar combiner boxes are rated for 600v when using fuses.

 

[hogback]

Do those ones have disconnecting capability? Thanks!

 

[DIYrich]

I didn't see it (other than pulling the fuse). You can add a separate disconnect before or after the combiner box.

 

[hogback]

Do you think that there is any eg4-specific reason they want breakers on the mppt inputs? I have them on my schneider 60-150s, but that's because I didn't understand the components when I built it. I'm thinking a 4-string IMO isolator right at the inverter/mppts would be good if I ran all four strings off the roof and only combined each pair after the IMOs. If one really wanted to mess around with isolating an individual string, you could break the IMO, disconnect some wires from the terminals, and close the IMO again.

 

[hogback]

The online manual says breaker/isolator. Pretty sure the one I consulted some months back only said breaker, so I figure I'm good with a big IMO.

 

[MrM1]

Look at the Combiners from Watts247

 

[Brucey]

Do those ones have disconnecting capability? Thanks!

Don't open those touch safe fuse holders under load they will arc. They aren't designed for hot work.

An IMO disconnect would be the simplest solution and allows you to interrupt both positive and negative under load in a safe manner.

IMO 600V DC Disconnect Rooftop Isolator Switch - 4 Pole (2 String)

Major Specifications Max Current Rating: 32A Max Voltage Rating: 700VDC Size: 7.08" x 3.85" x 4.2" Protection Rating: NEMA 4X Guaranteed arc suppression (3ms typical) Operator independent switching mechanism

www.currentconnected.com

 

[Brucey]

Also, my friend is interested in being able to disconnect the 4-module strings on the roof from each other. I myself wouldn't bother. What might I say to convince him otherwise? I any case, I do need some sort of box on the roof to connect emt so I can bring the home runs down off the roof. I was also planning on ditching the mc4s and crimping/sealing to pv wire

If he wants per string comtrol he'll need a separate imo for each string. Otherwise he could use a 2, 3 or 4 string imo disconnect to shut them all off at once.

 

[hogback]

I was thinking of a 4 string imo. In the rare case where friend wants to isolate strings, they can shut all 4 off and pull out a few connections and flip it back on again. I've been using individual midnite breakers on each string of my 3s3p (x2) ground mount for 5 years, and I don't think I've ever messed with those. I have on occasion used the clamp meter to confirm even production a couple of times....

 

[PVGeezer]

You don't need overcurrent protection on the PV side as long as you're not going more than 2 parallel strings. The fuses/breakers can never trip anyway. Just use the IMOs as disconnects and call it good.

 

[hogback]

I know. But I didn't five years ago when I did my own system.