Power during grid outage without batteries?

Pardon me if this has been answered before, but I did search...

Are there any grid-tie inverters out there that can provide power during a grid outage without the use of batteries? Obviously the panels would need to be supplying enough power for whatever loads were running, but I'm thinking about minimal loads during an outage.

On a related note, if I'm using 200W and my panels are producing 1kW at a given time, does that mean that only 800W is going to the grid, or am I effectively putting 1kW into the grid and using 200W from the grid? I ask because I'm curious about whether connecting to the grid affects ALL efficiency or just the effeciency of power that's not needed immediately.

Thanks for the clarification!
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Comments

  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Power during grid outage without batteries?

    "Are there any grid-tie inverters out there that can provide power during a grid outage without the use of batteries?"

    nope, not that i'm aware of. grid tied inverters that do not use batteries have anti-islanding in them to prevent your solar produced electricity from going out over the grid and endangering anybody during a power outage. in other words if there's no grid power there you won't have solar power there either and the inverters are made that way on purpose by law.

    "On a related note, if I'm using 200W and my panels are producing 1kW at a given time, does that mean that only 800W is going to the grid, or am I effectively putting 1kW into the grid and using 200W from the grid? I ask because I'm curious about whether connecting to the grid affects ALL efficiency or just the effeciency of power that's not needed immediately.'

    now this is an interesting question. bypassing battery charge/discharge inefficiencies is what makes going straight to the grid more efficient and that's limited by the wiring losses and inverter losses so inefficiencies will still be present. as to whether your power is coming from the grid or solar under those circumstances is like the chicken or the egg being first thing. that could be argued either way, but ultimately it amounts to 800w (not counting inefficiencies) going to the grid. my guess would be the solar going to your load first and then the rest to the grid(which is a load) because electric goes the least path of resistance making your load first inline.
    i'm editing this to give you and others food for thought in my believing my guess to be true. let's say you are 10 miles away from the utility generation plant and you are producing 1kw and using 200w. your next door neighbor is using 800w, so where is his power coming from? i say you and that it saved our grid system some stress by you providing that 800w instead of the utility generating plant.
  • RoderickRoderick Solar Expert Posts: 253 ✭✭
    Re: Power during grid outage without batteries?

    Yes, I agree with Neil. The UL 1741 standard requires the inverter to stop producing power within a half cycle of the grid going down, I believe.

    It might be a neat thing to have the only house on the block powered during an outage, but then again, outages are rare and brief where I live. And also, anyone with a gas powered generator could do the same thing. If the grid was unreliable, that would be a different story.

    Now that said, if a Katrina-class disaster (Hurricane, for those not in the US) happened, you could go and reconfigure your panels to deliver about 120 volts DC (assuming you had enough of them), run this to an extension cord, and power some things. Not everything would run, but it could be better than nothing in an emergency.
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Power during grid outage without batteries?

    do not configure your pvs for 120vdc as it just won't run things meant for 120vac, not even for a katrina class emergency. if you had to do an emergency reconfiguring, do it to charge 12v/24v batteries that could run small dc items or an inverter to run ac items.
  • mike95490mike95490 Solar Expert Posts: 9,047 ✭✭✭✭✭
    Re: Power during grid outage without batteries?

    I've always had a thought to (in a major outage)

    1 pull the main feed breaker (200A)

    2 use my 300W sine inverter, thru a 240V xformer,

    3 backfeed my panel, with all loads off, leaving my GT inverter connected.

    4 After GT comes up, (in a sunny afternoon) start switching loads on, I shoudl be able to run a fridge or 2, a quick load of laundry (if water is present) run a battery charger that the 300W sine is running off. I have a genset, but I suspect it's too unstable to get the GT to sync to, so I'd just plug a fridge or something into it directly.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • BB.BB. Super Moderators, Administrators Posts: 31,090 admin
    Re: Power during grid outage without batteries?

    Mike,

    I would guess that connecting a Grid Tie inverter together with a standard inverter will not work... Grid Tie inverters work on the assumption that the utility is a giant, near zero resistance, "AC Battery" network.

    Grid Tie's dump all available power from the solar pv panels into the network--some to be consumed locally, some to be shipped back out to the utility. I don't believe that a Grid Tie inverter would have the ability to regulate voltage as they are designed to just track the AC Main voltage.

    With a small inverter setup to "start" the grid tie--as soon as the home's load was less than the Grid Tied inverter's output power--the voltage would start to rise and the Grid Tie should detect "Islanding" and turn off... Also, at least one country, Germany, requires the inverters to measure the network impedance (Xantrex offers a German only model for this requirement). I would doubt that a 300 watt inverter + household loads would be able to look like AC mains.

