Author Topic: OFF GRID POWER; various thoughts on...  (Read 556831 times)

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Offline Dave Sparks

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Re: OFF GRID POWER; various thoughts on...
« Reply #375 on: March 08, 2010, 10:55:37 AM »
I do not know your inverter/charger and only use the Outback and Xantrex (SW's XW's) but your inv/chg has to be able to limit the charge current to run a small generator. You could have other problems also but this first step has to be adjustable in the programming of the inv/chg.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #376 on: March 08, 2010, 02:34:37 PM »
A long distance diagnoses is more a guess.

I too am not familiar with your inverter/charger.

It more or less sounds like the inverter is drawing more current than the generator can produce. That could be why the generator lugs as if overloaded and then goes back to normal, only to repeat the cycle. It could be the inverter circuitry sensing the overload or the generator itself. I'm not familiar with the little Hondas either.

The only generator failures I've experienced are total failures to produce power, never a partial failure.

Have you tried pulling all the AC power to the cabin distribution system to see if the charger alone will repeat the scenario? Is the charger section programmable as to maximum AC current use or maximum output? I'd try limiting either of those if possible to slightly below the generators maximum continuous output rating.

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 #377 on: March 08, 2010, 08:32:33 PM »
"Your Honda generator is 1000 watts?" Yes

"Did the Prosine charge controller work fine with the Honda prior to these events?" Yes

"Have you tried pulling all the AC power to the cabin distribution system to see if the charger alone will repeat the scenario?" Yes, I shut off the big breaker in the power shed...no AC going out at all, and the scenario repeats.

"Is the charger section programmable as to maximum AC current use or maximum output?" Ummmm..There are default settings, and there was a setup programming sequence that I had to go through.  The setup programming was ridiculously complex.  I haven't changed the settings since the initial programming...and I don't remember....so back to the book, that is next.  A cursory reading says the Prosine won't charge if the input voltage drops below 95.  I have to go back to the programming sequences to see if that can be altered...just seems logical that if it was working before I shouldn't have to change anything.

Today I also got an "instant" readout voltage meter on the gen to see what happens when the inverter switches to charge mode.  It's only sucking about 6 amps from the gen when the charge mode comes on.  The trouble is that it won't wait for the gen to get back up to speed before it kicks out of charge mode.  A week ago it did, and was working just fine since December 20 until the last few days. 

I also plugged a 7.8 amp drill into the gen, revved the drill up and put it to hard work several times.  The gen didn't mind and although there was a short (1 second or so) initial period when the gen's rpms dropped, they came right back and the drill didn't notice...held its performance steady. 

So now I'm going to find out something like there are different kinds of amps....thought I understood (mostly), but maybe not.  ???

I enjoy electricity because it makes so many things so convenient, but...this is probably the most difficult part of the entire project for me to get my head around. 








 

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Re: OFF GRID POWER; various thoughts on...
« Reply #378 on: March 09, 2010, 03:54:58 AM »
If it worked fine at some point within the last few months and you've changed no settings on your inverter/charge controller I'd say the problem is with your generator. Not that it's in the throws of death, but that something is interfering with the power getting to the charge controller before the charge controller kicks it off.

Maybe try putting a load on the generator before the charge controller so the generator is already running at a higher RPM. It might just be the time it takes the generator to rev up and increase the power output is too long for your charge controller.

Offline Redoverfarm

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Re: OFF GRID POWER; various thoughts on...
« Reply #379 on: March 09, 2010, 09:42:08 AM »
OK People this is completely out of my realm of comfort.  ???  I need to get busy and develope a system to operate at the cabin.  My main power and charging source will be a 12KW propane generator.  I would like to operate the generator as a charging system for a battery bank and run the cabin when the batteries are depleted.  Here is a list of what will I will be using.  Some of which are not listed as watts but rather amps and some I am not sure what they draw.

1100 watts of lighting.  That is a total but only a portion will be used at one time.
9.8 amp 110/120 well pump
1100 watt Microwave
2- exhaust fans. One is a bathroom exhaust and the other a 600CFM kitchen fan
1- Sure flow DC pump
3- ceiling fans

I know nothing about sizing the inverter or charging system or even the size or the amount of batteries.

Any information will be greatly appreciated.  If you have any sites that list the equipment that you feel are a good buy that would also be useful.

