[RE-wrenches] central vrs string inverters

[Marco Mangelsdorf]

Hey Al,

 

I had a similar choice to make several months ago.  There are not that many 
options out here in Hawaii—given the more demanding utility requirements for 
grid-tie inverters—for string inverters that are true 3-phase 120/208 while the 
choices are more abundant if you have 277/480 as the service voltage.  The 
Fronius Symo has a 12 kW @ 120/208 model which I plan to use soon.

 

For this last ~ 100 kW system we did, we used five SMA Tripowers and a 
step-down x-former to bring the voltage down to 120/208.  As for transformers, 
note that Dongan (made in the U.S.) offers such high-efficiency x-formers even 
in stainless steel enclosures at a very reasonable price.  Given the 1,000V DC 
max input possible for the Tripowers, we went into unknown territory with the 
AHJ here on the Big Island.  While I spec’ed out 1 kV-rated conductors for the 
+ and – DC conductors, I realized late in the game that I needed to use 1 
kV-rated EGC wire from the roof as well.  D’oh!  Trying finding some of that at 
your local electrical supply.  Finally, to my surprise and somewhat annoyance, 
we are being required to erect a protective barrier, i.e., fence, around the 
inverters—which are mounted on the exterior wall of a medical professional 
building—in order to keep them beyond the reach of the public, even though one 
would have to take covers off in order to expose the conductors.

 

Always an adventure.

 

marco

 

From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf 
Of Jason Szumlanski
Sent: Friday, June 26, 2015 9:39 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] central vrs string inverters

 

I don't have anything in terms of advice on the Tri-Power, but I have done 
microinverters on straight 208V three-phase and also 480V with a step-down 
transformer. While there are more potential points of failure, future service 
is straightforward. There are lots of capable people who can swap a micro. We 
have been called out to several 20-100kW central inverters that were 
essentially unserviceable due to obsolescence, bankruptcy, parts availability, 
and lack of qualified personnel. That could be a function of the crummy Florida 
commercial solar market, but it's something to consider. Lifetime service and 
replacement costs need to be considered in the ROI analysis, and despite 
micro's higher initial cost, there is a good argument to be made...

 

On the other hand, while I have never used a Tri-Power, SMA's Sunny Boy's have 
been rock solid around here in demanding conditions.

 

Jason Szumlanski


 

 

On Fri, Jun 26, 2015 at 9:26 AM, Allen Frishman  wrote:

Hi Wrenchers,

I am considering using 8 SMA Tri-power Inverters for a project with a 3 phase 
208V Grid which means I have to add a step down transformer (480V to 208V).
I am comparing this option to a central inverter.I have done many of the 
central inverter systems at the 208V but have yet to try the 20+ KW string 
inverters with the addition of a step down transformer.

 

I know that both systems have there own pros and cons and I will really 
appreciate some feedback from those that have experience doing both types.   

 

For the central inverter there are fewer inverters to malfunction however when 
one does the entire system is down.   In my experience the Central Inverters 
that I have used have been very reliable.   

- Anyone seeing reliability issues with the SMA Tri-power 20KW and 24KW string 
inverters?

 

Note:   My project is under NEC 2008.

 

All feedback is appreciated.

 

Al Frishman
AeonSolar

(917) 699-6641   - cell
(888) 460-2867  
www.aeonsolar.com  

 

 

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Re: [RE-wrenches] SnapNrack

[Jason Szumlanski]

Yeah, if you have a single module on two rails, you still need to use WEEBs
or another bonding method.

Jason



On Fri, Jun 26, 2015 at 5:49 PM, August Goers  wrote:

