3amp Fuse For Morningstar 300w SureSine

BMCM
BMCM Registered Users Posts: 6 ✭
in Off Grid Solar & Battery Systems #1
Helo,
I'm preparing to install the SureSine in my RV.
I think I have everything figured out with the exception of the 3A fuse that is called for on the black wire on the AC side.
I saw a reference to a 3A AC fuse, so I'm guessing a 12volt automotive fuse is NOT what I want. I Googled and checked Wind/Sun, but can't find a 3A AC fuse.
Looking for some guidance...

Thanks,

Robert
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Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: 3amp Fuse For Morningstar 300w SureSine

    Welcome to the forum, Robert.

    You are correct that you don't want to use a 12 Volt fuse on a 120 Volt circuit.
    3 Amp 120 VAC fuses aren't uncommon. It would be a glass tube type and probably have a 250 Volt rating (maximum Voltage it can safely interrupt). One example: http://www.homehardware.ca/en/rec/index.htm/Plumbing-Electrical/Electrical/Fuses/Household/Miscellaneous/3-Amp-250-Volt-Fast-Act-Glass-Fuse/_/N-ntjyh/R-I3644518
    You can use block holder or in-line holder (make sure it is rated for the current & Voltage).

    Not sure where you go that fuse requirement from. The inverter will fault before the fuse blows, btw.
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  • rgk1
    rgk1 Solar Expert Posts: 135 ✭✭✭
    #3
    Re: 3amp Fuse For Morningstar 300w SureSine

    I am sure there are more creative ways to do it, but i used an automotive type holder. I'm curious to see how others do it if they install it at all. The SureSine inverter has good built in protections.Attachment not found.
    4-Risen 320 watt in series/parallel, 8-215ah 6 volt GC2 batteries in series, Exeltech 1100 watt/48 volt inverter, Tristar 45 MPPT controller.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: 3amp Fuse For Morningstar 300w SureSine
    Cariboocoot wrote: »
    3 Amp 120 VAC fuse
    Not sure where you got that fuse requirement from. The inverter will fault before the fuse blows, btw.

    It's in the owners/installation manual that such a fuse should be in the AC hot line. I didn't use one in either of my two, because like you say, they will shut down if overloaded. I wondered if they were intended to help prevent damage to the inverter and possible fire, if somehow the inverter got back-fed from grid, or a generator.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: 3amp Fuse For Morningstar 300w SureSine

    Considering it's rated for 600 Watt surge I'd think they'd spec a 5 Amp fuse on the output.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #6
    Re: 3amp Fuse For Morningstar 300w SureSine
    Cariboocoot wrote: »
    Considering it's rated for 600 Watt surge I'd think they'd spec a 5 Amp fuse on the output.

    Exactly! I cannot understand their dictate for 3 amp. Just doesn't make sense and there's no way I'd get some of my heavy loads started with a 3 amp fuse in there, and why I ignored it.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #7
    Re: 3amp Fuse For Morningstar 300w SureSine

    I just fused the input side, and then fused the branch circuits ithe house with AC breakers. One would assume that the input fuse would blow before (assuming it is sized correctly) before the branch circuit breaker would blow. My load center is fed from a transfer switch so I have 15 amp breakers in the branches to protect the #14 wire in them. Occasionally I run an AC load off the genny (vacuum cleaner) I don't recall if the instructions when I bough mine called for a fuse in the output side. Personally, I am not sure I would worry, assuming that the input side is fused for the current of the input wire, and th inverter load. The small chunk of #12 between the inverter be the load center is pretty well protected, with the input fuse, and the battery fuses.

    Others may have a different opinion.

    Tony
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #8
    Re: 3amp Fuse For Morningstar 300w SureSine

    Just checked my owners manual to be sure I was remembering correctly, and sure enough - - calls for 3 amp in the output and, get this - - 100 amp on the input side! For the last almost 5 years I've run them with 60 amp fuses on the DC side because I considered 100 amp to be nuts on a little 300 watt inverter. Both SureSines have been overloaded to the point of shutdown MANY times over the years, and never once has an input fuse blown. Truly AMAZING inverters!
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #9
    Re: 3amp Fuse For Morningstar 300w SureSine

    I "branch" my 3500 Watt inverter with 15 Amp breakers: it faults before the breakers will trip.

    300 Watts on 12 VDC is about 25 Amps. Using the NEC formula you get 40 Amp input fuse/breaker. If you want to extend to the full 600 Watt surge capacity it would be double that: 80 Amps. They probably figure there's no such thing as an 80 Amp 12 VDC fuse/breaker and so round up to 100.

