GFCI Question

54d18
54d18 Solar Expert Posts: 81 ✭✭✭
in General Solar Power Topics #1
My inverter is a 1750w Eliminator sold by Canadian Tire,
these inverters are floating neutral, and I was curious as
to whether or not a GFCI would offer any protection.
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Comments

  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #2
    Re: GFCI Question

    My guess is not. I would be very surprised if the gfi would even hold with that inverter.

    Tony
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #3
    Re: GFCI Question
    icarus wrote: »
    My guess is not. I would be very surprised if the gfi would even hold with that inverter.

    Tony

    And there's the real possibility that the electronics in the GFI could be destroyed by the inverters square wave supply.
    Note that you can get a jolt off either of the two output terminals on most MSW inverters, as each output can be around 60 volts to ground, and is why grounding either one of the outputs to form a grounded neutral will short out and instantly destroy these inverters.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #4
    Re: GFCI Question

    It is also probable, as Wayne suggests tht grounding the gfi ( which you need to do to make it work) would destroy the inverter.

    Tony
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  • RCinFLA
    RCinFLA Solar Expert Posts: 1,485 ✭✭✭✭
    #5
    Re: GFCI Question

    I have never actually hooked a GFI up to a floating H-bridge MSW inverter.

    The GFI has a toroid transformer that has several turns on neutral and hot line wound in reverse directions. The transformer also has pick up winding that is amplified, detected and runs a trip solenoid. Principle is if current going out the hot exactly equals the current coming in the neutral no field is created in the transformer. A slight mismatch it the hot/neutral current means there must be some leakage path. It can detect 10 uA of leakage on 15 amps of hot/neutral current.

    The powering of the amp/detector and solenoid is from coupling caps to the hot and neutral lines.

    I doubt it will damage anything but I also doubt is will provide any benefit. The main problem with this inverter is neutral to negative battery terminal isolation, or lack there of. The sharp rise times of the MSW inverter will result in enough imbalance in the torroid field cancellation that the GFI may trip irratically.

    Many newer inverters have an opto-isolator on the DC-DC converter output feedback sense to at least isolate the battery side from 155 vdc DC boost switcher.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #6
    Re: GFCI Question

    This is one of the inverters I tested back in 2005. It's performance was disappointing to say the least.
    As others have said do not connect it to a GFCI nor in any way attempt to connect 'neutral' to ground. Not even temporarily.

    And start saving your money for a better inverter. These Motomaster units don't come up to snuff even for an MSW.
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  • 54d18
    54d18 Solar Expert Posts: 81 ✭✭✭
    #7
    Re: GFCI Question

    I definately want to upgrade to a better inverter,
    and at the same time I would go to 24v instead of 12v.

    The only thing I am concerned with upon upgrading when
    the time comes is noise, I installed a Magnum Inverter
    for a friend and found it was very noisy, ok for him because
    it is located in his garage, but mine is in the cottage and
    I could not put up with that constant hum and growl.

    Anyone have suggestions on a quieter unit?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #8
    Re: GFCI Question

    When you get to the over 1kW units they usually have two things that make noise: transformers and cooling fans. Can't say my Outback is particularly noisy except when the fan comes on. That only happens when it's in charger mode, btw, as it rarely runs at current levels that would produce significant heat.

    You could always build it a little cabinet outside the cottage; as long as it's protected from weather it will be fine.
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  • 54d18
    54d18 Solar Expert Posts: 81 ✭✭✭
    #9
    Re: GFCI Question

    If it were outside as you say, would the extreme cold
    affect it, we only use the cottage on weekends etc. and
    the temp. drops as low as -40C from time to time.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: GFCI Question
    54d18 wrote: »
    If it were outside as you say, would the extreme cold
    affect it, we only use the cottage on weekends etc. and
    the temp. drops as low as -40C from time to time.

    Same here. So far no problems. When running it will generate a bit of heat of its own. Turned off it doesn't matter. When you're not there you should switch the inverter off but leave the charge controller on (warm batteries are happy batteries). :D
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #11
    Re: GFCI Question

    From a quiet point of view, it's too bad that either you were staying with 12 volts, or that Morningstar would release a 24 volt version of their SureSine300. I have two of them in constant use, and the only way to hear any sound from either one of them is to press an ear against them. No fan, excellent design, excellent performance and reliability. What a shame they wouldn't offer a higher power version, and higher voltage versions as well.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #12
    Re: GFCI Question

    Higher power = more heat. More heat needs a way to get rid of it. Easiest way to do that = fan.

