Power Distribution Blocks

SolarPro

Senior Member
That's a product safety standard issue. The Code just says you have to use listed combiners. In practice, however, all of the listed combiners these days seem to have insulated covers over exposed busbars and terminals. So my guess is that the product safety standard requires this.
 

shortcircuit2

Senior Member
This field installed power distribution block for 120/240 volts AC supplying micro-inverter circuits inside this PV combiner needs an insulated cover though...right SolarPro?


IMG_3308 (480x640).jpg
 

SolarPro

Senior Member
Not sure what the product safety standard—or the NEC for that matter—has to say about this. It's not really what I would call a combiner box, as it's not aggregating PV source or output circuits. This is basically a transition wiring box for an ac circuit. It could be that the cover meets any applicable requirements. (Is this a a center-tapped trunk cable?)
 

Carultch

Senior Member
This field installed power distribution block for 120/240 volts AC supplying micro-inverter circuits inside this PV combiner needs an insulated cover though...right SolarPro?
I thought you are required to have overcurrent devices where you combine AC inverter output circuits without a product that is specifically listed for the purpose (like a microinverter trunk cable).
 

SolarPro

Senior Member
The connection is for 16 M-250's split into 2 branches of 8 to compensate for voltage rise.

ETL lists similar variations of this equipment as PV Combiners in this listing report...(page 11 in 7.0)

http://www.rstcenterprises.com/webfiles/fnitools/documents/listing_constructional_data_report.pdf

Right. Note that the description is specific to dc combiners:

The product covered by this report is a DC combiner box for use with a up to four photovoltaic
array inputs, and an output of a single DC source.
Are any companies specifically listing products for transitioning from microinverter trunk cables to THWN-2 in conduit to UL 1741? In other words, does anyone make a listed "center-tapping" product for this purpose?
 

jaggedben

Senior Member
As far as I'm concerned micro-inverter trunk cable can be spliced with any product that is listed for wet location splicing of AC wiring. The solar aspect is 100% irrelevant.

And no, additional overcurrent devices are not required at the location of the splice.
 

shortcircuit2

Senior Member
I found 314.28(E)(4) which prohibits un-insulated exposed live parts in junction boxes. But, if this is a DC PV combiner, it may not be acceptable to use it for connection of AC micro-inverter trunk cables. I don't see any harm in using the combiner this way except the exposed live parts.
 

jaggedben

Senior Member
I found 314.28(E)(4) which prohibits un-insulated exposed live parts in junction boxes. But, if this is a DC PV combiner, it may not be acceptable to use it for connection of AC micro-inverter trunk cables. I don't see any harm in using the combiner this way except the exposed live parts.
Personally I would be pretty annoyed if I had to service a system using that combiner for either AC or DC. Somebody better tell me that's in there before I open it up.

I also wonder whether it would do okay with non-isolated inverters if moisture got inside.
 

SolarPro

Senior Member
I found 314.28(E)(4) which prohibits un-insulated exposed live parts in junction boxes. But, if this is a DC PV combiner, it may not be acceptable to use it for connection of AC micro-inverter trunk cables. I don't see any harm in using the combiner this way except the exposed live parts.
I'd call that a junction box (assuming it is listed as such.) And they sell covers for these types of power distribution blocks.

While I've never used any SolaDeck products, my impression is that they are popular with some installation companies. It's basically an electrical box with the form factor of a roof vent. In theory, it should be labeled appropriately.
 

Zee

Senior Member
Thanks for the PDB link SolarPro!
That is a Soladeck. As we now know. :)
It can be purchased as a "pass thru" junction box, an ac combining box OR a DC combiner box.
It is extremely adaptable and approved for all those.
They just change the "guts" to various iterations of:
fuse blocks on DIN rail,
terminal blocks,
ac breakers,
......or nothing (j-box).

I am a big "fan". Heavy gauge steel (strong) , built specifically for pitched roofs, and sleek. Most importantly to me, the opening is large and faces the sky ====> very, very nice to work in when compared to a Bell box.

Just recently i combined two halves of a single micro inverter branch circuit, inside a soladeck, exactly as you indicated, 8 + 8 micros..... but i just used wire nuts in a soladeck empty box.
As Jben and SolarPro said: it' s just a j-box as equipped and it is applied here as a j-box for an ac branch circuit.

Carultch,
OCP is required if he were to combine more than one micro-inverter branch circuit. Here he says it combines parts of a single circuit.

-------The only thing that bothers me on the photo...is the PVC conduit on a roof! Code does not disallow PVC, but experience and rooftop conditions DEFINITELY do not support it' s use ever on a rooftop.:ashamed1:
 
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