Author Topic: OFF GRID POWER; various thoughts on...  (Read 557107 times)

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Offline EcoHeliGuy

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Re: OFF GRID POWER; various thoughts on...
« Reply #175 on: May 18, 2009, 11:40:33 AM »
Lighting just traveled a couple miles to the earth, I don't think you have to worry about the temp rating of the spark plug, that little bit of a tolerance won't matter.  d*

Also If this spark plug works, which I see no reason not too, its kind of pointless. just make sure you have a heavy duty grounding wire with in a few thousands of an inch away from a bare terminal between the PV array and any electronics. The charge will jump this gap and bypass the electronics.

I would be more worried about the charge passing through my PV array and the wiring, So I would do what ever possible with a Lighting rod at the array instead of trying to deal with it in the house  ;)

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #176 on: May 18, 2009, 12:07:02 PM »
Re: Lightning.

I was hoping I had made it clear that you need both types of lightning protection.

The module frames, mounts, etc. all need to be grounded to at least one 8 ft rod, or equivalent.

You also need the circuit to be protected to prevent equipment or people down the line from electrocution from lightning strikes.




"heat range, etc." was a joke... I added a  rofl   ... didn't stop to think not everyone was familaiar with my sense of humor.    :-[ :-[
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Offline EcoHeliGuy

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Re: OFF GRID POWER; various thoughts on...
« Reply #177 on: May 18, 2009, 12:22:15 PM »
I caught your sense of humor, its mine that was mistaken  d*

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #178 on: May 18, 2009, 07:05:22 PM »
Interesting idea.  :D
What heat range plug is suggested?
Should it be an resistor type?
Maybe a Bosch 4 electrode platinum, or a SpltFire?  ???

 rofl rofl rofl rofl

Delta arrestor modules are only $40.

I have a Delta arrestor at the power controller as he suggested, (Delta arrestors are pretty wimpy compared to a bolt of lightning - likely better to arrest it before it all makes it to the Delta)  but he said that is likely not enough and that the plug should likely be put at the wind generator tower base area on the positive cable and the negatives all earth grounded - likely following your guidelines above.

He is a real pro and does testing for Outback - they send him free stuff for evaluation.  I would suggest a non resistor type.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #179 on: May 21, 2009, 02:47:45 PM »
Batteries. I've talked pros and cons of various ones previously. I'm not sure if I stated what I was going to use. I've been asked what I'm going to be using at our cabin. The quick short answer is golf cart batteries, arranged in series/parallel for a 24 VDC based system.

Golf cart batteries are usually 215-225 amp-hours and are 6 volt units. I believe we have pared our electrical use down to where these will do the job for us. I've run the 'numbers' a number of times over 2 years time.

I selected golf cart GC2's for several reasons, even though they are not highly recommended by many alternate energy parts suppliers.

One reason is my experience to date with a bank of golf cart batteries in the RV. I try to follow a rigid maintenance schedule and have pulled 5 years of practical use from a set.

A better choice would be the L-16 type; also 6 volt with 370-400 amp-hours. I wouldn't need as many batteries and would have fewer parallel strings. L16's weigh about 130 pounds apiece. GC-2's are about half the weight. That is important to me.

The batteries will be sitting through several winter months. I believe that the equipment I've selected, from pV panels through to the charge controller is among the best. However, if something goes wrong and the batteries do not keep receiving their maintenance charge, there's a good chance the batteries could be harmed by the freezing weather.

When I look at the costs per year of the GC-2 vs the L-16, plus the other mentioned factors I decided to go "golf". Admittedly, it's a trade off.



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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #180 on: June 12, 2009, 03:07:44 PM »
Earlier on here, I spoke of grounding the PV system.

My grounding lugs finally arrived. Here's what they look like with the parts laid out and assembled.



They are made by Wiley Electronics. I got mine from thesolar.biz   Some vendors charge $10-11 each; they were half that. The thin stainless steel plate has 4 punched holes with tooth-like edges, on the bottom side. These grip and dig into the aluminum panel frame and make a very secure ground connection. The tin-plated clamp is suitable for AL and CU wiring. Here's the WEEB exploded installation image. The nuts, bolts and washers are stainless steel.





