Re: [RE-wrenches] 3 Phase With 2 Inverters?
Bill Brooks posted this in 2008. A couple of project-specific sentences were removed to avoid confusion. "The 6kVA value comes from the California Rule 21 that I worked on. It only applies to split-phase 240V systems (6kVA on 120V). There is no specific limit for imbalance on a 3-phase service. A basic rule for single phase generation on a 3=phase service is to rotate among the phases in a balanced manner... ...The best way to place the imbalanced single-phase generators on the service is to test the current on all three phases and put the inverter(s) on the most heavily loaded phase(s). This reduces the site imbalance by reducing the imbalance on the serving transformer (lowering current on the most heavily loaded phases). It is common for 3-phase services to have imbalances of 10 kVA or more, so single-phase inverters can reduce the problem rather than make it worse." For a brighter energy future, Andrew Truitt NABCEP Certified PV Installer™ (ID# 032407-66) Principal Truitt Renewable Energy Consulting (202) 486-7507 http://www.linkedin.com/pub/andrew-truitt/8/622/713 "Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless!" ~William McDonough On Tue, Nov 27, 2012 at 3:33 PM, Chris Mason wrote: > I really don't understand what your problem with this arrangement is. > How would this be different from a house on phase A-B installing an > inverter and the next house on Phase B-C installing an inverter? Or, > installing two single phase 240V A/C units in a three phase building? > Electricians have no issue with installing single phase equipment in three > phase buildings so why should small inverters be any more a problem. > While it is always neat to install three inverters n a three phase > configuration, 4,500 watts of imbalance is trivial. > > > On Tue, Nov 27, 2012 at 3:59 PM, wrote: > >> ** >> We were asked to inspect a GT system installed by others. Service is 208 >> 3ph with two (?) Fronius IG 4500 208v inverters. The inverter panel is 3ph >> with two 2pole breakers - one each side of the buss bar in a A/B, B/C >> configuration (??). Called Fronius and they said it would work, but they >> "don't recommend it". No other information was given as to why they don't. >> My electrician is very uncomfortable with doing work on this system as is >> (ME TOO!), so I am wondering if I might be able get some ammo to convince >> system owner to add a third inverter to get the system right. What problems >> might/will be encountered in this system if not modified? BTW - inverter >> LCD screens were crapped out, so we couldn't readily see if system was >> functioning properlyfrom metering, we think not. >> >> >> Holt E. Kelly >> Holtek Fireplace & Solar Products >> 500 Jewell Dr. >> Waco TX. 76712 >> 254-751-9111 >> www.holteksolar.com >> >> ___ >> List sponsored by Home Power magazine >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >> Options & settings: >> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org >> >> List-Archive: >> http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org >> >> List rules & etiquette: >> www.re-wrenches.org/etiquette.htm >> >> Check out participant bios: >> www.members.re-wrenches.org >> >> >> > > > -- > Chris Mason > President, Comet Systems Ltd > www.cometenergysystems.com > Cell: 264.235.5670 > Skype: netconcepts > > > ___ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > > ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] 3 Phase With 2 Inverters?
I really don't understand what your problem with this arrangement is. How would this be different from a house on phase A-B installing an inverter and the next house on Phase B-C installing an inverter? Or, installing two single phase 240V A/C units in a three phase building? Electricians have no issue with installing single phase equipment in three phase buildings so why should small inverters be any more a problem. While it is always neat to install three inverters n a three phase configuration, 4,500 watts of imbalance is trivial. On Tue, Nov 27, 2012 at 3:59 PM, wrote: > ** > We were asked to inspect a GT system installed by others. Service is 208 > 3ph with two (?) Fronius IG 4500 208v inverters. The inverter panel is 3ph > with two 2pole breakers - one each side of the buss bar in a A/B, B/C > configuration (??). Called Fronius and they said it would work, but they > "don't recommend it". No other information was given as to why they don't. > My electrician is very uncomfortable with doing work on this system as is > (ME TOO!), so I am wondering if I might be able get some ammo to convince > system owner to add a third inverter to get the system right. What problems > might/will be encountered in this system if not modified? BTW - inverter > LCD screens were crapped out, so we couldn't readily see if system was > functioning properlyfrom metering, we think not. > > > Holt E. Kelly > Holtek Fireplace & Solar Products > 500 Jewell Dr. > Waco TX. 76712 > 254-751-9111 > www.holteksolar.com > > ___ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > > -- Chris Mason President, Comet Systems Ltd www.cometenergysystems.com Cell: 264.235.5670 Skype: netconcepts ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] 3 Phase With 2 Inverters?
