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Advancement and Development of Electricity and Technology
Building Integrated PV
Bypass diodes
Determining low temperature that caused the inverter to go over voltage
Another NABCEP PVIP Certificate in the mail!

Most Popular Posts

Feeder PV Connections 705.12(D)(2)(1)(b)
Crimping MC4 Connectors without the tool
Converting kWh to pounds of CO2
NEC 310.15(A)(2) Exception, 10% or 10 feet or less for sizing conductors
PV Temperature coeficcients in V/C, mV/C and %/C with conversion examples

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Advanced PV Course
NABCEP PV Installation Professional Exam Prep Course
NABCEP PV Technical Sales Exam Study Group (which will evolve into a full course)
PV Boot Camp and NABCEP Entry Level Exam Prep Course
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HeatSpring PV Course Blog

Advanced PV Course

Determining low temperature that caused the inverter to go over voltage


Q:

Sean: Thanks for a great course. Two questions: I think I would like some additional training for the PV Installation Professional Certification Exam. Do you have any recommendations?
Also with the addition practice questions, I got really knotted up on questions 74 and 78. On question 78, when you state the temperature coefficient for the module, is this actually Voc x Temperature Coefficient Voc?
Again, thank you for two great classes. I look forward to meeting you in person someday, and perhaps attending hands-on training you might offer.

Advanced PV Class Review


Submitted: 05/21/2016
Training: 40-Hour Advanced Solar PV Installer Training / Online / Anytime

How would you rate this course?
10/10
What did you like about the course?:
That it continuosly answers questions that I've had or I get in the workplace. I like that Sean uses a lot of examples and does not limit to the short explanation of an answer.
How effective was the instructor's communication during the course?:
Great.
What would you change about the course?

Passed the NABCEP PVIP Exam!!

From HeatSpring Advanced PV Course Discussion Board

Q:

I took the April exam for the first time and just found out I PASSED. After the completion of this course I felt really prepared and confident going into it . This course definitely covered enough information to pass the NABCEP exam and much more that I will be able to apply in my future career in solar. Sean White's book is the "Swiss army knife "of study material. Somewhat small but jammed packed with all sorts of useful information.

2014 NEC 690.7 Maximum System Voltage 600V and 1000V Distinctions


Q:

Article 690 - Part II - 690.7(C): Maximum System Voltage. In your lecture you mentioned that the NEC distinguishes between 3 family dwellings (up to 1000V PV max system voltage), versus 1-2 family dwellings (up to 6000V PV max system voltage). Two questions: First, I proudly bought the book, but I do not see this distinction in 690.7. From what I read, it addresses 600V and 1000V. Second, it seems arbitrary to distinguish to maximum inverter size between 3 family dwellings vs.

PV Wire Sizing, Terminal Temperature Limits, 310.15(B)(2)(a), 310.15(B)(3)(a) and 310.15(B)(3)(c), 110.14(C), 110.14(C)(1)(a) and 110.14(C)(1)(b)


Q:

Dear Doc,
A little late question ,concerning article 310 and 110.14 (c),110.14(c)(1)(a) or (C)(1)(b)
When you talk about terminal ratings,I am aware of three areas in solar where wires terminate ,combiner box ,inverter and main panel ocpd.
Are we talking here about, adjustment and correction factors ,dealing with ocpd of the solar breaker in main panel or the equipment shutoff breaker ,I am assuming these articles are referring to the main panel termination or equipment shut off termination.

Rapid Shutdown Retrofits?


Q:

Hi Sean,
The new regulation for the 'rapid shutdown' function, was driven by first responders for their safety, do you think that they may request that the rapid shutdown be installed on existing large commercial systems?
Thanks

A:

Once something is built, inspected and permitted, the AHJ does not come back and make them change it. I am sure that they could request it.

Insurance companies and owners would probably be the driving force for something like this, seeing how they would like the firefighters to put out the fire, rather than watching it burn out of fear of shock.

