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Home backup power transfer switch question

Discussion in 'Off Grid Living' started by CaseIGL, Nov 3, 2012.

  1. CaseIGL

    CaseIGL Monkey

    Hi folks,

    I have two breaker panels, both with 20A Reliance Controls manual transfer switches on them. These accept L14-20 NEMA plugs from generators. I've got them wired to critical circuits like the furnace, fridge, and freezer and less critical ones like our home entertainment.

    I recently acquired one of the great Yamaha EF2000is 2000 watt generators. It provides a much cleaner approximate sine wave for my electronics and also is insanely quiet and sips gas compared to the 4500 watt monster I have.

    I also have a couple deep cycle RV batteries and a decent 2000 watt inverter (3800 surge) that I keep charged so that I can power a few lights, laptop computers, etc overnight without running any generators or during short term outages where I don't drag the generator out.

    Here's my challenge...I'd love to be able to use my transfer switches with either the inverter or the Yamaha to power just a few circuits, but both of these output your standard three prong 5-15 connector. There is no off the shelf 5-15 to L14-20 adapter available (that I have found), so I've been looking to build my own.

    From everything I can see and have read, the L14-20 just provides two 120V sources with ground. This enables you to support 240V loads on your transfer switch (I have none wired that way, they are all 15A 120V circuits).

    If I'm careful with the loads, it seems to be I can make an adapter that would feed a single 5-15 120V line into a L14-20 connector. This way I can plug this in when I want to run in "quiet mode" off the batteries or Yamaha but retain the flexibility of hooking either transfer switch up to the big generator as well.

    This would be for occasional use during power outages or disasters only, so even if it isn't the "ideal" it sounds like it could work. The whole Sandy situation got me thinking and during a longer term outage I could probably power most of what I need on the far more efficient Yamaha if fuel is an issue. I could also lose one generator and be okay, or do maintenance on one without losing power.

    Any gotchas I should be aware of here? Or is this an incredibly bad idea?
  2. TnAndy

    TnAndy Senior Member Founding Member

    If I understand what you want to do, which is connect your 120v Yamaha, or inverter/battery, to the transfer switch thru a 240v plug, then yes, it can be done.....sorta.....

    The twist lock plug has four terminals.....two for 120v 'hot', one for a neutral, and a ground. IF you examine the inside of the transfer switch/subpanel, you'll likely find just like a main house panel, you have two buss bars. It was designed to have 240v feed into it ( since it has the male side of the twist lock built in ), and 120v fed SEPARATELY to each bus bar.

    For the single pole circuits (120v), they could (and probably DO ) tap EITHER buss.....if you have 6 single pole breakers, likely 3 are on one buss, and 3 on the other, to attempt to balance the loads on the generator's output. The double pole (240v) tap both buss bars. ( Forgive me for that basic info, which you may or may not already know....just want to make sure we're on the same page, and not sure how extensive your electrical knowledge is )

    The problem, of course, is connecting the 120v line from the Yamaha/inverter source. You have 1 hot, one neutral, one ground.

    If you use the twist lock 240v plug, you have 4 terminals.

    If you simply leave one off, most likely half your single pole switches will not have power.

    SOoooo.....you're either gonna have to run a jumper of some kind inside the plug to connect your single hot to both hot terminals of the plug......which you probably CAN'T do, since they aren't set up with enough room between the connection area and the slide over cover....

    OR you're gonna have to put a splice/splitter in the line...split your single hot into 2 leads....probably solder two hot wires the one coming from your source, then tape the heck out of all, and have 4 wires running into the plug. Might look a bit ugly, and likely not code approved, but electrically it will work....with the following caveats:

    1. You will not have 240v ability, since you only have true single phase ( 240v actually IS poly phase.....2 - 120v sources on different sides of the cycle generation ).

    2. You'd have to be real careful about loads.....since you're now feeding a LOT less power to the transfer switch than was intended....I'd make sure the Yamaha has a breaker on it ( not familiar with that generator myself ), and same for the inverter, so if you draw too much thru the box, something 'pops' on the feed end.

    But, yeah, you can make it work........I've done far worse stuff I won't even confess too......ahahahahaaaa
  3. CaseIGL

    CaseIGL Monkey

    Thanks very much TnAndy. You are exactly right in your description of what I want to do and you described generally what I plan to do. Great to have a sanity check from someone else.

    You are also correct that my transfer switches are balanced, three circuits per 120V side. There is the capability of one 240V circuit in each switch, but I am not utilizing that so your point #1 is not a factor.

