Re: [RE-wrenches] offgrid system question
Hi Travis, thanks for the great insite, this helps a lot. So the higher the SEER number the more efficient the unit is. thanks, jay On Aug 22, 2008, at 7:40 AM, Travis Creswell wrote: 1 ton = 12,000 BTU's SEER = how many BTU's per kW (Since you asked about rough electrical load for this equation we're going to ignore the complexities for EER vs. SEER, COP at varying outdoor temps and so on. We'll leave that for someone else to discuss if they desire) Plus you'll want to add approximately 150 watts per ton for the air handler Assuming a 13 SEER AC unit the math is; 2.5 tons x 12,000 BTU's = 30,000 BTU's 30,000 BTU's/13 SEER= 2.3 kW 2.5 tons x 150 watts/ton for air handling = 375 watts For a total running kW of ~2.7. That's how I do it. Doesn't mean it's the right or only way. Best, Travis Creswell Ozark Energy Services -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of jay peltz Sent: Friday, August 22, 2008 9:23 AM To: RE-wrenches Subject: Re: [RE-wrenches] offgrid system question Can someone tell me how to convert AC tons to rough electrical load? or is there a way? I've got a customer who is wanting to install a AC unit and they tell me its a 2.5 ton and uses 9000 watts. ( they haven't given me make or model yet) thanks, jay ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 incoming message. Checked by AVG. Version: 7.5.526 / Virus Database: 270.6.6/1627 - Release Date: 8/22/2008 6:48 AM No virus found in this outgoing message. Checked by AVG. Version: 7.5.526 / Virus Database: 270.6.6/1627 - Release Date: 8/22/2008 6:48 AM ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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
Re: [RE-wrenches] offgrid system question
There are two figures of merit that can be used to make the conversion. The simplist is EER. First, how many tons the AC is rated at? Multiply that number by 12,000 BTU/hr per ton, to get the number of BTU/hr the AC system can pump out of the house. Second, EER is the ration of the BTU/hr to electrical power the AC consumes. Divide the BTU/hr by EER and you get the power consumption. There is a second figure of merit called SEER, it is similar to EER but takes a seasonal average. All ACs have a SEER rating. Example: 3 ton AC rated at a SEER of 10. 3 ton equals 36,000 BTU/hr and consumes 3.6 kW (15 A at 240 VAC). If you run the AC for four hours a day, the energy consumed is14.4 kWh. - Peter 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] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of jay peltz Sent: Friday, August 22, 2008 7:23 AM To: RE-wrenches Subject: Re: [RE-wrenches] offgrid system question Can someone tell me how to convert AC tons to rough electrical load? or is there a way? I've got a customer who is wanting to install a AC unit and they tell me its a 2.5 ton and uses 9000 watts. ( they haven't given me make or model yet) thanks, jay ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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
Re: [RE-wrenches] offgrid system question
Darryl, see my post yesterday (I think). If you have the tonnage and the SEER/EER you know the operating current, period. As for start up transient, I think we need to get help from someone who has actually measured the transient (I think I saw a post about that a couple of days ago?). And, when comparing the surge current with an inverter capacity, make sure you get the compliance voltage. An inverter that is rated at 25 A steady state, but claims to provide 40A for 4 sec, will do you no good if the voltage drops to 150 VAC while providing the 40A! - Peter Peter T. Parrish [EMAIL PROTECTED] -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Darryl Thayer Sent: Friday, August 22, 2008 2:30 PM To: RE-wrenches Subject: Re: [RE-wrenches] offgrid system question I use for a short cut 1 AC ton is 1 HP mechanical or 1kW electrical. So If I have a 3 ton heat pump I figure the compressor is about a 1 horse power motor and about 1 kW running load. If that is 240 volts that is about 4 0r 5 amps. Because I have had some starting problems, I say that the running amps times 10 are the start amps, so this unit should have inverter capable of starting 40 amps Surge.If the SEER is higher than 12 it will start comiing down, but I do not know for inverter sizing If you are doing and energy anaylsis you would want better numbers from your AC manufacturer. The 9000 watts for 2.5 tons is to high. Darryl --- On Fri, 8/22/08, jay peltz [EMAIL PROTECTED] wrote: From: jay peltz [EMAIL PROTECTED] Subject: Re: [RE-wrenches] offgrid system question To: RE-wrenches re-wrenches@lists.re-wrenches.org Date: Friday, August 22, 2008, 9:23 AM Can someone tell me how to convert AC tons to rough electrical load? or is there a way? I've got a customer who is wanting to install a AC unit and they tell me its a 2.5 ton and uses 9000 watts. ( they haven't given me make or model yet) thanks, jay ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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
Re: [RE-wrenches] offgrid system question
