Backup Inverter

NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
If the main inverter fails while I'm not at home, many bad things will happen.

It would be nice to have a small inverter (240V ~1500W) that would automatically come up when the main inverter fails.

Are there any inverters that are designed or could be used for this?

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Backup Inverter

    I can think of a couple of different ways to do it. Both involve relays held in one position by the main inverter and dropping into the other if its output fails.

    Either use an inverter with a built-in transfer switch (expensive) or get a separate automatic transfer switch. The function is the same as any auto back-up circuit: AC fails, transfer switch connects vital loads to alternate power source.

    If you can use an inverter that has a standby mode it can be "at the ready" while uses less than full power. If even that uses too much then you have to get a bit more complex so that the back-up inverter is started before the loads are switched to it.
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Backup Inverter
    Either use an inverter with a built-in transfer switch (expensive) or get a separate automatic transfer switch. The function is the same as any auto back-up circuit: AC fails, transfer switch connects vital loads to alternate power source.

    Thank you Cariboocoot.

    So, the transfer switch is the way to go. The problem here is that my distribution panel is in the house, may be 100 feet from the batteries, so I would have to switch the whole thing. Big transfer switches are expensive. Any way to get around without a transfer switch?

    May be I shouldn't worry about this. How often invertors fail?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Backup Inverter

    Not very often.

    You'd probably have to do some re-wiring; install a "critical load" sub-panel to switch. Bit of a pain to put it mildly.
  • BB.BB. Super Moderators, Administrators Posts: 32,026 admin
    Re: Backup Inverter

    Here are a couple of transfer switches at $60 to $120 each:

    wind-sun_2249_13407080PowerMax PMTS-50 Automatic AC Transfer Switch

    wind-sun_2249_13402657
    PowerMax PMTS-30

    I think they will do the job. The small one (at least) has a 15 second delay (to allow generator to warm up before taking load)--But, as I remember, there is a "test" switch that can disable the delay.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Backup Inverter
    NorthGuy wrote: »
    If the main inverter fails while I'm not at home, many bad things will happen.

    It would be nice to have a small inverter (240V ~1500W) that would automatically come up when the main inverter fails.

    Are there any inverters that are designed or could be used for this?
    If you have to have 240 V you could use a transformer with one of these. I have one that I keep my Refrigerator, Freezer and a couple lights on. Meanwell TN-1500 it comes 12v, 24V or 48 V run it in the UPS mode, $550 - $599.00. It's full featured, the charger isn't much, but has a 30 amp solar controller built in. This is my second year, no issues, I don't even turn it on till I am leaving. They have a remote for $29. The quality is impressive.

    http://www.meanwell.com/search/tn-1500/TN-1500-spec.pdf

    I got the " G " model with GFI plug in's, they have a hard wire, " F " model. There is just not much in the middle price range in TSW. You don't really have to have a sub panel for it, I just ran it off of the breaker in a loop like a UPS, meets my code.
    .
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Backup Inverter
    NorthGuy wrote: »
    If the main inverter fails while I'm not at home, many bad things will happen.

    How bad are the bad things that will happen?

    Our backup system is just a manual transfer switch that takes the inverter and battery bank completely out of the picture and switches everything to gen power. It requires manually starting the generator and manually throwing the switch**

    Attachment not found.

    You got a Genny Rack Guardian - right? So what'd you do with the EZ-Switch that comes with it? If you install that EZ-Switch it has all the auto-start paraphernalia in it already, and will start the Genny Rack and transfer to gen power 10 seconds after your inverter fails - automatically. It's what those generators were made for.

    Inverters don't fail very often.

