Ken Hall's posts

Posted by Ken Hall on Oct 5, 2008 11:45 am

#151 -  Renewable Energy > Technical Discussion: Other > Re: grounding a small DC/AC system?
Todd
Is there any other ac source in your building, or is the only ac from your inverter ?
 

Posted by Ken Hall on Oct 2, 2008 06:55 pm

#152 -  Renewable Energy > Technical Discussion: Other > Re: Need a little help
James:
Here is the UL listing for snap switches.
http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/showpage.html?name=WJQR.GuideInfo&ccnshorttitle=Snap+Switches&objid=1074128100&cfgid=1073741824&version=versionless&parent_id=1073995251&sequence=1
The 7th paragraph is
"General-use snap switches are classified into two categories: AC-DC general use and AC general use. AC general-use switches are marked "AC" to limit their use to alternating-current circuits. AC-DC general-use switches are not so limited; no such marking is required or generally provided."

The "AC" marking I am familiar with is "AC Only", It is in addition to the primary ac ratings.

It is not uncommon for the ac/dc devices to list only the primary ac ratings. The DC rating may not appear due to space. You may have to read the spec sheet, or other Mfg info to find the DC rating. Occasionally, you have to ask the mfg, directly.

Assuming
a)your switch is a snap switch
b)you listed all of the markings in the earlier posting

The absence of the seperate "AC only" (or equivelent) would lead me to believe that it is probably an ac/dc switch.
Hope this helps,
Ken


 

Posted by Ken Hall on Oct 2, 2008 05:36 pm

#153 -  Renewable Energy > Technical Discussion: Other > Re: Need a little help
When it comes to NEC, it is far easier to say what you can't do, rather than what you can. Each planning agency, inspection department, and even individual inspector, may have a slightly different interpretation of what the code says. 
In this specific case (a lighting wall switch), the code calls for an ac/dc general purpose snap switch. Under "strict interpretation", would preclude a DC only switch. It definitely forbids the use of an "AC only" switch.
AltE has a switch here:
http://store.altenergystore.com/Enclosures-Electrical-and-Safety/Miscellaneous-Electrical-Parts/Switches/DC-Switches/DC-Surface-Mount-Switch/p2356/
You can also ask your local supplier (Electrical Supply house, NOT Home Depot or your local hardware store) for a switch that is certified to meet the "ac/dc general purpose snap switch" requirement.

James has pointed out a couple of good alternatives.
Using a switched DC lamp (w/o a wall switch) would be another. The switch for a switched device falls under a different NEC/UL classification, than the "wall switch".
Another one is buy an inverter (even an inexpensive one). Then you can use the “AC Only” devices.

I am eager to hear what John Wiles (the real expert) will say. He addresses many code issues for solar systems.
http://photovoltaics.sandia.gov/docs/John_Wiles_Code_Corner.htm

Ken
 

Posted by Ken Hall on Oct 2, 2008 02:46 pm

#154 -  Renewable Energy > RE General Discussion > Re: Help with converting some energy used by pool motor to solar
Why are you specifying non grid tie ? Are you in a non-net metering area ?  If your local utility allows net metering, the easiest and least expensive option would be a grid tie inverter with enough panels to offset X dollars of your total bill.

Your pump is most likely 230V based upon your usage. It would require 2 inverters. So regardless of the grid tie/non-grid tie, it would be less expensive to offset the dollars elsewhere in your electric bill.

Does that pump really cost $100 bucks a month ?  Or is your bill higher than your neighbors and you are just attributing it to the pump ?   If your local utility does household energy audits, you might want to sign up for one.

Something isn’t “right” here.  That is a big pump, or it is being run too long, or something else. But it sounds like it is using more electricity than the average US household.
 

Posted by Ken Hall on Oct 2, 2008 12:57 pm

#155 -  Renewable Energy > Technical Discussion: Other > Re: Need a little help
The "any 12v switch will work" or "120vac with little amperage" share a common problem. They do not meet code.
While they are probably low risk, the consequences can be severe.  In the worst-case scenario of a fire, your homeowners insurance may refuse to cover losses, because of non-code compliant device/wiring.
 

