"online" quality UPS from a grid-interactive system: how feasible?

danielh
danielh Solar Expert Posts: 69 ✭✭✭✭
in Grid Tie and Grid Interactive Systems #1
I am seriously considering an AC coupled system at part of my 6.5kw PV install (see below for a synopsis of how I got there).
This system would provide basic UPS services to much of the house. However, it will not provide clean power (what wiki calls
online ups).

What would it take to upgrade to such a "online" ups services? Some kind of Ac to DC to AC conversion.
That means an AC battery charger to charge the battery, and an inverter to supply AC to the crictical loads panel (abstracting from
the gti portion of the ac coupled system)

In this solution, the "charger" part of the would not be used. In fact, the AC input to this inverter would not be used -- since the
goal is to force the inverter to invert (hence make clean) power.

But that isn't free.

First, what kind of stress does that put on the battery? A 200AH battery will be used (@48v), and while average demand
will be less than 2kw, occassionally 4kw will be needed.

Secondly,what equipment would be used, such as what AC battery charger.
It seems there are not a lot of great selections for 2kw+ AC battery chargers ( http://forum.solar-electric.com/showthread.php?10123-Question-about-battery-charger-selection-with-EU2000-generator.
In fact, off-grid inverters seem to have the best range of options for AC battery charging!

To save $$, it might be useful to have a simple inverter supplying the critical loads panel -- why pay for an charger that
won't be used? But from what I could determin, such a beast isn't any cheaper than an OGI.

And there is the issue of charging batteries from PV panels when the grid is off. How to get power to AC battery chargers, when the grid is offline?
I can think of hacky solutions (have the AC charger be one of the critical loads, and when the grid is down turn them on only when PV power is flowing)

I am not hopeful I can find a clever solution that is cost effective (i.e.; that doesn't halve my battery live).

But that's why this forum is so helpful!



=====================
The following is background, with some links to other threads.

Once learning the limits of grid-tied systems, I investigated what benefits a grid-interactive system might provide
(http://forum.solar-electric.com/showthread.php?16354-Grid-interactive-what-benefits-make-it-worthwhile).
There are 3 categories of services a "grid-interactive" system could provide:
  • Power during an outage
  • Most-of-house uninteruptible power supply (UPS)
  • Load shifting (time of use)
The last is not cost effective: losses from charging and discharging batteries (including battery degradation) are much greater than the likely savings from shifting
grid demand to off-peak hours

The first and second are valid, though many argue that a genset is a more practical means of providing outage power,
given that outages are 1 or 2 days a year.

Living through a few days of outage heighten my interest. Investigating possible solutions reveals that
(http://forum.solar-electric.com/showthread.php?16394-Cost-effective-grid-interactive-choices-Outback-vs-Xantrex-vs-magnm-vs ).
there is no general consensus on what is best, but viable alternatives do exist. An important point
is that battery sizing is important .

It seems my situation is somewhat atypical-- most PV production will be grid tied, and almost all the time the grid will
be up. So, it seems possible to reduce costs if I am willing to sacrifice some functionality, and still provide
reasonable most-of-house-ups and enough battery backup to make it a lot easier to weather an outage (with genset assistance and
2kw of pv production).

Despite warnings from some, I settled on an AC coupled system might be best.
Given my budget constraints, a smallish (200AH) battery will suffice (http://forum.solar-electric.com/showthread.php?16431-Sizing-your-backup-how-to-judge-risk-vs-cost-tradeoffs).

My contractors are willing to work with me, which (hopefully) will keep costs down

Consider the issue of UPS services

The quality of the UPS services from a basic grid-interactive, or ups coupled, system are (using
wiki defnitions at http://en.wikipedia.org/wiki/Uninterruptible_power_supply) are off-line (maintain power through
sudden outages) and surge protection), line-interactive (provide for voltage correction). And best of all is "on-line", where
power is conditioned, providing an "electrical firewall between the incoming utility power and sensitive electronic equipment."

My proposed ac coupled system will certainly provide "off-line" UPS, and might (depending on what charger/inverter is used)
provide "line interactive" protection.