NABCEP Exam Requirements and Cycles


Q:

Uh, did I miss something? I thought this course was until the end of this month. Or is this overlapping cycles? I was planning to take this class as part of the 58 hours I need to even qualify to take the NABCEP test this fall. I plan to return here to bone up after applying the lessons learned here on two more systems I'm planning to build to qualify also as the systems I built before my knee (and other body parts) crashed out in '12 don't qualify any more.

MPPTs Stacked Series and Parallel with Shading


Q:

You said, "if the entire string is shaded with MPPT, then the PV source circuit would operate as if the entire string was in the shade.." ...
But then what of the other strings still in the sun?
Assuming for this example that there is some flat horizontal object (like a neighboring building) that causes the bottom landscape series string to experience a lower light level (not zero). So therefore the amperage of that bottom string would be less than the other (parrallel) horizontally strung series strings above the lowest shaded string.

Message for those of you here preparing to take the NABCEP PV Installation Professional Certification Exam, which is in 8-days!


Message for those of you here preparing to take the NABCEP PV Installation Professional Certification Exam, which is in 8-days!

Now is time to study hard. No procrastinating. Learn the material, but do not get overwhelmed with a concept that is difficult to understand. Remember that the exam is a numbers game. There are many very difficult questions and nobody gets all of the questions correct. Budget your study time wisely and plan to not study hard the night before.

NABCEP Resource Guide Battery Question Explanation Hot and Cold Lead-Acid Battery Charging


Q:

Hi Sean,
NABCEP includes the following practice question in the NABCEP PV Installation Professionals Resource Guide:
  1. The battery bank for a backup utility-interactive PV System is located in a harsh environment with temp and humidity extremes. The system does not have a provision for temp compensation. What is the MOST LIKELY result on the battery state of charge?
c.) Overcharged in cold weather and undercharged in hot weather.
d.) Undercharged in cold weather and overcharged in hot weather.

Bypass Diodes and Shading


Q:

Sean,
Why are all three bypass diodes affected by shading on the short edge of the module? What about the wiring/arrangement of the diodes causes them to be affected this way?
Also, what does MPPT stand for?
Thank you,

A:

MPPT stands for Maximum Power Point Tracking.
As we showed on the IV curve, there is a "sweet spot" where PV will work best with the optimal voltage and current combination for a given temperature and irradiance. With temperature and irradiance constantly changing, the MPPT will shift to optimize the PV production.

Shading, bypass diodes, portrait and landscape


Q:

Hi Sean,
The layout of an array, landscape vs portrait was to install as many modules as possible in the available space, maximizing the size of the system. From your discussion regarding the bypass diode, I note that if there were any shading issues, orientation of the module, when positioned in landscape will have the least affect on the functionality of the bypass diode and thus module output.
Thanks

A:

That is correct for typical crystalline PV assuming the normal shadow pattern with the shadow coming from the lower part of the module as with inter-row shading as opposed to a shadow coming from the side.

National Permitting Process


Q:

Hi Sean,
Big picture here, in efforts to help deploy more solar in the residential market, do you foresee a national permit standard ever being adopted? I know of a few states who have moved to a statewide standard, bringing down cost of permit and turnaround times.
Also appreciate your breaking NEC into digestible sections (less intimidating).
Thanks again

A:

I think that it is part of our political culture. 50 states, 50 state governments and then many many more municipalities.

Expansion Joints, Metal Raceways and PV


Q:

Hi Doc,
here in Indiana land we mostly use schedule 40 conduit and armored cable and flexi steel conduit I have not had the opportunity to couple EMT,and my question is on 300 7 (B) expansion fittings,are these special couplings ,can you explain more of this,or a picture paints a thousand words ,and you could add some words to explain more .
Thanks much really enjoying this stuff.

A:

Here is a report that is about a famous PV fire on a rooftop in Bakersfield. Nobody was hurt and the building didn't burn down, but the fire led to a big push towards ungrounded PV systems, which would not have caught on fire in this case.

Great Review Make My Day!!


