3A fuse and holder for SureSine 120V output

Steve961
Steve961 Solar Expert Posts: 93 ✭✭✭✭
in Solar Beginners Corner #1
My SureSine manual tells me to add a 3A in-line fuse to the 120V output of the inverter. I am looking locally for this fuse and holder, but cannot find what I think would be appropriate. The ATC fuses and holders state that they are limited to 32V. I see that the 1/4" glass fuses will handle up to 250V, but all the inline holders I can find for these only go up to 32V.

Any suggestions?

Thanks.

Steve
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Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #2
    Re: 3A fuse and holder for SureSine 120V output

    To be honest--I am not sure why that 3 amp fuse is even in the circuit. The SureSine is rated for 600 watts for 10 minutes, which would blow a 3 amp fuse in nothing flat...

    A properly sized fuse would be around:
    • 600 watts * 1/(115 volts * 0.9 min voltage) * 1.25 fuse derating = 7.2 amps minimum fusing
    Given that the AC output is isolated--I do not see why any fuse would be needed. It cannot output more AC voltage or current because of physical limitations (isolation transformer, DC input fusing) and should not short from battery to AC output (again transformer isolation). And their 3 amp fuse rating is ridiculously too small anyway.

    Personally, I would just power your loads without any additional fusing unless you are using smaller than 14 or 16 awg wire...

    Remember the fusing is to protect the wire and would only be needed if, for example, you where running 20 awg 120 VAC wiring to a, small, remote load (say a 13 watt CFL: ceiling fixture). Then you would size the fuse to the maximum safe current rating of the wiring.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • notsobright
    notsobright Solar Expert Posts: 247 ✭✭
    #3
    Re: 3A fuse and holder for SureSine 120V output

    Im glad you ask because I have the SS300 also and this is something I overlooked.

    I am using a 3a round glass type fuse and I used a fuse holder I allready had in junk parts but I did not consider the voltage rating on it.

    and the 3a fuse.. I looked at it closely and the wire inside is barely even visible! I thought to myself how can this wire pass enough electricity to power anything!?!

    but I installed it inline as the manual shows. so far I have only tested the SS300 with an electric fan and it worked but I only turned it on for a few minutes and that was it.


    now that BB has shed more light on the subject I think I will look for a 7a fuse and proper 120vac fuse holder.

    I would probably skip the fuse with BB advice but mine is in an RV and it might be possible to short that cicuit with a 12vdc one somehow.. odds are slim though.

    at least now if it ever does give me problems I know its probably safe to "straight wire" it


    thanks
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,639 admin
    #4
    Re: 3A fuse and holder for SureSine 120V output

    If you where going to fuse the output against 12 vdc to 120 vac shorts--then you would need to use a pair of AC output fuses... From the manual:
    NOTE: The AC output is isolated, therefore AC line and neutral are interchangeable. Use UL Listed 12AWG (4 mm2) black wire for AC Line and UL Listed 12AWG (4 mm2) white wire for AC Neutral. The earth grounded leg defines AC Neutral.
    At least from the basic information and from my limited understanding of the SureSine output--A single fuse would not provide the 12 vdc to 120 vac protection.

    12 AWG wiring, per NEC, is usually approved for at least 20 amps--close to 2,400 watt output--the input DC current would be >240 amps--more than enough to pop the 100 amp input protection.

    Their AC output fusing recommendation, as it stands, is pretty squirrelly.

    Note: I do not work for SureSine and I have never seen one of their products "in the flesh"--So my opinions are just that--personal opinions.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #5
    Re: 3A fuse and holder for SureSine 120V output

    I wouldn't use a fuse, the inverter will shutdown if overloaded, which is all a fuse does for protecting the wire. If the Inverter blows up, the DC side protection will take care of safety concerns ... I'd guess its a "cover all the bases" recommendation from MorningStar
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