I got stalled by the rain and forgotten parts, so that's all the photos until next time.

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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #181 on: June 25, 2009, 07:20:27 PM »
More on the grounding...

Here's the ground rod. Right at two inches away from legal NEC depth I hit a rock that stopped the rod cold.No amount of pounding made headway.



I figure dirt piled on top will make it 8 feet or greater.

Here's the 'combiner' box I decided to use. It's an off the shelf Square D item. I added a block on the left to make it easy to connect the Delta lightning arrestor. The box is plastic; I used a nylon bolt to mount the block. It may not meet actual NEC code, but it is as safe as a more expensive 'proper' PV item. Since there's no inspection this is what I've used.



Please also note that the disconnect, although rated for up 48 VDC is not really legal under NEC. However, I don't plan on using it as a disconnect much at all. It's mainly a convenient and inexpensive item to use to connect the 10 AWG wire from the panels to the heavier 2 AWG wires that lead up the hill to the batteries and cabin.

The number 2 wires are not shown.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #182 on: June 25, 2009, 07:23:04 PM »
Also on the grounding theme...



Here are the grounding lugs as mounted to the PV frames.



The panels are not tilted as yet as the wires up the hill are not yet installed.  That's the dirt that will be moved to cover the in ground rod.

I drilled and tapped the steel pole and connected the ground wire there using a stainless steel 1/4 x 28 bolt and two S/S washers.
« Last Edit: June 25, 2009, 09:11:31 PM by MountainDon »
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Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #183 on: June 26, 2009, 05:41:43 AM »
Nice Job Don!
I have been lurking!  I have one last step for you (there never really is a last step) on your grounding.

The line from my mentors back at HP was "nothing electrical is complete unless it has been tested"
To test your ground system you need 2 ground bars or 2 ground systems. Here is how you find out if you need more. It is pretty simple! ??? OK, ready? Connect a decent ohm meter between the ground bars or if you have a UFER (wire in foundation) One wire to one ground bar and one to the other system. The two systems cannot be connected for this test but should be later in most cases.

If you do not read below 25 ohms you need to add another ground bar to find out which bar is not working.
Most people never do this but since we know you want to increase your odds of surviving lightning you should do this. Forgive me if you already discussed this after all I am a new guy with old tricks! Take care!
"we go where the power lines don't"

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #184 on: June 26, 2009, 08:21:10 AM »
Good point on the testing Dave. Thanks very much. It is appreciated.
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Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #185 on: June 26, 2009, 10:06:54 AM »
No problem! I almost ended up down by you instead of by Glen. It was a tuff call!

Since as I said "there never is a last step" and you are still getting this system together, I will give my humble opinion on Lightning.  You want to do all that you can, the arestors, spark-plugs, MOV's and the ultimate an 8 foot long bundle of wire from the array that you can disconnect and move  so there is an 8 foot gap.

The sad part, even the bundle disconnect can fail if your number is up! All the other steps are great if you are not at home when it hits. They are worth it!! The Arrestor may look wimpy but it is one hell of a lifesaver, if you are up on your luck!

Good Luck!
"we go where the power lines don't"

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #186 on: June 26, 2009, 12:09:45 PM »
My luck has been pretty good so far.  :D  I've been close personal witness to three strikes within close proximity; 100 foot range. Hair standing on end (that was years ago  ;D  ), bright flashes, big noises, bark flying off trees, sparks from hand to vehicle door, and so on.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #187 on: July 22, 2009, 07:37:24 PM »
A recent post elsewhere made me think of this...   How does one calculate the proper angle for the solar panels?

This is a function of latitude and time of year. Ideally the panel surface would be perpendicular to the rays of the sun at all times. (note angles are measured from the horizontal.) With the sun low in the winter sky the panels would be tilted more, to a larger, steeper angle.

There is a rule of thumb for panel tilt. That is for winter (December 21) the angle should be your latitude PLUS 15 degrees. For summer (June 21) the angle would be your latitude LESS 15 degrees. Our location in NM is  35.75 degrees. Therefore winter = 50.75 degrees and summer = 20.75 degrees.