Submitted: 03/11/2016
Training: 40-Hour Advanced Solar PV Installer Training / Online / Anytime

How would you rate this course?
10/10
What did you like about the course?:
Learning the code and how it should be applied/interpreted through real life solar examples provided by Sean.
How effective was the instructor's communication during the course?:
Impeccable.
What would you change about the course?:
I can't think of anything.

Crimping MC4 Connectors without the tool

From Advanced PVHeatSpring.comDiscussion Forum

Q:

Hey Sean,
This might not be specific to wire sizing (kind of is) but do you have a good way to crimp MC4 connectors? I am doing an array on my house and don't want to buy a crimping tool. They have pre-made MC4 wires and I was thinking about skipping the hassle and buying the pre-fabricated ones.

A:

That is a common thing that people try to do. I remember a job where someone tried it and the system wouldn't turn on. They had to spend a day taking apart things and figuring out under which module the bad connection was.

The 10-foot Tap Rule, 240.21(B)(1) is as solid as a flimsy 2014 NEC Code Book

FromHeatSpring.comAdv. PV Discussion Board

Q:

Hey Sean,
With the 10 foot tap rule, do you know where that came from? Do you see a lot of inspectors looking for this? It does not seem like a very solid rule, one of those that is more a of guideline.

A:

The 10-foot Tap Rule, 240.21(B)(1) is as solid as a flimsy 2014 NEC Code Book.

We have had the tap rules for plain old feeder taps for as long as I have been getting electrocuted (death by shock). I do not see the Tap Rules in the 1897 NEC here: https://www.

Bonding Neutral to Ground


Q:

Hi Doc,
assignment 23/36 you explain bonding of neutral to a sub panel,
question: is a subpanel specifically manufactured as thus ,or is it as its name applies,my thoughts are they are manufactured as thus,because of the raised neutral buss ,am I correct in assuming the latter?
thanks

A:


You can typically physically bond neutral to ground in many different places, including disconnects, panelboards (main panels and sub panels) and just about anywhere if you are determined.

Great Reviews Make My Day!


Training: 40-Hour Advanced Solar PV Installer Training / Online / Anytime
How would you rate this course?
10/10
What did you like about the course?:
Some of this stuff is very complicated, but Sean made it as clear as possible.
How effective was the instructor's communication during the course?:
Very clear.
What would you change about the course?:
N/A
If you enjoyed the course and are interested in providing a testimonial, please enter one here.

Roof Slope Calculation, 120% Rule breaker Sizing & Calculator on “smart” Phone

From HeatSpring Advanced PV Course Discussion Board

Q:
 
hi Doc ,really enjoying your humor and the way your talking points come through.
Two questions though:this pertains to assignment 16/36,
1)roof slope angle short cut,the inverse tan function is not on my calculator is there another long method of completing that function and 
2)the 120% rule the 50 amps *0.8 where did the 0.8 come from ?
appreciate all the help,ok forgive me one more thing,in the string sizing calculation when I click on the [1/x] function it displays

Feeder PV Connections 705.12(D)(2)(1)(b)

From HeatSpring Advanced PV Online Course Discussion Board
 
Q:
 
For the 705.12(D)(2)(1)(b) solution where the AHJ insists that the OCPD be placed at the current source, what does the OCPD setup look like? A small load center with a PV Breaker and a couple Ilsco taps?

A:

Hi Robert,
 
There are a number of ways this can look and since this is relatively new, there is not a standard.
 
Overview: 705.12(D)(2)(1)(b) gives us a way of connecting to a feeder and protecting the feeder with an overcurrent protection device.

PV Currents 690.8(A)(1) and 690.8(B)(1)

HeatSpring.comAdvanced PV Course Q and A

Q:


Sean,
I think 690.8 is a little confusing because I usually think of the "Conditions of use" derates applying to the conductor ampacity, and the Maximum Circuit Current applies to source circuit output. For garden-variety strings, am I understanding the application of 690.8(B)(1) and 690.8(B)(2) correctly?
For 690.8(B)(1), 
Minimum Conductor Ampacity 
= [Module Isc] * 156% 
(Roof temperatures 50C or less AND 3 or less Conductors)

For 690.
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