    My reasoning on the output side is that the 5 Amp fuse would handle 600 Watts for a while then blow (600 Watts being about 5.2 Amps @ 115 VAC) whereas the 3 Amp is only good for 345 Watts which wouldn't give much room for the 2X overload capacity. Fortunately fuses/breakers do not go instantly; perhaps they are weighing the surge rating time against the fuse blow time. Not sure how long the inverter can handle the full 600 Watts for.
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  • Dill
    Dill Solar Expert Posts: 170 ✭✭
    #10
    Re: 3amp Fuse For Morningstar 300w SureSine
    Cariboocoot wrote: »
    Not sure how long the inverter can handle the full 600 Watts for.


    15 minutes according to my manual. I would definitely fuse it for the 600 watt capability.
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  • BMCM
    BMCM Registered Users Posts: 6 ✭
    #11
    Re: 3amp Fuse For Morningstar 300w SureSine

    Have a bunch of the "glass tube" fuses. Had never paid attention to the volt markings, though. Of course I didn't have any 250 volt rated 3A, but Pep Boys was quick to accommodate. Also got the fuse holder with 12ga leads there.

    I'm going to wire the SureSine per the instructions since it's in an RV, and I don't understand all I know about electricity, especially the ground and what the instruction book calls the interchangeable AC line and neutral wire. It calls for running a 12g a wire from the white (AC) wire to the ground wire on the inverter.
    The ground (4ga) on the inverter will go to a ground buss bar, that has most, or all, of the camper 12v grounds attached to it. Seems that it all ends up back at the battery. Oh, well.

    Maybe I can get the wife to "touch test" everything before I go off camping. :p

    Thanks for all the input.

    Robert
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #12
    Re: 3amp Fuse For Morningstar 300w SureSine

    Personally, I would skip the AC fuse in the inverter's output. I don't think it adds any safety to the system (at least the way they have it in the manual).

    Also, I would skip Grounding the Neutral of the AC inverter's White Wire too unless you some thing like a 4' florescent tube fixture (there are a few 120 VAC device, like instant start florescent that need the white wire and earth/lamp grounds all tied together for reliable operation). But most devices will work just fine with floating AC power.

    Just make sure that the AC output of your inverter is never connected to AC utility power--You will not be happy. If you will be doing a mix of AC utility power and Inverter use with your RV--Then plug the RC electrical pigtail into the inverter (wire in an AC outlet to the MorningStar) or install an AC Transfer switch. You don't want any way that you can accidentally tie the AC Inverter and Utility Grid together. EVER.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BMCM
    BMCM Registered Users Posts: 6 ✭
    #13
    Re: 3amp Fuse For Morningstar 300w SureSine

    The inverter will be isolated from the rest of the electrical (shore/generator power). I am putting two receptacles on the inverter..Inverter>GFIC outlet>outlet. This inverter is just for those things that are sensitive to 'clean' power.

    So, as I understand it, I don't need the ground wire in the Romex? I've already pulled that wire, but everything is still open, so not a problem taking it out. Would be easier working without the ground wire cause where the GFIC box is going, it's really tight.
    Looking at the manual, I see there is no ground wire in the AC run. Sure didn't catch that before.
    Robert
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #14
    Re: 3amp Fuse For Morningstar 300w SureSine
    BMCM wrote: »
    The inverter will be isolated from the rest of the electrical (shore/generator power). I am putting two receptacles on the inverter..Inverter>GFIC outlet>outlet. This inverter is just for those things that are sensitive to 'clean' power.

    So, as I understand it, I don't need the ground wire in the Romex? I've already pulled that wire, but everything is still open, so not a problem taking it out. Would be easier working without the ground wire cause where the GFIC box is going, it's really tight.
    Looking at the manual, I see there is no ground wire in the AC run. Sure didn't catch that before.
    Robert

    welcome,
    am i to understand that you pulled a 4th wire through? if so this was not necessary as the ground wire would've been the bare 3rd wire present in a romex bundle.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #15
    Re: 3amp Fuse For Morningstar 300w SureSine

    Just connect the ground wire to the inverter/trailer frame ground and to the outlet ground.

    The inverter outlet is a floating output, if you do not ground the neutral.

    It is actually quite safe. You cannot get a shock touching just one inverter output.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • BMCM
    BMCM Registered Users Posts: 6 ✭
    #16
    Re: 3amp Fuse For Morningstar 300w SureSine

    The SureSine, GFIC and one other outlet downstream are all there will be. It won't connected to the campers 120v power in any fashion. Just wanted something to provide nice clean power for a computer and other sensitive electronics, and that was dependable.

    So, Romex with a ground wire isn't necessary, huh? I just looked at the manual and realized there wasn't a ground wire indicated in the AC circuit. Sure missed that.
    Makes wiring it up a bit easier..
    Just got back from Lowe's. Kid there said they didn't make a 12/2 without a ground wire. I've already run the 12/2 w/ground, so will just use it unless Home Depot or the local electrical supply has it.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #17
    Re: 3amp Fuse For Morningstar 300w SureSine

    The ground wire to the outlet (and outlet box if metal) is still a good idea. You don't want pieces of metal to become "Hot" with respect to other thing in the trailer. The chances that the ground wire will actually be used is probably remote (especially if you are plugging in two prong/double insulated appliances/tools).