    **I have a highly-trained and experienced OGW (Off-Grid Wife) that knows how to keep the power on if something fails when I'm gone - including knowing how to start the generator with the pull rope if the starter don't work, and how to switch to the backup generator if the primary tosses a rod into the next township. But if you have mission critical things going like Life Support Systems for fish in a tank or something, the Generac EZ-Switch can be rigged up to auto-start your generator and take over. The controller in the genset monitors the 240V input at the EZ-Switch and if it drops out of range it waits 10 seconds before starting the genset, then the EZ-Switch makes the transfer. But you do have to tap off power at the Customer Connection Block for manually running the generator for battery charging with the inverter, etc..
    --
    Chris
  • Blackcherry04Blackcherry04 Solar Expert Posts: 2,490 ✭✭✭
    Re: Backup Inverter

    lol.... OGW, I got one, she calls me, I am out of town, says the generator started, I am like ok, call me when it stops. She calls back in about 30 Minutes and says it stopped. I get home 2 days later and everything is ran down. I go to the generator shed and I am looking and try to start the generator, no joy. I look at the battery and the post is melted off and the cable is laying there. It never started, was just turning over on the starter. The way Kohler installed the starter solenoid was upside down and if it got moisture in it the spring would rust out and the contacts would drop down and let the starter run on it's own. Lesson learned, new battery, new cable, new starter, new solenoid .......re-educated wife..... and $500 problem solved.
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Backup Inverter

    That's what I'm saying - the highly-trained and experienced OGW is generally more reliable than automatic transfer switches because if something fails and the power goes out a good one WILL find a way to get it working again. You just have to make sure she's got enough resources to work with, and knows how to use 'em. My wife knows that we are the power company and there's nobody you can call if something goes awry. So she has taken enough interest in our system to learn every aspect of it, what the backups are, how to apply and use them, and how to detect a problem and take corrective action before the problem becomes an emergency.

    No matter how automatic and fool-proof you try to make something, it will fail at some point - usually when it's needed most. For off-grid power automatic has to be considered a convenience, not the primary method of fixing a problem.
    --
    Chris
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Backup Inverter

    Thank you everyone for your suggestions. Also, for the links to the products.

    I certainly think that my wife would do much better job than any automated system. The problem is that we usually go on vacation together and there's no one in the house.
    ChrisOlson wrote: »
    How bad are the bad things that will happen?

    My wife's friend told us a story. Her furnace ran out of propane, water pipes froze and broke down, then there was a flood and the water froze everywhere. The whole house was ruined.

    So, my main concern is something of that sort.
    ChrisOlson wrote: »
    You got a Genny Rack Guardian - right? So what'd you do with the EZ-Switch that comes with it? If you install that EZ-Switch it has all the auto-start paraphernalia in it already, and will start the Genny Rack and transfer to gen power 10 seconds after your inverter fails - automatically. It's what those generators were made for.

    My EZ-Switch is connected. It does not transfer anything, simply connects and disconnecs the generator to inverter. It's very useful as a quick disconnect to prevent power glitches when generator disconnects from the inverter. The generator also runs for about a minute after the disconnect without any load, which is supposed to prolong generator life.

    I also have a manual transfer switch, so I can bypass inverter and run all the house on the generator. But it's manual.

    I start the generator by disconnecting sensing wires, which simulates power outage. If the inverter fails, there will be real outage, so the generator will start, however it'll be connected to the dead inverter, so the power will not go into the house. So, it'll run until my return without any real use. To stop it, I would need to show it that the power is back, which would be a function for backup inverter.

    I certainly can keep the generator running, but to re-direct its power to the house, I would need another transfer switch. On the other hand, running generator for few small loads while it's plenty of solar power available seems like a huge waste. I thought a backup inverter would work the best.
    ChrisOlson wrote: »
    Inverters don't fail very often.

    May be I should relay on that. But, just as you said, if it fails, it'll be when you need it the most.
  • BB.BB. Super Moderators, Administrators Posts: 32,026 admin
    Re: Backup Inverter

    Turning of water/well pump, draining lines for hard freezes?

    Food in fridge/freezer is another big mess with a multi-day power failure.

    Then there is a remote alarm (neighbor, message to your phone) if the power fails (or lack of 2x a day "everything is good" message)--And is there somebody near by (you trust) that can address issues until you return.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Backup Inverter
    NorthGuy wrote: »
    I certainly think that my wife would do much better job than any automated system. The problem is that we usually go on vacation together and there's no one in the house.