Thanks  

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #380 on: March 09, 2010, 10:09:28 AM »
Dilemma time.

When I began playing with Don's spreadsheet I was able to put together what I envisioned as a minimalist remote cabin off-grid system.  400watts delivered via 2 200watt panels through a Blue Sky SB3024iL Charge Controller into 8 Golf Cart batteries and then feeding both 12vdc items as well as a Xantrex TR1512 1500 Watt, 12 Volt Inverter.  This would power some lights, a well pump, maybe a radio and a composting toilet fan.  Not much, but perhaps with enough reserve to make use of some other things (like maybe charging an ipod, or a cordless drill etc).

However, I may (may being a very operative word here) be able to afford to go with a little more...so I'm playing with the following:

3 of these panels:  SUN ES-A-210-fa3 210 watts, 11.48 Imp, 18 Vmp
I'm wondering if running them in series at 3100 feet in altitude would be too much for this controller:

Blue Sky SB3024iL Charge Controller 30A 24V MPPT

With 8 batteries as originally planned (need 8 in the winter and 6 in the summer except for at the coldest time of year when I'd really need 10-12 and probably more panels -- it's a trade off right?)....

And....

Xantrex Prosine 1800 Watt HW 12V Sine Wave Inverter w/transfer Switch

That would give me 1800 watts of AC and no modified sine wave so if we did decide to add a small MW oven we could.

Cost? 630 watts for about $3136 plus shipping and of course all the wiring etc.

vs. 400 watts for about $2328

A little more charging juice in t he winter might be nice I'm thinking and true sign wave may be handy at some point.  This doesn't really change my system much I think (1500 watt inverter vs. 1800 watts) except that it will produce a lot more power in the summer (north country -- could get more then double the sun I'd get in winter!  In fact, in the winter I'll get maybe 3 solid hours of sun but in the summer I could see 12!  ???

I doubt we'd need the generator for anything but heavy tool use in the summer but in the winter can imagine that we might need it during longer stays if the clouds are out and we can't get good sun exposure.

Anyway, please fire away!

Also, Don, you mentioned something about using higher input voltage to charge the batteries.  I took that to mean that on a 12 vdc battery string you would want 24+ vdc coming into the charge controller?

Also also :) ;)  I'm looking at wiring needs to the panels and was thinking that running the three panels in series triples the voltage to 54.9vdc right?  (if they are 18.3Vmp) and that Blue Sky charge controller is rated at no more then 57v I think....would I be better going with a slightly more robust controller?

I was thinking this is where the Xantrex XW MPPT 60 Amp Solar Charge Controller would come into it's own since it allows a higher input voltage to charge the 12vdc battery bank.

Thoughts?

THANKS!  [cool] c*

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #381 on: March 09, 2010, 11:43:42 AM »
John,

No PV panels, no wind, right, IIRC?

If that's correct you should seriously reconsider, or choose an inverter/charger unit that is smart enough to be able to sense battery voltage and then automatically start the generator. Otherwise you will drive yourself and your wife batty with constant monitoring the battery state of charge and/or deplete the batteries past the danger point too frequently and shorten their life.

The only inverter/chargers I have knowledge of, with that capability are Outback and the better Xantrex. There are others though. An auto start kit (relay & stuff) is required as well. There are 2 wire and three wire types as far as the generator connections go, I believe 3 wire can be considerably more expensive. I haven't looked into this much as for the present I'm not doing an auto start system. It's also handy to have an interior control for manually starting the generator.

The system is programmed so when the battery voltage drops to a certain value and for a certain length of time, the generator will start.

Note that the better units have the charger and inverter in one unit. The batteries normally supply the current needed for the AC demands placed on the inverter. The generator can be used to supply extra power when the inverters capacity is being overloaded.


Okay, what is the panel setup for? 120 VAC only or a 120/240 VAC?  That will determine the inverter setup. If you need 240 VAC in most cases you will have to have two identical inverters that are designed for stacking in series, to produce two 120 VAC legs. Also if 240 VAC is required the generator must be 240 VAC split phase.  Better inverters can also be installed in parallel to increase available current. Series/parallel also is used at times in larger systems.