I would agree that the imbalance at these power levels is not a major issue. If it appears that Phase A is most heavily-loaded, I'd install the inverters as A-B and A-C to help mitigate the existing imbalance. If you've got a lot of 1P loads on a 3P service-- lighting, office receptacles or whatever-- you could easily have a large imbalance on a regular basis. The 7kVA PV imbalance in your installation would happen extremely rarely. If this imbalance still makes you uneasy, then install three inverters and then a relay system to bring all the inverters down in case any of them fails. The SMA Power Balancer does this for their inverters and maybe some third-parties offer them too for these Fronius installs. This seems to make the most sense for decentralized systems with many string inverters, to ensure that a low phase voltage doesn't turn off a fraction of your inverters and cause a >100kVA imbalance. I've heard that some utilities have a max PV imbalance (calculated from the inverter ratings) of 6kVA. No utility to my knowledge requires an interconnection agreement for a 10kVA single-phase commercial water heater (to steal a Bill Brooks example) that would have a much stronger impact. Dave On 2012/11/27 15:14, penobscotso...@midmaine.com wrote: Hi Holt, We installed a commercial system a year ago for the National Park Service that was designed by a competitor (?) and signed off on by an engineer. It consisted of 13.2 kw of pv and two Fronius 7000 watt, 208 3 ph. inverters. It sounds a lot like what you are dealing with. I questioned the engineer on it and he said because the facility was so large (it was a large research and visitor "campus" for Acadia National Park with 20+ buildings)the transformer would never see the imbalance and therefore was not a problem. Fronius agreed, but prefaced that with the fact that it still was "not recommended". I can say that we have had no issues or complaints at all since the installation in August of 2011 and they monitor it continuously. It would have been a far better design to use three Fronius 4.5 inverters at 3 ph. I drafted a letter (CYA letter) to the powers that be about my concerns (transformer imbalance) and they chose to go ahead with the installation. Nothing like government work...many more stories about this installation than anyone has time for here. Daryl DeJoy NABCEP Certified PV installer Penobscot Solar Design We were asked to inspect a GT system installed by others. Service is 208 3ph with two (?) Fronius IG 4500 208v inverters. The inverter panel is 3ph with two 2pole breakers - one each side of the buss bar in a A/B, B/C configuration (??). Called Fronius and they said it would work, but they "don't recommend it". No other information was given as to why they don't. My electrician is very uncomfortable with doing work on this system as is (ME TOO!), so I am wondering if I might be able get some ammo to convince system owner to add a third inverter to get the system right. What problems might/will be encountered in this system if not modified? BTW - inverter LCD screens were crapped out, so we couldn't readily see if system was functioning properlyfrom metering, we think not. Holt E. Kelly Holtek Fireplace & Solar Products 500 Jewell Dr. Waco TX. 76712 254-751-9111 www.holteksolar.com ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] 3 Phase With 2 Inverters?
Hi holt, Just FYI, Fronius will pay you $250 each to swap the inverters. Larry Crutcher Starlight Solar Power Systems On Nov 27, 2012, at 12:59 PM, wrote: We were asked to inspect a GT system installed by others. Service is 208 3ph with two (?) Fronius IG 4500 208v inverters. The inverter panel is 3ph with two 2pole breakers - one each side of the buss bar in a A/B, B/C configuration (??). Called Fronius and they said it would work, but they "don't recommend it". No other information was given as to why they don't. My electrician is very uncomfortable with doing work on this system as is (ME TOO!), so I am wondering if I might be able get some ammo to convince system owner to add a third inverter to get the system right. What problems might/will be encountered in this system if not modified? BTW - inverter LCD screens were crapped out, so we couldn't readily see if system was functioning properlyfrom metering, we think not. Holt E. Kelly Holtek Fireplace & Solar Products 500 Jewell Dr. Waco TX. 76712 254-751-9111 www.holteksolar.com ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
Re: [RE-wrenches] 3 Phase With 2 Inverters?
Hi Holt, We installed a commercial system a year ago for the National Park Service that was designed by a competitor (?) and signed off on by an engineer. It consisted of 13.2 kw of pv and two Fronius 7000 watt, 208 3 ph. inverters. It sounds a lot like what you are dealing with. I questioned the engineer on it and he said because the facility was so large (it was a large research and visitor "campus" for Acadia National Park with 20+ buildings)the transformer would never see the imbalance and therefore was not a problem. Fronius agreed, but prefaced that with the fact that it still was "not recommended". I can say that we have had no issues or complaints at all since the installation in August of 2011 and they monitor it continuously. It would have been a far better design to use three Fronius 4.5 inverters at 3 ph. I drafted a letter (CYA letter) to the powers that be about my concerns (transformer imbalance) and they chose to go ahead with the installation. Nothing like government work...many more stories about this installation than anyone has time for here. Daryl DeJoy NABCEP Certified PV installer Penobscot Solar Design > We were asked to inspect a GT system installed by others. Service is 208 > 3ph with two (?) Fronius IG 4500 208v inverters. The inverter panel is 3ph > with two 2pole breakers - one each side of the buss bar in a A/B, B/C > configuration (??). Called Fronius and they said it would work, but they > "don't recommend it". No other information was given as to why they don't. > My electrician is very uncomfortable with doing work on this system as is > (ME TOO!), so I am wondering if I might be able get some ammo to convince > system owner to add a third inverter to get the system right. What > problems might/will be encountered in this system if not modified? BTW - > inverter LCD screens were crapped out, so we couldn't readily see if > system was functioning properlyfrom metering, we think not. > > > Holt E. Kelly > Holtek Fireplace & Solar Products > 500 Jewell Dr. > Waco TX. 76712 > 254-751-9111 > www.holteksolar.com > ___ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org List rules & etiquette: www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
