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Power Inverter to run boiler?

2

Comments

  • sunlight33
    sunlight33 Member Posts: 311


    My main consideration is to have something in place that I would monitor and control just to run the boiler should there be a power outage for a limited amount of time.

    a UPS would work well in this case.
    Solid_Fuel_Man
  • pecmsg
    pecmsg Member Posts: 1,979
    DO NOT USE A RELAY!!!

    Only approved transfer switches are allowed. There cheap so invest in one. When power comes back on the house lights are on so you will know.
  • nibs
    nibs Member Posts: 462
    I stand corrected, my idea would of course work, but if an approved device is available that is the way to go.
    Incidentally a friend who used to own a company that built and maintained high voltage power lines and transformer repair company will be joining us here in Mexico this weekend, will ask him for his views on the subject.
  • Leonard
    Leonard Member Posts: 903
    edited February 2019
    Biggest thing you have to check is total watts ( and VA) your loads needs. And how long you need them to run. That determines how much energy you have to store ( size of bats or gallons of gen fuel)

    Gas valve, sparker , controls can be an "easy" load for a bat. As add small motors ( circulator , motor for combustion air and oil pump ) it gets harder. 1hp air handler blower likely needs gen unless you have a LARGE bank of bats, I haven;t run the numbers.

    I've seen a car sized deep cycle bat , it only had ~ 50 amp-hrs, and to protect bat life you can only draw ~1/2 that .

    -----------------------------------------
    RELAYS...... not sure if building electrical code applies to appliances like furnaces. Might be able to attach relay as part of furnace , not as part of wiring feeding furnace. Likely a gray area so you have to check it out. Seems it might violate UL listing of furnace, but I don't know what code or fire insurance problems that creates.

    I have not seen any automatic trasnfer switches for single loads like a furnace. Closest thing I have seen are UPS units for computers. Might search the web. Before I got a generator I picked up a few free used computer UPS , junked the bad bats and brought out bat leads so I could jumper them to running cars.
    -----------------------------------------------------

    NY-ROB ....... yes it's the same type of alarm as I was thinking of.
    Solid_Fuel_ManNY_Rob
  • Leonard
    Leonard Member Posts: 903
    Lets see what one 50 amp hour 12V bat can do.

    Can only take ~ 1/2 that without reducing bat life so 25 amp hours.

    Assuming bat will let you take a max current of 20 amps out of it without lot of losses. Then that's 20 amps for 1.25 hours

    At 12 V thats 20x 12 = 240 watts asuming inverter give you 85 % efficiency that's 204 watts to the load. At 120VAC that's 1.7 amps

    Sounds like
    One 50 AH bat = 1.7 amps @ 120VAC for 1.7 hours. ....... going to need a lot more bats.

  • Leonard
    Leonard Member Posts: 903
    Typo .... less hours ....

    Sounds like
    One 50 AH bat = 1.7 amps @ 120VAC for 1.25 hours. ....... going to need a lot more bats.
  • Jamie Hall
    Jamie Hall Member Posts: 15,838
    Going to need a lot of bats... indeed! And that is exactly the problem. Even an 8D -- 210 amphours at the 10 hour rate -- would only give you 5 hours.. . And that is a big battery. Like Peterbilt size...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Leonard
    Leonard Member Posts: 903
    And in my example I think it's likely a big stretch to get 20 amps continuous for 1.25 hour from car sized bat ~ $125+ each

    Thats why they use generators. ( RV gens can self start on remote signal...... either manual remote switch or from automatic transfer switch)

    Energy density of chemical fuels ( gasoline) far exceeds that of bats.

    That 12V bat with 25 amp hrs of energy = 300 watt hrs
    1gal of gasoline -128kBTU = 37,513 watt hrs

    Even assuming gen is 17% efficient ( at full load) that
    1 gal of gas converts to 6,377 watt hrs of energy ...21X more !!!!