In most locations winter sunshine is less than in summer. So if you do not wish to get into seasonal adjustments, optimize the installation for the winter. Another approach would be a twice yearly adjustment. Set the tilt for the winter position in about mid October and back to summer position in mid March. Some folks will make 4 seasonal adjustments.

For those who are more anal about things like this (moi  Grin ) there is a more accurate formula. Take the latitude and multiply it by 0.9. Then add 29. That provides me with a winter optimum tilt of 61.175 degrees.

The angles apply to all things solar, PV panels as well as hot water heaters, etc.



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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #188 on: August 06, 2009, 04:59:00 PM »
Nice Job Don!
I have been lurking!  I have one last step for you (there never really is a last step) on your grounding.

The line from my mentors back at HP was "nothing electrical is complete unless it has been tested"
To test your ground system you need 2 ground bars or 2 ground systems. Here is how you find out if you need more. It is pretty simple! ??? OK, ready? Connect a decent ohm meter between the ground bars or if you have a UFER (wire in foundation) One wire to one ground bar and one to the other system. The two systems cannot be connected for this test but should be later in most cases.

This seemed like a good point. My problem with performing the test was that the 8 ft. ground rod is only a foot from the steel pole in the ground/concrete which is the only other ground at this end of the system. The ohm meter gave a reading of only 6 ohms when connected between the two, which is good but is also meaningless because of the closeness. At least it's my interpretation that two grounds that close are acting more or less as one.

My solution was to add another ground rod down by the array. I sunk a second 8 foot 5/8" copper clad ground rod in the ground 8 feet away from the other and connected the ground wire to it as well. Testing the reading between the two rods came up with 12 ohms. So it appears to be within the allowable limits.  :) 


I'm uncertain if I mentioned this before...  When the array and the balance of the system (charge controller, batteries, etc.) are distant the NEC allows the system to not require a third wire (ground) between the two system sections.

The NEC does not define "distant", but my research has come up with 50 feet or greater as being generally recognized as distant. My 300 foot distance would qualify. This saves the expense of a third run of expensive wire, #2 AWG in my system.

To omit this ground wire between array and charge controller there must also not be any other possible current paths; no metallic conduit, no wire fences, metal water pipes, etc. Again our system qualifies.

I just ran non metallic conduit and the #2WG wires from the array to the cabin.

http://countryplans.com/smf/index.php?topic=2335.msg95631#msg95631

It's not connected yet at either end. That will hopefully be completed in the next week we spend up at the cabin. Photos at that time.

« Last Edit: August 07, 2009, 01:53:17 PM by MountainDon »
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #189 on: August 07, 2009, 05:26:47 PM »
In an attempt to avoid the basket of snakes look that sometimes occurs with a battery bank of series and parallel connected batteries I have elected to use copper buss bars and copper bar battery interconnects. I built the buss bar assembly today, and here it is.







The mount board is 3/4 plywood. The standoff insulators secure to the board with 1/4 x 20 bolts; ditto for mounting the bars to the insulators. The fasteners are stainless steel. The buss bars are 3/16" x 3/4" copper bar stock, 72 " long. I have drilled a few pilot holes for the charge controller and inverter connections. The battery connection holes will be drilled on site when the battery positions are determined.

As indicated the upper bar will be positive 24 VDC and the lower bar will be negative 24 VDC. That size of copper bar can safely carry 250 to 300 amps. At full output my inverter is rated to draw 170 amps so there is reserve capacity for momentary overloads.

More pictures later.
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Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #190 on: August 09, 2009, 07:08:00 AM »
Nice busses, Don. 

I want to make mine similar so I can isolate each bank of batteries for equalization.  More than one bank of batteries on equalization at a time will not work well especially if one bank has a low cell.  Most of the power will flow to the good set rather than correcting the low cell.

