I don't think either one of us is "striding away from this issue". As Jeff pointed out, and I haven't seen included very much in this discussion, it is about far more than surge loads and surge responses, it is about time of operation. I don't care if it is a toaster or a whole-house AC or a window unit the most important aspect, after determining if the inverter can even handle the load, is how much time said unit will operate and if the system is designed to even manage a unit (toaster or AC) for the normal operating time without seriously degrading battery life and health.
Starting surges and instantaneous loads are important considerations but operating hours are equally important for good system design. I remember years ago Richard Perez describing the AC unit they installed in the Home Power offices and how important it was to know not only load but how long the unit would operate in relation to system sizing. And yes, I still think an AC of that size on a system of that size is nutty from a practicality standpoint unless they want their generator to run most of the time. Well reasoned guidance is absolutely important, as you point out, but the comments made were made about what was not being discussed in this particular case, and I still believe Jeff is right to point that out. T. ----- Original Message ----- From: Peter Parrish To: 'RE-wrenches' Sent: Wednesday, August 20, 2008 3:21 PM Subject: Re: [RE-wrenches] offgrid system question As the two of you stride away from this issue with self-congratulatory back slaps and dismissive comments about nutty clients, you might also find time to arm yourself with a modicum of facts about current surges in motors and surge response of inverters. A 3.5 ton A/C may be excessive, but is a 3/4 ton A/C, too? What about a swamp cooler, a whole house fan or a 1 hp water pump? Each client (in my book) deserves well reasoned guidance based on facts (regardless of how clients we need to provide it to). BTW, I agree 100% that we need to preach energy efficiency and heating with gas vs. electricity. - Peter Parrish Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 CA Lic. 854779, NABCEP Cert. 031806-26 [EMAIL PROTECTED] ------------------------------------------------------------------------------ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Elliot Sent: Wednesday, August 20, 2008 2:57 PM To: RE-wrenches Subject: Re: [RE-wrenches] offgrid system question Thank you Jeff, for asking the obvious. I've been agog that no one seemed to think this was a nutty situation for an off-grid home. T. ----- Original Message ----- From: Jeff Yago To: RE-wrenches Sent: Wednesday, August 20, 2008 10:57 AM Subject: Re: [RE-wrenches] offgrid system question I may be out of line here, but most of these comments have been related to making the right program settings and startup surge current issues. I did not read any comments that this client is nuts to try and run a 3.5 ton air conditioner from a solar off-grid system, let alone a system with such a very small capacity. I would be surprised if this small existing solar array and batteries can keep up with the regular loads like lights, kitchen appliances, refrigerators, and entertainment equipment, let alone also running a central air conditioner. . I would not just debate the problems of surge current, I would like to know how this little solar system is going to keep up with the constant load of approx. 4,000 watts for the AC unit plus another 500 watts for the air handling unit which he did not mention. With a constant drain of 4,500 watts, just how long do you think this battery bank will last? For most locations, during peak summer days a typical AC unit needs to run constantly 12 to 16 hours per day. I would be interested in hearing from others on this, but here in the humid and hot east it is not possible to provide air conditioning for an off-grid home unless we are just cooling one or two rooms with a low energy Sanyo type split system in the 1/2 to 3/4 ton range. Of course if you have enough solar modules and batteries you could run anything, but can you afford it? We do lots of off-grid systems and the first thing we tell clients is to not even think about having air conditioning, electric hot water heaters, or electric clothes dryers unless they have a really big bag of money. Jeff Yago ---------------------------------------------------------------------------- Netscape. Just the Net You Need. No virus found in this incoming message.Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.6.6/1624 - Release Date: 8/20/2008 7:11 PM ---------------------------------------------------------------------------- _______________________________________________ List sponsored by Home Power magazine [email protected] http://lists.re-wrenches.org/listinfo.cgi/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org No virus found in this outgoing message.Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.6.6/1624 - Release Date: 8/20/2008 7:11 PMNo virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.6.6/1624 - Release Date: 8/20/2008 7:11 PM ------------------------------------------------------------------------------ _______________________________________________ List sponsored by Home Power magazine [email protected] http://lists.re-wrenches.org/listinfo.cgi/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org No virus found in this outgoing message. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.6.6/1624 - Release Date: 8/20/2008 7:11 PM
_______________________________________________ List sponsored by Home Power magazine [email protected] http://lists.re-wrenches.org/listinfo.cgi/re-wrenches-re-wrenches.org List rules & etiquette: http://www.re-wrenches.org/etiquette.htm Check out participant bios: www.members.re-wrenches.org