As for how much inverter output required yo will need to make a list of everything that is likely to be used at the same time.  You can use the PV sizing tool   http://countryplans.com/smf/index.php?topic=8192.0 for doing the load and battery calculations.  You need to enter watts, so just remember amps x volts = watts

For the well pump:  9.8 amp 110/120 well pump, that is more like 10 x 120 = 1200 watts with a starting surge.  ??? on that

The manual/literature for the various fans should indicate power consumption. Or try the internet resources.


I hope that helps some.

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 #382 on: March 09, 2010, 12:04:42 PM »

...... you mentioned something about using higher input voltage to charge the batteries.  I took that to mean that on a 12 vdc battery string you would want 24+ vdc coming into the charge controller?

...... I'm looking at wiring needs to the panels and was thinking that running the three panels in series triples the voltage to 54.9vdc right?  (if they are 18.3Vmp) and that Blue Sky charge controller is rated at no more then 57v I think....would I be better going with a slightly more robust controller?

A quick partial response, no time at present for more.

The voltage going into the battery must be higher than the rated voltage of the battery system.  

That also generally means the voltage going into the charge controller must be higher than the battery voltage.  As a rule of thumb that working voltage input to the charge controller should be 1.5 times the battery bank/system voltage. That provides a safety factor for cloudiness as well high temperature voltage losses. Having the input to the CC even higher is fine with most of them. There is an upper limit listed in any good CC specs. You can not exceed that without (a) damaging/destroying the CC and (b) voiding the warranty.

When calculating the theorteical maximum voltage from the panels the Voc (voltage, open circuit) value must be used. Than fudge factors must be applied. Multiply the Voc x 1.25 x 1.25, That's right multiply by 1.25 once and then a second time. That will supply the likely maximum voltage that could ever be produced on a very cold, but very sunny morning as the first rays of the sun strike the panels. If that calculated value is near, at or greater than the charge controller maximum input do not use that panel and CC combination.

I'm pretty sure that Blue Shy model would smoke with that proposal: check the specs.

There is a PV panel string sizing tool available at Outback. It uses a database of hundreds of panels. Of course it is only 100% useful for system sizing when using Outback Charge Controllers, but it can give you the panel values and combination values that may be handy. It is also temperature compensating so you can dial in your own conditions and see how the outputs change.  Placing the mouse cursor on a colored square produces the cold Voc as well as other data.
« Last Edit: March 09, 2010, 12:34:30 PM by MountainDon »
Just because something has been done and has not failed, doesn’t mean it is good design.

Offline Redoverfarm

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Re: OFF GRID POWER; various thoughts on...
« Reply #383 on: March 09, 2010, 12:36:04 PM »
Don you are correct No solar or wind (not at this time).

The generator that I have and posted a picture earlier is a standby generator which will monitor the incoming power and when it notices a depletion it will automatically start.  So my thinking was to utilize the inverted power as my primary feed (just as grid power is normally used with the generator) and let the generator determine when it needs to start. I guess I need to contact the manufacturer and determine if this configurations with a inverter can be made.

The panel is completely 110/120 now but I did reserve a couple 220/240 breakers for future use.

The pump is a slow start and supposeably does not have a surge. 

The fan paperwork does not list any of the technical information only the installation guideline.  They used to put that in there was it's not on the particular fans that I have.

I guess the load and battery size will determine the inverter size?

 


Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #384 on: March 09, 2010, 04:59:06 PM »
John,  The total simultaneous loads will determine the inverter size. How long you want the batteries to supply those loads without the generator running will determine the size and number of batteries.

I’m having some trouble trying to get what I want to say condensed into a compact coherent paragraph or two. What I’m trying to clarify why what you propose could have problems because that’s not what the standby generator designers nor the inverter designers had in mind when they set out to build their products.


First, a standby generator will sense when there is no 120 or 240 VAC present at the house service panel, as in a grid power failure here at my home. That loss will cause the generator to start to replace the grid power. When the grid power returns the generator will shut down. A proper grid setup like this will also include an automatic changeover switch to be certain there would be no feedback from the generator into the grid. A standby generator itself has nothing to do with the batteries or an inverter.


Inverters. The better type like the Outback and Xantrex include a charger in the inverter. Inverters have a low battery voltage sensor and a circuit that turns the inverter off when a certain low battery voltage is reached. On the better ones that LBCO (low battery cut off) voltage is user programmable. There is, or should be, a battery voltage setting that will turn the inverter back on when the battery is recharged to a higher voltage; the LBCI low battery cut IN) voltage.

