Materials needed for an installation

System · September 2007

I am preparing an order for materials, and I'm looking for help in flushing out anything missing from the order and misconceptions I have. The big items are easy to identify (i.e., panels, inverter, rails), and once I receive the materials, and start the installation, I'm sure the smaller items would be more obvious -e.g., whoops

. I am going to go with Evergreen 180's, and the mounting hardware will come with the WattSun Trackers. Connecting to the panel, ground and power, won't be provided. I'm thinking Lay-In-Lugs (see below) will handle the panel grounding, which will connect to a ground rod at the trackers.
It looks like Evergreen provides a pigtail, coming out of the junction box, with MC connectors on the ends. Is this correct, and if so, is this an option (or on all Evergreen panels)? I'm assuming "MC" would mate with Multi-Connect connectors - is this correct?
It looks like I don't need to worry about bypass diodes, because they are integral to the panel - is this correct?
I'm planning on using a midnite solar combiner to combine the two strings (12 panels each), and using #8 (thhn) for the 150' run from the tracker to the inverter. Is it advisable to provide a D/C disconnect at both Wattsun trackers. I figure the mid-nite solar combiner can provide a means to disconnect at one of the trackers, but don't have anything planned to isolate the other tracker.
Are lightning arrestors worth putting in - We get Thunderstorms very infrequently, but I'm guessing it's cheap insurance worth installing???
Thanks in advance,
Michael

Solar Guppy · September 2007

Re: Materials needed for an installation

I would skip the combiner, first I doubt its 600V rated and second, it costs more than just running a second run. For 300ft round trip you can still use 10Awg, its 90 bucks at home depot for 500' spool last week. This run should be in conduit, non-metallic is fine around here and no, and disconnect is not required at the tracker as the inverter already has one assuming your going with the GT5.0

mike95490 · September 2007

Re: Materials needed for an installation

Michael_C wrote: »

Are lightning arrestors worth putting in - We get Thunderstorms very infrequently, but I'm guessing it's cheap insurance worth installing???
Michael

If you get a direct hit, consider everything toast, protection or not.
Protection seems to only help reducing whole house conflagrations, and near strike induced coupling effects. In California, the requirement is that frames & racks be grounded

System2 · September 2007

Re: Materials needed for an installation

Solar Guppy wrote: »

I would skip the combiner, first I doubt its 600V rated and second, it costs more than just running a second run. For 300ft round trip you can still use 10Awg, its 90 bucks at home depot for 500' spool last week. This run should be in conduit, non-metallic is fine around here and no, and disconnect is not required at the tracker as the inverter already has one assuming your going with the GT5.0

One of the things I liked about using the combiner box at the tracker was it provided fault protection for the wire (between the panel and the inverter).
Do you provide protection, or rely on the low probability?

I was also going to make use of the ground bar in the combiner to connect to the ground rod at the tracker and the ground going in the conduit (toward the inverter). How do you handle the connections for the ground from the "PV panels to rod" and the ground going to the inverter?

Yes, I still plan on going with the GT 5, so could run separately all the way to the inverter.

System2 · September 2007

Re: Materials needed for an installation

mike90045 wrote: »

If you get a direct hit, consider everything toast, protection or not.
Protection seems to only help reducing whole house conflagrations, and near strike induced coupling effects. In California, the requirement is that frames & racks be grounded

Good to get the input - the only reluctance I had to rule it out was it would provide another "desirable" pathway for the energy to travel (in addition to the ground wire to rod)

Thanks again,
Michael

Solar Guppy · September 2007

Re: Materials needed for an installation

Michael_C wrote: »

One of the things I liked about using the combiner box at the tracker was it provided fault protection for the wire (between the panel and the inverter).
Do you provide protection, or rely on the low probability?
the inverter.

Not needed, the fault current is ~zero watts , ie, short out the panels and its max current at near zero volts .. The VMP current is about 8 amps for the Evergreens, concider 10awg can handle 30 amps to NEC you will never have an issues and there is no code requirement

BB. · September 2007

Re: Materials needed for an installation

Basically, the wiring will not be damaged by any shorts--the Solar panels themselves are current limited so that a short anywhere in the cable will simply conduct only slightly more current than normal operation would have (check Imp vs Isc for the solar panels).

Placing a fuse/protection at the Charge Controller protects the panels/cables against a shorted charge controller from placing battery bus energy out to the solar arrays. A large fuse at the arrays would not protect the cable run from the arrays back to a direct connected charge controller in the case of a controller failure or other issues (like a shovel through the buried cable run).

Also, you will need to check the fusing for each solar panel... Normally, if you connect more than a couple in parallel, and each panel needs to be protected from the current of the other panels dumping into the shorted panel and causing a fire (say a 5 amp panel needs a 10 amp fuse--two panels in parallel only output 5 amps each--no problem. Three panels (or more panels) in parallel, the two+ good panels can output 10+ amps into the the shorted panel).

