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Old 12-13-2007, 01:34 PM   #1
Ozz
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Reverse polarity fuses

Check this out.
 
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Old 12-13-2007, 01:55 PM   #2
illapah
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Looks cool, now makes me wonder how they work in the power scheme???
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Old 12-13-2007, 03:22 PM   #3
Ozz
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They are wired so that a polarity reversal goes to ground, blowing the fuse. (To protect all loads downstream.)
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Old 12-13-2007, 03:27 PM   #4
illapah
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aha! Diode I suppose.
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Old 12-13-2007, 05:54 PM   #5
rogue
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Ozz, how do you reverse polarity? 1) hook up the battery backwards - yes 2) Inverter/charger goes bananas - maybe
3) TV wired backwards - yes 4) what else?
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Old 12-14-2007, 12:56 AM   #6
Ozz
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The campground power pedestal not wired correctly, but I thought the converter power supply fuses would blow first. If we had proper wiring diagrams and instruction books from the factory, we all wouldn't be scratching our heads.
I will contact Iota and see what I can do.
I contacted them, we will see....
The converter does have reverse polarity protection, so is the panel protection redundant? We will see about that also.
Here are two links:
http://www.iotaengineering.com/pplib/27vdlsmanl.pdf
http://www.iotaengineering.com/pplib/idp30.pdf
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Old 12-14-2007, 04:15 AM   #7
Cyrus
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Now I understand the term reversed polarity fuses. I interpreted it to mean a fuse detected a reversed polarity and I could not figure that out in my mine. Thanks for clearing it up for me.
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Old 12-14-2007, 04:50 AM   #8
Ozz
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Here is the resopnse from Iota:

'Jim
the fuses are for if the unit is connected incorrectly the fuses will pop...also if you are interested in documentation for our units you can go to IOTAENGINEERING.COM we dont have manuals or paper work for these units only whats on our web page
Lou'

Cyrus, the fuses actually do detect reverse polarity, and blow, as in the answer I got back from Iota above.

Crud, the first response timed out on the Forum.
As did my second try....
3rd, is the forum down????? This may take me an hour to post this....
Ok on edit, they all posted, but I waited until it timed out and there was no indication...oh well, I deleted the other two.
I'm done...
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Old 12-14-2007, 05:17 AM   #9
bob
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would this take the place of polarity protection from surge guard I realize that it wont stop a surge but would protect for miss wired box. Im correct
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Old 12-14-2007, 06:14 AM   #10
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Re thinking would the reverse p fuses be just for 12 volt side such as battery
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Old 12-14-2007, 06:28 AM   #11
SlickWillie
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Quote:
quote:Originally posted by bob

Re thinking would the reverse p fuses be just for 12 volt side such as battery
That's what I was thinking. They should only blow if the battery is hooked reversed polarity. I'm thinking if the campground plug is wired wrong, something would short out in the RV AC panel and either burn something up or trip the CG breaker. I would like to see a schematic for those converters. I have been out of the electrical field many years, but I'm thinking the converter transformer would protect the electronics from AC reverse polarity. Seems IIRC to determine the polarity on the secondary of the transformer, you merely ground one side of said secondary. Don't take that to the bank, and someone correct me if I'm wrong. Just throwing some ideas out.
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Old 12-14-2007, 10:46 AM   #12
Ozz
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Well, the converter wires run directly to the 12 volt panel. The batteries are charged from the converter.
The Iota guy stated the fuse will blow if the power to the 12 volt panel is wired incorrectly.
http://www.iotaengineering.com/pplib/27vdlsmanl.pdf
http://www.iotaengineering.com/pplib/idp30.pdf
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Old 12-14-2007, 01:18 PM   #13
SlickWillie
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Quote:
quote:Originally posted by Ozz

Well, the converter wires run directly to the 12 volt panel. The batteries are charged from the converter.
The Iota guy stated the fuse will blow if the power to the 12 volt panel is wired incorrectly.
http://www.iotaengineering.com/pplib/27vdlsmanl.pdf
http://www.iotaengineering.com/pplib/idp30.pdf
Fuses parallel you think?(55 amp converter) I notice the smaller units, 30 amp and under, only require one fuse. Bad fuse holder? Loose wire on 12 volt panel? Internal converter wiring short circuit? None of the above? HA! I think the Mountaineer has a 45 amp converter. No fuses in the panel, so they must be on the converter. Glad to know that anyway.
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Old 12-14-2007, 01:34 PM   #14
Cyrus
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Ozz,
If you read the description of the reverse polarity fuses at the top right of page 2 of your first link it says they protect the power converter if the wires to the battery are reversed. I don't see where this has anything to do with shore power/120V/220V coming to the camper/converter.
The only time they should blow is if the positive & negative battery connections are reversed to the converter. This could be at the converter end or the battery end.
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Old 12-14-2007, 02:03 PM   #15
Ozz
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It wouldn't have anything to do with the line voltage power, I agree.
The converter actually feeds the battery/12 volt power distribution center, from the line voltage power, it is 'upstream' and feeds, not being fed.
I see what you are saying now,I would have to put my meter on the Monty with the blown 30 am fuse, to see what is happening.
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Old 12-15-2007, 12:30 PM   #16
Dave e Victoria
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Hey guys, slow down. These fuses have NOTHING to do with the AC circuit. The way this sort of circuit typically works is there is a diode across the output on the DC side but downstream of the fuse. If the inverter is hooked up improperly(+ to- and - to +), current flows through the diode exceeding the fuse rating and it blows If the inverter is hooked up properly the only current through the diode will be leakage current. The fuse must be rated to handle normal load. The diode must be designed to handle max output of the inverter for the fuse blow time without frying. Actually a pretty simple solution that can protect a lot of polarity sensitive stuff.
The only problem with this type of protection is you cannot determine a latent failure of the diode . That is, if the diode is blown open, there is no protection and you can't tell. Fortunately, diodes "usually" short before they open.
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Old 12-16-2007, 01:01 AM   #17
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Who was talking about the AC circuit? We were discussing the 12 volt panel.
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Old 12-16-2007, 03:55 AM   #18
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On another thread, I had asked for any help on the 30 amp fuse blowing for the 12v system. The wiring to the battery has not been changed, the polarity is correct. The fuse has just started to blow while operating the slides in the last couple of months. The 3400 has been in service since May 06. I will take a look at the panel to see if possible a wire has come loose?
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Old 12-16-2007, 04:06 AM   #19
Ozz
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Was the fuse blowing one of the two in the 12 volt box? One of them in my picture I posted showing the fuse panel?
I started this thread to explain the reverse polarity protection in the 12 volt panel, your trailer is just like mine, (I think)
The panel check is always a good idea.
Good luck, keep us informed.
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Old 12-16-2007, 06:50 AM   #20
SlickWillie
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Good discussion! I realized today we have the GFCO converter and panel, not the Iota like the Montana's have. I had never paid any attention to the brand, although I had the distribution panel out earlier this year. We have the 45 amp, while the 08 Mountaineer fifth wheels have the 55 amp.

I'm sure thinking maybe a bad fuse holder here. I have had the ATC fuses blow due to a bad fuse holder on autos. IIRC, I took one of those fuse holders with the pig tails and soldered it in the fuse holder on a 82 Chevy I had. I just couldn't see changing out the whole fuse block. That is a PITA.
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