Every inverter has a pair of DC input connections as well as an AC output connection. An inverter/charger also has an AC input connection. When AC voltage is applied to the AC input terminals that current is passed through the inverter and split between powering the house and charging the batteries.

Inverters also consume a small amount of power just sitting there at your beck and call. It’s not much but adds up. Over time the batteries will be drawn down to the LBCO and the inverter will shut down. To get around this waste the better inverters have a search function. Virtually no power is used until something is turned on to demand power. At that point the inverter clicks on and things light up, hum or buzz.

These inverter/chargers are meant to be the main supplier for the AC house power. They are wired up so that when there is AC input to the inverter/charger they can charge the batteries and seamlessly continue sending AC power to the house panel.




It’s the charging connections I have trouble when trying to use the existing auto start system that is built in to the standby generator. Specifically where to hook the AC input of the charger up to. If the AC from the generator is connected to the AC inputs of the inverter/charger, that will charge the batteries. However, that will also send power through the inverter/charger (via the built in “pass though” that is a part of such units) to the service panel. There the AC power would be sensed as a return of the “grid” power and shut down the generator. At least that’s how I see it. I could be wrong, be misinterpreting something.

If you want the system to run without user intervention I believe it gets more difficult than need be.


If you used a separate inverter and a separate charger it might be easier, but that also might cost more than a single unit.


With all that in mind the first thing to do is determine the capacity required for the inverter output and the capacity required for the battery bank.

While you do that check the standby generator specs, or call the supplier. You would want to know if the remote start capability of the generator is a two or three wire setup. Also see if there is a delay system built into the generator. That is when it is called to start, is there a preset or a programmable delay between engine starting and connecting AC power output. I would think so, but not having worked with generators that were designed as a standby I’d like to know. It think there should be.


I hope I did not muddy the waters with that.  d*

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

Offline Redoverfarm

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Re: OFF GRID POWER; various thoughts on...
« Reply #385 on: March 09, 2010, 05:21:09 PM »
Yep clear as mud Don.  But no fault of yours.  Just a mental block on my end.  

I do have a automatic transfer switch and seperate breaker for the generator supplied by the manufacturer.  Normally there is a 60 amp wires ran from that transfer to the house panel box.  Normally the circuts for the house are wired to the 12 circuit generator panel (transfer switch).  I know it does have 3-4 smaller wires which I think are the monitoring wires which detect the power failure from the grid (via generator transfer panel)to the generator and that activates the generator. The transfer switch has two modes which are automatic or manuel.

I know I could probably just go with a battery charger from the generator to charge the batteries once the inverter shuts down and it would remain deactivated until the batteries are restored. I think that then the power would be restored to the panel and the generator should shut down after it detects power. Or at least in theory. 

You have given me a good bit to digest and I was aware that it would not be easy but I still think it can be done.  This is just one area that I am completely lost and it will take me a while to get it figured out.

Maybe someone has crossed this bridge before and may enlighten me some.

Thanks.    

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #386 on: March 09, 2010, 05:36:25 PM »
Dilemma time.

A..... I'm wondering if running them in series at 3100 feet in altitude would be too much for this controller:

B..... Xantrex Prosine 1800 Watt HW 12V Sine Wave Inverter

C..... I doubt we'd need the generator for anything but heavy tool use in the summer but in the winter can imagine that we might need it during longer stays if the clouds are out and we can't get good sun exposure.

D..... 54.9vdc right?  (if they are 18.3Vmp) and that Blue Sky charge controller is rated at no more then 57v I think....would I be better going with a slightly more robust controller?



A.....  Altitude has small effect on increasing the amperage output of a PV panels. No effect on voltage. Hot temperatures decrease voltage output, cold temperatures increase voltage output. Clearer skies, no clouds or less atmosphere sue to higher elevations increase the amount of sunlight that reaches the panels and that increases amperage output.

B & C..... No battery charger in that and you will need one.

D..... I think we covered that already. bad idea for those 3 panels and that charge controller. But do remember use Voc and those correction multipliers when totaling the input voltages.

Hope that makes sense...

 :D

My head/jaw hurts tonight.

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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #387 on: March 09, 2010, 05:44:13 PM »
FYI, on the cold weather and PV panel voltages.