-Bill

System2 · September 2007

Re: Materials needed for an installation

Solar Guppy wrote: »

Not needed, the fault current is ~zero watts , ie, short out the panels and its max current at near zero volts .. The VMP current is about 8 amps for the Evergreens, concider 10awg can handle 30 amps to NEC you will never have an issues and there is no code requirement

Good point
Thanks

System2 · September 2007

Re: Materials needed for an installation

BB. wrote: »

Basically, the wiring will not be damaged by any shorts--the Solar panels themselves are current limited so that a short anywhere in the cable will simply conduct only slightly more current than normal operation would have (check Imp vs Isc for the solar panels).

Placing a fuse/protection at the Charge Controller protects the panels/cables against a shorted charge controller from placing battery bus energy out to the solar arrays. A large fuse at the arrays would not protect the cable run from the arrays back to a direct connected charge controller in the case of a controller failure or other issues (like a shovel through the buried cable run).

No charging in my setup - understand a fuse at the panels wouldn't protect the wire.

Also, you will need to check the fusing for each solar panel... Normally, if you connect more than a couple in parallel, and each panel needs to be protected from the current of the other panels dumping into the shorted panel and causing a fire (say a 5 amp panel needs a 10 amp fuse--two panels in parallel only output 5 amps each--no problem. Three panels (or more panels) in parallel, the two+ good panels can output 10+ amps into the the shorted panel).

-Bill

I'm running with two strings - I'm assuming the caution you described wouldn't apply to my configuration - is this correct?

BB. · September 2007

Re: Materials needed for an installation

You have to look at the product details for your exact solar panels... For example, the BP 4175 modules (pdf file) on my home:

Electrical Characteristics2 BP 4175
Maximum power (Pmax)3 175W
Voltage at Pmax (Vmp) 35.7V
Current at Pmax (Imp) 4.9A
Warranted minimum Pmax 166.5W
Short-circuit current (Isc) 5.4A
Open-circuit voltage (Voc) 44.0V
Temperature coefficient of Isc (0.065±0.015)%/ °C
Temperature coefficient of Voc -(160±10)mV/°C
Temperature coefficient of power -(0.5±0.05)%/ °C
NOCT (Air 20°C; Sun 0.8kW/m2 ; wind 1m/s) 47±2°C
Maximum series fuse rating 15A (S, L)
Maximum system voltage 600V (U.S. NEC & IEC 61215 rating)

So, in my case, more than 3 strings (two strings supplying current to a shorted third string) would be 16.2 amps, and should be protected by a 15 amp fuse on each string...

Remember, this is how I read the code--I find that many people (inspectors, UL, etc.) don't always agree. If you can talk with you inspector for a pre-install system review--both of you would probably come out ahead.

Also, remember the inspectors are not there to catch problems (we had a suite in the city were I used to live where the inspectors obviously did not inspect a thing on the Condo-Development... Much was built below code and the buildings quickly started to settle and slide down slope--city had no liability). Also, on my remodel (for energy efficiency), had an electrician subcontractor that had just twisted and laced exposed wires together under our home with a new furnace install. Inspector did not even look.

Their best use is when you bring issues (that you have found) to the inspector that you want resolved by the installer.

-Bill

System2 · September 2007

Re: Materials needed for an installation

BB. wrote: »

You have to look at the product details for your exact solar panels... For example, the BP 4175 modules (pdf file) on my home:

So, in my case, more than 3 strings (two strings supplying current to a shorted third string) would be 16.2 amps, and should be protected by a 15 amp fuse on each string...

Remember, this is how I read the code--I find that many people (inspectors, UL, etc.) don't always agree. If you can talk with you inspector for a pre-install system review--both of you would probably come out ahead.

Also, remember the inspectors are not there to catch problems (we had a suite in the city were I used to live where the inspectors obviously did not inspect a thing on the Condo-Development... Much was built below code and the buildings quickly started to settle and slide down slope--city had no liability). Also, on my remodel (for energy efficiency), had an electrician subcontractor that had just twisted and laced exposed wires together under our home with a new furnace install. Inspector did not even look.

Their best use is when you bring issues (that you have found) to the inspector that you want resolved by the installer.

-Bill

Bill
Where should fusing be provided for a system which doesn't have "batteries/charging controller"?
I am running with two trackers. 12 Evergreen panels per tracker.
I'm not opposed to adding protection, but I'm not sure I understand your point - the Xantrex GT 5.0 has zero backfeed current, and I have two equally sized strings. What would be the source of the overcurrent?

Evergreen panels
180 - SL
Pp = 180
Vp =` 25.9
Ip = 6.95
Voc = 32.6
Isc = 7.78
Series Fuse Rating 15 A
310.8 volts under load - 6.95 amps/string

Michael

BB. · September 2007

Re: Materials needed for an installation

I agree, in this case you do not need any "distribution" fuses... The maximum current that could go into a shorted panel is Isc=7.78 amps. You would only need them if you had 3 strings in parallel (for a total of 15.56A>15A--actually pretty close--from two strings feeding into one shorted string).