    Lastly, I am guessing that you are in the US--so, at least, 90% of your loads are 120 VAC rated. If you have a Xantrex GT (or other larger Grid Tie inverter)--these are 240 VAC units and do not support the neutral connection... So, even if you managed to get the system working--you would probably end up frying some of your 120 VAC appliances because of unbalanced 120 VAC loads on the 240 VAC mains. (It might work if the loads were sharing the 120 VAC transformer connection with your inverter)...

    In the end, making these sorts of modifications/connections without using a transfer switch is probably illegal (against code and utility rules) and is dangerous if somebody flips the mains breaker back on while you have an inverter/generator connected...

    If you are really interested, you might try posting the question about trying to get a Xantrex GT to operate off-grid here:

    http://www.solar-guppy.com/forum/

    The forum owner is one of the designers of the Xantrex GT inverter.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • RoderickRoderick Solar Expert Posts: 253 ✭✭
    Re: Power during grid outage without batteries?
    niel wrote:
    do not configure your pvs for 120vdc as it just won't run things meant for 120vac, not even for a katrina class emergency. if you had to do an emergency reconfiguring, do it to charge 12v/24v batteries that could run small dc items or an inverter to run ac items.
    Thanks; quite right. Sorry, I didn't mean to suggest that anything designed for 120 AC will run on 120 DC. Certainly, it would be better to go with low-voltage DC, for anything that will take that directly. My panels are 24V nominal, unfortunately, and I'm not sure how many things I have that could run on that.

    As for things which I would expect to run on 120 DC, that would include my soldering iron, incandescent lights, compact fluorescent lights (but not the older type of fluorescent), hair dryer (as long as it's reasonably recent, with a rectifying diode inside and DC motor), toaster oven, and things with a line-switching power supply instead of a transformer (such as a desktop computer, or laptop, if it has a transformerless power brick).

    In reality, this is just a flight of fancy - if a huge disaster hit, and even if the panels miraculously survived, electricity would be low on my list. If I were concerned, I'd probably have a generator on hand, or maybe a 24V inverter of some kind (but I don't).
  • mike95490mike95490 Solar Expert Posts: 9,047 ✭✭✭✭✭
    Re: Power during grid outage without batteries?
    BB wrote:
    Mike,

    I would guess that connecting a Grid Tie inverter together with a standard inverter will not work... Grid Tie inverters work on the assumption that the utility is a giant, near zero resistance, "AC Battery" network.

    SNIP

    If you are really interested, you might try posting the question about trying to get a Xantrex GT to operate off-grid here:

    http://www.solar-guppy.com/forum/

    The forum owner is one of the designers of the Xantrex GT inverter.

    -Bill

    Well, I'm glad I mentioned it before I tried it. In retrospect, you are right about the 240V not being a 2 phase output, not using a neutral.
    As to the absence of a transfer switch, this was a thought for dire emergencies, when I doubt anyone would be working on wires for weeks. But maybe with a giant 240V CT transformer, someting could be rigged - for dire emergency use. More thought needed. 300V , 10 A DC, what can I do with that????
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • System2System2 Posts: 6,290 admin
    Re: Power during grid outage without batteries?
    niel wrote:
    "Are there any grid-tie inverters out there that can provide power during a grid outage without the use of batteries?"

    nope, not that i'm aware of. grid tied inverters that do not use batteries have anti-islanding in them to prevent your solar produced electricity from going out over the grid and endangering anybody during a power outage. in other words if there's no grid power there you won't have solar power there either and the inverters are made that way on purpose by law.


    now I'm a bit confused the Outback GTFX series of inverters seem to advertise that they can do this, provide power with the grid out and no batteries, am I reading the spec sheets wrong??

    Bob
  • BB.BB. Super Moderators, Administrators Posts: 31,090 admin
    Re: Power during grid outage without batteries?

    Well... You are correct, there are Outback and Xantrex (and others I am sure) that can supply AC power like a Grid Tied inverter does... The difference is that a "Grid Tied Inverter" is generally assumed to be nothing more than Solar Panels, a Grid Tied Inverter, and AC Mains (Utility Connected). There are no batteries and no method to supply power from the Solar Panels to an AC load other than when connected to AC Utility Power.