The Outback online calculator predicted a Voc from the panels in series, at the lowest temp I've recorded up there this winter, of 129 volts. The Outback FlexMax charge controller recorded a peak voltage of 127 volts for that time period. Pretty close, although I should add that I have also recorded 125 volts at temperatures that the calculator predicted would be 10 volts lower. ??? Goes to show there can be real world variance from theory. However, I have enough safety factor that even using a worst case scenario everything should be safe.  

Take that as a hint to not cut theoretical peaks too close to the stated hardware maximums.



Note: if your panels are not listed in the Outback calculator you can enter your own data. I believe Xantrex has a similar calculator with their equipment listed.
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Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #388 on: March 09, 2010, 06:07:17 PM »

I know I could probably just go with a battery charger from the generator to charge the batteries once the inverter shuts down and it would remain deactivated until the batteries are restored. I think that then the power would be restored to the panel and the generator should shut down after it detects power. Or at least in theory. 

I believe that is correct. That system though will have to be finely tuned to allow the generator powered charger to bring the batteries up to an absolute true full charge, before the inverter kicks back in and causes the genny to shut off. It should be possible but may require fiddling.

I now remember there was something I wanted to add. Beware of cheaper inverters that have the LBCO voltage fixed at something like 10.5 to 11.0 volts. As far as I'm concerned that is too low a voltage to use. The LBCO and LBCI shoiuld be adjustable by the user.

The charger you select should have the three types of charging; bulk, absorb and float as well as an equalization option. The EQ is not available on a number of stand alone chargers. You will need to be able to disable the generator start/run when you want to do an EQ or even treat the the battery to a complete full charge.



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 #389 on: March 09, 2010, 08:31:36 PM »
Dilemma time.

A..... I'm wondering if running them in series at 3100 feet in altitude would be too much for this controller:

B..... Xantrex Prosine 1800 Watt HW 12V Sine Wave Inverter

C..... I doubt we'd need the generator for anything but heavy tool use in the summer but in the winter can imagine that we might need it during longer stays if the clouds are out and we can't get good sun exposure.

D..... 54.9vdc right?  (if they are 18.3Vmp) and that Blue Sky charge controller is rated at no more then 57v I think....would I be better going with a slightly more robust controller?



A.....  Altitude has small effect on increasing the amperage output of a PV panels. No effect on voltage. Hot temperatures decrease voltage output, cold temperatures increase voltage output. Clearer skies, no clouds or less atmosphere sue to higher elevations increase the amount of sunlight that reaches the panels and that increases amperage output.

B & C..... No battery charger in that and you will need one.

D..... I think we covered that already. bad idea for those 3 panels and that charge controller. But do remember use Voc and those correction multipliers when totaling the input voltages.

Hope that makes sense...

 :D

My head/jaw hurts tonight.



Thanks Don -- so the Xantrex contoller if I want to run series then.

I was thinking the transfer was for the gen -- guess I need to re-read that.  Is there a decent true sine wave inverter for similar cost that also has the battery charger?

Offline OlJarhead

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Re: OFF GRID POWER; various thoughts on...
« Reply #390 on: March 09, 2010, 08:41:18 PM »
Yikes!  Just looked up true sine wave inverters with charge controllers and got shell shocked!  Guess it's back to modified sine wave for now.

With the Xantrex controller and the Xantrex inverter charger I should be set anyway, I was just toying with the idea of true sine wave becuase if we wanted a MW oven it might matter.....I think we ditch the MW idea *chuckle* and stick to the propane stove and cook fires!

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #391 on: March 09, 2010, 08:50:52 PM »
  Is there a decent true sine wave inverter for similar cost that also has the battery charger?

Xantrex Pro-Sine 2.0..... 2000 Watt Sine Wave Inverter/Charger


Magnum Energy.....  2000 Watt Sine Wave Inverter/Charger

More bucks though.
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Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #392 on: March 10, 2010, 03:34:31 PM »
"OK People this is completely out of my realm of comfort." Roger that


Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #393 on: March 10, 2010, 03:41:43 PM »
"With the Xantrex controller and the Xantrex inverter charger I should be set anyway, I was just toying with the idea of true sine wave becuase if we wanted a MW oven it might matter.....I think we ditch the MW idea *chuckle* and stick to the propane stove and cook fires!" 