> Chris,
>
>
>
> You are correct – there is just a bonding Unirac mid clamp. The new SM end
> clamp is basically the same as the old clamp but now comes preassembled
> with little rubberbands to keep it upright when placed on the rail.
>
>
>
> Best, August
>
>
>
> *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
> Behalf Of *Christopher Warfel
> *Sent:* Friday, June 26, 2015 2:41 PM
> *To:* re-wrenches@lists.re-wrenches.org
> *Subject:* Re: [RE-wrenches] SnapNrack
>
>
>
> Someone in this thread mentioned a Unirac integrated bonding end clamp.
> Our supplier has that on the packing slip, but it was still the same end
> clamp we always receive.  I have checked their website and do not see an
> integrated bonding end clamp; just mid clamp.  Does Unirac make an
> integrated bonding end clamp?  Thanks for any help.
>
> Chris
>
> On 6/25/2015 4:13 PM, Jason Szumlanski wrote:
>
> That decision was based on our distribution network offering better
> pricing on Unirac, and engineers being comfortable with it. Now with the
> integrated grounding from Unirac, I can't see moving away from it again
> barring a significant cost benefit. It also stacks and stocks easier than
> the Ironridge rails.
>
>
>
>
>
>
> On Wed, Jun 24, 2015 at 5:55 PM, Dana Brandt 
> wrote:
>
> Hi Jason,
>
> We've used Unirac for years but have been contemplating Ironridge. I'm
> curious what your experience was and why you went back to Unirac?
>
> Anyone else have input on best racking systems for flush-mounted
> residential systems on comp roof?
>
> Thanks,
>
>
> Dana
>
> Dana Brandt
> Ecotech Energy Systems, LLC
> www.ecotechenergy.com
> d...@ecotechenergy.com
> 360.318.7646
>
>
>
> On Wed, Feb 5, 2014 at 12:09 PM, Jason Szumlanski 
> wrote:
>
> By Snap N Rack, you mean Sun Run...
>
>
>
>
> http://cleantechnica.com/2014/02/05/sunrun-acquires-rec-solars-residential-business-aee-solar-snapnrack-means/
>
>
>
> I'm curious if these vertical integrators will still make their acquired
> brands available to small dealers through distribution. When SolarCity
> snatched up Zep, I had concerns about being able to service or add onto
> existing Zep systems we installed. That's definitely a concern going
> forward, and reason to perhaps stick with the most compatible racking
> solutions available. We used IronRidge for a while, which is largely
> compatible with Unirac, but now we're back on the Unirac bandwagon.
>
>
>
> Interesting times...
>
>
>
> Jason Szumlanski
>
> ​Fafco Solar​
>
>
>
>
>
> On Wed, Feb 5, 2014 at 12:45 PM, Max Balchowsky  wrote:
>
> We have been using Snap N' Rack for a while, Have lots of installs in
> Hawaii - so far no problems, I like the convenience of the design for
> snapping in the slider nut in mid rail, and also the ability to install the
> panels flush with the end of the rails….
>
>
>
> Max Balchowsky
> Design Engineer
> SEE Systems
> 1048 Irvine Ave Suite 217
> Newport Beach, Ca. 92660
> 760-403-6810
>
> "Building a Better Future For The Next Generation"
>
>
> --
>
> *From:* Allen Frishman 
> *To:* RE-wrenches 
> *Sent:* Wednesday, February 5, 2014 6:17 AM
> *Subject:* Re: [RE-wrenches] SnapNrack
>
>
>
> I am curious about the mid clamps on the snapnrack.   The flange that
> rests on top of the solar panel frame is so small ~ 3/16".Anyone
> experience any problems with these failing in a big storm?With solar
> panel frames not being square it is nice to have a little extra to grab - I
> am always curious as to why these clips are made with such a small area to
> hold the panels down.
>
>
>
> All feedback on these clips is appreciated.
>
> *Al Frishman*
> AeonSolar
>
> *(917) 699-6641 <%28917%29%20699-6641> - cell*
> *(888) 460-2867 <%2%29%20460-2867>*
> *www.aeonsolar.com *
>
>
>
> On Jun 1, 2013, at 10:41 AM, Max Balchowsky wrote:
>
>
>
> Have installed last three systems (35Kw)with snap n rack.
>
> love it
>
>
>
> Max Balchowsky
> Design Engineer
> SEE Systems
> 1048 Irvine Ave Suite 217
> Newport Beach, Ca. 92660
> 760-403-6810
>
> "Building a Better Future For The Next Generation"
>
>
> --
>
> *From:* Solarguy 
> *To:* 'RE-wrenches' 
> *Sent:* Friday, May 31, 2013 10:11 PM
> *Subject:* Re: [RE-wrenches] SnapNrack
>
>
>
> The only complaint with the Snapnrack rails is the thin wall can easily be
> distorted. This will allow the nut to drop out of its groove. Love the
> universal end clamps but have learned to assemble every one to check for
> proper fit before getting on the roof.
>
> Jim Duncan
>
> -Original Message-
> From: re-wrenches-boun...@lists.re-wrenches.org [mailto:
> re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Drake
> Sent: Friday, May 31, 2013 7:32 PM
> To: re-wrenches@lists.re-wrenches.org
> Subjec

