Check your fuses!!!

Discussion in 'Tech/Mech General' started by BreweryDave, Feb 22, 2014.

  1. BreweryDave

    BreweryDave Funster Life Member

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    I was doing a bit of DIY last week (fitting some LED strips) and whilst one side of the van went fine, the other side wouldn't work. Turned out a 12v fuse had blown in the e-box. (Burstner).
    When I checked it - it was a 20A fuse (yellow one) and the print on the fuse box stated 10A ! (...that explained why the yellow plastic bit was a tad melted!)

    I checked through all of them - and found 2 that had 20A fuses in which should've been 10A ! No issues fortunately, and all changed to the correct ones now - but maybe something to check if you are not the first owner!!!!:Eek!:
     
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  2. WynandJean

    WynandJean Funster

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    That's a bit naughty!:Doh:

    Too late for you now, perhaps, but I've changed all mine for LED fuses. The LED will light up if the fuse blows saving having to go through them all to find the one you need. :thumb:
    Obviously need to be the right amperage to start with as well!

    Wyn
     
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  3. Gooney

    Gooney Funster

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    I'm afraid it looks like you do have issues, you have 20a fuses where they should have been 10amp and they still blew, I suspect you have a problem on that circuit that need investigating, the previous owner probably had a problem with the 10amp blowing and replaced it with 20, naughty:Doh:
     
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  4. BreweryDave

    BreweryDave Funster Life Member

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    That particular circuit (as I now know!) provides power to the auto sat dish on the roof (which i dont use), 2 x 12v Sockets in the TV cupboard (which i dont use) then on to the 2 halogen downlighters. Seems quite a lot to me - which is maybe why the fuse was 'upped' - either that or he was just a donut!!!

    All I run on it now is an LED strip, and have replaced the halogens with LED bulbs - so feel pretty OK with that:thumb:
     
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  5. Gooney

    Gooney Funster

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    Sounds like you've got it Sussed Dave:thumb:
     
  6. tonyidle

    tonyidle Funster

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    It's worth considerably reducing the value of fitted fuses if you're replacing halogen or fluorescent lights with LED.
     
  7. SMB

    SMB Funster

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    I had a power drain on my leisure batteries and was assisted by a very helpful motorhomer who knew what he was doing unlike me! He used the following tool to check all the circuits in the fusebox and identified two circuits that were constantly drawing 2.5amps each when the control panel was active, even though no appliances were being used on one of them! i had some work done to the van before I left England and the electrics are obviously goosed. I have removed the fuses until I return, only replacing them if I need to use the affected appliances:
    http://www.amazon.co.uk/Automotive-Current-Detector-Standard-electrosmart%C2%AE/dp/B00CEZ3QGY/ref=pd_sim_sbs_ce_1?ie=UTF8&refRID=0005V6FM7ZSN28PMKEKY
    hope this helps
     
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  8. Ed Excel

    Ed Excel Funster

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    I don't see the point if you're not changing cable sizes. The fuse protects the cable, not the accessory. The cable is capable of carrying current up to the value of the original fuse. It could be confusing to others to reduce the fuse size. Sargent electrical panels have each circuit fuse rating printed on the lid.
     
  9. Tootles

    Tootles Funster

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    With low voltage DC electrics, it is advisable that both sides are fused, as there really is no 'true' pos/neg. You can have an ampage overload on the return, and have a situation develop
    which may not blow a fuse on the supply side, because of voltage drop within the affected cables.
    Now, it may be the case with modern integrated circuitry that this is taken care of, but with the older vehicles the problem can be acute. I have seen vehicle wiring catch fire, on the return cabling, without the related fuse on the supply side blowing. :Sad:
     
  10. Ed Excel

    Ed Excel Funster

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    You're right about some dc circuits having fuses in both conductors but it tends to be where the live and neutral are isolated from earth and there could be potential between the neutral and earth as well as the, more expected, live and earth. Central battery operated emergency lighting might be a case in point. Any earthed ELV systems (below 50V) don't have fuses in the neutral.
     
  11. Tootles

    Tootles Funster

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    But all inland waterways craft do! Either 12 or 24 volts, they are now required to have a return fuse for every supply fuse. Earth?? Surely DC dosent require an earth aspect? And in 12/24 volts DC, there is no 'neutral' as such??
     
