The way my Solar System is set up, as soon as it sees low voltage from the grid, the system will shut down. This is a safety feature so that a Linesman down the street doesnt get hit.

My question is, If incase of a major earthquake and power is down, is there a way to separate this system from the grid to be able to power the home without sending current down the street?


Fred

There are UL listed Transfer switches that range from a couple hundred dollars for a manual switch to much more for automatic switching and generator control.

HOWEVER, a pure Grid Tie designed inverter (like the Xantrex GT family and others) is designed to only track voltage/frequency of the utility grid--not to generate its own for off-grid power. For, as you say, safety of everyone involved with the Grid.

Could you connect a generator to a Grid Tied inverter--Solar Guppy would be the one to answer that question--but 1st, it might not be safe unless you know much more about the generator and inverter design than the average person; and 2nd, I don't think it would work and be stable in most ordinary circumstances (typical generator frequencies are not that stable and, I would guess that a grid tied inverter is not designed to regulate output voltage and current in the traditional sense--it is designed to pump power into an "unlimited" grid based on how much power comes from the solar panels.... If the house load is less than the solar panels, and pumping power back into a generator is not a great idea--the inverter would probably sense the grid is not stable and simply shut down for five minutes and try again).

There have been "requests" that a high voltage input (to match the 200-600 VDC input range of the Xantrex GT family) be created that would charge a battery bank and invert off-grid for emergency use... It would not have to be the most efficient or largest system out there. Most of us just can't stand the idea of having ~3,000 watts available on our roof and using candles when the power is out. Seems to be a waste of the ability of $15,000 worth of solar panels.

However, Solar Guppy has said that this is not the most practical request because the conversion of high voltage DC to low voltage battery power is not very efficient and would end up wasting a fair amount of power. That is (at least one reason) why no manufacturer has created such an animal to date.

When I bought my system, I thought about the same thing--but decided that installing an Off-Grid capable system (charger, inverters, batteries) was just not worth the expense (initial and on-going maintenance for batteries). Instead I bought a 6 pole manual transfer switch (about $200 or so) and a Honda eu2000i generator (about $900) and installed those.

Figured with a few gas cans with preservative (changed once a year) and a siphon hose for my cars, I could keep the house going for a couple of weeks real easily (fridge, freezer, a few lights, radio/tv).

In my area, the last week long power outage about about 50 years ago in a coastal neighborhood where I grew up (lots of trees). I just could not justify the costs for a solar hybrid system and since our big issue is earthquakes (SF CA), a natural gas powered standby generator seemed like it might be a big paperweight if I ever needed it for use after an earthquake (plus the small generator is portable--can take it if I need to leave the house and can also use it for other projects).

-Bill

I should also add that since I did lots of conservation work around my house, a 2kW generator would power all of my emergency loads very easily.

When looking at a standby generator, those are typically 10kW units or bigger... And those suck down the natural gas like nobody's business. Something like a $1 per hour (last I checked) to even run 1 CFL light bulb.

I have a friend that went around the big standby generators and purchased a smaller RV unit... Much smaller and lower fuel use--just did not have the exterior enclosure of the bigger standby generators.

I choose the smaller Honda because I can get around 8-15 hours of usage on just 1.1 gallons of gasoline (FYI eu2000i 1,600 watts is rated for 4 hours on 1.1 gallons of fuel).

Those typical 5kW $500 gensets use many times that amount of fuel--another reason I bit the bullet and got the more expensive/lower power rated generator for my home.

-BB

Thanks Bill for the reply, I did a search a few months back and the eu2000i was a winner with Ham Radio Operators and RV'ers. One thing that also stand out was that it was quiet.

I will look into that some more.


Fred

Along that line, is there any stand alone inverter that will take as input, 200-600V that could run daytime loads - freezer, washing machine, 12V battery charger for a single CFL at night....
Mike (with $22K parked on my roof, and no electricity..)
edit - no batteries - just running direct inverter off the PV's

Im sure there is a way to bypass the Inverter voltage shutoff and also shut down the ability to send current down the pipe to the street.

I will look into it some more, if I find out, I will post it.

Someone predicted a serious 6.5 earthquake within 2 to 4 weeks in Los Angeles area so thats why I had to ask.


Fred

No ... and I don't see anything comming anytime soon. The National Electric Code has some pretty stiff requirements for battery banks greater than 50 volts nominal, its a completely different thing for 12/24/48 volts sytems.