Re: [RE-wrenches] Battery Bank to Inverter Wiring

[Allan Sindelar]

  
  
As a matter of course I have always run the positive and negative
conductors of high-current cable pairs together, but have never
deliberately twisted them, and have never known of any related
problems. 
The most obvious example of this would be 4/0 battery/inverter
cables in a 24V system, with a 250A GJ-class breaker or (prior to
that) a 300A or 400A Class T fuse. It's pretty tough to thread a
twisted pair of 4/0 USE/RHH/RHW cables through a 2" elbow or LB from
inverter enclosure to battery enclosure.
I'm not an EE, but I can't see what difference twisting would make
in the absence of a building/collapsing field as is normal with AC.

I have twisted AC conductors together in the past when clients have
expressed concerns about EMF from their equipment and wiring, but
only AC.
Allan


  
  
  
  
  
  
  
  
  
  
  
Allan Sindelar
  al...@sindelarsolar.com
  NABCEP Certified PV
Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive
  Energy,
  Inc.
505 780-2738 cell


 
  

On 6/27/2015 2:40 AM, John wrote:


  
  
  
  
  
That
is why for years we have been twisting those leads around
each other.  I was told it was to cancel out the opposing
fields on the wires, but for whatever the correct technical
reason is,  we have always twisted those heavy
wires. John V.
 
From: RE-wrenches
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On
  Behalf Of jarmo.venalai...@schneider-electric.com
Sent: Saturday, 27 June 2015 5:45 a.m.
To: RE-wrenches
Subject: [RE-wrenches] Battery Bank to Inverter
Wiring
 
Hi:
  
  
  From
time to time over the years I've come across systems where
the routing of DC cables between the batteries and the
inverter has been the cause of  issues. 
  
  I'm
not referring to wire thickness or quality of terminations.
 For the purposes of this discussion, just assume that wire
thickness and terminations are perfect. 
  
  What
I am referring to is the routing of the positive and
negative battery cables.  In particular, the loop area
within the + and - cables as shown in the image below,
  
  
  
  The
problem I've seen in systems with a large loop in the setup
is that the inverter does not provide good surge power and
can even go into low voltage shutdown during large surges.
  
  
  Recently
this happened again and I wanted to get a better feel for
it, so I did some math.   
  
  For
a cable length of about 12', the loop is an inductor which
has a value of inductance of about 1 uH for side by side
cables and as much as 6 uH for cables about 1 foot apart.  
  
  
  This
inductance is greatly multiplied by any ferrous metal in the
loop and can easily be in the range of 10's to 100's of uH.
 Examples being cables which run in steel conduits or along
the steel frame of a motor home. 
  
  Inductance
causes a voltage drop proportional to the rate at which the
current is changing.  To get an idea of how large that rate
can be for typical inverters, I did surge tests with a 5kW
inverter and found that the rate of change of current can be
as high as 100A per milli-second or 100,000 Amps/second.
  
  
  Given
that, the voltage drop of the wire inductance is then ,
Vdrop = (rate of change of current) x (inductance), 
  
  Vdrop
for 1 uH = (100,000 A/s) x (0.01 H) = 0.1V 
  Vdrop
for 10 uH = (100,000 A/s) x (0.01 H) = 1.0V 
  Vdrop
for 100 uH = (100,000 A/s) x (0.01 H) = 10.0V    clearly
this is a problem. 
  
  Have
any of the wrenches had systems with this issue?  If so, how
often. 
  
  
  JARMO
  
  
  
   
  _
  
  
  Jarmo Venalainen
 |   Schneider Electric  
  |  Xantrex Brand  |   CANADA  |   S

Re: [RE-wrenches] SnapNrack

[Benn Kilburn]

Chris,
It sounds (to me) that you are describing the bonding "tooth" dug through
the aluminum frame and into the glass? or at least compressed the frame
enough to break the glass?  If that is the case then i'm betting that the
clamp bolt was way over-torqued.

You need to check the recommended tightening torque for the module and for
the racking system you are using.  For example, what we are using these
days, Kinetic, the tightening torque for mid and end clamps is 12 ft-lb and
here are some recommended clamping torques from some different module
mfgrs
Conergy 8 NM - 6 ft-lb
Hanwha 5 NM - 3.7 ft-lb
JA Solar 18-24 NM - 13-18 ft-lb
These likely vary based on the construction of the module frame.
I've also found that some module mfgrs do not list recommended tightening
torques in their install manuals, so best to use discretion.