Isolating and equalizing each series set will eliminate that problem.
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Offline harry51

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Re: OFF GRID POWER; various thoughts on...
« Reply #191 on: August 15, 2009, 07:40:53 PM »
I predict future happiness for Americans if they can prevent the government from wasting the labors of the people under the pretense of taking care of them.
Thomas Jefferson

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #192 on: August 15, 2009, 08:01:00 PM »
Interesting battery Harry.  I think I would like more panels also, but we are steadily getting better.
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Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #193 on: August 17, 2009, 05:57:44 AM »
Don,
I know the NEC is not clear on distant grounds but you definately want the array ground bars and lightning system connected to the house or panel/battery ground system. A # 6 would be fine for this. With you second bus bar how does the 6ohm path to the concret bar ground measure? You may want to tie that ground in also.

Ciao!
"we go where the power lines don't"

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #194 on: August 17, 2009, 08:15:21 PM »
The grounding information I have used comes from my own reading as well as from John Wiles at the Southwest Technology Development Institute at New Mexico State University in Las Cruces, NM. I have used his recommendations for grounding our system.

The array position has the aforementioned twin ground rods, plus the steel pole in concrete in the ground.

Up at the cabin the AC system has a ground rod from when I did the original interior wiring. The AC system at the cabin also includes a Delta arrestor. Sixteen feet away from the AC rod is what I call the DC ground rod, even though the two are connected. The reading between them (disconnected) was less than 12 ohms; can't remember exactly. It seemed good enough and that was all I cared about.

As well, the steel roof and steel chimney have their own grounding leads and ground rod at the other end of the cabin.

I have a small fortune invested in copper and copper clad steel rods.  :D   Hope it all does its job. I was thinking I had it pretty well covered, or at least covered better than many. Maybe I'm only almost there.


« Last Edit: August 17, 2009, 08:31:34 PM by MountainDon »
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Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #195 on: August 18, 2009, 06:28:06 AM »
Cool Beans!  Just remember some of Wiles info is continuously updated with code changes and some of it is for residential which may or may not apply offgrid!  Also not a bad idea to have plants that get watered in summer near your ground systems if your ground resistance goes up in summer.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #196 on: August 18, 2009, 07:28:45 AM »
Excellent point on the updating of the information over time. I've read everything I've found that he's written since the mid nineties. It is interesting to note the changes since then. I sometimes have to go back and verify what the latest info is.


Great idea on the watering. I guess that is a side benefit of the current graywater drainage area from the kitchen sink. It's near the DC ground rod. Maybe I should route the shower drain line over near the SC groun d rod. (I refer to them as the DC rod or the AC rod to keep them sorted in my mind... I could have numbered them but I find SC/DC easier... DC on the left (south) and AC on the right (north).  ???
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #197 on: August 19, 2009, 05:55:43 PM »
I began building cables to connect the battery series strings to the bus bars this evening. I purchased the Brute crimping tool and gave it a try. The two ends in the photo show one lug connector just crimped and the other end with the shrink tubing. I did each end of the length of 2/0 I bought to try it out. I'll fit, cut and complete them up at the cabin this weekend.



The lugs are tin plated solid copper from Quickcable, as is the heat shrink tubing. I also realized the Brute tool is marketed by Quickcable; never realized that before somehow. $30 for the tool.

I did one crimp using the vice and the other using a big ball pein hammer. The hammer was easier to use and crimped a little tighter.

I took a reading with the cheap meter I had here at home. It didn't prove anything as the reading was the same as touching the probes to each other. My good meter is up at the cabin.

The Quickcable heat shrink has a heat activated adhesive inside the tube that helps with sealing the tubing to the cable and lug.

I also have 4/0 cable and lugs for the inverter.
« Last Edit: August 19, 2009, 06:16:52 PM by MountainDon »
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Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #198 on: August 20, 2009, 05:22:52 PM »
Cool cable lugs, Don.  Looks like that beats mashing a piece of copper tubing over the cable with a hammer and drilling a hole in it - while securely holding it with a pair of pliers. d*
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #199 on: August 20, 2009, 05:54:47 PM »
Yeah, hanging onto the mashed tube while drilling a hole in copper can be a bear. The bits sure like to hog into the copper.  


I broke a few bits while trying to drill holes in the buss bar stock holding my Ryobi 18V rechargable. The bar stock was clamped to the trailer and the drill braced against my leg, so the bit was the weak point. Results were better with the drill press though there the bits would hog in and the belts slip. 
Just because something has been done and has not failed, doesn’t mean it is good design.

 

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