Posted by Ken Hall on Sep 29, 2008 08:13 pm

#156 -  Renewable Energy > RE General Discussion > Re: What kind of wind turbine is this?
Nick
You have the classifications correct.

Ken
 

Posted by Ken Hall on Sep 29, 2008 12:26 pm

#157 -  Renewable Energy > RE General Discussion > Re: What kind of wind turbine is this?
It is a subvarient of a Darrieus type design. The video is not clear enough to tell whether it is a Giromill or a Cycloturbine. If you trust the windspeed estimate of the photographer, it would most likely be a cycloturbine.

My guess is that it is a home built, not a production machine.
 

Posted by Ken Hall on Sep 27, 2008 12:15 pm

#158 -  AltE > Discussion > Re: Microhydro system /off grid
John B has it right. You will use more energy pumping than you will get from generation.

Pumped storage plants have a typical round trip efficiency of 50-60%.  They are only economical for utilities who use low cost night time generation for pumping and then get top dollar value for the electricity during the daytime peak.

A home built system will probably be 40% (or less) efficient. You will be spending $100 to get $40 back.
 

Posted by Ken Hall on Sep 26, 2008 02:01 pm

#159 -  Renewable Energy > Technical Discussion: Other > Re: 12v Switches for interior lights/outlets
James

I need to make it clear (for everyone), that I wasn't questioning the rating of your switch. I was only trying to clarify what the T rating is.  Unfortunately, in making a short reply, it could appear otherwise.

“AC-DC General Use Switches” are usually NOT marked AC-DC. (Life would be simpler if they were.) The markings on your switch are totally consistent with the AC-DC General Use switches that I have used, showing the AC ratings only.

Just as a side comment, it would be nice if you had a picture of the switch on that page, so people could see what it looks like.

Ken
 

Posted by Ken Hall on Sep 26, 2008 12:26 pm

#160 -  Renewable Energy > Technical Discussion: Other > Re: 12v Switches for interior lights/outlets
The T rating indicates that the switch is approved for tungsten filament lamp loads. It does not indicate DC approval. There are AC only snap switches that are T rated.


 

Posted by Ken Hall on Sep 25, 2008 04:02 pm

#161 -  Renewable Energy > Technical Discussion: Other > Re: Need a little help
The table supplied is based upon a 10% voltage drop.
It is totally useless for solar systems.
Using it for house or cabin wiring, violates the NEC maximum recommendation.

 

Posted by Ken Hall on Sep 25, 2008 01:13 pm

#162 -  Renewable Energy > Technical Discussion: Other > Re: Battery Charger
James:
I believe that Smith is located in Nigeria, and would need a 230V/50H 12vdc charger.
I would guess his inverter to be a Xantrex CR1512E or equivalent. Grid backup, not tie.
Those batteries are being pushed real hard already.

Ken
 

Posted by Ken Hall on Sep 23, 2008 02:42 pm

#163 -  Renewable Energy > Technical Discussion: Other > Re: Southwest Windpower Whisper 100 Slip Rings
It has slip rings.
 

Posted by Ken Hall on Sep 18, 2008 01:41 pm

#164 -  Renewable Energy > Technical Discussion: Other > Re: Micro Hydro Power Syst. question?~
If you try putting a turbine in and pumping the water, you will be lucky to get 60% back.
So, you will pay $1,000 in your electric bill, to generate maybe $600 worth of electricity.
That is the best possible outcome, it could be a lot worse.

Assuming that you are pumping from the pond to the tank, you could consider putting in a solar powered pump system. Any water pumped by the solar system would reduce the running time on the grid powered pump. Whether the second system would be economical or not will depend on the vertical height that the water needs to be pumped, the horizontal distance between the two locations, and your cost per kilowatt hour of electricity.
 
