Grid-tie inverter running at 135v...

DolsonDolson Registered Users Posts: 2
Hi all!

Am very new to the site and hope am in right spot to ask a few questions and maybe start a discussion.

I've always been interested in solar and wind, finally took the plunge at bought two 235W 24v solar panels. I also have a 24 volt grid-tie inverter. I hooked them all up and I have power! However, I took a few reading and noticed the nominal voltage for my cottage is 125V then when I plug in my grid-tie it's up to 135V! The grid-tie is rated at 90V-130V. Although everything seems to be working good, my concern is that I may melt my $500 inverter if it keeps up at 135V. Any suggestions or possible things to do/check? Very much appreciated!
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  • BB.BB. Super Moderators Posts: 26,872 admin
    I guess you are in Canada (Toronto area--roughly)?

    It sounds like your Cottage wiring may be having some issues. Perhaps too small of wiring/long of wiring run, or bad connection (check breaker and bus bar screws that hold the wires, make sure clean and tight, and no "brown/black" around the screws from overheating).

    The amount of solar power you have installed of 2x 235 Watts would output ~3 amps at 120 VAC typically. That is not much current for a typical 14 AWG @ 15 amp household branch circuit.

    For the line voltage to rise from 125 VAC to 135 VAC is unexpected. For example, if you plugged in a 1,200 Watt space heater, the voltage would go from 125 VAC to ~95 VAC... That is way too much drop and could indicate bad wiring (above) and run the risk of a fire (roughly 300 Watts of wasted energy going into heating bad wiring or bad electrical connections).

    Regarding your question, in the US, house hold voltage is around 102 to 132 VAC to be "legal" (interestingly, there is "no legal" voltage range I could find--It is up to the utility, but around 110 to 125 VAC is "normal").

    Your GT inverter is supposed to turn off when the AC voltage is >~132 VAC to protect your house wiring/appliances/people. Is your GT inverter UL/CSA/NRTL Listed?

    So--I would worry less about your inverter at the moment and check the cabin wiring. Unless you run LED lighting and a few low power appliances, I am worried about the wiring in the cabin. It does not sound right, and the GT inverter just got you out there to measure voltage with your meter--And may be uncovering other issues.

    There are issues with "plug and play" GT inverters regarding safety--But we can discuss that later.

    And, there is always the possibility of a problem with your meter (check the meter's batteries, if it has them). Or you used a long, thin extension cord, to connect from your cabin the the GT inverter (and you are just seeing the voltage drop/rise from the extension cord).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • bill von novakbill von novak Solar Expert Posts: 711 ✭✭✭✭
    Dolson said:
     Although everything seems to be working good, my concern is that I may melt my $500 inverter if it keeps up at 135V. Any suggestions or possible things to do/check? Very much appreciated!
    Like the "other Bill" said, I'd worry less about the inverter than about the wiring it is connected to.  If it's really a poor connection somewhere, then that connection may be getting pretty warm.
  • EstragonEstragon Registered Users Posts: 1,616 ✭✭✭✭
    I don't know much about grid tie, but as a matter of interest, how and where are the cabin and inverter grounded?
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • EstragonEstragon Registered Users Posts: 1,616 ✭✭✭✭
    Also if neutral is bonded to ground. Thx
    Off-grid.  
    Main daytime system ~4kw panels into 2xMNClassic150 370ah 48v bank 2xOutback 3548 inverter 120v + 240v autotransformer
    Night system ~1kw panels into 1xMNClassic150 700ah 12v bank morningstar 300w inverter
  • mvasmvas Registered Users Posts: 298 ✭✭✭
    edited May 31 #6
    My electrician friend says he calls AEP whenever the voltage is below 114 Volts or above 126 Volts at the factory.
    AEP guarantees 120 Volts AC within +/-5%.
    Many inverters will run at +/-10% volts, some even at +/-15% 

    What if the Inverter is raising mostly the Peak AC Value (distorted AC) and not raising the entire Sine Wave (not True RMS) ?
    And the Volt Meter is just calculating the RMS Voltage as 0.707 x Peak?
    Could that explain how the meter is displaying such a high reading vs True RMS.

    I find it hard to believe that 400 Watts from an Inverter would cause a True 10 Volt RMS Increase.
    That means a 400 watt load would cause a 10 Volt RMS decrease.
    10 Volts is very obvious and should have been noticed by now.

    It would take 600 feet of 14 AWG Extension Cord to drop 10 volts at 3 amps. 
  • DolsonDolson Registered Users Posts: 2
    Your experience and knowledge of this type stuff is invaluable! Can't thank you guys enough!

    You're very correct, am located about four hours north of Toronto.