We had a module break after clamping it down.  The crew described it as
'putting the module in place, clamping it down and turning around to grab
the next module and hearing a 'crack' followed by the crackling glass sound
(if you have ever heard a module break, the crackling sound can last for a
few minutes).  The break pattern in the glass seemed to focus on a
particular mid clamp.  I used a torque wrench, set at around 10 ft-lb and
checked all the mid-clamp bolts, increasing the torque setting by a few
ft-lb each time until it finally turned a bolt instead of clicking.  I
found that most of the bolts were close to 30 ft-lb and the one that
appeared to break the glass was about 34 ft-lb.
Suffice to say, we were getting carried away with tightening using cordless
impact drivers.
At that point i and the rest of the crew started using the torque wrench as
we were going along until we had a better feel for what was the proper
torque.  (i've done this before, but it is something that needs to be self
"re-calibrated" often.


*Benn Kilburn *
CSA Certified Solar Photovoltaic Systems Electrician, SkyFire Energy Inc
6706 – 82 Ave NW | Edmonton, AB | T6B 0E7
P: 780-474-8992 | F: 888-405-5843 | www.skyfireenergy.com
[image: email]  [image: facebook]
 [image: twitter]
 [image: linkedin]

 [image: google] 

[image: SkyFire Energy Logo_horizontal]

On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester 
wrote:

> Hi Jason,
>
> Have you or others been using the new UniRac SM mid and end clamps with
> the integrated bonding yet? My concern is the “Stainless steel Midclamp
> points, 2 per module, pierce module frame anodization to bond module to
> module through clamp.”
>
> We had an MSI Alpha + self-bonding midclamp shatter the glass on an LG 280
> last fall, as the factory set point was sticking out too far, so as it was
> being tightened down, on top of the module the point dug through the
> module’s top frame hitting the glass, shattering it.
>
> I do wonder if there are any issues with this “point” on the UniRac
> midclamps potential for doing the same damage?
>
>
>
> Chris Worcester
>
> Solar Wind Works
>
> NABCEP Certified PV Installer
>
> Office 530-582-4503
>
> Cell 530-448-9692
>
> Fax 530-582-4603
>
> www.solarwindworks.com
>
> ch...@solarwindworks.com
>
>
>
> *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On
> Behalf Of *Jason Szumlanski
> *Sent:* Thursday, June 25, 2015 1:13 PM
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] SnapNrack
>
>
>
> That decision was based on our distribution network offering better
> pricing on Unirac, and engineers being comfortable with it. Now with the
> integrated grounding from Unirac, I can't see moving away from it again
> barring a significant cost benefit. It also stacks and stocks easier than
> the Ironridge rails.
>
>
>
>
>
>
> On Wed, Jun 24, 2015 at 5:55 PM, Dana Brandt 
> wrote:
>
> Hi Jason,
>
> We've used Unirac for years but have been contemplating Ironridge. I'm
> curious what your experience was and why you went back to Unirac?
>
> Anyone else have input on best racking systems for flush-mounted
> residential systems on comp roof?
>
> Thanks,
>
>
> Dana
>
> Dana Brandt
> Ecotech Energy Systems, LLC
> www.ecotechenergy.com
> d...@ecotechenergy.com
> 360.318.7646
>
>
>
> On Wed, Feb 5, 2014 at 12:09 PM, Jason Szumlanski 
> wrote:
>
> By Snap N Rack, you mean Sun Run...
>
>
>
>
> http://cleantechnica.com/2014/02/05/sunrun-acquires-rec-solars-residential-business-aee-solar-snapnrack-means/
>
>
>
> I'm curious if these vertical integrators will still make their acquired
> brands available to small dealers through distribution. When SolarCity
> snatched up Zep, I had concerns about being able to service or add onto
> existing Zep systems we installed. That's definitely a concern going
> forward, and reason to perhaps stick with the most compatible racking
> solutions available. We used IronRidge fo

Re: [RE-wrenches] SnapNrack

[Ray Walters]

Besides your note that cordless impact drivers can over torque the 
clamps, also they spin the bolts too fast which can lead to spalling of 
the SS hardware.
We now hand torque those connects.  Finally, most torque specs are for 
lubricated bolts.  We use anti-seize on the threads before torquing.
Using a cordless impact driver and no lube can cause not only module 
damage but also clamp damage, and end up with clamps not actually 
securing the modules, because the bolts spalled out before fully clamping.