 

Posted by Ken Hall on Sep 18, 2008 01:39 am

#165 -  Renewable Energy > Technical Discussion: Other > Re: Micro Hydro Power Syst. question?~
Not economically.  It would be a waste of energy.  If those are gasoline driven pumps, you are far better off just putting the gasoline in a generator.
 

Posted by Ken Hall on Sep 15, 2008 08:14 am

#166 -  Renewable Energy > Technical Discussion: Other > Re: Generate amps or Generate watts?
How many gallons of drinking water do you need a day ?
Why are you trying to take it from the air, instead of the creek.  Is there something wrong with the water ?
 

Posted by Ken Hall on Sep 14, 2008 11:45 am

#167 -  Renewable Energy > RE General Discussion > Re: wire and ground
You need to use the short circuit amperage, which I believe is 3.35 for your panel. Then multiply by 1.56. So the following is based on 5.226 amps per panel.

You are OK on #12 for the one panel.
If you are going expand to 5 panels, you will be looking at either a #6 or #4, depending on the exact distance.

I would use what you are calling "ac power wire".
 

Posted by Ken Hall on Sep 14, 2008 11:33 am

#168 -  Renewable Energy > Technical Discussion: Other > Re: Generate amps or Generate watts?
Whoops, I forgot that the OP had originally specified no batteries.
So, the array would be somewhere between 100kW and 150kW, depending on the peak daytime temperature and humidity.
Water production would drop way off. My guess would be somewhere around 350 gallons a day, depending on exact temp and RH.

I don’t think the intended location is an arid desert. This type of device works best under high humidity. My guess would be someplace in the tropics.

If Smith would spell out the problem, where he is trying to put it, how many gallons a day is needed, etc, we might be able to help solve the problem.

 

Posted by Ken Hall on Sep 14, 2008 04:02 am

#169 -  Renewable Energy > Technical Discussion: Other > Re: Generate amps or Generate watts?
It looks like you sized the array for the hourly requirement, not the daily.

The "dehumidifier" needs to run 24 hours a day to produce the 1700 gallons a day. The best production is at night, as the temperature drops.

So, you are pushing 2400kWh a day, possibly more depending on temperature, humidity, etc. 5 hours of sun would make that array at least 480kW. 

I don’t even want to think about a battery bank for that much energy.




 

Posted by Ken Hall on Sep 13, 2008 05:02 pm

#170 -  Renewable Energy > Technical Discussion: Other > Re: Help Selecting a Solar Water Pump Solution
I haven't used one in saltwater. But the Shurflow pumps are fairly chemical resistant.  I would contact them about how saltwater safe the pump is, and which one they feel would be best for your application.
Another idea would be to contact bilge pump manufacturers (Attwood, Lovett, or Rule, are three that come to mind).  Their products are definitely saltwater resistant.  The question with them would be whether they make one that would operate under continuous duty for 4-6 hours a day at the 30 foot lift requirement.

Before I contacted them, I would think about water storage.  A tank, “pool”,  pond, etc.. If you place the storage above your production process, you could gravity flow or siphon it to meet your once a month production schedule.   Where the storage is placed could add a few feet to your lift requirement.
 

Posted by Ken Hall on Sep 13, 2008 01:32 pm

#171 -  Renewable Energy > RE General Discussion > Re: wire and ground
What is the distance (by the wire route) between your panels and your batteries ?
What percentage voltage drop are you shooting for ?

The #12 may be too small.

You should be looking at stranded wire, not solid.
 

Posted by Ken Hall on Sep 13, 2008 01:17 pm

#172 -  Renewable Energy > Technical Discussion: Other > Re: Help Selecting a Solar Water Pump Solution
The "requirements" of pumping once a month and doing it in 2 hours or less, are driving the system costs.
Your 1200 gallons a month is about 40 gallons a day.  Why not pump daily Huh
The task could be accomplished with a small panel driving a small pump. NO batteries.
 

Posted by Ken Hall on Sep 8, 2008 02:28 am

#173 -  Renewable Energy > Technical Discussion: Other > Re: voltage amps output
You are at open circuit voltage, plus or minus. That is normal for no current flowing. You will have to give a better status of you system if you want help on figuring out why the current isn't flowing.
 