    I should also note that this is a guest house and its a fair size mobile home. Two bedroom, bathroom, living room, kitchen but never the less, a mobile home. I did some checking in and around the electrical panel but found nothing worth noting. I turned the power off, tighten some screws, got up close and personal. No burn marks of any kind, no usual smells, all wires are intact and screwed in tight. I thought maybe since it's a mobile home it might of had some rodents underneath messing about with the wires but nothing, totally intact. So as far as inside wiring there's nothing going on there. It's plugged into a certified 30amp "trailer plug" (The actually cottage has 200amp service).

    Now something worth noting is that there's a 10 kWh solar generation setup literally the next property over to me. It's privately owned but connected to the grid on government contract, anything he doesn't use in his cottage gets bought from the power company. His cottage/house will almost never use 10 KW, a lot is put into the grid. I measured the voltage throughout the day and as the sun died down the voltage dropped back to 120V. Im thinking this is playing a HUGE role in it all and it setup may just not be possible.

    I measured my voltage drop with a 1,450W vacuum. On the opposite side of the trailer I had a 7 volt drop. Not bad, not great. I originally wanted to have the grid-tie setup on the trailer as oppose to the "real" cottage because the lights dim noticeably when using big items like microwave/toaster/kettle. Extra 3 amps directly into the closest wall socket sounded great! But know may not be able to use it at all. I thank you kindly for you expertise and advice! I will continue to update this discussion if have any improvements but due to the solar generation system literally next door with 125V-130V nominal power. I really don't know.

    Best regards!
    Dylan
  • BB.BB. Super Moderators Posts: 26,872 admin
    Very possible that your next door neighbor's Grid Tied system is the problem and not your little GT system.

    Rural areas, power lines that go down a long country road, etc. can be difficult for the power company to regulate--Add GT Solar and now they not only have to deal with voltage drops (variable loads), but with voltage rise from GT solar power systems.

    And, the GT power systems can be a bigger issue than loads. A 10 kWatt GT system is probably 2-4x larger current (peak around noon) than the average home/cottage uses.

    Assuming that the 135 volts is because of the other GT system (i.e., yours is disconnected and voltage is still high)--Call your utility. Worst case, they may tell the other guy to disconnect his system (or do they tell you "tough luck").

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • jonrjonr Solar Expert Posts: 876 ✭✭✭✭
    edited June 1 #9
    > On the opposite side of the trailer I had a 7 volt drop. 

    More than double what I would expect.  Maybe your meter isn't accurate.  Or your wiring is abnormally small.

    If high voltage is causing problems for some loads, there are regulators to bring it down:

    http://www.ebay.com/itm/5000-Watt-Voltage-Converter-STABILIZER-110-220V-Up-Down
    (a self adjusting transformer that should drop the voltage by 20V)
  • mvasmvas Registered Users Posts: 298 ✭✭✭
    edited June 1 #10
    Dolson said:
    Hi all!

    Am very new to the site and hope am in right spot to ask a few questions and maybe start a discussion.

    I've always been interested in solar and wind, finally took the plunge at bought two 235W 24v solar panels. I also have a 24 volt grid-tie inverter. I hooked them all up and I have power! However, I took a few reading and noticed the nominal voltage for my cottage is 125V then when I plug in my grid-tie it's up to 135V! The grid-tie is rated at 90V-130V. Although everything seems to be working good, my concern is that I may melt my $500 inverter if it keeps up at 135V. Any suggestions or possible things to do/check? Very much appreciated!
    If your Inverter is actually running at 135 Volts then I believe the Inverter has a 140 Volt Upper Limit rating.
    Since 135 Volts is less than 140 Volts, your inverter is most likely operating within normal parameters.
    If the Line Voltage was too high, then your Inverter would (should) auto-shutdown.

    What is the distance to the nearest Step Down Transformer on the Electric Pole?

    Dolson said:
     It's plugged into a certified 30amp "trailer plug" (The actually cottage has 200amp service).

    Dylan
    Typically, a 30 Amp Trailer Plug provides only one Leg of 120 Volts via a Hot, a Neutral & a Ground wire.
    How long is this cable ( all the way  back to the cottage ) ?
    Is it 10AWG Wire or thicker?

    Could there be a "bad neutral" between the cottage and the pole?
    When you have a "bad neutral" then the ground rods provide a very poor neutral connection.
    This allows the voltage between Leg 1 & Neutral to increase, while the voltage be Leg 2 & Neutral to decrease.
    A "bad neutral" will allow the varying loads to create wild voltages, similar to what we are seeing.

    You say the cottage has 200 Amp Service.
    That means the Pole Transformer should keep the Line Voltage very stiff.

    Is the voltage between Leg 1 and Neutral and between Leg 2 and Neutral both equal 135 Volts simultaneously?
    I don't think you can know this from the Guest House.
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