Any issues with adding fuses to my DC Negative inside the combiner box?

[Amy@altE]

Heyco http://www.heyco.com/Solar_Power_Com...wer_Components

[HX_Guy]

Heyco http://www.heyco.com/Solar_Power_Com...wer_Components

That looks like a nice liquid tight connection BUUUT that would mean I would have to take apart the MC4 cable that residing inside the combiner box and I don't have the tool to reassemble it. So I ask again, can I put some silicon sealant on the outside?

[HX_Guy]

By the way what is that single red wire for?

Are you talking about the red cable from in from the conduit and connection to the MC4 connector inside the box?

That is linking the PV- from one panel to the PV+ of of another panel. The reason it goes through the combiner is because one panel is on one end of the roof and the other is on another, so the cable goes through conduit in the attic and pops back up here at the combiner.

See red arrow:

[Amy@altE]

The inside of the Hayco is a rubbery insert. You may be able to remove it and slit it to open it, and then when it is reinserted and tightened, it would hold it back together. I can't answer about the silicon.

[HX_Guy]

The inside of the Hayco is a rubbery insert. You may be able to remove it and slit it to open it, and then when it is reinserted and tightened, it would hold it back together. I can't answer about the silicon.

Yes but I would still need to fit the connector though the round part that tightens it all together, no?

[bcroe]

Heyco http://www.heyco.com/Solar_Power_Com...wer_Components

Those will keep the bugs out too, if everything else is really tight. Important in this
area on the ground. A little duct tape along some seams can make them really snug.

Bruce Roe

[sensij]

It is addressed here. Its pretty obvious if there is a ground fault in my array,
or just some leakage current over dozens of panels, there could be hundreds
of volts on either array lead. Working on the inverter DC wiring would not be
safe just because a single pole disconnect switch was opened. This all became
obvious when some array wiring had to be relocated, and the ground fuse blew.
Now there are disconnects for every array current carrying wire. This
issue seems to generally ignored. Bruce Roe

Ignored by whom? Not by code... 2011 NEC 690.5(A) requires ground fault detection and interruption. 690.5(B)(1) says that the ungrounded conductors need to be disconnected in the event of a fault, and 690.5(B)(2) says that the inverter will cease to supply power to output circuits when this occurs.

More Edit:
In non-isolated transformers, the ground fault detection does not use a fuse to ground. There is more information here. Even though your Fronius has a ground connection through the fuse, because it isn't permanent, and no other bond exists, your system should be treated as ungrounded, and disconnects and OCPD are required on both + and -. The Fronius manual describes an installation as you've described, without a bond wire, as ungrounded.

One more edit... looking at the manual, it looks like the Fronius built-in fuses are on the DC+ only. That seems insufficient for an ungrounded system, and is maybe the source of my confusion understanding what you are trying to say. In any case, none of this seems especially applicable to the SolarEdge inverter, unless I am missing your point.

[bcroe]

Ignored by whom? Not by code... 2011 NEC 690.5(A) requires ground fault detection and interruption. 690.5(B)(1) says that the ungrounded conductors need to be disconnected in the event of a fault, and 690.5(B)(2) says that the inverter will cease to supply power to output circuits when this occurs.

More Edit:
In non-isolated transformers, the ground fault detection does not use a fuse to ground. There is more information here. Even though your Fronius has a ground connection through the fuse, because it isn't permanent, and no other bond exists, your system should be treated as ungrounded, and disconnects and OCPD are required on both + and -. The Fronius manual describes an installation as you've described, without a bond wire, as ungrounded.

One more edit... looking at the manual, it looks like the Fronius built-in fuses are on the DC+ only. That seems insufficient for an ungrounded system, and is maybe the source of my confusion understanding what you are trying to say. In any case, none of this seems especially applicable to the SolarEdge inverter, unless I am missing your point.

I am in agreement, and in compliance. Fronius must be too, because their internal DC disconnect
switch breaks both poles. An external disconnect should do the same? What I take here is
essentially all string PV systems would require breaking both poles; how many PV systems don't?

If the SolarEdge inverter isn't isolated, its disconnect would need to break both poles.

I know, there are other ways to detect a ground fault, than a fuse. Bruce

[SunEagle]

Are you talking about the red cable from in from the conduit and connection to the MC4 connector inside the box?

That is linking the PV- from one panel to the PV+ of of another panel. The reason it goes through the combiner is because one panel is on one end of the roof and the other is on another, so the cable goes through conduit in the attic and pops back up here at the combiner.

See red arrow:

Are you allowed to use that combiner box as a "raceway"?

In some installations you can't just run a wire through a box using it as a piece of conduit. Hopefully I am wrong on this one.

Thanks for clearing it up the "red" wire for me.

[HX_Guy]

Are you allowed to use that combiner box as a "raceway"?

In some installations you can't just run a wire through a box using it as a piece of conduit. Hopefully I am wrong on this one.

Thanks for clearing it up the "red" wire for me.

I...don't know. Would seem a little ridiculous for it to not be allowed...I mean you can have wires terminate there, but not pass through? What's the difference?

[HX_Guy]

Also I had a chance to get up on the roof and inspect the combiner box situation a little closer and it seems the install will be a little easier and cleaner looking than I originally imagined.

The 6AWG white wire (going to the inverter) does indeed reach up to where I could put in another busbar similar to the PV+ busbar at the top. Plus, the leads for the PV- coming from the MC4 connectors reach all the way up to the fuse holders as well, I thought I was going to need to replace those with new MC4 connectors with longer wires. Also, 2 more fuse holders definitely fit on the DIN rail.

[SunEagle]

Also I had a chance to get up on the roof and inspect the combiner box situation a little closer and it seems the install will be a little easier and cleaner looking than I originally imagined.

The 6AWG white wire (going to the inverter) does indeed reach up to where I could put in another busbar similar to the PV+ busbar at the top. Plus, the leads for the PV- coming from the MC4 connectors reach all the way up to the fuse holders as well, I thought I was going to need to replace those with new MC4 connectors with longer wires. Also, 2 more fuse holders definitely fit on the DIN rail.

Looks like you have a good action plan that will work.

[HX_Guy]

Looks like you have a good action plan that will work.

Yep, just put an order in for a new finger busbar, 2 fuse holders, and 6 20A fuses.

[Amy@altE]

Yes but I would still need to fit the connector though the round part that tightens it all together, no?

darn, I just tested it with a 3/4", just a wee bit to big to fit. If you can get a 1" one, you'd be golden. (I'm not sure what size that hole is in the box)

[HX_Guy]

darn, I just tested it with a 3/4", just a wee bit to big to fit. If you can get a 1" one, you'd be golden.

Thanks for checking Amy. Unfortunately the opening is only a 1/2" opening.