# solar



## backstay (Feb 3, 2011)

24 big guy said:


> any funky codes or tips about doing pv panels. just the wiring side not the mounted they have already been done. any special disco's. this is a MA application thanks


Make sure your disco and ocp are dc rated.


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## 24 big guy (Jun 29, 2011)

here are the drawings any breakdowns would be helpful


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## rexowner (Apr 12, 2008)

Are the PV panels on a separate building from the main meter (additional
ground rod, and #2 AWG for voltage drop?). Not a code issue, but
I don't think I'd call the SqD panel on the utility side a "sub panel".
I have usually hooked up on the load side of the meter. Seems like
that would be OK here unless the CH panel is out of space or some other
access reason.


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## rexowner (Apr 12, 2008)

BTW, it's THWN, not TWHN.


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## vida (Feb 21, 2012)

is there a really attractive female at this place where you are installing?


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## vida (Feb 21, 2012)

are you in the habit of adding a sub panel for one inverter? There are a lot of mistakes on here, the two diagrams dont even say the same thing. Probably not that cool to put your customers info up, no?


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## backstay (Feb 3, 2011)

If the array is located on a dwelling, you will need to add a gf breaker


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## 24 big guy (Jun 29, 2011)

everything you guys are saying are ther same questions i have. this is my 1st solar job. and i agree the diagrams dont match up. based on looking at the setup whats wrong and where and whats the right way


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## 24 big guy (Jun 29, 2011)

its on the roof of a single family dwelling. and there was plenty of room in the main panel


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## 24 big guy (Jun 29, 2011)

vida said:


> is there a really attractive female at this place where you are installing?


no why.


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## 24 big guy (Jun 29, 2011)

rexowner said:


> BTW, it's THWN, not TWHN.


 
thanks for both responses but i didnt draw these 
they were provided by the contractor


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## backstay (Feb 3, 2011)

24 big guy said:


> its on the roof of a single family dwelling. and there was plenty of room in the main panel


The ground faults need to be in the DC wires coming from the panels. Not in the house panel or between inverter and house panel.
Item#: MNDC-GFP63
Midnite Solar

The 2011 NEC requires a GFP now on all systems. It used to be that they were required only when PV panels were installed on the roof of a dwelling. Now even if you Solarize your doghouse, a ground fault protector is required in order to pass inspection.

If you're still on 2008 then only a dwelling needs one.


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## vida (Feb 21, 2012)

24 big guy said:


> no why.


because based on some of the gear you are using, it looks like you want to go back there a lot! :laughing:


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## vida (Feb 21, 2012)

Maybe its a MA thing, but what is wrong with the GFDI in the inverter?





backstay said:


> The ground faults need to be in the DC wires coming from the panels. Not in the house panel or between inverter and house panel.
> Item#: MNDC-GFP63
> Midnite Solar
> 
> ...


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## 24 big guy (Jun 29, 2011)

theres 1 in the inverter


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## vida (Feb 21, 2012)

24 big guy said:


> no why.


because based on the equipment you are specifying, you want to go back there quite a bit! :laughing:


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## vida (Feb 21, 2012)

backstay said:


> The ground faults need to be in the DC wires coming from the panels. Not in the house panel or between inverter and house panel.
> Item#: MNDC-GFP63
> Midnite Solar
> 
> ...


Althought that is the wrong device (150 VDC breaker for 350 Voc strings), you are correct that 3 strings of modules will require fusing as the series fuse is probably 15 amps and will anyway because that inverter has no dc fusing inside. 
Yes I originally thought it was weird that they put a sub panel for 1 device, but I think you are right they put the fusing in a combiner on the wrong part of the one line/

which is it dood? a 150 amp or 200 amp service panel?


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## ElectricJoeNJ (Feb 24, 2011)

backstay said:


> The ground faults need to be in the DC wires coming from the panels. Not in the house panel or between inverter and house panel.http://www.solar-electric.com/mndc-...t=600&width=550&inlineId=eyInsets&modal=false
> Item#: MNDC-GFP63
> Midnite Solar
> 
> ...


Most, if not all PV inverters have GFP built into them.


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## ElectricJoeNJ (Feb 24, 2011)

I agree there is ALOT wrong with both drawings. Regardless of a 150 or 200 amp main panel the breaker size for the PV backfeed should be 30a which by code will fit within the 120% of the bus rating on either size service. #2 is wayyyy over sized. Typically we always run #6 because our utility wants no smaller than number 6 going to the production meter pan (if it's a utility loan customer) so on this job I would install a 30 amp breaker and run # 10 to a outdoor CB disco with a 60 amp breaker, and run # 6 from the disco through the new meter pan and then on to the inverter. No need for a sub panel. The reason I install a 60 amp(it could technically be a 40 50 or 60) is so i can land the # 6 wire legally. If that inverter dosent have individual fuse protection on the strings then you will need to install fuse holders in the combiner box.


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## vida (Feb 21, 2012)

ElectricJoeNJ said:


> I agree there is ALOT wrong with both drawings. Regardless of a 150 or 200 amp main panel the breaker size for the PV backfeed should be 30a which by code will fit within the 120% of the bus rating on either size service. #2 is wayyyy over sized. Typically we always run #6 because our utility wants no smaller than number 6 going to the production meter pan (if it's a utility loan customer) so on this job I would install a 30 amp breaker and run # 10 to a outdoor CB disco with a 60 amp breaker, and run # 6 from the disco through the new meter pan and then on to the inverter. No need for a sub panel. The reason I install a 60 amp(it could technically be a 40 50 or 60) is so i can land the # 6 wire legally. If that inverter dosent have individual fuse protection on the strings then you will need to install fuse holders in the combiner box.


somebody owes this guy cutzies at the plan check desk.
:thumbup:
Thats exactly right, where I was going, but I was gonna draw it out some more for my ego :laughing:


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## ElectricJoeNJ (Feb 24, 2011)

vida said:


> somebody owes this guy cutzies at the plan check desk.
> :thumbup:
> Thats exactly right, where I was going, but I was gonna draw it out some more for my ego :laughing:


Thanks. Fortunately a bulk of my current job requires me to do all the pre site visits for our commercial installs and a plan check before the plans are sent to the engineer.


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## dogleg (Dec 22, 2008)

*old school*

For just a grid tied system and no battery storage has anybody used micro inverters ? If you did how did you wire the system?Is it much easier and less switchgear?


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## ElectricJoeNJ (Feb 24, 2011)

dogleg said:


> For just a grid tied system and no battery storage has anybody used micro inverters ? If you did how did you wire the system?Is it much easier and less switchgear?


Residential or Commercial? Your comment about switchgear confuses me. We've done quite a few micro systems for houses. All depends on the layout. Actually doing a ground mount system with micro inverters. You'll basically have more circuits, but the same AC output as you would have with regular inverters.


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## dogleg (Dec 22, 2008)

*Never stop learning even at my age.*

I was referring to residential and by switchgear I should have used the word disconnect.From what I understand the microinverters sense grid power and produce power.When the grid fails or stops producing the microinverters have a way of sensing this and stop producing.This takes the place of a transfer switch as not allowing power from the array to backfeed the utility lines?
Also how do you combine your Ac coming from the arrays? Are the micro inverters paralleled to provide a certain wattage per circiut to feed the grid tied panel(is there a standard)?If so where are the disconnects from the arrays located?
I have read some about them but if you could enlighten me it would much be appreciated.


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## vida (Feb 21, 2012)

lol. you said "enlighten"


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