Although I haven't had any obvious problems with power quality, maybe having a "on line" quality would be useful.
For one, I could continue to use a big box (generac) genset, rather then upgrading to an interactive genset).
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Comments

  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #2
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    A 200Ah battery doesn't sound like enough to provide power/power buffering for "much of the house".
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #3
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    danielh wrote: »
    I am seriously considering an AC coupled system at part of my 6.5kw PV install (see below for a synopsis of how I got there).
    This system would provide basic UPS services to much of the house. However, it will not provide clean power (what wiki calls
    online ups).

    What would it take to upgrade to such a "online" ups services? Some kind of Ac to DC to AC conversion.

    That's an ugly way to go when there are so many good interactive inverters out there. Two GTFX inverters, one XW6048 or one GS8048 would do that for you. It's not as perfect as an online system but most systems aren't even going to notice the switchover.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    A 200Ah battery doesn't sound like enough to provide power/power buffering for "much of the house".

    It isn't. It's totally inadequate. This has been explained to the OP before.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #5
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    bill von novak wrote: »
    That's an ugly way to go when there are so many good interactive inverters out there. Two GTFX inverters, one XW6048 or one GS8048 would do that for you. It's not as perfect as an online system but most systems aren't even going to notice the switchover.

    Are you concerned about spikes, noise, and other waveform distortions as well as variations in voltage caused by other users, rather than just short or long term outages, when you talk about "clean" power? If so, then there are passive power conditioning systems that can handle that part of your needs more cost-effectively than running a full-time UPS.
    If you really need to be concerned about very short interruptions during the transition from grid to inverter power, then you have atypical loads. Standard power supplies on computers and other electronics can usually ride through a power interruption of only a few cycles.
    SMA SB 3000, old BP panels.
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  • danielh
    danielh Solar Expert Posts: 69 ✭✭✭✭
    #6
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    A 200Ah battery doesn't sound like enough to provide power/power buffering for "much of the house".

    Much of the house does not include any heavy draws. Just some lights, tv, computers. Average of < 1000W, 90th percentile of 2000w. Perhaps an occasional spike for fridge and boiler.

    Is 200AH really not enough to protect that from infrequent transient spikes and outages? Forgive me I sound churlish, but I have yet to hear a good explanation of why it isn't.
    I must reiterate that battery usage will be infrequent, so small degradations in battery life are acceptable. This is NOT an off grid situation.

    BTW: I have concluded that the grail of "online" quality ower" (i.e. correcting wave form distortions; think of the difference between an inverter and a big box genset) is not worth the
    time or effort for me.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #7
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    What sorts of usage do you have that demands "cleaner" power than the grid can supply?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    Actually most off grid sine wave inverters produce cleaner power than many utility companies offer. :roll:

    Your system demands are confusing. First you say you want back-up power for when the grid goes down. That's understandable. Then you say you want protection from transient spikes. That's a different kettle of fish.

    You can have a UPS that cuts in when the power cuts out, or you can have a continuous UPS that "cleans up" the power and supplies it consistently no matter what the grid is doing. That is two different things.

    Your power needs to provide back up need to be expressed in Watt hours, not just Watts or peak Watts or "90th percentile of 2000 Watts".

    With a mere 200 Amp hours even at 48 Volts you have at most 4800 Watt hours DC to work with. Yes you can draw them down deeper and disregard battery life. The lower they go, the faster they fall off in capacity. Some batteries will take more discharge than others. Add in feeding the inverter and the conversion efficiency and you end up with about 4300 Watt hours AC. That sounds like a lot until you start running the refrigerator, TV, computers, and some lights. I go through a bit more than half that in a day running this place, and there's no TV (or a lot of other stuff).

    For such a system you would not need any PV if you had sufficient battery capacity to last 'til the power comes back. That would depend on both the length of time and how well you can keep things switched "OFF" during the outage. You can not rely on PV for supplementary backup power during an outage because it only produces when the sun shines, which is not necessarily when you need to use the power (frequently it is not as most power demands are at night in a typical household).

    You have to settle on what exactly it is you're after or you'll never be able to utilize any of the answers given on the forum.
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  • danielh
    danielh Solar Expert Posts: 69 ✭✭✭✭
    #9
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    What sorts of usage do you have that demands "cleaner" power than the grid can supply?

