Lightning Surge Arrester at the Dc disconnect box?

midijeep

Are there any problems installing a Lightning Surge Arrester at the Dc disconnect box?  I have a grid-tied SMA SunnyBoy 3000TL-US -22 with the DC disconnect at the bottom of the SunnyBoy.

BB.

Just make sure the lightning/surge has someplace to go safely (such as to a ground rod/grounding system at the base of the box).

-Bill

midijeep

The electrician who installed the PV system did place a 10 gauge copper ground wire on the outside of the disconnect.  this ground wire is coming out of  the disconnect box.  I am assuming that that is grounded to the AC system somehow?

BB.

Probably is. But you need to verify.

6 awg to a ground rod, plus grounding to ac system (probably, need details) is best.

Less than 6 awg is not really enough for lighting (in my humble opinion).

-Bill

midijeep

The inverter is located in my garage. I can run the 6 awg wire over to the grounding system that was put in when the home was built.  The grounding system is tied into the foundation via rebar.  Would this work as far as the "grounding rod"?

vtmaps

midijeep said:

 The grounding system is tied into the foundation via rebar.  Would this work as far as the "grounding rod"?

Yes, it's called a Ufer ground.   --vtMaps

midijeep

I took off the DC disconnect cover and found that the ground goes to a shunt on the outside of the DC disconnect box. Basically, the ground from the PV combiner goes to a ground shunt on the outside of the DC disconnect, then a short ground wire goes from the shunt on the outside back into the DC disconnect box to a connection.  This doesn't seem truly ground to me?  Should I do as you suggested and run a 6 awg wire to the grounding rod for the house?  (See attached pics)

Dave Angelini

Who did the installation?

midijeep

A licensed Electrician.  Actually two electricians at two different occasions.  First occasion the inverter was placed outside on the garage and the picture you see is how it was wired at the time of initial installation.  Then, I had another electrician come out to do my battery backup and at the same time move the inverter from outside of the garage to inside the garage (picture you see now).  The picture you see now is the inverter inside the garage.  The grounding rod/system is about 20 feet away.

JAZ140

I just finished up installing 2 sma xxxxtl-22 inverters so maybe I can help.

Those inverters do not require a GEC.  Only a EGC.   Running a #6 to a cee/ufer would fall under auxiliary grounding.  
Also hard to tell but it looks like that FMC is not bondend properly if your array is running over 250 volts.
Not sure why the EGC is going to the lug on the outside of the DC disco, it's redundant.  Maybe the inspector on your area prefers it?

midijeep

JAZ140 said:

I just finished up installing 2 sma xxxxtl-22 inverters so maybe I can help.

Those inverters do not require a GEC.  Only a EGC.   Running a #6 to a cee/ufer would fall under auxiliary grounding. 
Also hard to tell but it looks like that FMC is not bondend properly if your array is running over 250 volts.
Not sure why the EGC is going to the lug on the outside of the DC disco, it's redundant.  Maybe the inspector on your area prefers it?

Should the ground wire from the panels go directly to the board, not the way it is routed now?
With the 7 panels I have (38 volts each) I am running around 266 volts in series.  How exactly can I fix this problem?
As far as GEC vs EGC, you mention ths for the inverter, does this grounding apply for the PV panels them self?

Also, I want to put a Midnite solar surge protector that  is rated for 300 VDC.  Can I follow the (+) & (-) & Ground connections in the disconnect to place it? 

JAZ140

These little suckers will take care of the bonding.  They even have two piece ones that you dont have to un wire the array to put it on.

JAZ140

How many watts are your panels?  That inverer would operate better with a higher voltage string..  The ground from the area is a EGC and can go right to the EGC terminal.  That's the three ground terminals in the DC disco.

midijeep

JAZ140 said:

How many watts are your panels?  That inverer would operate better with a higher voltage string..  The ground from the area is a EGC and can go right to the EGC terminal.  That's the three ground terminals in the DC disco.

I have seven - 255 watt panels @ 38 volt each

JAZ140

voltage could be a little low depending on how hot it gets.  Are you using a tracker or fixed array?  A few more panels would help you stay above the lower limits of the mppt on the inverter. 

Vic

midijeep said:

JAZ140 said:

How many watts are your panels?  That inverer would operate better with a higher voltage string..  The ground from the area is a EGC and can go right to the EGC terminal.  That's the three ground terminals in the DC disco.

I have seven - 255 watt panels @ 38 volt each

Assume that for a 255 W PVs are 60 cells,   and would assume that the Vmp would be about 30-ish volts,  with  Voc  of about 38 volts.

Could not easily find an SMA String Sizer,  but,  most Sizers that I've seen use Vmp  as the dominant String Sizing factor,  with a Voc confirmation thrown in at the end.

midijeep,  what is the Vmp and Voc of the PVs that you are proposing to use?

Thanks,   Vic

midijeep

JAZ140 said:

voltage could be a little low depending on how hot it gets.  Are you using a tracker or fixed array?  A few more panels would help you stay above the lower limits of the mppt on the inverter. 