    The Systems (like Outback and Xantrex) that can supply AC power to on and off grid connections require (as far as I know) a battery bank for the inverters to get their DC power to invert into AC power... And these units can do all sorts of wonderful things... They can go off grid, use grid power to charge the batteries, use solar (and wind) to charge batteries, and will even interface with a generator (automatic start/stop). They can be powered to use battery power during peak power periods (when utility power is most expensive), and they can charge the battery banks using Off-Peak utility power.

    The big difference is that with a true "Grid Tied" inverter (as defined), there are no batteries, no battery inefficiencies, and, typically, the grid tied inverters are much cheaper (and simpler) than the systems that use chargers/inverters/and battery banks.

    With Grid Tied inverters, it is assumed that you will be operating with a Utility that allows net metering and the Utility will be your "battery bank"... Some places with net meter in a one month cycle (at the end of the month you pay a connection charge and for any power that you may have used in excess of what your solar generated--if you generated more than you used, you will not get any money back and still will owe the connection/minimum fee).

    And many states have 1 year net metering periods... In my area, I have very net positive generation of power during the summer, and consume more power than I generate during the winter (net negative). So, over a one year period, I have a "bank" that I can draw on during winter and deposit during summer. I still pay a minimum fee, plus at the end of one year (or monthly, if I want) I pay the negative balance in the bank account (if I consumed more than I used), or if there is a net positive amount, the balance is reset to zero.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Power during grid outage without batteries?

    Yes it gets confusing. When most people mention grid tied inverters the first thing that I think is, with or without batteries. The vast majority are without batteries, but my inverters (Xantrex SW2512) are called grid tied as well and definitely need batteries as well as all the inverters in the Outback line.

    You can get away with a small bank with these inverters, but they need something to stabilize the incoming solar or wind power for the inverters. Otherwise as loads were added the input voltage would drop off quickly and the inverters would shut down because of low voltage or if you had a cloud pass over the inverters would shut down. I believe someone used a string of large capacitors in place of a battery bank and it supposedly worked. The other issue is these battery grid tied inverters are more expensive and require additional wiring and usually a charge controller and of course batteries so it quickly becomes more expensive.

    The way they work is you have loads on the downstream side of the inverter or the house side. Those loads will continue to run as long as you have battery and/or solar power. The grid or upstream side is disconnected from the grid within 1/2 cycle so power can no longer flow out in that direction.

    In my case I have certain circuits in my house on an "inverter" panel connected to the downstream side of the inverter and those loads get power no matter what. The majority of my house, my main breaker panel, will loose power if the grid fails. Depending on the size of your battery bank and inverters you can add more or less circuits to this sub panel or even your entire home if your system is large enough.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • boBboB Solar Expert Posts: 980 ✭✭✭✭
    Re: Power during grid outage without batteries?

    " would guess that connecting a Grid Tie inverter together with a standard inverter will not work... Grid Tie inverters work on the assumption that the utility is a giant, near zero resistance, "AC Battery" network."

    Yes, you CAN actually connect a batteryless PV interter to a battery based inverter !  I've done this and know
    others that have done this.   What I did was to connect an SMA Sunny Boy to an OutBack FX inverter which is
    connected to a small battery.   When I did this, I also had an MX60 and one PV module connected to the
    batteries....  Not that it was necessary to use the MX though.

    The FX inverter is acting as the grid for the Sunny Boy.  What you have to watch out for is the battery voltage getting too high if
    there are not enough loads.  Since the FX is bidirectional, powerwise, the AC voltage that is steadily going up from the SMA, will
    also raise the battery voltage.  So you should use the diversion output to either switch on a dump load or have it disconnect or
    disable the Sunny Boy while the voltage is too high.   What will eventually happen though is that the Sunny Boy will go out
    of AC voltage range and disconnect all by itself after a while.   This only if there isn't enough AC and/or DC draw to use the
    PV energy up.

    The SMA Sunny Island is a similar "solution".  (I don't really like to use that word though!)

    boB
  • nielniel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Power during grid outage without batteries?

    too many conversion processes and that is a waste plummeting efficiency way down. if you'd wish to do it this way during an emergency or outage, it would work though.
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Power during grid outage without batteries?

    I don't know, it sounds like you would have less losses then using a straight battery system since most of the solar would go right to the loads without the voltage step down and back up like in a traditional battery system. I didn't know that an outback inverter would charge the batteries from the output side, or that it would try to charge the batteries as the voltage went up? Or do you mean it just tries to float them with whatever power is available?

