Transfer switch from inverter to generator

LifetideLifetide Registered Users Posts: 19
I have a small off grid cabin that is powered by day with a Xantrex XPower 1500watt inverter and in the evenings by a Honda eu2000i generator. It's a simple, low power system without any service box; and up until now, I just unplugged one source and plugged in the other every evening. Now I want to put a transfer switch inside the cabin, but nothing expensive. I tried using a standard 3 way light switch as a transfer switch (that worked fine for me for years on a smaller system in another cabin), but I ended up frying the inverter. I've ordered a new inverter and done a little research, and now I'm ready to give it another try. Both the generator and the inverter put out less than 15 amps, and the cabin actually draws much less than that (just some compact florescent lights, a radio, and a laptop). Leviton makes 15 amp, dual pole, dual throw, center-off, maintained contact switch (Leviton part # 1282) that I think should do the trick, but it is not usually used for the purpose I'm considering. It's usually used to transfer a single power source to two different loads (or to reverse the direction of a motor), while I want to use it to transfer between two different power sources to a single load. The DPDT switch has six terminals--three on each side, but I'm not sure how to wire it for my purpose. I've done a fair amount of standard wiring, but this is beyond my technical ability to figure out. Can anyone tell me if I am correct in assuming that this switch will work for me; and beyond that, how to wire it. Oh yeah, the cabin's lights and outlets are wired with 14/2 Romex. Thanks in advance for any help.

Comments

  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: Transfer switch from inverter to generator

    Technically such a DPDT center off switch will work. But it probably won't last long, depending on how much power you use. Although rated at 15 Amps, they're not really meant to carry power like that continuously.

    Your first inverter probably caught some of the AC from the gen feeding back on its output as those 3-way switches don't necessarily have "break before make" function. A true transfer switch will, and it will have quite a sturdy "snap" to it as it is made to handle the rated current load all the time.

    As for wiring that switch, the "middle" terminals are going to be the commons for the two poles (each side being a pole) and the "ends" would be the contacts. You can check the function with an Ohm meter to be sure you understand which one goes where when. So your load line would be attached to the middle terminals, the generator to one end, and the inverter to the other. Watch out for AC polarity and any neutral-ground bonds that might have been installed (you don't want one in this application).
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Transfer switch from inverter to generator

    A very simple and inexpensive option would be to use an automatic transfer switch. I bought a PowerMax model PMTS - 30. These run about $55-$60 online: [URL="http://www.solarseller.com/iota_automatic_transfer_switches__iota_power_distribution_pa nels__inverter_load_.htm#pmts_30_amp_inside"]http://www.solarseller.com/iota_automatic_transfer_switches__iota_power_distribution_pa nels__inverter_load_.htm#pmts_30_amp_inside[/URL]

    This model has a built-in 30 second delay circuit. On one side of the box, you'll connect your inverter. On the other side, the generator. In the middle, the load (cabin). When the generator is off, the power to the cabin will be from the inverter. When you start up the generator, the transfer circuit will detect the voltage, and start the time delay circuit. After 30 seconds, the power will transfer over to the generator.

    This gives the generator a little time to warm up and the power to stabilize. This transfer switch was designed for the RV industry, and specifically to do exactly what you need. It's very simple to connect.

    I have one of these with my home power setup. I did modify my setup slightly. I will leave my inverter up and running all the time. Some appliances will run from the inverter exclusively. Other appliances will only run from the inverter when grid power is not available. For those items, I needed a transfer switch. The issue with this method is the transfer switch is looking to transfer the load 30 seconds after it detects power available from a second power source (a generator in your case, inverter in mine). But I wanted the inverter running all the time.

    My fix was to add another relay to the time delay circuit. When grid power is available, the relay will be engaged, disconnecting the time delay circuit. When the grid goes down, the relay drops out, and the time delay cycle begins. 30 seconds later, everything is running from the inverter.

    The 30 second delay is beneficial for my setup because the power sometimes bounces on/off before going completely down. This can sometimes cause the GFCI breaker on my inverter to pop. The delay will let the grid go completely down rather than bouncing the load between the grid and inverter a dozen times in a few seconds.

    Sorry for the low audio, but here's a demo of how this transfer switch will work in my application:

    [video=youtube_share;I138es1LD0k]
  • LifetideLifetide Registered Users Posts: 19
    Re: Transfer switch from inverter to generator

    Thanks 2manytoyz for the advice. The automatic transfer switch you've shown is inexpensive and handy, but I like the idea of being able to easily shut down the power to the place when I'm not there. The Leviton DPDT switch fits that requirement nicely. Flipping the switch manually is no big deal to me and it's a step up from plugging and unplugging cords from the two power sources. Anyway, I'll consider your suggestion because it does have a lot of merit. Thanks again.
  • LifetideLifetide Registered Users Posts: 19
    Re: Transfer switch from inverter to generator

    Thanks Cariboocoot for your feedback to my question. As I understand you, the Leviton DPDT switch can be visualized to operate pretty much like a DPDT knife switch only--where the workings are obvious--except that the workings are hidden in plastic. I'll continue on that assumption if I go with the Leviton. As for the short life time that you mentioned: I draw very little power through the switch--just a few cfl lights, a radio, and a laptop. Maybe if I bought the same switch with a 20 Amp rating for a few dollars more, it would last longer. It seems like a switch that costs $50 or more should last for a while under light duty. I mean the Leviton light switched last forever. Anyway thanks again for the input.
  • ywhicywhic Solar Expert Posts: 621 ✭✭
    Re: Transfer switch from inverter to generator

    ??

    with this Attachment not found.