    To point number two, both the Yamaha and the inverter have overload protection that will trip if you try to pull too much. Additionally since this all has to be hooked up manually I plan to be VERY careful about loads running in this configuration. Most of the circuits that would be used in this setup won't have any "surprise" loads. Learned my lesson on that one when our teenage daughter did her hair with blow dryer and straightener and VERY quickly drained batteries, haha. Most of what will be powered are critical loads like freezer, furnace, fridge that I've measured with my Kill a Watt and have a good idea what the max requirements are.

    In terms of the construction, my plan was to purchase a short 20AMP cord with the twist lock on both ends, remove the plug side and wire a new 5-15 plug connector with the wires appropriately soldered or screwed down depending on what kind of plug I can russle up. I'll try to post up some pictures when I've completed it, unless I burn down something in the process! ;)

    Thanks again.
  4. TnAndy

    TnAndy Senior Member Founding Member

    Ah, yes, of course....I was thinking on the other end.....that would work fine, simply leaving one lead out of the 5-15.
  5. BTPost

    BTPost Old Fart Snow Monkey Moderator

    That wouldn't do it, Andy... If you leave one of the 120Vac Hots out of the 5-15, then you only will be driving half of the 120 Vac circuits in the Transfer Switch Breaker Box.... You need to put BOTH AC Hots together in the 5-15 Plug and then wire the Neutral and Ground as per Normal. This then will feed the 120Vac output of either the Genset/Inverter, or Inverter , to both Legs of the Transfer Switch Breaker Box input, and correspondingly to all the 120Vac Breaker outputs to the critical Loads. He will also have to check his Neutral/Ground Bonding Points in each Source, and in the Transfer Switch Breaker Box, to make sure he only has ONE Neutral/Ground Bonding Point in the whole system, at any one time, no matter which source is used. ..... YMMV.....
  6. CaseIGL

    CaseIGL Monkey

    That's right BTPost. I believe I am okay on the neutral/Ground issue since the transfer switches are already installed. I have only powered one at a time to date though. If I remember correctly, my subpanel comes off the main panel on a 60A breaker and the neutral/ground is shared back to the main panel. I ended up with two transfer switches due to the location of number of circuits that needed to be powered and the cost required to do a full transfer setup on the 200A main panel. I'll have to pull the subpanel cover to refresh my memory on the neutral/ground issue.
  7. CaseIGL

    CaseIGL Monkey

    I received a message about if I ever got this working. I figured I would paste my response here in case anyone in the future comes across it.

    The short answer is YES I figured out how to do this. I modified the transfer switch instead of hacking together a cord that would probably not be up to code.

    My transfer switch (Leviton 5278-C 15 Amp, 125 Volt, Flanged Inlet Receptacle, Straight Blade, Industrial Grade, Grounding, White - Amazon.com). I installed that into the transfer switch so that it can accept standard plugs from my inverter/battery bank or from the generator directly. You just have to connect both "hot" wires from the transfer switch to the single hot on the Leviton. The only issue was that the Leviton receptacle is just SLIGHTLY too small for the opening, so I had to use some washers to attach it securely rather than using the predrilled holes. If I was going to unplug and plug things every day it could be an issue, but it's stayed nice and snug. I have been leaving things wired up anyway so I just need to flip a couple switches.
  8. Cruisin Sloth

    Cruisin Sloth Special & Slow

    I would ask if there are any 220 V loads in any of the circuits , that could make that poor Yammy a real rice cooker.
    That would make a HUGE difference

  9. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Actually No, Sloth.... by connecting both of the 120 Legs to a single 120 Vac Output... Any 220Vac Loads would just NOT Work, Period... As the Voltage on both Legs would be the same, with no reference to Ground, unless someone put a Neutral Center Tap in the 220 Vac Load, which is not usually done on 220 Vac Loads.
  10. Kingfish

    Kingfish Self Reliant

    We solved that by splitting our Loads into three panels. Our 200 amp main panel contains all of our 220 circuits. That panel has a Isolation plate that allows either the Main 200 amp breaker to be on or the first 220 breaker on the right side to be on. Power from the lines comes in through the main breaker and power from our 8000 watt Generac comes in through the 40 amp 220 breaker. Either one can feed the entire house 220 or 110. I didnt stop there. I had two 100 amp sub panels installed of the main panel with necessary and unnecessary 110 circuits split between them. These panels are also protected by Isolation Sliders meaning they get their power from either my 200 amp panel via the main or the first breaker on the right. I power those two panels separate or ganged with a 3000 watt 120 volt Honda Generator . This way I can keep the freezer and fridge running without firing up the 8000. I can run any of the three panels independently or all together. I can run three separate feeds like my 8000 watt Generac running just the main panel, solar on sub number one and wind on sub number two or any other power source. I like the versatility of having multiple panels. I have 500 gallons of propane in reserve to run 220 appliances and for now use gasoline to run 120 volt stuff. Most of our power outages have been under 6 days so we just run the Honda to keep the cold stuff running and only fire the Generac when we need water, Electric dryer or the Range.

