Author Topic: OFF GRID POWER; various thoughts on...  (Read 556871 times)

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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #400 on: March 13, 2010, 08:34:46 PM »
I am still not convinced that it will kill me.... [waiting]

Only if you can figure out how to get your head inside and turn it on.    [crz]
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #401 on: March 15, 2010, 02:44:26 AM »
"The microwave uses a lot of watts but only for a short period of time, so it is not all that bad on the batteries if they are decent sized."

I'd love to have a battery bank that is double or triple the current size as well as 3 times as many panels.....its on the "list".

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #402 on: April 04, 2010, 06:08:28 PM »
I am still not convinced that it will kill me.... [waiting]

Only if you can figure out how to get your head inside and turn it on.    [crz]


I heard it's hell on cats.... Note to self... do not dry Fluffy in the microwave....



The extra capacity is handy, considerations.

Nothing like a delayed response, eh? [waiting]
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Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #403 on: April 04, 2010, 07:12:01 PM »
Who is using what for 12v sockets?

I'm curious because I thought there was a typical household receptacle for 12vdc but um, not so much.

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #404 on: April 04, 2010, 07:52:40 PM »
I don't mess with 12v.  I invert everything and run 120 or 240 full sine.  Others have done some though I know.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #405 on: April 04, 2010, 08:03:05 PM »
There is no such thing as an off the shelf quality low voltage DC receptacle or plug.

However a NEMA 6-20P configuration receptacle or plug makes a good choice. They are 20 amp 250 VAC rated and accepted by the NEC for use in DC circuits as long as there is no 220/240 VAC in the same structure.





I use them.  I wire the 'vertical' connector + and the 'horizontal' one negative. That's with the units oriented as pictured.

« Last Edit: April 04, 2010, 08:23:08 PM by MountainDon »
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #406 on: April 04, 2010, 08:24:23 PM »
Thanks Don -- just saw that also at BackWoodsSolar.com

I'm not sure how much 12vdc stuff I'd need (or 24vdc for that matter) but want to plan to run some lines for it incase I find a use (or buy a chest freezer or fridge in 12 or 24vdc).

Just in the planning stages right now. 

Saw COSTCO has 6v Golf Cart batteries for $78 ea.  220 ah rating.  Didn't buy them becuase I wasn't ready but I wonder if maybe I should have just got them anyway.

Need to look around more though.  But Walmart doesn't carry them so that's out.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #407 on: April 04, 2010, 08:32:50 PM »
And remember common wall switches areAC only.

My SamsClub has 210's for $68.   $9 core.   I pa7d no sales tax either as in NM everything used in PV or wind is tax exempt. Check on WA state.

Those are what I bought. They've been the same price for over a year. Don't buy too early as they age just sitting there.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline MountainDon

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Just because something has been done and has not failed, doesn’t mean it is good design.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #409 on: April 04, 2010, 08:38:22 PM »
Thanks

Was playing with the PV calculator again and am wondering about something:

If you run a 24vdc bus / battery bank -- what do you do for 12vdc appliances?

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #410 on: April 04, 2010, 08:53:13 PM »
1.  Run a center tap to take off 12 VDC with a hot wire tap.   bad.

2.  Use a 24 VDC to 12 VDC converter. They are solid state, high efficiency, and usually work in either direction. 24 to 12 or 12 to 24. I have one made by Solar Converters.

http://www.solarconverters.com/product_frame.html     
Select  Battery Equalizers/DC Autotransformers

Just because something has been done and has not failed, doesn’t mean it is good design.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #411 on: April 04, 2010, 09:46:53 PM »
1.  Run a center tap to take off 12 VDC with a hot wire tap.   bad.

2.  Use a 24 VDC to 12 VDC converter. They are solid state, high efficiency, and usually work in either direction. 24 to 12 or 12 to 24. I have one made by Solar Converters.

http://www.solarconverters.com/product_frame.html     
Select  Battery Equalizers/DC Autotransformers



Great!  Thanks.

I'm thinking 24v might be better to use and have noticed some differences when using the calculator (which I found interesting).

My solar panels (by the way) will be 46 feet from the cabin when I plan to install the batteries (assuming I plan to put them where I've chosen).  The well head is 125 feet from the solar panels and over 150 feet from the spot where the batteries should be.

My cistern is 446 feet from the cabin corner (24 feet from battery corner) and about 50-70 feet above the cabin in elevation.

I'm thinking that the 46 feet from the panels to the cabin won't be a problem for 24v given that yours are MUCH further away.