    This sounds like a good setup for someone with a larger grid tied array since 99% of the time they can go right to the grid with the power thus reducing loss at that and. And then just have a small battery bank and a second inverter to turn the batteryless grid tied inverter on. I had always wondered if that would work good to know the results.

    When you did this did you have a 240vac setup? Stacked Outbacks or a T240 or ?

    It does sound dangerous for a person who doesn't understand what is happening.

    I have also wondered about a batteryless grid tied inverter and a nice genset ;)
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • boBboB Solar Expert Posts: 980 ✭✭✭✭
    Re: Power during grid outage without batteries?

    "When you did this did you have a 240vac setup? Stacked Outbacks or a T240 or ?"

    It was one of those 700 or 750 Watt Sunny Boys that were 120 Volt outputs. You could use a T240 though and
    a 240V SB.

    Since the SB is in parallel with the inverter output in invert mode and it is "in sync" as well, the SB tries to raise the
    inverter AC sine wave output voltage which sends power from the FX's output, through its internal transformer to
    the DC side and into the battery. It is like battery charging, but is uncontrolled and unregulated. That's why
    you need the dump load, a big enough load or some other means to keep the AC and DC voltage from getting too high.

    Kind of fun stuff.

    Hope everybody's turkey day was at least as good as mine :-D
    boB
  • BrockBrock Solar Expert Posts: 633 ✭✭✭✭
    Re: Power during grid outage without batteries?

    Ahhh, makes since now.
    3kw solar PV, 8 L16's, xw 5548, Honda eu2000i, iota DLS-54-13, Leaf EV, 4 ton horizontal geothermal, grid tied - Green Bay, WI
  • 20yrDCman20yrDCman Registered Users Posts: 23
    I found something you can use or expand on!!

    I think this item has great use for having 120 ac power with no batteries and no grid power. It's pretty cool. There's a video showing the uses for it. Note: there is no batteries or capacitors running the equipment. However to protect itself it shuts down if the panel cannot support the load. There is a timer before the inverter turns back on. You CAN connect a battery to it at night time to keep the inverter going. Let me know what you guys think.
    http://store.mwands.com/charge-controllers/12-volt-suntaqe-pwb-charge-controller-with-inverter/


    Linus wrote: »
    Pardon me if this has been answered before, but I did search...

    Are there any grid-tie inverters out there that can provide power during a grid outage without the use of batteries? Obviously the panels would need to be supplying enough power for whatever loads were running, but I'm thinking about minimal loads during an outage.

    On a related note, if I'm using 200W and my panels are producing 1kW at a given time, does that mean that only 800W is going to the grid, or am I effectively putting 1kW into the grid and using 200W from the grid? I ask because I'm curious about whether connecting to the grid affects ALL efficiency or just the effeciency of power that's not needed immediately.

    Thanks for the clarification!
  • mike95490mike95490 Solar Expert Posts: 9,047 ✭✭✭✭✭
    Re: I found something you can use or expand on!!
    20yrDCman wrote: »
    I think this item has great use for having 120 ac power with no batteries and no grid power. It's pretty cool. There's a video showing the uses for it. Note: there is no batteries or capacitors running the equipment. However to protect itself it shuts down if the panel cannot support the load. There is a timer before the inverter turns back on. You CAN connect a battery to it at night time to keep the inverter going. Let me know what you guys think.
    http://store.mwands.com/charge-controllers/12-volt-suntaqe-pwb-charge-controller-with-inverter/

    There is either a super cap or Li xx battery in that "PWB" box. That inverter will not run off pure PV. And it's a cheap mod-sine inverter. And no power after dark. PV panel NOT included.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    solar: http://tinyurl.com/LMR-Solar
    gen: http://tinyurl.com/LMR-Lister ,

  • bill von novakbill von novak Solar Expert Posts: 891 ✭✭✭✭
    Re: I found something you can use or expand on!!
    20yrDCman wrote: »
    I think this item has great use for having 120 ac power with no batteries and no grid power.
    There is currently one mainstream inverter series on the market that does that - the SMA Sunnyboy TL-US series. It will provide up to 1500 watts of power while the grid is off-line to a separate outlet. No batteries required.
  • 20yrDCman20yrDCman Registered Users Posts: 23
    Re: I found something you can use or expand on!!