    The generator lugs in the middle would be to the generator 110v line

    The power cord lugs on top would be to the 110v inverter output via power cord (or hard line)..

    The panel lugs on the bottom would be to a 110v 'panel' in my cabin...

    Does this sound correct for wiring??

    Not worried so much on the 30 second delay after I start the generator.. I may want to use a generator for 3-4 hours per day to run a small A/C..
  • westbranchwestbranch Solar Expert Posts: 5,163 ✭✭✭✭
    Re: Transfer switch from inverter to generator
    Lifetide wrote: »
    I have a small off grid cabin that is powered by day with a Xantrex XPower 1500watt inverter and in the evenings by a Honda eu2000i generator. ......
    the cabin actually draws much less than that (just some compact florescent lights, a radio, and a laptop). ... the cabin's lights and outlets are wired with 14/2 Romex. .

    I read this thread a few days back and see that my initial question to self has not come up, that is why are you running the generator in the evening? If you are like me, I like my evening solitude, and we as you, use lights, the laptop and speakers to watch a video, and a fan to circulate the heat from a direct vent heater in the guest cabin while construction proceeds.

    My question is ... why are you running the gen at night? why not charge the battery in the AM?
    Also why such a large inverter for 'light' loads?
    I notice you did not mention PV panels...

    cheers
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • icarusicarus Solar Expert Posts: 5,362 ✭✭✭✭
    Re: Transfer switch from inverter to generator

    Iota, available from our site sponsor, make s a very nice transfer switch, for under $100 if memory serves. You have to live with a momentary drop of AC when it switches, the only cosiquence is my modem shuts down.

    Tony
  • BB.BB. Super Moderators, Administrators Posts: 29,746 admin
    Re: Transfer switch from inverter to generator

    Tony, Iota has stopped making the transfer switch. It was not UL Listed and they did not want to take the time and money needed to get it approved (per NAWS/Windsun a few months ago).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Transfer switch from inverter to generator
    icarus wrote: »
    Iota, available from our site sponsor, make s a very nice transfer switch, for under $100 if memory serves. You have to live with a momentary drop of AC when it switches, the only cosiquence is my modem shuts down.

    Tony

    Iota no longer makes a 30A transfer switch. The one pictured in previous posts is said to be a direct replacement.

    For TVs, cable boxes, computer network stuff, I have those all connected to UPS units. We have enough power bumps to cause this equipment to reboot otherwise. The UPS will also keep things running while the transfer switch is busy doing its thing.

    I don't have to buy UPS units. People keep bringing them to me. I replace the batteries for some folks, others already purchased new ones, and just want me to dispose of them. I swap the battery out, and put it to use. Got so many at this point, I'm selective on which ones I'll use. Some are square wave (argh), most are a modified sine wave, a few are true sine wave.
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Transfer switch from inverter to generator

    Sounds right. Since this is the direct replacment for the Iota transfer switch, here's more information on how this product works, and how to wire it: http://www.iotaengineering.com/pplib/30rman.pdf

    The delay on mine is actually closer to 18 seconds (measured). If you decide you want an instant transfer, there's a switch on the time delay board to defeat the delay.
  • 2manytoyz2manytoyz Solar Expert Posts: 373 ✭✭✭
    Re: Transfer switch from inverter to generator
    BB. wrote: »
    Tony, Iota has stopped making the transfer switch. It was not UL Listed and they did not want to take the time and money needed to get it approved (per NAWS/Windsun a few months ago).

    -Bill

    That makes sense. Funny part is I don't think Iota ever made it. The PowerMax model I have is said to be a direct replacement. It looks exactly like the Iota one. When I received it, it had a cheesy decal slapped on the front cover. I could see a decal below it, so I carefully peeled off the PowerMax decal. Turns out it didn't say Iota as I expected, but rather Furrion. Furthermore, the Furrion logo is molded into the side of the box. I believe this company probably made the Iota version too...

    http://www.furrion.com/products/66/30a-and-50a-automatic-transfer-switch.html

    Might be wrong. If anyone has an actual Iota transfer switch, take a look on the side and see if you can find "Furrion" embossed in the plastic case.
  • vcallawayvcallaway Solar Expert Posts: 157 ✭✭✭✭✭
    Re: Transfer switch from inverter to generator

    I don't see that on mine.

    I bought a PowerMax 50A from NAWS for my Motorhome. The relays inside look just like the ones in the IOTA.

    I would recommend something a little more simple. A Xantrex inline transfer relay. It is designed specifically for what you are doing.
  • LifetideLifetide Registered Users Posts: 19
    Re: Transfer switch from inverter to generator

    In reply to Westbranch. Actually, the cabin I'm speaking of is just one of four that are serviced by the system I have. The others are not as large and I am not planning to change the plug and unplug routine for switching between inverter and generator in them. I do have four 120 watt panels that charge the batteries during the day; but during the evening hours (about 6:00 to midnight), I turn on the quiet little Honda and switch to powering all the cabins directly from it. I also run a battery charger off it that gives the batteries an additional charge. So it's basically a hybrid solar/generator system rather than a solar with generator for back up system. The main draw on the system is from several small refrigerators that run directly off the inverter and a couple of 12 volt water pumps (water is from catchment, so the pumps are required for water pressure). So that's why I have the larger inverter and also why I run the generator at night.
Sign In or Register to comment.