    In standard house wiring having Neutral/White wire tied to the ground bus (in the main power panel) and then connected to a ground rod/water pipes/conduit/etc. is part of the safety system.

    Basically, if there is a "fault" from Hot (black or red wire in 120/240 VAC systems), if it touches any metal/conduit/sinks, etc. in the home, it will pop the circuit breaker (rather than energizing the piece of metal/stove cabinet, etc.).

    In this case, the TSW AC inverter is a floating transformer output. Just like a 12 volt car battery--if you touch one terminal, there is still no current flow/shock/etc. because there is no return path through the other terminal. This is actually quite safe and used in some places as shock reduction setup (especially before GFI outlets were invented):

    [FONT=fixedsys]TSW Inverter Transformer output (floating)

||(========
||(
||(120 VAC output
||(
||(========

   ------------ Earth Ground
   |
-----
////


TSW Transformer output (grounded neutral)
             fuse
||(====o~o= (Black/Hot)
||(
||(120 VAC output
||(
||(=+====== (White/Neutral)
      |
     +----------- Earth Ground
      |
   -----
   ////[/FONT]

    So, in the second diagram is the grounded neutral, and now a (6 amp) fuse in the black/hot wire "makes sense" in the standard electrical wiring scheme. If there is a short between Hot/Black and Neutral or Ground or grounded metal--then the fuse/breaker will open and power will be removed from the short/failure area.

    If the first digram, even if there is ONE short, there is still no current flow.

    If you use a GFI outlet--You may have some odd behavior in diagram #1. For example, a single fault to ground will not trip the GFI. And, a GFI is sort of redundant in this setup.

    In diagram #2, a single fault to ground (black for sure, probably white/neutral too) will cause more than 5 mAmps (0.005 amps) to flow and trip the GFI outlet. (note this is a connection to "local ground"... For example a short to any metal inside the trailer. But because the trailer is on rubber tires--A fault to earth (dirt/ground, puddle outside the trailer) may not trip the GFI as there is no electrical connection through the rubber tires. If somebody has a foot in a puddle and then grabs the metal door handle--then it can trip (and safe the person from a shock).

    I hope this makes sense--it is kind of difficult to type a short and clear explanation of what the options are and what the results may be.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #18
    Re: 3amp Fuse For Morningstar 300w SureSine

    I don't think you will find Romex without a ground,,just because it has the ground doesn't mean you have to use it.

    Tony
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  • BMCM
    BMCM Registered Users Posts: 6 ✭
    #19
    Re: 3amp Fuse For Morningstar 300w SureSine
    niel wrote: »
    welcome,
    am i to understand that you pulled a 4th wire through? if so this was not necessary as the ground wire would've been the bare 3rd wire present in a romex bundle.

    Thanks.

    No, didn't pull 4th wire.. Just the 12-2 Romex.
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  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    #20
    Re: 3amp Fuse For Morningstar 300w SureSine
    BMCM wrote: »
    Thanks.

    No, didn't pull 4th wire.. Just the 12-2 Romex.
    There used to be 12-2 Romex without ground, and there may still be a supply sitting around in somebody's old stock, but all current product and all used in new construction in the US will have the ground wire.
    SMA SB 3000, old BP panels.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #21
    Re: 3amp Fuse For Morningstar 300w SureSine
    inetdog wrote: »
    There used to be 12-2 Romex without ground, and there may still be a supply sitting around in somebody's old stock, but all current product and all used in new construction in the US will have the ground wire.
    Haven't seen it for sale here in Canada during my lifetime. (I'm no longer a spring chicken) What I did see had already installed, was already old, and the rubber covering on each of the two wires was hardened and would crack and break away if moved.
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  • BMCM
    BMCM Registered Users Posts: 6 ✭
    #22
    Re: 3amp Fuse For Morningstar 300w SureSine

    Finally got the inverter up and running after a few issues, mainly to do with the installer, got resolved.
    Seems that the GFIC box has a small light that comes on when the box is tripped, unlike the one in the house that is lit when it's working. Saw a light, figured it was working. Lack of power said otherwise. Once I figured out which button to push on the outlet box, all was well.
    After a bit more hair pulling I figured out that if you want to change the position of the dip switches on the inverter, you have to kill the power to that thing first. I'd change a dip switch position and get 2 red lights. Flip them back, lights would go green. Flip another...two more red lights.

    To test the inverter, I hooked up a Dish Tailgater Sat antenna and receiver and a 20in flatscreen LCD TV. Let it run for an hour and 20 min. At 20 min, the batteries had come down to 12.6v. An hour latter they were at 12.59v, with an occasional bounce to 12.6v. The batteries are 2x12v 110Ahr AGMs. I was reading the voltage on a SolarBoost 2000e charge controller.
    So far, so good...
    Thanks for all the help..

    Best,

    Robert
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