Rooftop Solar Installation

[Blazingrits]

I have 40, 290 watt solar modules with power optimizers ready to be installed on my personal residence. The power leaves the roof as D.C. and I was planning to run a conduit from 10 inches below roofline, within house, to basement where I have two 7.6 kw inverters ready to convert.

QUESTION BEING... Is use of PVC acceptable in this appplication. The run uses a coat closet to get to basement from the attic. I have been looking at NEC 2011 and just wanted to check with this great forum before I purchase and install materials

Thanks fellas!


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[jaggedben]

If it's inside the building it can't be PVC until you get to a readily accessible disconnecting means. Code reference is 690.31(E) in the 2011 code, or 690.31(G) in the 2014 or 2017. The 2011 and 2014 are a bit vague about an optimizer circuit but the 2017 simply says 'dc circuits' so ultimately the requirement still applies.

 

[ggunn]

If it's inside the building it can't be PVC until you get to a readily accessible disconnecting means. Code reference is 690.31(E) in the 2011 code, or 690.31(G) in the 2014 or 2017. The 2011 and 2014 are a bit vague about an optimizer circuit but the 2017 simply says 'dc circuits' so ultimately the requirement still applies.

Agreed; moreover, with some AHJ's if it's DC and inside, it has to be in metal and there has to be a DC disco on the roof.

 

[SolarPro]

Agreed; moreover, with some AHJ's if it's DC and inside, it has to be in metal and there has to be a DC disco on the roof.

Don't let them pull that BS if you are using optimizers and building to meet rapid shutdown requirements. The logic (always dubious and never supported by the NEC) for a rooftop dc disco before entering the building off of the roof does not hold water if you can control the dc circuits from the ground.

 

[Carultch]

Agreed; moreover, with some AHJ's if it's DC and inside, it has to be in metal and there has to be a DC disco on the roof.

That's only true if there is a combiner or other unit with serviceable fuses on the roof.

The metal part IS true, as DC has to be in metal conduit or metal clad cable, until the first readily accessible disconnect. Other than flat roofs with walk-up stairways or permanent ladders, rooftops are not readily accessible.

 

[ggunn]

That's only true if there is a combiner or other unit with serviceable fuses on the roof.

Not so in Austin. If DC goes through the building there must be a disco at the array. This is a policy formalized by a city ordinance; I just now read it again so as to be sure before I said anything. It makes no exception for uncombined strings or optimizers.

 

[jaggedben]

We've got some local ordinances like that around here, too. Both 690.31 and such ordinances probably ought to be updated to reflect rapid shutdown.

 

[Blazingrits]

Thanks fellas.

I was planning on running the 3 string sets to the D.C. Disconnects in the basement in EMT. I'm sure this covered in 2017 NEC, but is the basement an acceptable location for the disconnects ?

 

[Blazingrits]

Not so in Austin. If DC goes through the building there must be a disco at the array. This is a policy formalized by a city ordinance; I just now read it again so as to be sure before I said anything. It makes no exception for uncombined strings or optimizers.

I was planning on running the three string sets in EMT to basement and mount D.C. Disconnects down there. Is that considered proper installation to your knowledge? I am sure it is in the 2017 NEC but just trying to gather some knowledge from guys/gals who have Photovoltaic experience

 

[Blazingrits]

Don't let them pull that BS if you are using optimizers and building to meet rapid shutdown requirements. The logic (always dubious and never supported by the NEC) for a rooftop dc disco before entering the building off of the roof does not hold water if you can control the dc circuits from the ground.

So its it's your view, based on 690 that if I were to run EMT to basement to the D.C. Disconnects, this would be acceptable? Thanks in advance !

 

[Blazingrits]

That's only true if there is a combiner or other unit with serviceable fuses on the roof.

The metal part IS true, as DC has to be in metal conduit or metal clad cable, until the first readily accessible disconnect. Other than flat roofs with walk-up stairways or permanent ladders, rooftops are not readily accessible.