I have a microwave and a Prosine (Xantrex) inverter.   I still use the franklin stove and the crock pot for cooking.  The most use the MW got is popcorn (it was a load test).  I heat rolls, melt butter, that's about all....My system is small for a "real" house and an MW is a wattsucker.

Offline Redoverfarm

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Re: OFF GRID POWER; various thoughts on...
« Reply #394 on: March 10, 2010, 04:57:59 PM »
"With the Xantrex controller and the Xantrex inverter charger I should be set anyway, I was just toying with the idea of true sine wave becuase if we wanted a MW oven it might matter.....I think we ditch the MW idea *chuckle* and stick to the propane stove and cook fires!" 

I have a microwave and a Prosine (Xantrex) inverter.   I still use the franklin stove and the crock pot for cooking.  The most use the MW got is popcorn (it was a load test).  I heat rolls, melt butter, that's about all....My system is small for a "real" house and an MW is a wattsucker.

What size microwave do you have?  I looked at a 700 but there is just enough room to warm a cup of coffee.  But hey that's about all I will use it for. Not a big fan of cooking in one anyway. 

Offline MountainDon

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Re: OFF GRID POWER; various thoughts on...
« Reply #395 on: March 10, 2010, 06:16:57 PM »
We have an 800 at the cabin. It serves us well for warming things. Keep in mind that the rating you see in the ads is cooking power. Our 800 draws 1100 or so when working.   That may seem like a lot but when it's only for 2 minutes that is almost 37 watt hours which is like an 18watt lamp burning for 2 hours. It doesn't seem like so much when I look at it like that.  Maybe it's me.
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Re: OFF GRID POWER; various thoughts on...
« Reply #396 on: March 10, 2010, 07:06:40 PM »
John, looking over that list of power loads you provided, I had a thought. You listed a pump that draws 1200 watts and a microwave that draws 1100 watts. (That was the power use on the microwave, or was it the cooking power?) Add those: 1200 + 1100 = 2300 watts. Or if the 1100 was cooking power the actual use is likely around 1650 (ours in the house is that), so 1200 + 1650 = 2850 watts. Unless you want to have to check if the pump is running any time you want to use the microwave (and hope it doesn't start while the microwave is in use), you need an inverter that will handle a load of 2300 or 2850 plus some extra in case there are some lights or whatever in use at that time.


Does that make sense?

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

Offline Redoverfarm

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Re: OFF GRID POWER; various thoughts on...
« Reply #397 on: March 11, 2010, 03:15:31 AM »
Completely. Thanks Don

Offline considerations

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Re: OFF GRID POWER; various thoughts on...
« Reply #398 on: March 13, 2010, 07:06:11 PM »
"With the Xantrex controller and the Xantrex inverter charger I should be set anyway, I was just toying with the idea of true sine wave becuase if we wanted a MW oven it might matter.....I think we ditch the MW idea *chuckle* and stick to the propane stove and cook fires!" 

I have a microwave and a Prosine (Xantrex) inverter.   I still use the franklin stove and the crock pot for cooking.  The most use the MW got is popcorn (it was a load test).  I heat rolls, melt butter, that's about all....My system is small for a "real" house and an MW is a wattsucker.

What size microwave do you have?  I looked at a 700 but there is just enough room to warm a cup of coffee.  But hey that's about all I will use it for. Not a big fan of cooking in one anyway. 

The inside of the MV oven is about 12 x 12 x 9 inches.

The little label on the back says .95 Kw, but just like someone on this forum said, it pulls 1100 watts (I have a Kill-a-Watt) when running.  I don't use it if the gen is on and unplug the fridge and the freezer till I'm done.  Almost not worth the trouble, but I don't always have a fire going with spring coming. 

My mother gave (force fed) it to me recently, and I felt compelled to make her feel good by reporting that it works, she cannot imagine life without one...and it does, just have to be sure nothing else is going to tax the system when its in use  [waiting] 

Offline glenn kangiser

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Re: OFF GRID POWER; various thoughts on...
« Reply #399 on: March 13, 2010, 08:06:14 PM »
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.  It all depends on the system though.

We have a 1250 watt inverter microwave.  It gets the job done fast.  I am still not convinced that it will kill me.... [waiting]
"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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