NABCEP preparation

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andykee

Member
Location
United States
Heyo all,

I'm new to the forum, studying for the Nabcep exam on the 11 April so just trying to absorb as much knowledge as possible. Any tips from past pupils more than welcome. I know this one is a little easy but I done a question early this morning and was wondering if someone would verify my answer.

The installation calls for (10) PVmodules that are 62? inches by 39? inches in size. The modules will be mounted in 2 rowsof 5 with 1 inch between modules for mid-clamps and 3 inches on both ends of each rowfor end-clamps. Based on the rule of no more than 2 feet at the end of rails and 4 feetbetween attachments, how many attachments must be used?

No trusses are mentioned so I don't think that's a factor, I got "20" attachments, the answer sheet says "24" but I think the source may be wrong.
 

Carultch

Senior Member
Location
Massachusetts
Heyo all,

I'm new to the forum, studying for the Nabcep exam on the 11 April so just trying to absorb as much knowledge as possible. Any tips from past pupils more than welcome. I know this one is a little easy but I done a question early this morning and was wondering if someone would verify my answer.

The installation calls for (10) PVmodules that are 62? inches by 39? inches in size. The modules will be mounted in 2 rowsof 5 with 1 inch between modules for mid-clamps and 3 inches on both ends of each rowfor end-clamps. Based on the rule of no more than 2 feet at the end of rails and 4 feetbetween attachments, how many attachments must be used?

No trusses are mentioned so I don't think that's a factor, I got "20" attachments, the answer sheet says "24" but I think the source may be wrong.


Are you required to stagger the attachments, in order to distribute the load onto alternating structural members at 2 ft O.C.? I can see that as requiring 2 additional supports per row, thus 4 additional supports.

20 is what you'd need if you align the supports in a rectangular grid.
 

andykee

Member
Location
United States
Thanks.


Yeah i did a bit of rearranging at what not to get the 24, but I think they just rounded up when calculating the middle for reasons unstated. This is the solution given.

3? for end clamps is sort of strange, but we must use the numbers given to us (1.5? - 2? is more likely) Total width of modules to be supported: 39? x 5 = 195?, plus clamps: 4 mid-clamps = 4?, & 2 end-clamps = 6?, total of 10? total to be supported = 205? 205? ? 48? (because of 24? at each end) = 157? 157? / 48? (allowed between attachments as per instructions) = 3.27, so 4 will be needed total per row of 5 = 6 attachments (one at each end and 4 in middle) total for array = 24 needed, because of 2 rows
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Thanks.
... 157? 157? / 48? (allowed between attachments as per instructions) = 3.27, so 4 will be needed total per row of 5 = 6 attachments (one at each end and 4 in middle) total for array = 24 needed, because of 2 rows

The part in red is just wrong.
4 spans requires 5 attachments. One per span on left side of each span, plus one more on the right to complete the last span.
It's a general rule: n spans requires n+1 supports.
 

Carultch

Senior Member
Location
Massachusetts
Thanks.


Yeah i did a bit of rearranging at what not to get the 24, but I think they just rounded up when calculating the middle for reasons unstated. This is the solution given.

3? for end clamps is sort of strange, but we must use the numbers given to us (1.5? - 2? is more likely) Total width of modules to be supported: 39? x 5 = 195?, plus clamps: 4 mid-clamps = 4?, & 2 end-clamps = 6?, total of 10? total to be supported = 205? 205? ? 48? (because of 24? at each end) = 157? 157? / 48? (allowed between attachments as per instructions) = 3.27, so 4 will be needed total per row of 5 = 6 attachments (one at each end and 4 in middle) total for array = 24 needed, because of 2 rows

If it is my choice, I would round to the standard rail length of 17 ft. There is no situation with these constraints, within which 24 supports would be required.

See this picture:
 

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SolarPro

Senior Member
Location
Austin, TX
It doesn't look like this question came out of the NABCEP Resource Guide.

Whose curriculum are you using? It's entirely possible that someone put it together without having it fact-checked.
 

Zee

Senior Member
Location
CA
"NABCEP certification, the one that is hard to get." :p
If someone is giving you wrong answers.......No wonder!:jawdrop::happyno:

I am a big fan of NABCEP by the way, it really is a meaningful certification and was much tougher than the contr lic exam.
....and as a voluntary one, it shows initiative.
So good luck!
 

SolarPro

Senior Member
Location
Austin, TX
It looks like there's three or four different NABCEP certs.Wonder how much each one costs?

Wonder no more. Behold the miracle of Google:

http://www.nabcep.org/certification/how-to-apply

Application fee: $125?$175
Exam fee: $375 (1st time); $275 (re-exam)

Re-certification requirements are here:

http://www.nabcep.org/recertification-requirements

There are basically three current NABCEP Certification options (since "Small Wind" was retired):

  1. PV Installation Professional
  2. Solar Thermal Installer
  3. PV Technical Sales

There is also a NABCEP company accreditation, but there are only four companies nationally that have been able to complete the requirements, which suggests that NABCEP set the bar too high, as it must cost more to manage that program than they make in fees.
 

andykee

Member
Location
United States
If I had of spotted ImagineSolar in January I would have definitely went for it, oh well.

Another question for the Solar elite:

Relating to Grounding Electrode System and ground rods as covered in NEC 2011.

Say I have 2 TPM (12 module 260W strings on each ) poles are 25' apart which then runs about a 100' to each mppt of a 6000tl-us-22 transformerless inverter to finish with a loadside connection on an existing residence service with an existing GEC and ground rod.

So my question is really "according to the 2011 code book" am I all right in sizing this on 690.47(C) referencing 250.166. with no additional ground rods.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
If I had of spotted ImagineSolar in January I would have definitely went for it, oh well.

Say I have 2 TPM (12 module 260W strings on each ) poles are 25' apart which then runs about a 100' to each mppt of a 6000tl-us-22 transformerless inverter to finish with a loadside connection on an existing residence service with an existing GEC and ground rod.

So my question is really "according to the 2011 code book" am I all right in sizing this on 690.47(C) referencing 250.166. with no additional ground rods.

690.47(C) (1), (2), or (3)?

At least if you're on the 2011 code I agree there are no additional ground rods required. The solar GEC can go to the existing residential grounding electrode system.
 

Carultch

Senior Member
Location
Massachusetts
690.47(C) (1), (2), or (3)?

At least if you're on the 2011 code I agree there are no additional ground rods required. The solar GEC can go to the existing residential grounding electrode system.

Transformerless inverters with ungrounded DC systems don't need a GEC either. The AC EGC will do all the grounding of the inverter to the premises grounding system as required. The code isn't clear on this rule, but you can find articles that discuss it.
 
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