    So it takes 21 bats ( ~ $2,600+) to store same energy as $2.20 1gal of gas

    Solid_Fuel_Man
  • EricPeterson
    EricPeterson Member Posts: 77
    Clearly a generator is the way to go for extended time periods. But for a few hours I am still considering the power inverter.
    Here is a website with some good information on such a setup: link
    First though I need to determine the power draw of my boiler setup (electronics, vent damper, 1/25 HP pump, 3 zone valves).
    Then I will be able to make an informed decision.
  • sunlight33
    sunlight33 Member Posts: 311
    Get a killawatt usage monitor for the energy draw in 24 hours.
    Solid_Fuel_Man
  • pecmsg
    pecmsg Member Posts: 1,979

    Clearly a generator is the way to go for extended time periods. But for a few hours I am still considering the power inverter.
    Here is a website with some good information on such a setup: link
    First though I need to determine the power draw of my boiler setup (electronics, vent damper, 1/25 HP pump, 3 zone valves).
    Then I will be able to make an informed decision.

    Why are you worried about a Few Hours???
  • ChrisJ
    ChrisJ Member Posts: 11,565
    edited February 2019
    NY_Rob said:

    ^ the nice thing is with a DPDT relay it would be pretty much impossible to feed the inverter output back into the grid. By design only one set of contacts can be closed at any time.




    I use a 50 amp DPDT relay to charge my Chevy Bolt (Electric Vehicle) it will easily handle the 32amp draw from the Bolt all day long if needed.

    I tried using a contactor like this to turn a fan on when I cut power to the coil and it failed miserably. To my surprise, by it's design the contacts have almost no pressure on them when the coil isn't energized. It rests against the upper set, just barely.

    This caused one of them to arc a lot with only a few amps being drawn. No matter what I did, I couldn't get it to work and yet the typically used bottom set of contacts (coil energized) worked great.

    It made me wonder if the upper set are ever used on these and if they are, for what.

    The one I used was a 40 or 50A brand name contactor.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • NY_Rob
    NY_Rob Member Posts: 1,370
    Leonard said:


    So it takes 21 bats ( ~ $2,600+) to store same energy as $2.20 1gal of gas

    Now you see the difficulty in designing/building Electric Vehicles.

    My Chevy Bolt has a 60kWh battery with an EPA range of 238miles. That 60kWh battery weighs 960 lbs.

    Even an inefficient automobile that gets just 20mpg would use 11.9 gal of gas to drive 238miles. That 11.9 gal of gas would only weigh 75lbs compared to my Bolt's 960lb battery.

  • Leonard
    Leonard Member Posts: 903
    edited February 2019
    Pretty telling that ~$2 of gasoline and a $500 gen can replace ~ $2600 of bats..

    Bat Amp-hr capacity is NOT a constant, as you raise amps drawn , bat amp-hr capacity drops. So if you go with bat backup find bat amps you need and check bat for corresponding amp-hr capacity.
    I just looked at this link, I think reduced amp-hr capacity will surprise you
    8D bat specs -- > https://www.trojanbattery.com/product/8d-agm/


    Another thing I didn't mention is you need to start off with even more bats than that just to maintain capacity over time . They lose capacity as they age. Also have to replace them every ~ 10 years even with proper care. All I see with bats is $$$$$$$$$$$$$$$$$.

    Kill-a-watt meter $20, VERY useful, can measure KWH too, and KW, VA, PF, volts-rms, amps-rms
    https://www.amazon.com/P3-P4400-Electricity-Usage-Monitor/dp/B00009MDBU/ref=sr_1_1?ie=UTF8&qid=1549655142&sr=8-1&keywords=kill-a-watt+meter

    I forgot about RV inverter/chargers ( with bat bank) they may have automatic transfer switches. Not sure.

    I didn't talk about lithium bats because their exstream cost cancels out their high energy density. ( they too suffer from aging capacity reductions.)