    Nope, no cap no battery. It says batteryless. Has a voltage stabilizing module in it. I'm sure they'll include the panel. Also they have the same kit with panel and pond aeration pump. Apparently pond pumps are loud and the ac one they use is whisper quiet. Also would you care if your running a fan with a modified inverter??? See last video first. There's no way to fake it man. You can smile. Check out videos
    http://www.youtube.com/watch?v=LtnN_z2LOS8&list=UUnaa_80Xxuoq0jNA68uddaw
    and
    http://www.youtube.com/watch?v=kZ1BzbzdrGY&list=UUnaa_80Xxuoq0jNA68uddaw
    and
    http://www.youtube.com/watch?v=jXTayFPl6u4&list=UUnaa_80Xxuoq0jNA68uddaw
    and
    http://www.youtube.com/watch?v=4JSZSZR0qTU&list=UUnaa_80Xxuoq0jNA68uddaw
    mike95490 wrote: »
    There is either a super cap or Li xx battery in that "PWB" box. That inverter will not run off pure PV. And it's a cheap mod-sine inverter. And no power after dark. PV panel NOT included.
  • PhotowhitPhotowhit Solar Expert Posts: 5,371 ✭✭✭✭✭
    Re: I found something you can use or expand on!!

    Just want to post an opinion about Missouri Wind and Solar...

    They are basically the used car sales people of solar and Wind. If they would answer a question, I might change the opinion, but I have repeatedly asked questions about their DC thermostat Max voltage, UL ratings, and they haven't responded. If you search here you will find others who have had problems with them or their equipment. Personally If I want to run a radio and a fan, I'd run them directly off a 12v nominal panel. Most car radio's will handle the voltage range as will most DC motors.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • BB.BB. Super Moderators, Administrators Posts: 31,090 admin
    Re: I found something you can use or expand on!!

    Yep--It can work fine. He are appears to be using a DC to DC converter to take the "variable" voltage from the solar panel and down convert it to ~13 volts (stable) to run a 12 vdc to 120 VAC Inverter.

    He calls it a "relay" in the last video--It appears to be a switch mode converter. Nothing wrong with that.... And as long as the output of the solar panel exceeds the draw of the loads (i.e., 120 watt panel and 38-60 watt load), it will work fine.

    There is an issue in that this inverter latches off if the input voltage falls below 10.5 volts. He may have added a relay to "cut" 12 VDC power to allow the inverter to reset--Not sure of those details.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • 20yrDCman20yrDCman Registered Users Posts: 23
    Re: I found something you can use or expand on!!

    Pretty cool huh. I asked them about the reset today and they said they do have a detector with relay that will reset the inverter. Also they said if you connect the module to a battery at night you can run the inverter like that too. Even during the day because the volt stabilizer won't allow overcharge it's ok to leave the batt on there. What do you think??
    BB. wrote: »
    Yep--It can work fine. He are appears to be using a DC to DC converter to take the "variable" voltage from the solar panel and down convert it to ~13 volts (stable) to run a 12 vdc to 120 VAC Inverter.

    He calls it a "relay" in the last video--It appears to be a switch mode converter. Nothing wrong with that.... And as long as the output of the solar panel exceeds the draw of the loads (i.e., 120 watt panel and 38-60 watt load), it will work fine.

    There is an issue in that this inverter latches off if the input voltage falls below 10.5 volts. He may have added a relay to "cut" 12 VDC power to allow the inverter to reset--Not sure of those details.

    -Bill
  • 20yrDCman20yrDCman Registered Users Posts: 23
    Re: I found something you can use or expand on!!

    Hmm, that's odd. They usually answer my questions fairly quickly. Give them another try for the answer. What it looks like to me is that the thermostat can handle the typical 250volts. Probably also made to handle DC pretty well.
    And to your comment about running fan and radio directly from solar, well...you could do that but because solar is higher voltage than typical 12v items would see they will most certainly run hot, fast, hard, and fryyyy. Looks like they put a lot of R&D into it and a fair amount of brains to pull it off. Could see this for RV'ers, campers, on and on.
  • BB.BB. Super Moderators, Administrators Posts: 31,090 admin
    Re: Power during grid outage without batteries?

    I am a big fan of getting rid of batteries and brushed motors. If daytime operation works for your needs. Go for it.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • PhotowhitPhotowhit Solar Expert Posts: 5,371 ✭✭✭✭✭
    Re: I found something you can use or expand on!!
    20yrDCman wrote: »
    Hmm, that's odd. They usually answer my questions fairly quickly. Give them another try for the answer. What it looks like to me is that the thermostat can handle the typical 250volts. Probably also made to handle DC pretty well.
    And to your comment about running fan and radio directly from solar, well...you could do that but because solar is higher voltage than typical 12v items would see they will most certainly run hot, fast, hard, and fryyyy. Looks like they put a lot of R&D into it and a fair amount of brains to pull it off. Could see this for RV'ers, campers, on and on.