I have planned a 400 watt system but if finances allow I'll probably do 600 watts.  If I did that I'd be running something like 54+vdc from the panels (3 in series) which again will have no problem with the 50 foot run I'm thinking.

I also plan to run 8 of the 220ah batteries.

With all my current calculations this is more then I need but I suspect that once we start using it we'll want more...we're human after all!

I also found some 60 watt CFL's that run about 12watts so that will help a bit too and I read that it's better to use more direct lighting to reduce the need for lots of overhead lighting.

My next thing to check is LED's.  I might like to install some DC LED's in the kitchen and in areas where reading might be done.

The bathroom should have a fan too so I have to add that but all in all I think we'll have a great system

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #412 on: April 05, 2010, 07:54:05 AM »
I have a wire size calc if you to run some numbers. Need max amps, distance, voltage.....


We have no ceiling lights at all, mostly table lamps with 23 watt CFL... 100 watt incan equiv


We have provision for bath fan, but no fan. Window opens.

Just because something has been done and has not failed, doesn’t mean it is good design.

Offline davidj

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Re: OFF GRID POWER; various thoughts on...
« Reply #413 on: April 26, 2010, 08:31:15 PM »
I'm designing and installing my electrical and solar setup right now. I'm trying to work out what sort of panel to get - a "main lug" (without breakers on the power feed) or "main breaker" (with breakers).  The feed to the panel will be protected already as there will be a pair of linked 30A two-pole breakers forming a transfer switch between the inverter and a direct generator feed.  The cost difference isn't huge - I'm more worried about doing what's gonna work best and what the inspectors expect to see rather than saving $20.

Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #414 on: April 27, 2010, 03:26:30 AM »
"I'm thinking that the 46 feet from the panels to the cabin won't be a problem for 24v given that yours are MUCH further away."

My panels are 75 feet from the cabin, and it is a 12v system, but the inverter is in the power shed (panels being on the roof of the shed) and the cables from the panels to the inverter are only about 8' long. 

I think where the distance issue comes up is with DC...not so much with AC....

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #415 on: April 27, 2010, 05:28:21 AM »

I think where the distance issue comes up is with DC...not so much with AC....

AC or DC does not matter.
Long wire runs become a concern with higher loads (amps or watts) running on low voltages. Powering a 1200 watt device on 12 volts, AC or DC, requires heavier wire than the same load on 240 volts, AC or DC.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #416 on: April 27, 2010, 05:35:09 AM »
I'm more worried about doing what's gonna work best and what the inspectors expect to see rather than saving $20.

I like to think of the electrical as being made of two parts; the regular AC portion from the main service panel into the rest of the cabin/house and the alternative power portion. That would mean there should be an AC mains breaker in the main service panel.
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #417 on: May 10, 2010, 08:40:07 PM »
We are finally nearing the point that we will be buying all of our solar power stuff and this is what I'm contemplating:

1 -- it is most likely we will use the cabin on weekends only with maybe 2 or 3 one week trips per year.  Thus a large store of battery power may not be required.  So 6 batteries should suffice if using the calculator is any indication.

2 -- 1500 watts is plenty of AC power for our application (I'm thinking 1000 watts would be adequate but couldn't find a decent inverter/charge in that range.

3 -- due to winter conditions and the possibility of low sun exposure due to trees and the north west climate (actually we probably get 275-300 days of sun there but it can also be cloudy for a while) and the desire to possibly run the well pump longer or use the heater on the composter 600 watts is more desirable then 400 watts -- this gives us better charging in low light conditions.

So this is what I am thinking of doing:

3 SUN A-200-fa3 (11.05imp) panels in series (600 Watts)

6 Costco 220ah Golf Cart batteries
SUN-1012 Sinewave Inverter (if it will work but I think it should)
http://sunelec.com/index.php?main_page=product_info&cPath=6_40&products_id=788

And the Xantrex C40 charge controller.

That puts me around $2000 :)




Offline NM_Shooter

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Re: OFF GRID POWER; various thoughts on...
« Reply #418 on: May 11, 2010, 05:18:41 AM »
Something to keep in mind when designing the system, is that many of the electronics (inverter, DC-DC converters) consume electricity even if you are not applying them to a load. 

Note the Sun 1012 inverter... it has a MAX efficiency of 85%.  This is almost always calculated at full output power.  So if you are using a full 1000 Watts, you are burning 150W just to run the inverter.  Same with DC/DC converters.  There is a quiescent power draw for all of these devices, even if you are not using the power that they are putting out. 