    Too bad politicians don't examine the technical facts before they push for battery storage of solar power. hummm...... maybe I can get a grant to study the problem..... and bring them up to speed on what technical people already know.
    Solid_Fuel_Man
  • nibs
    nibs Member Posts: 462
    So as promised yesterday, I am sitting with my lineman friend and have asked him about two things.
    1) how do you check if a downed line is hot?
    "we carry a stick with a meter on it and check every line before we touch it." If the line is dead we connect a ground to it, so then we know it will not go live on us".
    2) When there is a power outage at your house how do you connect a genset?
    "I throw the main breaker and plug a generator into a wall socket".
    Keep it simple stupid, he says.
  • ChrisJ
    ChrisJ Member Posts: 11,565
    I suspect, or rather hope that the Pocos setup is a lot more efficient than a portable generator.

    That's not a valid comparison in my book.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • sunlight33
    sunlight33 Member Posts: 311
    nibs said:


    2) When there is a power outage at your house how do you connect a genset?
    "I throw the main breaker and plug a generator into a wall socket".
    Keep it simple stupid, he says.

    This is doable but one needs to watch the power level to avoid starting an electrical fire.
  • Leonard
    Leonard Member Posts: 903
    edited February 2019
    Gasoline internal combustion engines are ~ 17% efficient (at fullload, less at partial load), at converting fuel energy into electricity. I've calculated that on 5kw to 60kw gens. Didn't calculate larger ones but I have no reason to believe they are better. Diesel might be little better.

    Think utility steam turbine gens with combined regenerative steam cycles are ~ 40%. Turbines lose efficiency RAPIDLY when not run at full load,that's why they stage several of them in power plants.

    Worked at GE on fuel cell R&D, we were shooting for higher efficiency, direct energy conversion from hydrogen to electricity. DOE funded R&D after arab oil embargo. Hydrogen to be obtained from coal reforming.
    ----------------------------------------------

    "I throw the main breaker and plug a generator into a wall socket".
    Keep it simple stupid, he says.


    Technically can work fine, not legal though, insurance won't cover damages or liability. Have a outage when your not home, Wife or kid forgets to open main breaker to street , street line becomes live. Street transformers will happily run in reverse and turn your 120V into 25kV. Utility workers have died that way, (they don't always ground the line) and home owners went to jail for murder...has happened. Besides when power comes back on your gen will let the magic black smoke escape.

    During outages before working on lines utility repair crews check out houses with gens they hear running. IF they are illegally backfeeding into a wall outlet they pull meter, cut and remove powerline from house to street pole. Your left on $$$$$$$$$$ gen power for month or more till your court date comes up and judge tells you why you were wrong and gives you a large fine. Then utility puts you in the que to eventually get around to reconnecting you, at your cost.
    Jean-David Beyer
  • nibs
    nibs Member Posts: 462
    Was quoting a very experienced pro, who wired his house and hundreds of miles of high voltage transmission lines.
    I thought it humorous that he used the lowest tech method possible, but understand that he did it from a knowledge base that most of us are unaware of.
    In other words, "Don't do this at home folks".
    The interesting thing for me, was that competent linemen are not likely to get a shock from the negligent use of a home generator. His mantra is "if it is not grounded, it is not dead".
    He tells the story of a lineman, who had a habit of not grounding the lines he was working on. The lineman is now minus two limbs as works as a safety instructor for the trade.
  • ChrisJ
    ChrisJ Member Posts: 11,565
    edited February 2019
    Hmmm.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Leonard
    Leonard Member Posts: 903
    edited February 2019
    They're taught to ground everything, but sometimes don't . Maybe was tired at end of shift and didn't want to go back down and haul those heavy grounding jumpers up pole.

    One story I read was a dead end street with few houses on it. Utility guy was working on restoring power to house at end of street. He had shut off utility power to his location. House looked to be empty and heard no gen running so didn't go thru usual line grounding procedure. House at end of road was backfeeding to street and line he grabbed was live. He died. Home owner went to jail for murder.

    I don't know, maybe homeowner was using a battery bank inverter so it wasn't making gen noise??

    Worst case senerio......... but it occasionally happens.