R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 6/28/2015 3:06 PM, Benn Kilburn wrote:

Chris,
It sounds (to me) that you are describing the bonding "tooth" dug 
through the aluminum frame and into the glass? or at least compressed 
the frame enough to break the glass?  If that is the case then i'm 
betting that the clamp bolt was way over-torqued.


You need to check the recommended tightening torque for the module and 
for the racking system you are using.  For example, what we are using 
these days, Kinetic, the tightening torque for mid and end clamps is 
12 ft-lb and here are some recommended clamping torques from some 
different module mfgrs

Conergy 8 NM - 6 ft-lb
Hanwha 5 NM - 3.7 ft-lb
JA Solar 18-24 NM - 13-18 ft-lb
These likely vary based on the construction of the module frame.
I've also found that some module mfgrs do not list recommended 
tightening torques in their install manuals, so best to use discretion.


We had a module break after clamping it down.  The crew described it 
as 'putting the module in place, clamping it down and turning around 
to grab the next module and hearing a 'crack' followed by the 
crackling glass sound (if you have ever heard a module break, the 
crackling sound can last for a few minutes).  The break pattern in the 
glass seemed to focus on a particular mid clamp.  I used a torque 
wrench, set at around 10 ft-lb and checked all the mid-clamp bolts, 
increasing the torque setting by a few ft-lb each time until it 
finally turned a bolt instead of clicking.  I found that most of the 
bolts were close to 30 ft-lb and the one that appeared to break the 
glass was about 34 ft-lb.
Suffice to say, we were getting carried away with tightening using 
cordless impact drivers.
At that point i and the rest of the crew started using the torque 
wrench as we were going along until we had a better feel for what was 
the proper torque.  (i've done this before, but it is something that 
needs to be self "re-calibrated" often.



*Benn Kilburn *
CSA Certified Solar Photovoltaic Systems Electrician, SkyFire Energy Inc
6706 – 82 Ave NW | Edmonton, AB | T6B 0E7
P: 780-474-8992 | F: 888-405-5843 | www.skyfireenergy.com 

email  facebook 
 twitter 
 linkedin 
 
google 


SkyFire Energy Logo_horizontal


On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester 
mailto:ch...@solarwindworks.com>> wrote:


Hi Jason,

Have you or others been using the new UniRac SM mid and end clamps
with the integrated bonding yet? My concern is the “Stainless
steel Midclamp points, 2 per module, pierce module frame
anodization to bond module to module through clamp.”

We had an MSI Alpha + self-bonding midclamp shatter the glass on
an LG 280 last fall, as the factory set point was sticking out too
far, so as it was being tightened down, on top of the module the
point dug through the module’s top frame hitting the glass,
shattering it.

I do wonder if there are any issues with this “point” on the
UniRac midclamps potential for doing the same damage?

Chris Worcester

Solar Wind Works

NABCEP Certified PV Installer

Office 530-582-4503 

Cell 530-448-9692 

Fax 530-582-4603 

www.solarwindworks.com 

ch...@solarwindworks.com 

*From:*RE-wrenches
[mailto:re-wrenches-boun...@lists.re-wrenches.org
] *On Behalf Of
*Jason Szumlanski
*Sent:* Thursday, June 25, 2015 1:13 PM
*To:* RE-wrenches
*Subject:* Re: [RE-wrenches] SnapNrack

That decision was based on our distribution network offering
better pricing on Unirac, and engineers being comfortable with it.
Now with the integrated grounding from Unirac, I can't see moving
away from it again barring a significant cost benefit. It also
stacks and stocks easier than the Ironridge rails.


On Wed, Jun 24, 2015 at 5:55 PM, Dana Brandt
mailto:d...@ecotechenergy.com>> wrote:

Hi Jason,

We've used Unirac for years but have been contemplating Ironridge.
  

Re: [RE-wrenches] SnapNrack

[Glenn Burt]

I think you are referring to galling, not spalling which is a concrete and rock 
phenomenon.

Sincerely,
Glenn Burt
Sent from my 'smart' phone so please excuse grammar and typos.

