Build Your own PV Combiner

[rickgomes26]

I recently went out to an inspection and when I asked the installer for the Installation manual for their PV Combiner Box they offered me a printout from this website http://(removed) You have to pay to become a member before you can download the whole article which I didn't.

Has anyone run into this before. This "combiner" box uses a bunch of UL listed components but the assembly is NOT UL listed. I'd like to hear your thoughts on this.
Thanks

 

[augie47]

In TN, the assembled unit would need NRTL (U.L.) approval.
An unlisted assembly of UL component s will not meet the State's requirement.

 

[Cold Fusion]

I recently went out to an inspection and when I asked the installer for the Installation manual for their PV Combiner Box they offered me a printout from this website ...

I'm not too familiar with PV installations. What is in a "combiner box"? Is it just a bunch of terminals and DIN rail mounted fuse holders?

cf

 

[iwire]

I'm not too familiar with PV installations. What is in a "combiner box"? Is it just a bunch of terminals and DIN rail mounted fuse holders?

cf

Pretty much.

 

[Cold Fusion]

In TN, the assembled unit would need NRTL (U.L.) approval.
An unlisted assembly of UL component s will not meet the State's requirement.

Augie -
Would that be state law - and not NEC?

I ask because I didn't see anything in (2005) art 690 that required listed combiner boxes. Disconnects are not required to be listed or even service rated. Art 690.32, Component Interconnections, do not require listing, unless they are intended to be concealed at thew time of on-site assembly.

Just curious - does the great State of TN also not allow panels assembled under Art 409? I don't see much diference between this and a combiner box not listed as an assembly.

cf

 

[ty]

Do you have a pic of the combiner box?

what is the violation?

 

[iwire]

I ask because I didn't see anything in (2005) art 690 that required listed combiner boxes.

Check out 2008 - 690.4(D)

 

[ty]

Check out 2008 - 690.4(D)

ok, so Bob gave you the Code, but what did you cite?

Also, what Code cycle are you on? the above is a change from 2005NEC.

Did you check the Fill calculation?
Did they use standard wirenuts anywhere?

 

[ibew501ed]

off topic but where does it state no wire nuts on pv (is it the 600v dc rating)

 

[ty]

it doesn't.

It would be the manufacturer spec.

But they are not recommended for low voltage(<50v) DC.

 

[ibew501ed]

manufacturer of the PV or the wire nut

I understand pv systems don't use wire nuts even though the 1st opportunity to use a wire nut would be at the combiner box, where the voltage would be 160 - 600 v dc

unless I'm missing something ( still new to the tech.)

 

[iwire]

it doesn't.

It would be the manufacturer spec.

But they are not recommended for low voltage(<50v) DC.

What does low voltage have to do with it?

Who says wire nuts are not recommended?

Any combiner box I have worked on had DC operating voltages between 400 and 550 volts.

There was also no need for wire nuts.

 

[ty]

What does low voltage have to do with it?

Who says wire nuts are not recommended?

As the voltage is lowered, the amperage goes up.
So a 190watt at 60v is going to be less amps than 190watts at 30volts.

any and all training courses that I have taken call out wirenuts as unacceptable splicing for PV systems.

 

[rickgomes26]

I'm in CA so 2005NEC applies here. I don't have my 05' with me yet today but I believe very early in the article it states that all equipment has to be listed and marked for use in PV systems. In 08' it expands the language with details in 690.64 (D).

Typically in a combiner box the transition from USE-2 to THWN occurs. This will take place in a terminal and doesn't require a wire nut or other "connector".

I agree with Augie that NRTL would have to certify this in the field to make it legit, BUT, not sure if that is in compliance with 05'. I know as the AHJ I've got some leeway on where I can go with that requirement and at this time they will have to get the assembly certified from NRTL.

Side topic coming off of this regarding wire nuts. When a combiner isn't used to make the transition from USE-2 to THWN a NEMA 3 junction box will be located on the rooftop next to the array to make that transition to the less expensive THWN wire. Here I have seen wire nuts used and voltages ALWAYS exceed 50 so that's not a problem. I do require the wire nuts to be listed for wet locations though.

Here's a pic of a combiner box with 8 strings coming in. Each string is protected by a 10a fuse.

 

[iwire]

As the voltage is lowered, the amperage goes up.
So a 190watt at 60v is going to be less amps than 190watts at 30volts.

Well thanks for the ohms law primer.:grin:

But if the wire nut is listed for a certain size conductor don't you figure it can handle the current that conductor can carry?

20 amps at 5 volts is 20 amps at 600 volts, assuming the correct size condutor is used I see no issue.

any and all training courses that I have taken call out wirenuts as unacceptable splicing for PV systems.

Been doing PV systems for 2 years and I am a NABCEP trained installer, never heard anything about wirenuts being bad for PV systems.

 

[augie47]

Augie -
Would that be state law - and not NEC?

I ask because I didn't see anything in (2005) art 690 that required listed combiner boxes. Disconnects are not required to be listed or even service rated. Art 690.32, Component Interconnections, do not require listing, unless they are intended to be concealed at thew time of on-site assembly.

