[RE-wrenches] central vrs string inverters
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 amfr...@aeonsolar.com 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 tel:%28917%29%20699-6641 - cell (888) 460-2867 tel:%2%29%20460-2867 www.aeonsolar.com http://www.aeonsolar.com/ ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] SnapNrack
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 aug...@luminalt.com 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 d...@ecotechenergy.com 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 ja...@fafcosolar.com 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 m...@seesolar.com 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 amfr...@aeonsolar.com *To:* RE-wrenches re-wrenches@lists.re-wrenches.org *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 http://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 nt...@1scom.net *To:* 'RE-wrenches' re-wrenches@lists.re-wrenches.org *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 Subject: [RE-wrenches]
Re: [RE-wrenches] Battery Bank to Inverter Wiring
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 |
Re: [RE-wrenches] SnapNrack
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] b...@skyfireenergy.com [image: facebook] https://www.facebook.com/SkyFireEnergy [image: twitter] https://twitter.com/SkyFireEnergy [image: linkedin] https://www.linkedin.com/company/283735?trk=tyahtrkInfo=tarId%3A1408655033432%2Ctas%3Askyfire%2Cidx%3A2-2-5 [image: google] https://plus.google.com/+SkyFireEnergy/ [image: SkyFire Energy Logo_horizontal] On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester 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 d...@ecotechenergy.com 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 ja...@fafcosolar.com 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
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 http://www.skyfireenergy.com/ email mailto:b...@skyfireenergy.com facebook https://www.facebook.com/SkyFireEnergy twitter https://twitter.com/SkyFireEnergy linkedin https://www.linkedin.com/company/283735?trk=tyahtrkInfo=tarId%3A1408655033432%2Ctas%3Askyfire%2Cidx%3A2-2-5 google https://plus.google.com/+SkyFireEnergy/ SkyFire Energy Logo_horizontal On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester ch...@solarwindworks.com 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 tel:530-582-4503 Cell 530-448-9692 tel:530-448-9692 Fax 530-582-4603 tel:530-582-4603 www.solarwindworks.com http://www.solarwindworks.com ch...@solarwindworks.com mailto:ch...@solarwindworks.com *From:*RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org 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 d...@ecotechenergy.com mailto:d...@ecotechenergy.com wrote: Hi Jason,
Re: [RE-wrenches] SnapNrack
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 r...@solarray.com Sent: 6/28/2015 17:27 To: RE-wrenches re-wrenches@lists.re-wrenches.org 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 http://www.skyfireenergy.com/ email mailto:b...@skyfireenergy.com facebook https://www.facebook.com/SkyFireEnergy twitter https://twitter.com/SkyFireEnergy linkedin https://www.linkedin.com/company/283735?trk=tyahtrkInfo=tarId%3A1408655033432%2Ctas%3Askyfire%2Cidx%3A2-2-5 google https://plus.google.com/+SkyFireEnergy/ SkyFire Energy Logo_horizontal On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester ch...@solarwindworks.com 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 tel:530-582-4503 Cell 530-448-9692 tel:530-448-9692 Fax 530-582-4603 tel:530-582-4603 www.solarwindworks.com http://www.solarwindworks.com ch...@solarwindworks.com mailto:ch...@solarwindworks.com *From:*RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org 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
Re: [RE-wrenches] SnapNrack
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 mailto:r...@solarray.com Sent: 6/28/2015 17:27 To: RE-wrenches mailto:re-wrenches@lists.re-wrenches.org 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 http://www.skyfireenergy.com/ email mailto:b...@skyfireenergy.com facebook https://www.facebook.com/SkyFireEnergy twitter https://twitter.com/SkyFireEnergy linkedin https://www.linkedin.com/company/283735?trk=tyahtrkInfo=tarId%3A1408655033432%2Ctas%3Askyfire%2Cidx%3A2-2-5 google https://plus.google.com/+SkyFireEnergy/ SkyFire Energy Logo_horizontal On Thu, Jun 25, 2015 at 5:11 PM, Chris Worcester ch...@solarwindworks.com 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 tel:530-582-4503 Cell 530-448-9692 tel:530-448-9692 Fax 530-582-4603 tel:530-582-4603 www.solarwindworks.com http://www.solarwindworks.com ch...@solarwindworks.com mailto:ch...@solarwindworks.com *From:*RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org
Re: [RE-wrenches] Battery Bank to Inverter Wiring
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 mailto: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 ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address
[RE-wrenches] Battery Combiner
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* ___ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/maillist.html List rules etiquette: www.re-wrenches.org/etiquette.htm Check out or update participant bios: www.members.re-wrenches.org