    My long term plans are to build a battery bank and Inverter to replace the Honda and eventually run all my 120 needs with solar/battery/inverter. We should have had this all in place but the Wife lost her Nursing position due to injury and we just dont have the money to finish it right now. Most of you guys have seen our panel setup. KF
    CaseIGL and kellory like this.
  11. CaseIGL

    CaseIGL Monkey

    Absolutely only using 120V loads while on the transfer switches, nothing is wired for that.
  12. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Best is to go to this sight : Solar Electric Power Discussion Forum by Northern Arizona Wind & Sun

    There are great folks who know there. &

    KF, Range should be Propane , and the dryer could be a hills clothesline fd88001_rotary8_ob_hero2_web.

    Just my view on your setup KF.
    As with the rest (panels & breakers ) ,,everyone is different,so no commit on the setup . Each setup is tailored for each type of power production & use .

  13. Akheloce

    Akheloce Monkey++

    BTPOST is right, both circuits need to be 180 out of phase, and have a ground reference.

    I recently signed book 3 at the IBEW local with my experience, but no IBEW actual time. Based on my interview alone, I beat out a Book 1 tested Journeyman for the job, but I decided on another better job. The Book 1 Tested Journeyman didn't know what a 965 tester was. Additionally, a tested journeyman residential wireman said to me once "I'd really like to know how to figure out the wire size for a circuit... That shit confuses me."

    In my opinion, IBEW certs are worth their weight in wire stretchers.
  14. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Don't need sparks flying
  15. Cruisin Sloth

    Cruisin Sloth Special & Slow

  16. Akheloce

    Akheloce Monkey++

    I would advise you to consult the 1996 changes to the NEC. Tying neutral and ground is no longer proffered, as if they get broken individually to each other, excess voltages on the neutral can damage equipment. If one doesn't agree with that, they can argue with the NEC
  17. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Ok-dokey then .
    & yes , I do know those "Newer Regs" .
    OP asked a question without his address,age of NEC requirements ETC. or his loads , appliances, I asked ONE (1) question.
    I'm old & in the way .
  18. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Ok, Let us clarify, the issues here.... In a Electric Dryer, Yes, they do bring a Neutral into the machine. HOWEVER, If you look at the wiring diagram for such a unit,
    the Timer, and, or, Control Systems run on 120Vac, which is One Hot Leg to the Neutral. The actual Heat Elements are powered between the two Hot Legs, and have NO Neutral Connection. This is, as per UL, and NEC, in that, if the heating element opens up, or goes to Ground, somewhere along the Resistive Element, it does NOT return, on the Neutral, but blows the Fuses, on one, or the other, or both, of the Hot Legs, to Open the Circuit on the 240 Vac Inputs. It is the same on Electric Stoves, and Ovens. The Calrod Heating elements are across the two Hot Legs, and have NO Neutral Connection.

    Feeding both HOT Legs of a 240 Vac Panel, from the same 120Vac Source, into any such 240 Vac Load, will produce, 120Vac for the Timing & Control Circuits, just fine, but NONE of the 240VAC Heating Elements will draw any current, as both ends, of said Heating Elements, will be at the SAME Potential, having NO Connection to the Neutral, and thus NO Current will flow thru those loads.
  19. Cruisin Sloth

    Cruisin Sloth Special & Slow

    Your correct ,
    I give.

    Go to the sight posted ^^^^ in Post 12.
    Very knowledgeable folks with links to regs & tables .
  20. Yard Dart

    Yard Dart Vigilant Monkey..... Moderator Site Supporter++

    I guess that depends your local and how they enforce training standards and proficiency.... we do not have those kind of issues down in our area- LU 46. If you don't know what you are doing, you are not doing it for us..... safety, quality and production are the three critical areas in any good journeyman.
    There is a reason ropers stay in the residential work or do light commercial with MC all day, they can't cut real commercial or industrial let alone any type of service projects.
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