-Original Message-
From: "Ray Walters" 
Sent: ‎6/‎28/‎2015 17:27
To: "RE-wrenches" 
Subject: Re: [RE-wrenches] SnapNrack

Besides your note that cordless impact drivers can over torque the 
clamps, also they spin the bolts too fast which can lead to spalling of 
the SS hardware.
We now hand torque those connects.  Finally, most torque specs are for 
lubricated bolts.  We use anti-seize on the threads before torquing.
Using a cordless impact driver and no lube can cause not only module 
damage but also clamp damage, and end up with clamps not actually 
securing the modules, because the bolts spalled out before fully clamping.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 6/28/2015 3:06 PM, Benn Kilburn wrote:
> Chris,
> It sounds (to me) that you are describing the bonding "tooth" dug 
> through the aluminum frame and into the glass? or at least compressed 
> the frame enough to break the glass?  If that is the case then i'm 
> betting that the clamp bolt was way over-torqued.
>
> You need to check the recommended tightening torque for the module and 
> for the racking system you are using.  For example, what we are using 
> these days, Kinetic, the tightening torque for mid and end clamps is 
> 12 ft-lb and here are some recommended clamping torques from some 
> different module mfgrs
> Conergy 8 NM - 6 ft-lb
> Hanwha 5 NM - 3.7 ft-lb
> JA Solar 18-24 NM - 13-18 ft-lb
> These likely vary based on the construction of the module frame.
> I've also found that some module mfgrs do not list recommended 
> tightening torques in their install manuals, so best to use discretion.
>
> We had a module break after clamping it down.  The crew described it 
> as 'putting the module in place, clamping it down and turning around 
> to grab the next module and hearing a 'crack' followed by the 
> crackling glass sound (if you have ever heard a module break, the 
> crackling sound can last for a few minutes).  The break pattern in the 
> glass seemed to focus on a particular mid clamp.  I used a torque 
> wrench, set at around 10 ft-lb and checked all the mid-clamp bolts, 
> increasing the torque setting by a few ft-lb each time until it 
> finally turned a bolt instead of clicking.  I found that most of the 
> bolts were close to 30 ft-lb and the one that appeared to break the 
> glass was about 34 ft-lb.
> Suffice to say, we were getting carried away with tightening using 
> cordless impact drivers.
> At that point i and the rest of the crew started using the torque 
> wrench as we were going along until we had a better feel for what was 
> the proper torque.  (i've done this before, but it is something that 
> needs to be self "re-calibrated" often.
>
>
> *Benn Kilburn *
> CSA Certified Solar Photovoltaic Systems Electrician, SkyFire Energy Inc
> 6706 – 82 Ave NW | Edmonton, AB | T6B 0E7
> P: 780-474-8992 | F: 888-405-5843 | www.skyfireenergy.com 
> 
> email  facebook 
>  twitter 
>  linkedin 
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>
> On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester 
> mailto:ch...@solarwindworks.com>> wrote:
>
> Hi Jason,
>
> Have you or others been using the new UniRac SM mid and end clamps
> with the integrated bonding yet? My concern is the “Stainless
> steel Midclamp points, 2 per module, pierce module frame
> anodization to bond module to module through clamp.”
>
> We had an MSI Alpha + self-bonding midclamp shatter the glass on
> an LG 280 last fall, as the factory set point was sticking out too
> far, so as it was being tightened down, on top of the module the
> point dug through the module’s top frame hitting the glass,
> shattering it.
>
> I do wonder if there are any issues with this “point” on the
> UniRac midclamps potential for doing the same damage?
>
> Chris Worcester
>
> Solar Wind Works
>
> NABCEP Certified PV Installer
>
> Office 530-582-4503 
>
> Cell 530-448-9692 
>
> Fax 530-582-4603 
>
> www.solarwindworks.com 
>
> ch...@solarwindworks.com 
>
> *From:*RE-wrenches
> [mailto:re-wrenches-boun...@lists.re-wrenches.org
> ] *On Behalf Of
> *Jason Szumlanski
> *Sent:* Thursday, June 25, 2015 1:13 PM
> *To:* RE-wrenches
> *Subject:* Re: [RE-wrenches] SnapNrack
>
> That decision was based on our di

Re: [RE-wrenches] SnapNrack

[Ray Walters]

Thanks Glenn.  I always get those wrong.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 6/28/2015 5:15 PM, Glenn Burt wrote:
I think you are referring to galling, not spalling which is a concrete 
and rock phenomenon.