    Without a transfer switch , Problem is it's easy to forget a little thing ( open main breaker) when your concentrating on getting the bigger job done. How many times on the job have you forgotten a part, tool , or forgot to connect a wire , I have . Are called mistakes, we're not perfect. So law requires a transfer switch to protect lives.

    Here for whole house gen they allow interlocks on main breaker panel instead, ~ $50 and no removing meter to install. That's what I'll use. Only heard of 1 state that doesn't allow interlocks, New Jersey

    whole house interlocks ---> https://natramelec.com/
    furnace transfer switch ----> https://www.northerntool.com/shop/tools/NTESearch?storeId=6970&ipp=48&Ntt=Model#+TF151
    NY_RobSolid_Fuel_Man
  • ChrisJ
    ChrisJ Member Posts: 11,565
    edited February 2019
    > @Leonard said:
    > They're taught to ground everything, but sometimes don't . Maybe was tired at end of shift and didn't want to go back down and haul those heavy grounding jumpers up pole.
    >
    > One story I read was a dead end street with few houses on it. Utility guy was working on restoring power to house at end of street. He had shut off utility power to his location. House looked to be empty and heard no gen running so didn't go thru usual line grounding procedure. House at end of road was backfeeding to street and line he grabbed was live. He died. Home owner went to jail for murder.
    >
    > I don't know, maybe homeowner was using a battery bank inverter so it wasn't making gen noise??
    >
    > Worst case senerio......... but it occasionally happens.
    >
    > Without a transfer switch , Problem is it's easy to forget a little thing ( open main breaker) when your concentrating on getting the bigger job done. How many times on the job have you forgotten a part, tool , or forgot to connect a wire , I have . Are called mistakes, we're not perfect. So law requires a transfer switch to protect lives.
    >
    > Here for whole house gen they allow interlocks on main breaker panel instead, ~ $50 and no removing meter to install. That's what I'll use. Only heard of 1 state that doesn't allow interlocks, New Jersey
    >
    > whole house interlocks ---> https://natramelec.com/
    > furnace transfer switch ----> https://www.northerntool.com/shop/tools/NTESearch?storeId=6970&ipp=48&Ntt=Model#+TF151

    Please stop repeating something that isn't true.

    Some towns in NJ may not allow them. I don't even know if that's true or not. All I could find is that some inspectors didn't like them.

    There is no "state code" that I could find.

    If you know of a place it's stated please post a link.


    Anyone that plans on doing such work needs to contact their building official and find out what is actually allowed and what isn't allowed in their area. This "I heard" bologna doesn't work.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • NY_Rob
    NY_Rob Member Posts: 1,370
    edited February 2019
    Leonard said:


    Without a transfer switch , Problem is it's easy to forget a little thing ( open main breaker) when your concentrating on getting the bigger job done. How many times on the job have you forgotten a part, tool , or forgot to connect a wire , I have . Are called mistakes, we're not perfect. So law requires a transfer switch to protect lives.

    I hate to admit it, but I used to back-feed my generator into my panel via two dedicated 20amp outlets (each on a different panel leg) and a switched off main breaker.
    One day after testing my generator under load, I flipped the main breaker before flipping off the two 20amp outlet breakers - the generator was still running. All that happened was the two 20amp breakers instantly flipped to off. No damage to the generator, outlets, etc. I got lucky.
    Point is... it's too easy to make mistakes when taking shortcuts.

    Older and wiser... I now have a proper UL approved interlock switch and proper generator inlet port on the outside of the house so it's impossible to back-feed into the grid no matter what I do or don't do.

    Solid_Fuel_Man
  • Leonard
    Leonard Member Posts: 903
    edited February 2019

    Please stop repeating something that isn't true.
    Some towns in NJ may not allow them. I don't even know if that's true or not. All I could find is that some inspectors didn't like them.There is no "state code" that I could find.



    ChrisJ ....... OK
    i'm just quoting some guys from NJ on Onan gen sub-forum of Smokstak.com that keep repeating that. One is a licensed electrician. Maybe it's just his city, but he talks about NJ as a whole. I'll look for the link later.