    None that require it. If I could of gotten it for minor cost, than perhaps my consumer electronics would be better protected.
    But it won't happen for a minor cost. So I am forgetting about that aiming for "online" quality UPS services (the "interactive" UPS services
    that are normally provided in ac or dc coupled systems are good enough)
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  • danielh
    danielh Solar Expert Posts: 69 ✭✭✭✭
    #10
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    Cariboocoot wrote: »
    Your system demands are confusing. First you say you want back-up power for when the grid goes down. That's understandable. Then you say you want protection from transient spikes. That's a different kettle of fish.
    It seems to me that they aret strong complements, requiring essentially the same equipment (so long as one is willing to accept less-than-optimal performance)
    You can have a UPS that cuts in when the power cuts out, or you can have a continuous UPS that "cleans up" the power and supplies it consistently no matter what the grid is doing. That is two different things.
    Yes, I understand. I was curious as to whether the latter option was worth considering, given my budget. Clearly, it is not.
    Your power needs to provide back up need to be expressed in Watt hours, not just Watts or peak Watts or "90th percentile of 2000 Watts".
    Yes, watt hours are key. I mention the peaks and 90th % iles to try to get a sense if these kind of loads will be significantly detrimental.
    (I could delve into what "significant" means)..
    With a mere 200 Amp hours even at 48 Volts you have at most 4800 Watt hours DC to work with. Yes you can draw them down deeper and disregard battery life. The lower they go, the faster they fall off in capacity. Some batteries will take more discharge than others. Add in feeding the inverter and the conversion efficiency and you end up with about 4300 Watt hours AC. That sounds like a lot until you start running the refrigerator, TV, computers, and some lights. I go through a bit more than half that in a day running this place, and there's no TV (or a lot of other stuff).

    For such a system you would not need any PV if you had sufficient battery capacity to last 'til the power comes back. That would depend on both the length of time and how well you can keep things switched "OFF" during the outage. You can not rely on PV for supplementary backup power during an outage because it only produces when the sun shines, which is not necessarily when you need to use the power (frequently it is not as most power demands are at night in a typical household).
    A 500w/h average is what I expect in outage situations (which might include 2kw for 10 minutes when the microwave is running, 300w when just the fridge and one laptop are on ,etc).
    If that gets me 8 hours, that is a real benefit. If nothing else (ie.; ignoring the possiblity that PV doubles that time) it allows the genset to be run shorter and more efficiently, and allows the use of nicer (quieter) genset.

    You have to settle on what exactly it is you're after or you'll never be able to utilize any of the answers given on the forum.

    Settling on "exactly" is iterative process of balancing costs and benefits, with neither easily measured.

    The answers here have been VERY helpful. I may not agree with everything said (an impossibility given the range of opinions), but
    the forum has been invaluable in helping me learn what the questions are and how to think of the answers.

    IOW: I again thank you all. Assuming you are interested in what I learn (including how I might get burnt from cutting it to close), I
    intend to report back once a system (whatever it might be) is operational.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #11
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    Yes, we are very interested in what you come up with as your solution for your needs...

    We all try here to present information and available choices. We try not to say "...this is the only way to do what you want...". Because, there are almost always multiple ways to accomplish a task, and what would be an "optimum" solution for me--may very well not be for you.

    The minimum surge support of C/2.5 -- For flooded cell batteries when charging or discharging (and for AGM when charging and nearly 100% full), seems to be a good rule of thumb to ensure that there is enough battery capacity (low charge/high charge/cold/hot/old/new) that you will have a well functioning system that will meet the demands of your loads (inverters/chargers/etc.) over time.

    Certainly, taking a battery outside of its ability to "regulate" voltage is not good for it (too high of current will overheat and warp plates, excessive gassing will erode plates/oxidize positive grids)--And over voltaging a battery system can damage the attached loads (inverters, chargers, DC loads)... So, while the battery may survive a short over voltage event, the some of the loads may not.

    If you have a C/2.25 (+10%) rate of charge/load--Will it kill something--probably not... Just a bit more likely to happen when you are at one of the other extremes (old batteries, batteries in float when an edge of cloud event peaks charging current).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    500 Watt draw average per hour would take that 4kW hour capacity down in 8 hours. (BTW, that's about 4 times my hourly average). The other concern is those spikes. It's the Peukart Effect rearing its head again. A 'frige spiking 1.2 kW on a 48 Volt system will draw approximately 25 Amps, which is only 1/8th of a 200 Amp hour battery. The trouble is that there are already loads drawing on the battery which not only add to the total Amps but at the same time reduce the battery's effective capacity at that moment making the 'frige start-up spike a higher percentage of the actual capacity. That's where you start to get into trouble with battery capacity and load spikes.