    Another thing you will find about living off-grid is that an off-grid home can never be left unattended for any length of time. The home requires a house sitter if you're going to be gone for long. That's especially true for us in the winter where our only source of heat is the wood furnace. But getting a house sitter is the best because it gives you peace of mind so you can enjoy your vacation instead of worrying about whether or not something went wrong.

    Yeah, I know there's a lot of people here that have part-time off-grid cabins or such that just walk away and leave them for weeks. But that's not the same as a full-time off-grid home where failure to even run the well pump once a day in winter can result in frozen underground water pipes and sewer drain field here.
    --
    Chris
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Backup Inverter

    Well if by "just walk away" you mean drain the water lines, disassemble the pump, clean out the septic, put away the generators, lock up the shed, remove all the stuff from the 'frige and anything that might freeze, shut everything down, disconnect the inverter, check the batteries, finally lock up and hope you get down the road through the mud ... well, then yes. Takes me two days to 'close up'.

    It's never easy no matter which way you do it.
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Backup Inverter
    Takes me two days to 'close up'.

    Exactly, and a good example of a seasonal cabin or off-grid home. I know people who have off-grid cabins that they leave for a week at a time and only go there on weekends too. But there's still a "shutdown" procedure that they follow - make sure everything is turned off, make sure there's nothing in the 'fridge that will spoil, etc..

    For a full-time off-grid home where you expect it to be sort of "normal" when you walk in the door, the most reliable thing I've found to make sure it's that way when we get home is my folks coming to live in it while we're gone. There's too many daily chores that have to be done, right down to even watering the house plants, to do it any other way. We'll leave it for 2-3 days unattended in the summer time, but never more than that - we have somebody come and house sit because there's too many things that could go wrong. And truthfully, all the stuff that could go wrong is the automatic stuff in our power system that normally takes care of itself. It's a lot more complicated than a grid connected home is, and the more complicated something is, the more likely it is to have a problem.
    --
    Chris
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Backup Inverter
    ChrisOlson wrote: »
    Exactly, and a good example of a seasonal cabin or off-grid home. I know people who have off-grid cabins that they leave for a week at a time and only go there on weekends too. But there's still a "shutdown" procedure that they follow - make sure everything is turned off, make sure there's nothing in the 'fridge that will spoil, etc.

    Coot needs to go through this difficult shutdown procedure because it is seasonal and will not be heated, supplied with water/electricity etc. during the worst time of the year. If he wanted to come back three days later, he might've decided not to go through that procedure, but would rather live everything on.

    For the house, your ability to leave it for a while depends on the specific systems that you use. If you have a wood burning furnace you cannot leave the house for a long time during winter. It would be the same for both on-grid and off-grid house. In any house, when you leave, something may brake, e.g. furnace may stop working, worse yet, something may overheat and cause fire.

    Off-grid power generation is a complex system, which certainly adds to the list of things that may happen. Some maintenance has to be done manually - e.g. you need to add water to batteries (althhough they make auto-watering systems too), or snow may need to be cleared from panels. However, most of the maintenance tasks can be automated, and today's technologies make it rather easy to set up. It is quite possible to build a system that would let you leave for a week (or a month) and reasonably expect that everything will keep working.
  • solar_davesolar_dave Solar Expert Posts: 2,382 ✭✭✭✭
    Re: Backup Inverter
    NorthGuy wrote: »
    Coot needs to go through this difficult shutdown procedure because it is seasonal and will not be heated, supplied with water/electricity etc. during the worst time of the year. If he wanted to come back three days later, he might've decided not to go through that procedure, but would rather live everything on.

    For the house, your ability to leave it for a while depends on the specific systems that you use. If you have a wood burning furnace you cannot leave the house for a long time during winter. It would be the same for both on-grid and off-grid house. In any house, when you leave, something may brake, e.g. furnace may stop working, worse yet, something may overheat and cause fire.