Thank you! I will run the 1" EMT to basement to the accessible dc disconnect(s), then to inverters

 

[Blazingrits]

If it's inside the building it can't be PVC until you get to a readily accessible disconnecting means. Code reference is 690.31(E) in the 2011 code, or 690.31(G) in the 2014 or 2017. The 2011 and 2014 are a bit vague about an optimizer circuit but the 2017 simply says 'dc circuits' so ultimately the requirement still applies.

Is the combiner box required to have OCPDs ? Are the D.C. disconnects located on the inverter acceptable? In other words, can I run the string sets in EMT through the house (10" from roofline), land them on the terminals of the inverter, provide an A.C. disconnect between the inverter and the 200amp panel which will be tapped with insulation piercing tap connectors?

 

[jaggedben]

Is the combiner box required to have OCPDs ? Are the D.C. disconnects located on the inverter acceptable? In other words, can I run the string sets in EMT through the house (10" from roofline), land them on the terminals of the inverter, provide an A.C. disconnect between the inverter and the 200amp panel which will be tapped with insulation piercing tap connectors?

I would not have a combiner box if I were installing your system. Yes, the DC disco in the inverter is usually acceptable. If you're tapping, then your AC disco needs to be fused. Interconnection is a whole other ball of wax compared to your original question about DC wiring methods, you might want to be more specific and/or review past threads.

 

[GoldDigger]

Is the combiner box required to have OCPDs ? Are the D.C. disconnects located on the inverter acceptable? In other words, can I run the string sets in EMT through the house (10" from roofline), land them on the terminals of the inverter, provide an A.C. disconnect between the inverter and the 200amp panel which will be tapped with insulation piercing tap connectors?

If you will be paralleling three or more strings of panels, then you must have OCPD matching the requirement on the panel label for maximum string OCPD. Two strings in parallel or up to 4 going to two MPPT inputs and you do not need OCPD for each string.

 

[ggunn]

Is the combiner box required to have OCPDs ? Are the D.C. disconnects located on the inverter acceptable? In other words, can I run the string sets in EMT through the house (10" from roofline), land them on the terminals of the inverter, provide an A.C. disconnect between the inverter and the 200amp panel which will be tapped with insulation piercing tap connectors?

If you combine on the roof you must have a load break rated disco in the combiner or within 6' of it per 690.15(C).

 

[Carultch]

If you combine on the roof you must have a load break rated disco in the combiner or within 6' of it per 690.15(C).

Can it be on the opposite side of a wall or roof deck? Or is it 6ft and visibility that is required? Example: combine in a Soladeck on a rooftop, with a disconnect immediately below in the attic.

 

[SolarPro]

Can it be on the opposite side of a wall or roof deck? Or is it 6ft and visibility that is required? Example: combine in a Soladeck on a rooftop, with a disconnect immediately below in the attic.

The Code-Making Panel wants that disconnect readily accessible from the equipment being services (i.e., the fuses).

 

[Carultch]

The Code-Making Panel wants that disconnect readily accessible from the equipment being services (i.e., the fuses).

Ok, so you can't require a portable ladder or tool to get from the combiner to the disconnect, unless one is already in place to get to the combiner and you stay on it to get to the immediately adjacent disconnect. What if I can get between the two units just by walking and they are 6 ft or less from one another, but they are still visibly separated?

 

[SolarPro]

Ok, so you can't require a portable ladder or tool to get from the combiner to the disconnect, unless one is already in place to get to the combiner and you stay on it to get to the immediately adjacent disconnect. What if I can get between the two units just by walking and they are 6 ft or less from one another, but they are still visibly separated?

Seems like that would meet the intent of the Code. The service tech has ready access to the fuses and the equipment disconnecting means. That is more important than line of sight, in my opinion.

 

[ggunn]

Can it be on the opposite side of a wall or roof deck? Or is it 6ft and visibility that is required? Example: combine in a Soladeck on a rooftop, with a disconnect immediately below in the attic.

My interpretation is that the disco has to be on the roof with the combiner, not in the attic.