Sincerely,
Glenn Burt
Sent from my 'smart' phone so please excuse grammar and typos.

From: Ray Walters 
Sent: ‎6/‎28/‎2015 17:27
To: RE-wrenches 
Subject: Re: [RE-wrenches] SnapNrack

Besides your note that cordless impact drivers can over torque the
clamps, also they spin the bolts too fast which can lead to spalling of
the SS hardware.
We now hand torque those connects.  Finally, most torque specs are for
lubricated bolts.  We use anti-seize on the threads before torquing.
Using a cordless impact driver and no lube can cause not only module
damage but also clamp damage, and end up with clamps not actually
securing the modules, because the bolts spalled out before fully clamping.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 6/28/2015 3:06 PM, Benn Kilburn wrote:
> Chris,
> It sounds (to me) that you are describing the bonding "tooth" dug
> through the aluminum frame and into the glass? or at least compressed
> the frame enough to break the glass?  If that is the case then i'm
> betting that the clamp bolt was way over-torqued.
>
> You need to check the recommended tightening torque for the module and
> for the racking system you are using.  For example, what we are using
> these days, Kinetic, the tightening torque for mid and end clamps is
> 12 ft-lb and here are some recommended clamping torques from some
> different module mfgrs
> Conergy 8 NM - 6 ft-lb
> Hanwha 5 NM - 3.7 ft-lb
> JA Solar 18-24 NM - 13-18 ft-lb
> These likely vary based on the construction of the module frame.
> I've also found that some module mfgrs do not list recommended
> tightening torques in their install manuals, so best to use discretion.
>
> We had a module break after clamping it down.  The crew described it
> as 'putting the module in place, clamping it down and turning around
> to grab the next module and hearing a 'crack' followed by the
> crackling glass sound (if you have ever heard a module break, the
> crackling sound can last for a few minutes).  The break pattern in the
> glass seemed to focus on a particular mid clamp.  I used a torque
> wrench, set at around 10 ft-lb and checked all the mid-clamp bolts,
> increasing the torque setting by a few ft-lb each time until it
> finally turned a bolt instead of clicking.  I found that most of the
> bolts were close to 30 ft-lb and the one that appeared to break the
> glass was about 34 ft-lb.
> Suffice to say, we were getting carried away with tightening using
> cordless impact drivers.
> At that point i and the rest of the crew started using the torque
> wrench as we were going along until we had a better feel for what was
> the proper torque.  (i've done this before, but it is something that
> needs to be self "re-calibrated" often.
>
>
> *Benn Kilburn *
> CSA Certified Solar Photovoltaic Systems Electrician, SkyFire Energy Inc
> 6706 – 82 Ave NW | Edmonton, AB | T6B 0E7
> P: 780-474-8992 | F: 888-405-5843 | www.skyfireenergy.com
> 
> email  facebook
>  twitter
>  linkedin
> 
 


> google 
>
> SkyFire Energy Logo_horizontal
>
>
> On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester
> mailto:ch...@solarwindworks.com>> wrote:
>
> Hi Jason,
>
> Have you or others been using the new UniRac SM mid and end clamps
> with the integrated bonding yet? My concern is the “Stainless
> steel Midclamp points, 2 per module, pierce module frame
> anodization to bond module to module through clamp.”
>
> We had an MSI Alpha + self-bonding midclamp shatter the glass on
> an LG 280 last fall, as the factory set point was sticking out too
> far, so as it was being tightened down, on top of the module the
> point dug through the module’s top frame hitting the glass,
> shattering it.
>
> I do wonder if there are any issues with this “point” on the
> UniRac midclamps potential for doing the same damage?
>
> Chris Worcester
>
> Solar Wind Works
>
> NABCEP Certified PV Installer
>
> Office 530-582-4503 
>
> Cell 530-448-9692 
>
> Fax 530-582-4603 
>
> www.solarwindworks.com 
>
> ch...@solarwindworks.com 
>
> *From:*RE-wrenches
> [mailto:re-wr

[RE-wrenches] Battery Combiner

[Mac Lewis]

Hi REwrenches,

Does anyone know where I can get a UL listed battery combiner good for
<1500A DC, 48V, preferably with a shunt?

Does this exist?