The Switching losses really mount up if one was to make/design a charger controller for 200-600V input with a 48V output ( 60 amps ) .. you would need something close to the size of the GT heatsink and hence unit size to do this!

What can be done, and I have in two of my arrays is the ability to reconfigure the arrays with switch banks in the garage.

This requires every 48V string of panels home run to the garage, which I had anyways as my first inverters were Sunties. The small toggle switchs ( which one MUST trip the GT offline first or one would smoke the switches under a load) can send a string to the common circuit breakers or make a series path. So, normally I run the ( 8 ) 48Volt strings in 2 series string to the GT5.0 per array, when doing design work, I drop some panels out and have 48volts nomial that goes to the office lab AND the SC-60 on the left. This then allows me to charge my small 220ah/48Vagm battery bank connected to GTVX3048, which powers my office and kitchen appliances.

I have enough solar, I can run the GTFX flat out AND still do a full charge on the battery bank ( which then carrys the loads for the night )

I am not a "Solar Guppy" power supply grade of designer--but I do know, roughly, how the generic switching supply and control networks operate.

I would not be so sure that there is a way of by-passing the shutdown without the original schematics, CPU firmware, and a fair amount of cuts/jumps and component changes.

Regarding the Honda eu2000i generator, try these two sites (heard good things about both and bought from one):

http://www.wisesales.com/ (cheapest? Also has an "overpriced" siphon rig to connect a 5 gallon gas can to generator for extended run time)

http://www.mayberrys.com/ (I bought one here last year + extra filter, spark plug).

Don't know about the prices now--but got mine for just under $900 including a filter change, spark plug, DC battery charge cable, and shipping.

If you need more power, you can put two eu2000i in parallel using a jumper box to run a large A/C during the day, then cut back to one generator during morning and night to save fuel. By the way, they sell a box to combine parallel the two generators. I don't think that is needed at all. From looking at the manual it seems like you should be able to take two male 120 VAC plugs and wire them to one 30+ amp plug. The only issue is that male plugs are a shock hazard--and I thing the jumper plugs from the manufacturer are better shielded (it also includes a 30 amp circuit breaker--but that seems redundant to me).

In the end, get the generator, a couple gas cans, siphon, fuel stabilizer, carbon monoxide detector, oil, heavy duty extension cord (to place generator away from home), and a cable lock (to prevent theft).

If you don't get it now, you probably will not be able to get it when you will need it.

-Bill

But an inverter that I could hook up to my 400V array (or a switch on the GT) would be SO much more simpler.

About the only thing the GT is missing, is a way to "regulate" the output voltage, in the absence of the "Grid". (and a switch to turn it on without the grid) Make it a hard thing to convert, so it can't be done casually - and fry the lineman, but having it be possible would be nice. Almost as nice as having a top on a automobile in the winter in Alaska.
(this is to the inverter marketing guys - not directed to us minions posting here)

Even if you got a "battery-less" solar powered inverter up and running--would you be willing to live with brown outs (or inverter forced blackouts) every time a large bird flew over or the clouds blew in? Not many AC appliances that I would want to run on something like that (plus I would have to be constantly watching my loads on anything but a full sun day).

I think that Solar Guppy's switching strings to 50-125 VDC and connecting to a MPPT controller like the Mx 60 (or Xantrex equivalent) is the only way to go...

You have to bite the bullet for the extra wiring. I would have to divide my two ten BP 175 watt panel strings into 3 panel strings--but with two panels left over (6 strings of 3) if I wanted the full 3kW... That is now 6 + 2 oddball strings of wiring instead of the two that I needed for the Xantrex GT 3.0

Perhaps, instead, you would just converter some subset of strings (and have limited solar power).

-Bill

Sorry Fred, not a chance ... UL1741 stuff is run by an auxiliary CPU that’s encrypted code ... and even when all the V/Hz trips are off, the GT is a current source design, it has no ability to regulate voltage, it just follow the voltage and sends current into the load. Without a load, the voltage just rises, hence why very low impedance, like a grid, is needed.

Now connect a GT to a genny, and assuming the GT likes the V/Hz, its will start to dump as much solar INTO the genny as it can ... if the Genny is powering a load greater than what the GT can backfeed, it might work, but you have to make sure the loads are more than the GT can power, 100% of the time, every 60hz cycle, and thats near impossible

Stand-alone inverters are voltage controlled based, and they work with a varying output load with a FIXED input (battery bank), the GT is just the opposite, it’s a varying input to a fixed output. There is nothing, ever, no way, that a GT could be made to run stand-alone