    Off-grid power generation is a complex system, which certainly adds to the list of things that may happen. Some maintenance has to be done manually - e.g. you need to add water to batteries (althhough they make auto-watering systems too), or snow may need to be cleared from panels. However, most of the maintenance tasks can be automated, and today's technologies make it rather easy to set up. It is quite possible to build a system that would let you leave for a week (or a month) and reasonably expect that everything will keep working.

    I had a friend that lived in Wonderview, CO (9200 ft elevation) back in the 80s. Heated primarily with wood, but had electric backup. He and the wife took a needed vacation trip to Mexico in January one year setting the electric heat to 55F. If you ever live at 9200 ft you would understand the need. They had a 3 day power outage while gone. They returned to find every pipe in the house had burst, the toilets all cracked and water running everywhere in the house, the power came back on about 48 hours before their return and thawed everything out.
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Backup Inverter

    Had it happen with the 'new' house before we got fully moved in: came up with another load (January) and found the furnace igniter had quit. Nothing like dropping the house temp to -20C to show up all the flaws. Fortunately the plumbing wasn't much good anyway. :p

    It is impossible to plan against every contingency. You'd have a ridiculous amount of redundant back-ups that most of the time would just sit there being a wasted investment. Weigh the cost of back-ups against the cost of repairs/replacements on a "likely to happen" basis and try to find a practical compromise.
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Backup Inverter

    Just three weeks ago we had a thermostat on one of our water heaters fail to click out. The wind was blowing like a banshee and instead of shutting off when the pre-heater got hot and shutting the turbines down like it's supposed to, it kept heating. It blew that popoff valve on the top of the water heater and sprayed boiling water all over in the laundry room. We got hoses on those popoff valves that are routed down by the floor drain but never planned for having the hose whip around like a wild snake.

    Running boiling water down the drain like that in winter time will freeze the drainfield up tighter than a drum if you don't catch it right away and run some cold water to prevent the drainfield from steaming. Shutting all that down to leave for a week in the winter won't work because the wind turbines depend on it to have someplace for power to go when the wind is blowing - the bank can't handle the full output from the turbines. So it's like, how much do I shut down here just to leave for week? Or it is easier to just get somebody to baby sit the whole thing in case something like that would happen?

    Automatic stuff is nice because it's convenient and cool. But it's kind of like automatic transfer switches on emergency standby generators - we learned years ago that they don't work unless they are tested and certified on a regular preventive maintenance schedule - so when the time comes when it HAS to work the rodents that chewed up a bunch of insulation and made a nice nest in the switchgear have already moved to a different nice warm place so the switchgear works.
    --
    Chris
  • NorthGuyNorthGuy Solar Expert Posts: 1,913 ✭✭
    Re: Backup Inverter
    ChrisOlson wrote: »
    Or it is easier to just get somebody to baby sit the whole thing in case something like that would happen?

    It is entirely possible that the "home-sitter" may not notice what happened fast enough, or doesn't know that it's necessary to put cold water down the drain.

    It may be harder to educate people about your system than have automatic safety devices, which will react as you programmed them to. Of course you need to test your stuff regularly.

    Backup Inverter is a good thing to have even if you're at home when main inverter fails because it may take at least several days to repair an inverter or get a new one.
  • ChrisOlsonChrisOlson Banned Posts: 1,807 ✭✭
    Re: Backup Inverter
    NorthGuy wrote: »
    Backup Inverter is a good thing to have even if you're at home when main inverter fails because it may take at least several days to repair an inverter or get a new one.

    The thing is, inverters that are running 24/7 are not that likely to fail unless hit by lightning or something. 11 years this coming June and we have never had one go bad. I don't know how other off-grid folks have fared with their inverters but I think it is a quite rare occurrence to have one just suddenly quit working. It seems that most folks that have had problems with an inverter either hooked something up wrong, it sits around without being used for awhile, or it gets hit by lightning.

    Yes, it can take a few days - but despite what others say about Schneider Tech Support, Mike and Wendy and the others there seem quite knowledgeable, have answered every question I ever had, and they will get you back up and running pronto if there's a problem. And you got the generator while it's down.

    That's my 2 cents on it.
    --
    Chris
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