    I have an emergency that just happened. my only circultor died and I don't have spare parts. I'm in Manchester, NH. going to 13 deg tonight. I'll start a new thread on it and post info, after I check it out more.

    Motor keeps short cycling, suspect it's going out on internal thermal

    Oiled it few weeks ago,suspect pump is dragging. More news after I check it out more. Thinking of oiling it with penetraing oil
  • ChrisJ
    ChrisJ Member Posts: 11,565
    @Leonard I dont want a link to a forum, I meant a link to an official document.

    :)


    Regarding your pump, I would post a separate thread.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Leonard
    Leonard Member Posts: 903
    On electrical code I don't have any other knowledge on that for NJ. I will ask about it on that other website though. You raise a good point.
  • Jamie Hall
    Jamie Hall Member Posts: 15,838
    The comment "some inspectors don't like them" is the bottom line on that one. I've misplaced my electrical code -- and anyway it's a couple of decades out of date. What I can say, though, is that when I was a building inspector -- far away and long ago, in a different galaxy -- I, at least, would have required a UL or CSA listed transfer switch...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ChrisJ
    ChrisJ Member Posts: 11,565
    edited February 2019
    > @Jamie Hall said:
    > The comment "some inspectors don't like them" is the bottom line on that one. I've misplaced my electrical code -- and anyway it's a couple of decades out of date. What I can say, though, is that when I was a building inspector -- far away and long ago, in a different galaxy -- I, at least, would have required a UL or CSA listed transfer switch...

    So, you as an inspector would fail a UL approved interlock made by the manufacturer of the panel even though code says it's ok?

    What would this decision be based on?
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Jamie Hall
    Jamie Hall Member Posts: 15,838
    No, @ChrisJ , inspectors don't make code, although you might be amazed at how many situations come up which aren't covered in the code -- or which are contradictory. They have to use their best judgement -- which, granted, isn't always correct. To the best of my recollection, the question of an interlock as distinct from a transfer switch never came up -- but that was some forty years ago, and I'm not sure they even existed then. Honestly all I ever saw were either manual or automatic transfer switches -- if they had them at all, and we required them.

    The business of being a building inspector -- particularly in a very rural state (which Vermont, where I was doing this, was at that time) was an interesting one. I wouldn't want to do it now -- the regulations and codes now are much stricter, and there is very little room for intelligent (we hoped) and safe (we hoped) improvisation nowadays. But back then, and in that environment, we not only inspected (and we were all cross-licensed in at least two and usually three of the major trades -- plumbing, heating/steam fitting, electrical -- as well as being PEs with at least agricultural and sanitary and usually structural qualifications), we often would help with drawing plans and specifications for people -- and not infrequently pitching in to do some of the work ourselves. The work was wildly varied -- everything from vetting the plans for a super clean manufacturing facility to finding a septic system (if there even was one) on some farm to helping run a well drilling rig to... you name it. We could be -- and were, once in a while -- pretty tight on interpretations, but most of the time the emphasis was on figuring out how to make something work right and safely, rather than on being a ****. A tremendous amount of personal responsibility -- but I really enjoyed it -- and learned a lot. The tales I could tell... !
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Solid_Fuel_Man
  • Leonard
    Leonard Member Posts: 903
    edited February 2019
    On that gen website there are a lot of electricians. Some have seen old breakers that continued to supply current when the breaker was in the off position. I'm guessing that is the concern. There was one breaker manufacture in particular, pacific something or other maybe. They might have gotten their UL listing pulled.