Panels are fixed on the roof.  I am going to add some more panels in a few months, probably in the 325 watt per panel range.
I am wanting to put a SPD  i.e Midnite solar surge protector that  is rated for 300 VDC at the SMA disconnect box.  But after opening up the box I am not sure how to wire it in correctly.  Any hints?  can this be done?

midijeep

Vic said:

midijeep said:

JAZ140 said:

How many watts are your panels?  That inverer would operate better with a higher voltage string..  The ground from the area is a EGC and can go right to the EGC terminal.  That's the three ground terminals in the DC disco.

I have seven - 255 watt panels @ 38 volt each

Assume that for a 255 W PVs are 60 cells,   and would assume that the Vmp would be about 30-ish volts,  with  Voc  of about 38 volts.

Could not easily find an SMA String Sizer,  but,  most Sizers that I've seen use Vmp  as the dominant String Sizing factor,  with a Voc confirmation thrown in at the end.

midijeep,  what is the Vmp and Voc of the PVs that you are proposing to use?

Thanks,   Vic

The current panels I have are seven Solarworld Sunmodule Plus SW 255, Vmp =  30.6 V , Voc = 38.7 V.  The panels I want to get are the Solarworld Sunmodule Pro XL 325W Panels - 72 Cell,   Vmp = 37V , Voc = 46.1V.

 

JAZ140

I found the Manual.  The 300 may be too low if you add more panels.  The 600 volt one is for grid tie inverters.   I would have your electrician wire that up.  + - and GND...

Vic

midijeep said:

Vic said:

midijeep said:

JAZ140 said:

How many watts are your panels?  That inverer would operate better with a higher voltage string..  The ground from the area is a EGC and can go right to the EGC terminal.  That's the three ground terminals in the DC disco.

I have seven - 255 watt panels @ 38 volt each

Assume that for a 255 W PVs are 60 cells,   and would assume that the Vmp would be about 30-ish volts,  with  Voc  of about 38 volts.

Could not easily find an SMA String Sizer,  but,  most Sizers that I've seen use Vmp  as the dominant String Sizing factor,  with a Voc confirmation thrown in at the end.

midijeep,  what is the Vmp and Voc of the PVs that you are proposing to use?

Thanks,   Vic

The current panels I have are seven Solarworld Sunmodule Plus SW 255, Vmp =  30.6 V , Voc = 38.7 V.  The panels I want to get are the Solarworld Sunmodule Pro XL 325W Panels - 72 Cell,   Vmp = 37V , Voc = 46.1V.

 

OK,   Thanks ...  Selection of the SPD will depend  upon the String voltage that you ultimately wind up with.

There ARE Sunnyboy string sizers,  this one may not be the exact one that you will need:
http://www.smainverted.com/2015/05/11/installers-sunny-boy-tl-us-string-sizing-tool-now-available/

FWIW,   Vic

midijeep

Decided to go up in the attic and see what the electrician did.  Basally,  two - black and one green wires enter from outside to a blue plastic  junction box and wire nuts are used with an orange wire exiting and goes down to the DC disconnect inside the garage.  I haven't looked close enough but I am assuming he didn't a combiner box for the PV wiring because  the panels are wired in series ,so maybe they tie into the 3 -wires to the junction box in the attic)?   It looks like the seven 255 Watt panels are 1 string.  I see no other wiring to support 2 strings of PV panels. 

There is no breakers or any kind of protection from the PV panels to the DC disconnect.

So my question(s):
1) Even though I have 1 string, I feel like I need a combiner box with breakers and lightning surge protection to protect especial from a direct or near by lightning strike to the panels.  Should I go ahead and purchase a combiner box with the breakers and lightning surge protection and where should I locate it i.e. before the PV wiring enters the attic or close to the disconnect?
2)  What combiner box would you recommend as well as what breakers and surge arrester?

JAZ140

No combiner panel is necessary.  That sma DC disconnect can accept 4 strings.  2 per mppt.   Just so you don't hurt yourself please hire someone to put the SPD in at the DC disconnect.  This is a very simple but potentially deadly circuit.  Very high DC voltage is present with very little sunlight.  

midijeep

JAZ140 said:

No combiner panel is necessary.  That sma DC disconnect can accept 4 strings.  2 per mppt.   Just so you don't hurt yourself please hire someone to put the SPD in at the DC disconnect.  This is a very simple but potentially deadly circuit.  Very high DC voltage is present with very little sunlight.  

Jaz - thanks for the info and advice.  I will ask a license electrician to do the work.  As far as a DC surge arrester, do you have any recommendations?  Will a type 2 do or should it be a Type 1 surge arrester.  I want to purchase it may self and have the electrician place it.

westbranch

Read up on MidNite SPD's, search here or http://www.midnitesolar.com/productPhoto.php?product_ID=283&productCatName=Surge Protection Devices&productCat_ID=23&sortOrder=1&act=pc

disregard the price as that is the MSRP  NAWS sells for less
 http://www.solar-electric.com/catalogsearch/result/?q=spd&cat=0