You're right Mick, It is an XW 6048, there's only one and I really think I'm going to find that the biggest problem is that there is not enough inverter capacity capacity with just one unit (the scematic shows a 60 amp breaker on the output). The system is new ( installed within the last 4 months and the batteries were new) The AC unit is 240 volt. Max Balchowsky SEE Systems mick abraham [EMAIL PROTECTED] wrote: Max wrote about the problem child system which is tripping off when the AC unit tries to start. Mick says: you didn't mention what brand of inverter is on board the system, but in any case there's probably an error code that you can find to explain the shutdown. The error could be due to the low voltage disconnnect point being reached on the battery, or it could be due to excessive AC amperage demand from the air conditioner...the latter case seems quite likely because of the 3.5 ton thing, but even if you address that part of the problem there still may be nuisance shutdown problems if there are battery health issues going on. You mentioned MPPT60-150 as the charge controller. From that, I assume Xantrex XW...and one might assume the inverter is from that same product line. They build two 48 volt units...I'll bet if there's an XW inverter in the system that it's probably model 6048...6 kW continuous with a 12 kW surge. Please confirm. I have a client who tried running (two different) 5 ton air conditioners using XW 6048 based gear. He didn't even try with a single but he found that inverter doubles succeeded with one of his refrigerated air systems and not with the other one. The difference was due to a different SEER rating. He added a third inverter/charger and now has plenty of cranking power for either air conditioner. My big concern now is the grinding effect that such an intense load has on his battery bank, but I digress...if there's XW gear involved in your problem child system, throw another inverter at the load but watch the battery for signs of puckering. If you do stack a second XW machine, there is some setup involved in naming the two units and in setting one up as the slave. Mick Abraham, Proprietor www.abrahamsolar.com Voice: 970-731-4675 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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
Re: [RE-wrenches] offgrid system question
Hi Max AC surge I would never put that large an AC on that small a system. The inverter surge must be considered, and the 104 amps surge from the AC does sound real. I think you are correct, the soft Start is no more than an extra capascitor. (I approximate the AC at 1kW/ton so the running load about 3.5 kVA (12 to 15 amps) The surge varies on each start, but expect 10x running current, expect up to 120-150 amps. DC surge Different batteries handle surge Differently. Some have a much better surge capability. The battery voltage will dip upon surge, and some batteries dip much further than others. As a battery system ages its surge capability drops. The amount of cycling and strength of surge determines the life and surge capability. A 120 amp 240 volt AC surge is about a 650 amps! and the battery must hold about 44 volts. Sorry for such a long post, and just to end, I think the batteries need to be looked at, use a peak hold meters to get voltage min, and current maximum. Darryl --- On Mon, 8/18/08, Max Balchowsky [EMAIL PROTECTED] wrote: From: Max Balchowsky [EMAIL PROTECTED] Subject: Re: [RE-wrenches] offgrid system question To: RE-wrenches re-wrenches@lists.re-wrenches.org Date: Monday, August 18, 2008, 3:00 PM Dear wrenches, going to look at a system installed by others and would like some input from some of you with more off grid experience than I have ( 4 systems over the years). the system was put on a new home - off grid 20 sharp ND123UJF panels 4 modules in series - 5 parrallel strings, 2460 total array dc voltage. mppt 60-150 charge controller, 12 sun extender sealed AGM batteries, 305 AH at 12 vdc, wired for 915 AH at 48 volt DC. The system is tripping off when the AC unit trys to start - AC is comfortmaker 3.5 ton 13 seer. They say start up inrush is 104 amps (sounds high to me) and they put a DST 10 soft start on the unit (I think that's just a big capacitor). I haven't been on site yet but it sounds to me that they just didn't design enough inverter capacity into the system.. What are your thoughts? Max Balchowsky SEE Systems ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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
Re: [RE-wrenches] offgrid system question
Max, Let us know if the AC unit is 120 or 240Vac, what inverter/s are used, and how they are stacked. Mario Monesterio Best Power Intl. - Original Message - From: Max Balchowsky To: RE-wrenches Sent: Monday, August 18, 2008 3:00 PM Subject: Re: [RE-wrenches] offgrid system question Dear wrenches, going to look at a system installed by others and would like some input from some of you with more off grid experience than I have ( 4 systems over the years). the system was put on a new home - off grid 20 sharp ND123UJF panels 4 modules in series - 5 parrallel strings, 2460 total array dc voltage. mppt 60-150 charge controller, 12 sun extender sealed AGM batteries, 305 AH at 12 vdc, wired for 915 AH at 48 volt DC. The system is tripping off when the AC unit trys to start - AC is comfortmaker 3.5 ton 13 seer. They say start up inrush is 104 amps (sounds high to me) and they put a DST 10 soft start on the unit (I think that's just a big capacitor). I haven't been on site yet but it sounds to me that they just didn't design enough inverter capacity into the system.. What are your thoughts? Max Balchowsky SEE Systems -- ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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 ___ List sponsored by Home Power magazine RE-wrenches@lists.re-wrenches.org 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