    Granted they likely were old breakers. But one of the electricians brought up the issue breakers are only rated for 240V . If utility and gen happen to be fully out of phase then breaker contacts could see 480V across them , possible breaker damage and not shut off. At least that was the claim.
  • Jamie Hall
    Jamie Hall Member Posts: 15,838
    edited February 2019
    Federal Pacific was the company, and the specific breakers were their "Stab-Lok" models. They have not been available for over 25 years, but I dare say that there are some still out there. The problem was that the breakers didn't trip reliably -- and, perhaps worse, sometimes remained closed even when they were manually operated to open or looked as though they had tripped.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    ChrisJSolid_Fuel_Man
  • ChrisJ
    ChrisJ Member Posts: 11,565
    edited February 2019
    > @Leonard said:
    > On that gen website there are a lot of electricians. Some have seen old breakers that continued to supply current when the breaker was in the off position. I'm guessing that is the concern. There was one breaker manufacture in particular, pacific something or other maybe. They might have gotten their UL listing pulled.
    >
    > Granted they likely were old breakers. But one of the electricians brought up the issue breakers are only rated for 240V . If utility and gen happen to be fully out of phase then breaker contacts could see 480V across them , possible breaker damage and not shut off. At least that was the claim.

    Federal Pacific.... They're dangerous.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Leonard
    Leonard Member Posts: 903
    edited February 2019
    Luckily we have Square D panel, nice solid feel as you switch the breakers. Years ago handled some other ones at Home depot, real wimpy feel to switch action. Felt broke, not a firm click , real sloppy. I'm a mechanical engineer, I didn't like the feel..... I wouldn't have them in my house if they were free.

    Transfer switch ........However if I lose power and NEEDED heat before I put in interlock ....I'ld likely be forced use garage hi-power outlet (240V 50 amp 3 wire), 7KW gen....... one time event.........but I'ld be REAL certain to open main breaker to street.

    Would HAVE to connect gen neutral to outlet ground, but I KNOW ground wire from outlet all way back to main breakers is 10 AWG copper, same as the hots. Without that neutral , voltage on house hots could be anything, 0 to 240V depending on house loads.
  • nibs
    nibs Member Posts: 462
    Since there is no practical way to ensure that a house or any other edifice is not going to back feed power into a downed line,
    Darwin suggests that the lineman take extreme due care at all times.
    As my friend John says "if it ain't grounded it ain't dead".
    And his friend who lost an arm and a leg because he did not ground the line, now teaches linemen to take due care.
  • pecmsg
    pecmsg Member Posts: 1,979
    nibs said:

    Since there is no practical way to ensure that a house or any other edifice is not going to back feed power into a downed line,
    Darwin suggests that the lineman take extreme due care at all times.
    As my friend John says "if it ain't grounded it ain't dead".
    And his friend who lost an arm and a leg because he did not ground the line, now teaches linemen to take due care.

    The only Proper way is with an Approved Transfer Switch

    Never back feed a panel
  • nibs
    nibs Member Posts: 462
    @pecmsg
    Problem is you cannot stop idiots from doing that.
  • ChrisJ
    ChrisJ Member Posts: 11,565
    Any time I work on a circuit, even in my own house I ensure it's not live.

    This includes working on electronics as you never know if a cap is charged.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • Leonard
    Leonard Member Posts: 903
    edited February 2019
    Used to rebuild window A/C units for resale. Always shorted the motor cap before working on it. Store energy on some would throw a good arc when shorted with screwdriver.

    Made a 2 ft long plastic rod and wire to discharge TV pic tubes before I worked on TV's circuits.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,665
    My generator comes with an approved transfer switch. It is, essentially, a DPDT relay capable of switching 200 amperes. And the contacts are guaranteed to be break-before-make both ways. There must be no risk of connecting the power company to the backup generator, EVEN IF SOME HARDWARE FAILS. If you violate this, you can kill a lineman who "knows" the power is off, but you are putting power into the line.
    The controller will start the generator and then throw the transfer switch to generator if the line voltage gets too low, and it will switch back to the power company once their electricity has been on long enough. It also diddles the phase of the generator's output to be the same as the power company before throwing the switch.

    A friend of mine's father used to work for Stone and Webster, a really heavy electric equipment manufacturer. He tells the story of someone who failed to adjust the phase before putting a generator back on-line at a major power plant. Apparently, the generator came right out of the floor.
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