    But I'd like to see them expand the Morningstar inverter line too, just to see what they come up with. That 300 Watt unit is great. If you could only stack them ... :D
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #13
    Re: GFCI Question

    You can stack them,, in a fashion. You can use 2, one each to energize each side of a split buss panel, giving you 600 watts of AC loads (Plus the surge capacity of inverters). You just can't get 600 watts continious from any one circuit.

    In my ideal world, they would make it ~600-1000 watts and it would be the ideal inverter. My guess is perhaps they are working on some such thing. We can hope.

    T
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #14
    Re: GFCI Question

    Technically that isn't stacking it's paralleling systems.

    Just think what it would mean if you could couple the AC output on four of these. Most of the time we use less than 300 Watts which could be handled by one. The other three could remain in standby mode drawing only 6 mA each. Refrigerator or other big load comes on: they wake up for the surge, then go off as needed to keep power consumption minimal. But such stacking requires more components than the existing units have room for; it would have to be an all-new design.

    It's just silly that an inverter capable of powering a conventional 'frige (around 1kW) consumes as much power as my 3.5 kW OB. Some are a marginally better, but on the whole they don't come close to the low power requirements of the Morningstar.

    I hope people can see what I'm getting at here; it's not exactly clear. :blush:
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #15
    Re: GFCI Question

    It's interesting how Morningstar can get things to run so cool and without cans, whether it be their Sure Sine inverter, or their MPPT, TS-60 controller. They prove it can be done. Meanwhile my MX-60's fan is blowing hot air.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #16
    Re: GFCI Question
    waynefromnscanada wrote: »
    It's interesting how Morningstar can get things to run so cool and without cans, whether it be their Sure Sine inverter, or their MPPT, TS-60 controller. They prove it can be done. Meanwhile my MX-60's fan is blowing hot air.

    It's all about having enough heat sink area and contact surface with components capable of operating at a given thermal level. Or in English, getting the heat out of the semiconductors. The closer the components are run to their maximum current, the more heat they generate. Run 80 Amp components at 40 Amps, less heat. Run them at 80 Amps, more heat. You can only remove so much of that so fast without a fan. How much depends on the surface area of the component in contact with the heat sink (conductance) and the thermal difference between that and ambient. Put a fan in the design and suddenly you can lose a lot more heat very quickly. That's why so many companies do that.

    Any minute now an engineer is going to come in to this thread and go into great detail about what I've just alluded to. ;)
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  • ggunn
    ggunn Solar Expert Posts: 1,973 ✭✭✭
    #17
    Re: GFCI Question
    Cariboocoot wrote: »
    It's all about having enough heat sink area and contact surface with components capable of operating at a given thermal level. Or in English, getting the heat out of the semiconductors. The closer the components are run to their maximum current, the more heat they generate. Run 80 Amp components at 40 Amps, less heat. Run them at 80 Amps, more heat. You can only remove so much of that so fast without a fan. How much depends on the surface area of the component in contact with the heat sink (conductance) and the thermal difference between that and ambient. Put a fan in the design and suddenly you can lose a lot more heat very quickly. That's why so many companies do that.

    Any minute now an engineer is going to come in to this thread and go into great detail about what I've just alluded to. ;)
    No great detail to add, only that heat is the #1 enemy of electronics. A larger inverter running at 50% capacity will probably last significantly longer in the field than a smaller one running at 100%. It's just another factor to consider in sizing system components.
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  • boB
    boB Solar Expert Posts: 1,032 ✭✭✭✭
    #18
    Re: GFCI Question

    A heat sink that has a very large area will appear to be cooler at any one place on that heat sink compared with a smaller heat sink that has to dissipate the same amount of power for that unit. Larger heat sinks don't need a fan as much as a smaller heat sink to dissipate the same amount of power (watts).

    The power wasted (dissipated) depends solely on the efficiency of that unit at a particular power level, input and output voltage.

    boB
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