If possible, find a way to supply power to these converters only when you need to use power.  Many of them have an enable input that allows you to turn them on and off. 
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #419 on: May 11, 2010, 05:51:10 AM »
That inverter does have a Loading Sensing (Power Saving)mode listed in the specs. That means it can be set to put itself in a standby mode. What they do not list is the power used while in standby. They do list 150 to 220 watts next to the Loading Sensing (Power Saving) line. That seems to be very high. My Outback will do it's standby thing and be using 24 watts while waiting. It will sense down t0 something less than a 3 watt load to go out of standby to working. It would seem that the Loading Sensing (Power Saving) feature of the Sun may not be very useful.

It would be nice to be able to get a download of the manual someplace. Perhpas it would explain the Loading Sensing (Power Saving) better. Another thing that would be good to know is is there is a connection point to have a remote on-off switch for the inverter. I have one with the Outback and a cheap Cobra I used to have had provision for one as well, though I never used it.

It's nice to see the charger built in, but it would be nice to see if it was capable of equalizing. The spec sheet lists 2 modes, so I'd guess that could mean no equalizing, but that's a guess. . Again it would be nice to read a manual.
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Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #420 on: May 11, 2010, 06:51:39 AM »
That inverter does have a Loading Sensing (Power Saving)mode listed in the specs. That means it can be set to put itself in a standby mode. What they do not list is the power used while in standby. They do list 150 to 220 watts next to the Loading Sensing (Power Saving) line. That seems to be very high. My Outback will do it's standby thing and be using 24 watts while waiting. It will sense down t0 something less than a 3 watt load to go out of standby to working. It would seem that the Loading Sensing (Power Saving) feature of the Sun may not be very useful.

It would be nice to be able to get a download of the manual someplace. Perhpas it would explain the Loading Sensing (Power Saving) better. Another thing that would be good to know is is there is a connection point to have a remote on-off switch for the inverter. I have one with the Outback and a cheap Cobra I used to have had provision for one as well, though I never used it.

It's nice to see the charger built in, but it would be nice to see if it was capable of equalizing. The spec sheet lists 2 modes, so I'd guess that could mean no equalizing, but that's a guess. . Again it would be nice to read a manual.

I've requested more information.  My thinking was that the cost is so much less then comparable inverters by Xantrex etc that it might be worth the expense to try it out and see how it lasts.

It's possible it will be junk and need to be replaced in a year or two but then who knows really and at about $500 cheaper.....

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #421 on: May 13, 2010, 06:31:58 AM »
No reply -- I've had this problem before :(  I hate it when people don't reply.

Offline davidj

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Re: OFF GRID POWER; various thoughts on...
« Reply #422 on: May 14, 2010, 06:21:12 AM »
I'm trying to decide on what's the best way to connect my solar panels to my 12:12 standing seam (clip-style)  metal roof.

The obvious way is to use the Unirac standing seam clips but the guy who is selling me my system advised against them as they are fiddly to install.  Given our 100psf snow loads, it also seems somewhat lightweight of a connection.

The alternative is to use a Unirac rail system, which has L brackets to connect the rack to the roof (#6 on the diagram).  Apparently I can just screw through the roof panels into the framing with lag screws and caulk (or butyl tape??) in the hole and under the bracket will make it waterproof.  My worry here is that the movement of the metal during hot/cold cycles will lead to water leaking through the penetration and/or buckled roof panels.

Does anyone have any experience with either of these approaches?  Any opinion on what would work best?

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #423 on: May 15, 2010, 06:41:06 PM »
I meant to comment sooner but got side tracked.

Was eliminating all those holes that you'd have with a ribbed panel roof one of the reasons you selected standing seam metal? If so it seems a shame to drill even a few holes to mount the rail system.  On the other hand there would not be many holes and the use of self sealing butyl tape would go a long way to help prevent problems. Fasteners with synthetic rubber washers tightened properly (= not too tight) are a must.

Another thought of mine. Panels need to be spaced high enough off the roofing to allow for good air circulation behind the panels. As the panel temperature rises their output falls. Most panels manufacturers should be able to supply that info. It becomes even more important to ventilate the panels properly in warmer/hotter climates. Almost any knid of a roof will radiate a lot of heat  around the panels elevating the local microclimate temperature.

The panels, being dark colored, get hot anyways. Restricted air circulation can make that worse. On a bright sunny day the panels can get hot enough to be uncomfortable to touch.

Something to keep in mind..

(someplace I have (had?) the typical highest temp a panel in full sun can reach on a roof. It's higher than one might think. I can't find it though.   ???
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Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #424 on: May 18, 2010, 10:04:47 AM »
Come-on Don! Tell him to put them on a top of pole mount and be done with it! It is the only sane way short of what the trogledite did. d*
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