My GT 3.0 installation with two series panels also did not have any fuses installed.

Again, I am not an inspector (I was an engineer that had to design to similar requirements for my computer systems). You want to do this for safety--and there is no obvious reasons for the fuses in your installation. Plus, fuses and their connections, would need extra enclosures and tend to be unreliable components--so you would want to avoid them if you can.

The issues with the back-feed current depends on the design. Typically, a line connected inverter has multiple levels of isolation to prevent line to solar panel shorts--much easier with AC coupled Line to Panel inverter designs (the installation manual will layout the protective devices needed)...

A DC solar charging system may not have isolation.

-Bill

niel · September 2007

Re: Materials needed for an installation

quoted: "I was also going to make use of the ground bar in the combiner to connect to the ground rod at the tracker and the ground going in the conduit (toward the inverter). How do you handle the connections for the ground from the "PV panels to rod" and the ground going to the inverter?"

from what i read here are you saying you'll have a 3rd wire running along side of the + and - for the ground? if so i'll advise against it. instead place the wire in the ground and you'll need at least #8 solid bare copper anyway with my recommending at least #6. each tracker array should have its own 8ft copper ground rod in addition to the ground rod for the electrical system back at the house. these all need tied together as you know, but put it underground to prevent possible cross interactions into the wires from lightning emp. i recommend at least 1 foot down, but i don't believe the nec has a standard on the depth. the deaper it is the less likely of accidentally severing or exposing the wire through gardening, contractors, errosion, etc. the wire in the ground will also increase your effective grounding area many fold given the distances you've indicated. this is like an extension on your ground rod, but with wire as there is more contact area with the earth.
hmmm, that reminds me i better recheck mine as i had a contractor dig a hole where mine sits for a fence post. they remarked of finding it and i said they could go around it, but can't sever it as it is an electrical ground. it wouldn't surprise me if they did break it and not say anything given the quality of work they did.

System2 · September 2007

Re: Materials needed for an installation

niel wrote: »

quoted: "I was also going to make use of the ground bar in the combiner to connect to the ground rod at the tracker and the ground going in the conduit (toward the inverter). How do you handle the connections for the ground from the "PV panels to rod" and the ground going to the inverter?"

from what i read here are you saying you'll have a 3rd wire running along side of the + and - for the ground? if so i'll advise against it. instead place the wire in the ground and you'll need at least #8 solid bare copper anyway with my recommending at least #6. each tracker array should have its own 8ft copper ground rod in addition to the ground rod for the electrical system back at the house. these all need tied together as you know, but put it underground to prevent possible cross interactions into the wires from lightning emp. i recommend at least 1 foot down, but i don't believe the nec has a standard on the depth. the deaper it is the less likely of accidentally severing or exposing the wire through gardening, contractors, errosion, etc. the wire in the ground will also increase your effective grounding area many fold given the distances you've indicated. this is like an extension on your ground rod, but with wire as there is more contact area with the earth.
hmmm, that reminds me i better recheck mine as i had a contractor dig a hole where mine sits for a fence post. they remarked of finding it and i said they could go around it, but can't sever it as it is an electrical ground. it wouldn't surprise me if they did break it and not say anything given the quality of work they did.

I had thought the purpose of the wire going from the tracker, in my situation, to the house ground system is bonding. E.g. to keep the grounds at the same potential. I'll think more about routing the ground wire in the earth, but I'm unsure of the "connection" mechanics at the trackers.

I would want to use a stranded wire, or strap, to handle the tracker movement, but had planned on using solid wire the rest of the way. If this was a good thing, then there would need to be a place to join these disimilar "wires". Originally, I thought I would have a ground wire going from the panels to a ground rod next to the concrete. I could see the possibility of looping the wire through the ground rod's clamp, and continuing from tracker A to tracker B. When the ground wire from tracker A get's to Tracker B, I could terminate this wire at tracker B's ground rod (via a clamp). Tracker B's ground wire could loop through a second clamp, and continue to the house ground system.
However, it's that section of ground wire going from one side of the pivot to the stationary post needing a solution.. Using a bus bar(s) to handle the stranded ground wire connection to solid seemed like a reasonable approach - as long as I dealt with the stranded wire properly - e.g. using ferrule, etc. Does this seem reasonable to you???

niel · September 2007

Re: Materials needed for an installation

the series stringing is fine if not seperated too too far, but i'm just saying that the 3rd wire should be buried and not made to travel with the + and - in the conduit. the buried ground wire should always be a solid wire because the stranded will have more surface area to corrode and fail. even solid wires corrode when in the ground and is why i recommend the use of #6 rather than #8. we've had many discussions along this line and i don't know if any of them are still on the forum or not, i have no time to look for them right now.

Materials needed for an installation

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