Just curious - does the great State of TN also not allow panels assembled under Art 409? I don't see much diference between this and a combiner box not listed as an assembly.

cf

TN State Law:


0780-02-01-.03 APPROVAL OF ELECTRICAL PRODUCTS.
[FONT=Arial,Arial][FONT=Arial,Arial](1) Approved Testing Laboratories.
(a) The State Fire Marshal will accept as satisfactory (when properly installed or used) materials, equipment, devices, or applicants which:
1. Bear a label, symbol, or other identifying mark of one of the following independent testing laboratories:
[/FONT][/FONT]

 

[ty]

Well thanks for the ohms law primer.:grin:

:grin: thought you would like that :grin:

But if the wire nut is listed for a certain size conductor don't you figure it can handle the current that conductor can carry?

20 amps at 5 volts is 20 amps at 600 volts, assuming the correct size condutor is used I see no issue.

You would think.

ibew501ed, there is one publication by ATP that is in partnership with NJATC, that you might find interesting.

Been doing PV systems for 2 years and I am a NABCEP trained installer, never heard anything about wirenuts being bad for PV systems.

I've known you a long time, Bob and admire your intelligence.
I am not a huge fan of NABCEP for different reasons. (nothing to do with this discussion).
what is NABCEP Trained Installer? Does that mean you didn't take the exam?
NABCEP does not offer training directly.

 

[rickgomes26]

To clarify, the pic I posted above is NOT the one that started this conversation for me. Its just one that I found on the web. Someone had asked for a pic of a combiner box so I obliged.

With regard to 05' and this situation, while we don't have the language that the 08' has, we DO have article 90.4, "Enforcement....The Authority having jurisdisction for enforcement of the CODE has the responsibiliity for making interpretations of the rules, for deciding on the APPROVAL OF EQUIPMENT and materials, and for granting special permissions...."

That said, I have no problem in requiring NRTL certification for field built equipment.

 

[iwire]

I am not a huge fan of NABCEP for different reasons.

You will not get any argument from me on that. But in this area many jobs can only be bid by companies with NABCEP certification.

what is NABCEP Trained Installer?

Not much really other than 60 hours of Monday nights at the local Community Collage and paying $85 to take a test. I passed my test so now I am ...

Entry Level

The NABCEP PV Entry Level Program is designed for those individuals wanting to get into the solar field; achievement of the NABCEP PV Entry Level Exam is a way for candidates to demonstrate that they have achieved a basic knowledge of the fundamental principles of the application, design, installation and operation of grid-tied and stand-alone PV Systems.

Upon successful completion of coursework offered by a registered NABCEP PV Entry Level Exam Provider, a student is eligible to sit for the PV Entry Level Exam. Prior to taking the NABCEP PV Entry Level Exam, students should have demonstrated a basic understanding of the principles outlined in the Learning Objectives.

The knowledge demonstrated by passing this test does not replace the knowledge, skills or abilities of the electrical or other construction trades, or those of other professions or degree programs that require considerably more academic and/or practical experience.

Individuals passing the NABCEP PV Entry Level Exam should not be confused with NABCEP Certified PV Installers. The latter can only be achieved by highly experienced individuals who have passed a much more rigorous examination and have demonstrated the capability to supervise complete PV system installations, and who have a detailed working knowledge of the electrical codes, standards and accepted
industry practice associated with PV installations.

As the market grows for photovoltaics, students achieving this industry-sponsored Entry Level Exam may find that their employment opportunities are enhanced by starting the job with an understanding of the basic terms and operational aspects of a PV system. However, completing coursework and passing the exam does not qualify an individual to install PV systems.

Now I can sit for the NABCEP Certification test.

PV Installer Certification

The NABCEP PV installer certification is a voluntary certification that provides a set of national standards by which PV installers with skills and experience can distinguish themselves from their competition. Certification provides a measure of protection to the public by giving them a credential for judging the competency of practitioners. It is not intended to prevent qualified individuals from installing PV systems nor to replace state licensure requirements.

The target candidate for NABCEP certification is the person responsible for the system installation (e.g., contractor, foreman, supervisor, or journeyman).

The NABCEP PV Installer certification has been developed in accordance with the the certification field?s best practices. NABCEP is a member of the National Organization for Competency Assurance (NOCA) and has endeavored to follow the requirements of ISO/IEC Standard 17024: General Requirements for Bodies Operating Certification Systems of Persons.

All it really means is the company I work for will be able to bid more jobs.

 

[augie47]

To clarify, the pic I posted above is NOT the one that started this conversation for me. Its just one that I found on the web. Someone had asked for a pic of a combiner box so I obliged.

With regard to 05' and this situation, while we don't have the language that the 08' has, we DO have article 90.4, "Enforcement....The Authority having jurisdisction for enforcement of the CODE has the responsibiliity for making interpretations of the rules, for deciding on the APPROVAL OF EQUIPMENT and materials, and for granting special permissions...."

That said, I have no problem in requiring NRTL certification for field built equipment.

Wise choice, IMHO.
As strict as California is, I'm surprised they don't have a State law (as does TN) requiring NRTL or even a California Standard.