    Through Ebay, through their web site, by phone... How many chances do you want me to give them!!!!!!!!!!!

    I actually understand how it works, the reason I specified a car radio... I'd be glad to run my O2Cool for quite a while, I've run one off an 18v battery pack to get some idea of capacity, it actually didn't seem to run hotter, but it has sorta built in cooling. ran for about 2 hours before it appeared to slow down.

    BTW-DC is a LOT different than AC, something that can handle 250 volts AC is different from DC since DC can sustain and arc. You statement is the exact reason I was asking questions. Likely since it wasn't inspected for safety they didn't want to say anything, incase someone burned down their house! Don't use AC rated breakers for DC applications!

    I still would like to run a DC direct to a heating element, using a thermostat as the 'controller' with no other and at about 175 volts... Yes, I'd like to know if they can handle 175 volts DC.
    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Prosine 1800 and Exeltech 1100, 660 ah 24v ForkLift battery. Off grid for @16 of last 17 years. Assorted other systems, and to many panels in the closet to not do more...lol
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: I found something you can use or expand on!!

    You know, for light-duty "12 Volt" loads it's easy enough to knock down 17.5 Vmp to "battery level" and stabilize it with a capacitor. I can think of a couple of ways without getting fancy.
  • 20yrDCman20yrDCman Registered Users Posts: 23
    Re: I found something you can use or expand on!!

    I am going to gather some specific knowledge and even ask them if they could get me some additional info. Like I said I usually get answered fairly quickly.
    As for running solar direct to the element if that's what you're doing then that is kinda in depth. You figure out the element ohm and current. ps I wouldn't try and run 175vdc even if the stat will handle DC well. That could be long arc, harder to break than lower volts dc. Also if you connected 175vdc to a low ohm element you would probably get disappointing results like low amps with low volts when applied. I don't forsee a house burning down though, the most that might happen is a contact could seize or simply burn a hole, inside a metal enclosure like the stat is you'd be hard pressed to make the exterior metal hot enough to ignite anything. You'd most likely either have the contacts stick closed in which case your water heaters blowoff valve would release the pressure (ps never cap the blowoff valve in any way) OR the contacts would burn and you would get a permanent open circuit.
    Here goes: voltage drop across a resistor x amperage flowing = wattage. you don't want to drop a panels voltage from voc lower than vmp soooo for example if 24v panels voc is 36 and the vmp is like 28 then you do not want to see voltage lower than 28 when applied to load. Because typical amps out of a 24v panel is about 8amp x vmp28 = 224 wattsP = E x I. if your panel is 224 watts nameplate for example, and it produces about 8 amps nameplate then R = P / I 2, resistance = 224 watts / 64. 3.5ohm resistance is the magic number after doing the math. P = E ² / R. 224 watts = 784 / 3.5ohm which happens to be two 24 volt 400 watt dc water heating elements wired in series. Just don't exceed 800 watts of panels. If that is a mind blower then My advice would be to use a simple diversion controller capable of handling your solar panels parallel amperage wired directly to a minimum amount of crap batteries (probly 2 car batts in series) as they won't be deeply discharged if only diverting. Again, don't use more solar panel wattage than the element/s in whole are designed for or you will overcharge your batts and/or damage the element. Also make sure your solar wire in parallel will handle the amps coming from array.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: I found something you can use or expand on!!

    Don't count on panels putting out rated Wattage, and especially not Vmp.
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: I found something you can use or expand on!!
    You know, for light-duty "12 Volt" loads it's easy enough to knock down 17.5 Vmp to "battery level" and stabilize it with a capacitor. I can think of a couple of ways without getting fancy.
    This reminds me about how you nailed the the Soft Starter Technology. Everyone said it wasn't a capacitor until one was finally cracked opened and well'a, a great big ole capacitor. It did have a circuit board with some elaborate controls, but it relied on the capacitor to do it's thing with good results.
  • oil pan 4oil pan 4 Solar Expert Posts: 766 ✭✭✭✭
    Re: I found something you can use or expand on!!

    Once you get over 100 volts DC you can establish a very stable arc.
    Switches that worked with 120v AC now are not nearly wide enough to put out a DC arc.
    I have an old stick welder I converted to DC, one of the settings I built in ups the OCV to 125VDC. It will throw an arc as long as 3 inches.
    The AC settings peak at 86 volts and will only let me stretch an arc out about 3/4 of an inch or less.

    Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.

    Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.

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