    Living off-grid I can tell you things don't work out as simple as they should. Yes, the refrigerator spike is a big one but my system is designed to handle it with the concurrent loads (which as I noted are much smaller than you anticipate). The other big loads are totally under my control, and I switch them on when I know the power is available or leave them off. That said, loads have still grown (despite my husbandly protestations) and I would be more comfortable with 2X the battery capacity and 2X the panel to charge it with. I'd also then need more generator capacity as well, because there still would be times when that would be necessary.

    I agree that the continuous UPS is not a good solution for most people. As for economics ... if that were my only concern I sure wouldn't be coming to you live via satellite from somewhere in the Cariboo wilderness! Although we do try to warn people about the cost of solar power, sometimes that is not something that matters. I've helped put together enough systems that I can say with certainty trying to minimize every aspect of a solar electric power system in order to save money is a false economy. The results can be devastatingly disappointing. On the other hand it often means I get another bunch of free batteries to sell for scrap. :D
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  • vtmaps
    vtmaps Solar Expert Posts: 3,741 ✭✭✭✭
    #13
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    daniel,

    A year old thread that I had forgotten about just got updated. It concerns a grid tie AC coupled system with battery UPS. It is innovative and not overly simple. :roll: http://forum.solar-electric.com/showthread.php?12041

    --vtMaps
    4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i
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  • danielh
    danielh Solar Expert Posts: 69 ✭✭✭✭
    #14
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    Cariboocoot wrote: »
    . As for economics ... if that were my only concern I sure wouldn't be coming to you live via satellite from somewhere in the Cariboo wilderness! Although we do try to warn people about the cost of solar power, sometimes that is not something that matters. I've helped put together enough systems that I can say with certainty trying to minimize every aspect of a solar electric power system in order to save money is a false economy. The results can be devastatingly disappointing. On the other hand it often means I get another bunch of free batteries to sell for scrap. :D
    Economics is a social science that attempts to discern how tradeoffs are made. Money is a convenient measure, when available.Often it is not.

    Which is a long winded way of saying... penny wise pound foolish is .... foolish. But I am not living off-grid, and my PV investment is much larger than the amount I am considering
    on the "off-grid" component. An investment that I have attempted to be sensible about, at least in the long term. The "off-grid" component is a bit of a luxury, so I am trying to keep
    it right-sized.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #15
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    Cariboocoot wrote: »

    With a mere 200 Amp hours even at 48 Volts you have at most 4800 Watt hours DC to work with.
    And not to put too fine a point on it, that's about 50 cents worth of grid power.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #16
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    And not to put too fine a point on it, that's about 50 cents worth of grid power.

    4800 Watt-hours of power when the grid is on: $.50
    4800 Watt-hours of power when the grid is off: Priceless :-)
    And then there is 4800 new Watt-hours every day for as long as your batteries last....

    Depends on what you need the power for, of course. And a small generator may be cheaper than adding the batteries and inverter to an existing grid-tie system. Or charging the batteries from the grid and ignoring the solar source.

    There is a large matrix of needs, desires and tradeoffs, and knowing that your are talking about 50 cents worth of grid power is certainly an important factor to weigh.
    SMA SB 3000, old BP panels.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #17
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    inetdog wrote: »
    4800 Watt-hours of power when the grid is on: $.50
    4800 Watt-hours of power when the grid is off: Priceless :-)
    And then there is 4800 new Watt-hours every day for as long as your batteries last....

    Depends on what you need the power for, of course. And a small generator may be cheaper than adding the batteries and inverter to an existing grid-tie system. Or charging the batteries from the grid and ignoring the solar source.

    There is a large matrix of needs, desires and tradeoffs, and knowing that your are talking about 50 cents worth of grid power is certainly an important factor to weigh.
    Yes, it is, and it's something I bring up in those discussions I occasionally have with folks who think that they want to "get off the grid". Nearly always, they don't.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #18
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    Yes, it is, and it's something I bring up in those discussions I occasionally have with folks who think that they want to "get off the grid". Nearly always, they don't.

