I just read where someone paid $200.00 for a 200 Amp fuse between their battery and their inverter.  Look on E Bay under car amplifier circuit breakers.  They can be reset instead of a one time thing and they are listed at under $10.00.  At that price it would be prudent to use them at all battery feeds!

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Comment by Matthew Tritt on December 10, 2012 at 10:46pm

There are fuses and then there are fuses. I suspect that for $10. for three 200 amp fuses with holder and shipping you're not getting the same stuff you would when the holder is $30. and each fuse is $15.00 It must be Chinese or a hijacking! ;>) I also believe that installing a "just in case" fuse at the battery post is a really good plan: it's truly astounding what a few hundred amps of 13 VDC jamming through unprotected 4/0 cable can do in the way of welding and/or fire starting.

Comment by Tumble bug on December 10, 2012 at 9:35pm

I thinkI paid under $10 delivered for 3 fuses and fuse holder.  200amp

Comment by Jimco_W001 on December 10, 2012 at 2:44am

Matthew,I always use a T fuse at the battery or battery bank when installing hard wired DC to AC inverters.The amp draw on the battery wires can be 1000 DC amps or more if they short.

Comment by Matthew Tritt on December 9, 2012 at 3:59pm

Right-on, John. I'm not exactly on the technological cutting edge these days either, but I think it's a really good idea to instill good electreeycul practices among RVers when possible. I doubt that many people realize just how big an arc and how much heat is generated by a good DC short. =(:>o

Comment by John "T" Nordhoff on December 9, 2012 at 1:04pm

  Matthew,  "A circuit breaker is both an over-amperage protection device AND a handy disconnect."

 For sure, and besides its a good practice to ocassionally "exercise" a circuit breaker anyway, although their design is typically NOT intended they be regularly used as a "switch". In AC lighting applications, however, they manufacture breakers suitable for use as switches as I recall, but its been too many years since I was a power distribution design engineer and Im a tad rusty lol

 

 Fun chat, hope were helping

 

 John T

Comment by Matthew Tritt on December 9, 2012 at 12:39pm

Just to clear up a little misconception about inverters... Reputable inverter manufacturers do NOT include a DC (input) protection device within the device's enclosure; you must provide that yourself. The breakers that they DO include are 120 AC (output) only. The only acceptable arrangement for the DC input is to have either a DC rated "Class T" fuse in a rated fuse holder located as close to the DC source (battery) as possible - or an acceptable DC circuit breaker mounted within an appropriate enclosure. In my business, which is battery-based off-grid power systems, we use Heinemann or Midnite breakers, not ones designed for audio systems. This is because we have to follow the NEC (National Electrical Code) requirements, which clearly state that all devices in a system have to meet minimum requirements for the application. A 250 amp fuse is a lot less expensive than a 250 amp circuit breaker, but you must then carry replacements AND include a quick-throw disconnect in-line before the fuse. A circuit breaker is both an over-amperage protection device AND a handy disconnect.

Comment by John "T" Nordhoff on December 8, 2012 at 10:09am

I have the SAME question as Richard. What some people loosely call "fuses" most items Ive seen advertised for car stereo system protection are actually re settable circuit breakers. As long as they trip out (open) at the amperage indicated and do so within a reasonable nearly instantaneous time (i.e. they are NOT slow blow or delay type devices) I see no reason they wont suffice BUT I DONT HAVE THEIR SPECS IN FRONT OF ME SO I CAN NOTTTTT SAY, so dont anyone have a calf if this isnt correct!!!!

One advantage of a re settable circuit breaker versus a one time mechanical fuse is that once the fuse blows its done for and needs replaced after the problem is cured while you simply re set the breaker.

Another thing some lay persons dont understand is that the fuze or breaker, if used to protect the downstream wiring from conducting current beyond its ampacity (overheat and start a fire), needs to be located at the SOURCE NOTTTTTTT way down the line where the load is. Sure, the load is still protected from excess available ampacity if placed there and the source is likewise protected BUT the feed wires from source to load are NOT protected unless the fuze/breaker is located at the source as it should be....

As a retired electrical distribution design engineer I can tell you the way things are done is to FIRST compute the load,,,,,size the wiring to feed that load such that its ampacity isnt exceeded,,,,,,,size the overcurrent protection device (fuze or breaker) to PROTECT THE FEED WIRES

I i were designing a battery and inverter system and wished to protect the battery and feed wiring and inverter, Id compute the load out of the battery,,,,,,,,,size the feed wires from battery to inverter,,,,,,place an overcurrent protection device AT the battery so the wiring from battery to inverter input is protected,,,,,,,Compute the loads OUT OF the inverter,,,,,,,,size the feed wires for those circuits,,,,,protect those wires (each circuit) with an overcurrent protection device.

AGAIN BEFORE ANYONE HAS A CALF This may well be overkill and Im NOT saying it allllllllll has to be done, IM ONLY describing the process and engineering reasons of proper overcurrent protection....

Hope this helps, yall take care n keep safe now

Ol John T in Indiana

Comment by Richard W. Cobbs on December 2, 2012 at 7:32pm

Jmco,

Are you saying that the 12 volt DC circuit breakers in various sizes (20 to 300 Amp is what I saw) that are advertised for large car stereo installations are not adequate for an inverter (which usually has a built-in fuse)?  I'm not trying to be confrontational here, I just don't understand your comment.

Comment by Jimco_W001 on December 2, 2012 at 7:06pm

The correct fuse is not that much money.This type of fuse is known as a catastrophe fuse.Please follow the electrical code when hard wiring large DC to AC inverters.

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