Posted by Ken Hall on Sep 8, 2008 02:15 am

#174 -  Renewable Energy > RE General Discussion > Re: Small Solar System
230V ac is two phases of 115V that are 180 degrees out of phase to each other. A transformer will not solve the problem.
You could do it with two piggy backed inverters.
But you might find it cheaper to change the motor/pump.
 

Posted by Ken Hall on Sep 5, 2008 01:37 pm

#175 -  Renewable Energy > RE General Discussion > Re: 2 long questions from a Newbie... regarding solar hot water space heating
I have no personal experiance with the company. But here is their BBB listing.
http://alaskaoregonwesternwashington.bbb.org/WWWRoot/Report.aspx?site=114&bbb=1296&firm=22087910

The cheapest price is not always the best price.  You want to deal with a company that you can put your faith in. A company that will help you with problems. And in the case of selling other manufacturers equipment, will help you deal with the Mfg, when your complaints are valid.

 

Posted by Ken Hall on Aug 30, 2008 11:35 am

#176 -  Renewable Energy > Technical Discussion: Other > Re: Declination, Elevation, Complication -
Here is an article on the optimum orientation of panels.
http://www.macslab.com/optsolar.html
Take a look at the last graph that show the difference between a fixed angle, adjusting four times a year, and tracking.
 

Posted by Ken Hall on Aug 28, 2008 02:32 am

#177 -  AltE > Discussion > Re: Solar EV charging station
In both 2 & 3 you talk about AC other than from the panels. In 2 you mention from the grid. 
In 4, you say "The system cannot be grid tied.  I currently don't have the desire to grid tie and would like it to be stand alone."


 

Posted by Ken Hall on Aug 27, 2008 03:12 pm

#178 -  AltE > Discussion > Re: Solar EV charging station
Item #4 seems to be conflicting with items 2&3.

What EV's are you talking about ? Some of them can consume more than 1,000 watts. Splitting it between "several" may not be practical.
 

Posted by Ken Hall on Aug 19, 2008 02:34 pm

#179 -  Renewable Energy > Technical Discussion: Other > Re: Grid Parallel Inverter
I do not make "early" recommendations of equipment. My experience is that people who start with or concentrate on inverters and associated equipment, end up spending way too much money on bells and whistles. They then end up skimping on batteries and PV panels. 

If you want to build a good reliable system that really does the job, start with a load inventory. It will drive your design. It will show you where you can conserve energy. Conservation is always cheaper than generation.  It will also help identify which loads must be put on the system for the few outages that you have.  It will help make the decisions about which loads can be easily transferred to the system, and how much re-wiring will be required.

The loads (device and monthly/weekly/daily draw) that you decide to put on the system, plus the reserve factor (e.g. you want 4 days) will drive the sizing of your battery bank and PV array.

Often, this is the point where the budget realities start kicking in. You may re-evaluate how many loads you are going to put on it. So it may take a couple of iterations to arrive at a good sizing.

Once you have a good sizing on the battery bank and PV array, you start looking more closely at the equipment. This is what you need to do the job for this size system. Finally, you consider future expansion and make reasonable allowances for it.

Ken
 

Posted by Ken Hall on Aug 18, 2008 03:37 pm

#180 -  Renewable Energy > Technical Discussion: Other > Re: Xantrex C-35 contoller
Assuming the factory defaults are OK, or that someone has already set them for your system, there is no reconfiguration needed. The difference is in the wiring. Wired between the PV and the battery it is a PV charge controller. Wired between the battery and a dump load, it is a shunt regulator or diversion/dump controller.

In this mode, it monitors the voltage on the battery terminals. When the voltage exceeds the charge settings, it diverts excess wattage to the dump load, lowering the voltage on the battery terminals to the appropriate bulk or float charge voltage.
Assuming an active source (wind,hydro) the PWM should function in diversion mode, when there is excess wattage.
 

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