    Indeed!
    Off-grid power comes at a price. If you're worried about the price, you're probably not willing to pay it. :p
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #19
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    Cariboocoot wrote: »
    Indeed!
    Off-grid power comes at a price. If you're worried about the price, you're probably not willing to pay it. :p

    My impression is that off-grid's real value is to allow you to live someplace really nice that you would not be able to manage comfortably otherwise. That sounds like your situation exactly, from your descriptions.
    SMA SB 3000, old BP panels.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #20
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    inetdog wrote: »
    My impression is that off-grid's real value is to allow you to live someplace really nice that you would not be able to manage comfortably otherwise. That sounds like your situation exactly, from your descriptions.

    Yes. Not all of a "price" is money. :D
    But if you don't mind sharing the yard with deer, moose, bears, hummingbirds, eagles, ravens, chipmonks ....
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #21
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    heck, i'm on the grid and i share it already with many of those listed excepting moose and bears. not too sure of those birds being here, but we've got owls, woodpeckers, crows, and i'm not sure if those are hawks around here as they have huge wingspans. oh and there's also racoons, groundhpgs, turkeys, and i've even seen a few foxes (4 legged) in the area in the past all in a somewhat urban area.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #22
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    niel wrote: »
    heck, i'm on the grid and i share it already with many of those listed excepting moose and bears. not too sure of those birds being here, but we've got owls, woodpeckers, crows, and i'm not sure if those are hawks around here as they have huge wingspans. oh and there's also racoons, groundhpgs, turkeys, and i've even seen a few foxes (4 legged) in the area in the past all in a somewhat urban area.
    I'm on the grid in the SE corner of Austin, inside the city limits, and I've got deer, raccoons, armadillos, possums, foxes, feral cats, roadrunners, hawks, buzzards, crows, owls, hummingbirds, lots of other birds, and the occasional coyote wandering through my back yard. It's like the freakin' Nature Channel out there! :D

    No moose or bears, though.
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #23
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    I'm on the grid in the SE corner of Austin, inside the city limits, and I've got deer, raccoons, armadillos, possums, foxes, feral cats, roadrunners, hawks, buzzards, crows, owls, hummingbirds, lots of other birds, and the occasional coyote wandering through my back yard.

    We're in a canyon preserve in San Diego and get deer, all sorts of rodents, seabirds, hawks, eagles, snakes, bobcats, hummingbirds, rabbits, coyotes etc. We also have owls which sit outside our bedroom and hoot all night.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #24
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    bill von novak wrote: »
    We also have owls which sit outside our bedroom and hoot all night.
    Get yourself a slingshot. :D
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #25
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    I like the hoot owls. And the loons. Especially the loons.

    What I don't have is people. :D
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #26
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    No one mentioned skunks. Last summer my and my daughters dashounds got skunked. I was the one that gave them baths. Was really lucky that they didn,t get the 100% skunk stream. solarvic
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  • bill von novak
    bill von novak Solar Expert Posts: 891 ✭✭✭✭
    #27
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    Get yourself a slingshot. :D

    I'm thinking a really, really bright flashlight.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #28
    Re: "online" quality UPS from a grid-interactive system: how feasible?

    solarvic,
    we've got them down here too, but they only rarely come around and you know it when they do. phewwww.

    all,
    i think we've deviated enough on this and need to allow the original subject matter to continue to be addressed.
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #29
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    solarvic wrote: »
    No one mentioned skunks. Last summer my and my daughters dashounds got skunked. I was the one that gave them baths. Was really lucky that they didn,t get the 100% skunk stream. solarvic
    Did you use tomato juice to bathe them? Something in tomato juice works to neutralize skunk, um, effluent, or so I hear.

    OK, back to solar stuff... :D
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  • danielh
    danielh Solar Expert Posts: 69 ✭✭✭✭
    #30
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    ggunn wrote: »
    Did you use tomato juice to bathe them? Something in tomato juice works to neutralize skunk, um, effluent, or so I hear.

    OK, back to solar stuff... :D

    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #31
    Re: "online" quality UPS from a grid-interactive system: how feasible?
    danielh wrote: »
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.
    all work and no play makes jack a dull boy.all work and no play makes jack a dull boy.

    All work and no play makes "jack". :-)
    SMA SB 3000, old BP panels.
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