Thanks

-- 



Mac Lewis

*"Yo solo sé que no sé nada." -Sócrates*
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Re: [RE-wrenches] Battery Bank to Inverter Wiring

[b...@midnitesolar.com]

On 6/28/2015 9:20 AM, Allan Sindelar wrote:
I'm not an EE, but I can't see what difference twisting would make in
the absence of a building/collapsing field as is normal with AC.

It is little known that with the typical inverters that use the heavy 
power transformers,
have a lot of AC 120 Hz (or 100 Hz for 50 Hz systems) current mixed in 
with that DC battery current.


The AC output current reflects back to the input as ripple current.  
This is why you want to
have at least short as possible Sbattery cable runs AND keep the wires 
as close together as possible.


Twisting the battery cables may help a bit but that is probably overkill.

The problem has to do with inductance in the battery cables.  You can 
use as big of cable
as you can fit in to reduce resistance, but that will not help to lower 
the inductance.
The problems you can sometimes have with high inductance is that L-C 
resonance at the
inverter can raise the peak voltages seen at the inverter input 
terminals and can be hard on

the inverter.

Then again,  the high frequency, lighter weight inverters will typically 
keep most of that ripple
inside,  between the DC input and AC output and battery cable inductance 
will not be as much

of a problem on the battery cables.

boB Gudgel




On 6/28/2015 9:20 AM, Allan Sindelar wrote:
As a matter of course I have always run the positive and negative 
conductors of high-current cable pairs together, but have never 
deliberately twisted them, and have never known of any related problems.
The most obvious example of this would be 4/0 battery/inverter cables 
in a 24V system, with a 250A GJ-class breaker or (prior to that) a 
300A or 400A Class T fuse. It's pretty tough to thread a twisted pair 
of 4/0 USE/RHH/RHW cables through a 2" elbow or LB from inverter 
enclosure to battery enclosure.
I'm not an EE, but I can't see what difference twisting would make in 
the absence of a building/collapsing field as is normal with AC.
I have twisted AC conductors together in the past when clients have 
expressed concerns about EMF from their equipment and wiring, but only AC.

Allan

*Allan Sindelar*
al...@sindelarsolar.com 
NABCEP Certified PV Installation Professional
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder (Retired), Positive Energy, Inc.
*505 780-2738 cell*

**

On 6/27/2015 2:40 AM, John wrote:


That is why for years we have been twisting those leads around each 
other.  I was told it was to cancel out the opposing fields on the 
wires, but for whatever the correct technical reason is,  we have 
always twisted those heavy wires. John V.


*From:*RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] 
*On Behalf Of *jarmo.venalai...@schneider-electric.com

*Sent:* Saturday, 27 June 2015 5:45 a.m.
*To:* RE-wrenches
*Subject:* [RE-wrenches] Battery Bank to Inverter Wiring

Hi:

From time to time over the years I've come across systems where the 
routing of DC cables between the batteries and the inverter has been 
the cause of  issues.


I'm not referring to wire thickness or quality of terminations.  For 
the purposes of this discussion, just assume that wire thickness and 
terminations are perfect.


What I am referring to is the routing of the positive and negative 
battery cables.  In particular, the loop area within the + and - 
cables as shown in the image below,


The problem I've seen in systems with a large loop in the setup is 
that the inverter does not provide good surge power and can even go 
into low voltage shutdown during large surges.


Recently this happened again and I wanted to get a better feel for 
it, so I did some math.


For a cable length of about 12', the loop is an inductor which has a 
value of inductance of about 1 uH for side by side cables and as much 
as 6 uH for cables about 1 foot apart.


This inductance is greatly multiplied by any ferrous metal in the 
loop and can easily be in the range of 10's to 100's of uH.  Examples 
being cables which run in steel conduits or along the steel frame of 
a motor home.


Inductance causes a voltage drop proportional to the rate at which 
the current is changing.  To get an idea of how large that rate can 
be for typical inverters, I did surge tests with a 5kW inverter and 
found that the rate of change of current can be as high as 100A per 
milli-second or 100,000 Amps/second.


Given that, the voltage drop of the wire inductance is then , Vdrop = 
(rate of change of current) x (inductance),


Vdrop for 1 uH = (100,000 A/s) x (0.01 H) = 0.1V
Vdrop for 10 uH = (100,000 A/s) x (0.01 H) = 1.0V
Vdrop for 100 uH = (100,000 A/s) x (0.01 H) = 10.0V  clearly this 
is a problem.


Have any of the wrenches had systems with this issue?  If so, how often.


JARMO




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