  12. PeterCarole29

    PeterCarole29 Read Only Funster

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    Forgive as i am a doughnut when electrics are conserned.I am fitting 2 x 230amp hr batteries to an inverter with a mega fuse on the positive side .Should i fit a mega fuse to the negative to the chasis if so what size
     
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  13. Tootles

    Tootles Funster

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    I cant advise you what to do, because I'm not a qualified electrician, however, the problems I related were about accessories connected to a DC system, and not about the wiring of the source, ie, a battery(s) in this case. From the battery, power next arrives at the fuses/breakers. It seems any problems are from there onwards.
     
  14. Ed Excel

    Ed Excel Funster

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    Sorry, I am not familiar with marine installations.

    On motor vehicles the neutral conductor is the body/frame, for the most part, with some cabled cross connections from accessories. The electrical systems wouldn't work without a neutral to return the current to the source. Some people refer to the body/frame as earth, which is not strictly correct but is probably used because it is not a separately identifiable group of conductors.

    On dc emergency lighting systems in buildings there is an earth to provide a fault return path, because the voltages tend to be higher than ELV and, consequently, dangerous.
     
  15. Ed Excel

    Ed Excel Funster

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    I would suggest you refer to the manufacturers recommendations but I personally wouldn't fit a fuse in the neutral. There should be no potential between the neutral cable and the chassis, because your connecting them together, so no current will flow. The potential(voltage) is between the live conductor and the chassis, so the live is where you need a fuse.

    All the above assumes you're fitting the equipment in a motor vehicle.
     
    Last edited: Feb 24, 2014
  16. tonyidle

    tonyidle Funster

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    Very true. However depending on the construction of the accessory (in this case LED lights) and the nature and location of the fault more damage than necessary can be caused to the accessory or its associated controls & wiring. In the worst case it could take fire. There is never any point in having a fuse rated at a higher current than necessary. Printing a new list of fuses to place in the control panel shouldn't be too difficult especially as the move to LED lights is likely to be permanent.
     
  17. tonyidle

    tonyidle Funster

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    The only reason to fuse the negative supply rail is where both positive and negative are isolated from the rest of the vehicle metalwork. This is not the case for most motor vehicles including motorhomes.

    When connecting batteries in parallel there is a need to fuse the link between the two positive terminals if the batteries are not adjacent to each other just in case the link wire can be damaged & make contact with the metalwork of the vehicle.

    A battery does not have a live or neutral (those terms are reserved for AC distribution wiring). It has a positive and a negative. The negative, normally connected to vehicle metalwork, is by convention often referred to as earth.

    Mains connections do not have polarity (that term is reserved for battery supplies & refers to the poles of the battery). Mains can have a live (or line) and neutral reversal. It cannot have reversed polarity.

    Whilst the last two paragraphs make me appear pedantic (who, me?) I believe misuse simply adds to the mystique and confusion amongst those whose understanding of electrical systems is limited.
     
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  18. Tootles

    Tootles Funster

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    Marine installations require that ALL DC related items have a connected return to the source. At no time must the hull be used as a return, hence the need to fuse on both feed and return.
    This makes fitting accessories, (fridge etc), very difficult, especially when distances of up to 70' one way are required. (x2 for the return, 140'). With 12volt DC current, the core of the cable does not conduct, just the outer layer of wires, therefore on fitted equipment requiring say 4amp draw, over distance, 10mm cable is often used. Not easy when you cant use the boat hull, (chassis), as a return.
     
    Last edited: Feb 25, 2014
  19. Ed Excel

    Ed Excel Funster

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    I think you may be hinting at this in the top line of your reply; people need to be sure that the equipment/ accessory is capable of operating within the rating of the circuit protection. Having confirmed that, I still don't see a need to change the fuse size. My internal lighting, on the MH, is protected by a 15A fuse, which the LED lighting must be rated for. However, all the above assumes you know what you are doing so I would concede it may be wise, for those that are unsure, to change the fuse.
     
  20. Ed Excel

    Ed Excel Funster

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    Nothing wrong with being pedantic about your field of experience, however, I think you'll struggle convincing people reversed polarity is incorrect, a term used for ac circuits by qualified engineers.
     
    Last edited: Feb 25, 2014
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