boB covered the main points perfectly. Manufacturers of UL-certified products are subject to unannounced spot-checks several times a year by the issuing NTRL to verify the products coming off the production line are absolutely identical to the products submitted for UL testing. Any major deviation in the production units from lab-tested units can result in immediate de-certification and possible recall of any affected product(s). "Major" in this case could be different software, mechanical changes, or a substitution of any components that affect safety or unit operation in any manner with unauthorized components .. for openers.
By the way .. for anyone who's not met boB in person .. I had the good fortune to do so at the Midwest Renewable Energy Fair in Wisconsin this past June. Great guy. Dan --- On Tue, 10/19/10, boB Gudgel <[email protected]> wrote: From: boB Gudgel <[email protected]> Subject: Re: [RE-wrenches] Inverter 1741 Listing Process To: [email protected], "RE-wrenches" <[email protected]> Date: Tuesday, October 19, 2010, 12:42 AM On 10/18/2010 9:53 PM, Matt Lafferty wrote: Thanks for the info Dan and boB. What production tests required to maintain listing? Do you happen to know if there is a different regimen for micro vs string vs central inverters? You mean, a difference between the two when UL, ETL, CSA comes by for their pop inspection ?? Off hand, I don't see why one inverter would be given any different kind of attention than the other type. The UL/ETL followup inspections are basically to make sure you are following the proper manufacturing and testing processes such as, software version, verification that you are using UL recognized sources of parts and materials, hi-potting at the correct voltages, etc. They are both grid-tie inverters so the testing processes are very similar. I'm sure that Dan will pick up on anything important that I forgot. boB I'm working on developing a detailed commissioning procedure. Detailed yet generic. There will be at least two versions for inverters. One for string and one for central. In my book, central inverters have re-combiners (standalone or integral) and string inverters don't. I'm trying to understand which functions are tested in the factory on every unit so I can avoid unnecessary duplication by the commissioning people. Thanks in advance for any light you can shed on the subject! Matt Lafferty From: [email protected] [mailto:[email protected]] On Behalf Of Exeltech Sent: Monday, October 11, 2010 10:04 AM To: RE-wrenches Subject: Re: [RE-wrenches] Inverter 1741 Listing Process Matt, The 5-minute delay is verified in the group of inverters sent to the test laboratory. Then, as long as the software and hardware don't change, it's presumed the delay in all production units meets the value(s) measured in the tested units. An alteration in either hardware OR software can result in a unit being required to completely re-test (as Bob pointed out). NRTLs get copies of the source code and can and do periodically compare their copy as submitted with the original test units to the software being programmed into the inverters during production to verify it's the same. NRTLs conduct unannounced "field audits" by simply showing up on site and randomly selecting various aspects of the product for verification -- including the software. The overall UL1741 certification process is extremely complex, very time consuming, and quite expensive. Dan --- On Fri, 10/8/10, boB Gudgel <[email protected]> wrote: From: boB Gudgel <[email protected]> Subject: Re: [RE-wrenches] Inverter 1741 Listing Process To: [email protected], "RE-wrenches" <[email protected]> Date: Friday, October 8, 2010, 9:26 PM On 10/8/2010 6:04 PM, Matt Lafferty wrote: Hola Wrenches, Does anybody know off the top of their head if the "5-minute-wait-to-interconnect" function is tested on 100% of inverters produced? (i.e. every single inverter is tested with AC & DC within the start parameters of the unit for at least 5 minutes) Thanks! Matt Lafferty Good question. I bet it's not 100% tested because if the software does not change, then they may just not wait the extra 5 minutes in order to save money on testing. Or, maybe they do a random sampling for this test. Theoretically, it shouldn't matter as long as the software does not change and the hardware is tested enough in other ways, like, timers and clocks etc. BTW, Nowadays, there are two options for manufacturers of grid interactive inverters.... And the UL spec has gotten more stringent. One option is that you have to have the code (software) blessed by the NRTL in a separate process (another UL specification, (UL 1998 –Software in Programmable Components") OR, if they don't go for that option, then if software changes need to be done to the inverter, the inverter must (technically) go through the UL1741 listing process all over again. boB -----Inline Attachment Follows----- _______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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: [email protected] 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
