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06-10-2020, 09:35 PM
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#1
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Senior Member
Join Date: Mar 2011
Posts: 202
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Inverter : Melted Fuse and fuse block
Magnum inverter errored today; stopped inverting; and would not allow "Auto Connect" so no 110v power to the coach...
Looking at the graphs the inverter was pulling ~150Amps @ ~12.6 volts when it shut down.
The coach had 12v power; and the solar charger was reporting good battery voltage.
Magnum's "Low Battery Volts" error seemed strange, until... I checked the fuse from the battery bank to the inverter. It was blown, and the fuse block was melted...
Not being familiar with this type of fuse, I grabbed my wrench to remove the wires from the lugs; and discovered the nuts were only finger tight - on both sides of the fuse block.
Question: Would loose nuts cause a 150 amp load to exceed the 350 amp fuse rating? Or do I have another problem I need to track down?
In the meantime; I've rewired the electric panel to eliminate the inverter - so we can run on shore power; and I have a replacement fuse and block on order. I'll ask Newmar to ship replacements too under warranty...
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06-10-2020, 11:13 PM
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#2
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Senior Member
Newmar Owners Club Nor'easters Club Appalachian Campers Ford Super Duty Owner Coastal Campers
Join Date: Dec 2007
Posts: 2,462
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Short answer, yes.
Long answer, the increased connection resistance due to the finger tight nuts at 150A heated the thermal elements in the fuse up until it blew, the same as the fuse would at over 350A (usually way over 350A) with properly tightened connections.
__________________
Stewart, Brenda and kids
2008 Newmar Canyon Star 3410, now at a new home
2006 Roadtrek Versatile 210
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10-15-2020, 03:02 PM
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#3
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Senior Member
Join Date: Nov 2012
Location: WATERBURY, CT.
Posts: 1,194
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Quote:
Originally Posted by ChrisFSB
Magnum inverter errored today; stopped inverting; and would not allow "Auto Connect" so no 110v power to the coach...
Looking at the graphs the inverter was pulling ~150Amps @ ~12.6 volts when it shut down.
Attachment 289095
The coach had 12v power; and the solar charger was reporting good battery voltage.
Magnum's "Low Battery Volts" error seemed strange, until... I checked the fuse from the battery bank to the inverter. It was blown, and the fuse block was melted...
Not being familiar with this type of fuse, I grabbed my wrench to remove the wires from the lugs; and discovered the nuts were only finger tight - on both sides of the fuse block.
Attachment 289096
Question: Would loose nuts cause a 150 amp load to exceed the 350 amp fuse rating? Or do I have another problem I need to track down?
In the meantime; I've rewired the electric panel to eliminate the inverter - so we can run on shore power; and I have a replacement fuse and block on order. I'll ask Newmar to ship replacements too under warranty... |
We have twins, thanks for chiming in on my thread.
Like I said this is a crappy set up, that fuse block needs to have nuts under the fuse so proper torque can be applied to the connection.
If the plastic gets even remotely warm it will deform causing lost tension and lose connection, High amperage draw due to increased resistance.
I suggest you switch to either blue sea or the ME-400F https://www.invertersupply.com/index...hoCBXMQAvD_BwE
__________________
My name is Ted, My coach 2019 NEWMAR Ventana 4369 (Vickie) Cummins L9 451 Horsepower.
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10-15-2020, 04:35 PM
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#5
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Senior Member
Join Date: Sep 2018
Posts: 970
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Quote:
Originally Posted by ChrisFSB
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From the Marinco data sheet:
Recommended torques:
Both 10mm (3/8”) and 12mm (1/2”)
studs: 21.5 Nm (15.9 lbf)
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10-15-2020, 04:42 PM
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#6
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Senior Member
Join Date: Sep 2018
Posts: 970
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Poor setup for sure!
As can be seen in the OP picture, the two rubber or plastic insulators had melted, most likely the cause of them loosening off. As Luv2go chimed in, the heat caused the thermal link in the fuse to open prematurely, that is how thermal fuses work, the melting of the thermal link with (usually) too much current.
I would recommend like Vickie 4369 says and install a 2nd nut under the fuse or even in any connection block like this, then you have metal to metal to torque too.
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10-15-2020, 05:13 PM
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#7
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Senior Member
Join Date: Mar 2011
Posts: 202
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Quote:
Originally Posted by OldWEB
I would recommend like Vickie 4369 says and install a 2nd nut under the fuse or even in any connection block like this, then you have metal to metal to torque too.
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Thanks - will do!
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10-15-2020, 05:36 PM
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#8
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Senior Member
Join Date: Nov 2012
Location: WATERBURY, CT.
Posts: 1,194
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Quote:
Originally Posted by ChrisFSB
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15 lb ft
__________________
My name is Ted, My coach 2019 NEWMAR Ventana 4369 (Vickie) Cummins L9 451 Horsepower.
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10-15-2020, 08:04 PM
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#9
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Senior Member
Join Date: Nov 2012
Location: WATERBURY, CT.
Posts: 1,194
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Quote:
Originally Posted by ChrisFSB
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I had added shut off switches to all 3 Positive leads when I installed the Lifeline batteries, that made it easy to fix the fuse situation.
Ted.
__________________
My name is Ted, My coach 2019 NEWMAR Ventana 4369 (Vickie) Cummins L9 451 Horsepower.
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10-15-2020, 08:38 PM
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#10
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Senior Member
Join Date: Jun 2011
Location: FL
Posts: 10,794
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Yep, loose nuts running around create electron friction which is the same thing that lights an incandescent bulb. Fuses melt do to heat. That can be external heat as you have found. Of course it was a combination of the heavy current flowing in the fuse and the added heat nearby.
Annual maintenance should include finding these large nuts and tightening them.
A carefully wrapped wrench can even do it while the circuits are live if you are incredibly careful.
__________________
Certified Senior Electronic Technician, Telecommunications Engineer, Telecommunications repair Service Center Owner, Original owner HR 2008
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10-16-2020, 02:21 PM
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#11
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Senior Member
Join Date: Nov 2012
Location: WATERBURY, CT.
Posts: 1,194
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Quote:
Originally Posted by YC1
Yep, loose nuts running around create electron friction which is the same thing that lights an incandescent bulb. Fuses melt do to heat. That can be external heat as you have found. Of course it was a combination of the heavy current flowing in the fuse and the added heat nearby.
Annual maintenance should include finding these large nuts and tightening them.
A carefully wrapped wrench can even do it while the circuits are live if you are incredibly careful.
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If they were backed by nuts instead or plastic, they would never come lose.
Ted.
__________________
My name is Ted, My coach 2019 NEWMAR Ventana 4369 (Vickie) Cummins L9 451 Horsepower.
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10-16-2020, 02:29 PM
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#12
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Senior Member
Join Date: Apr 2011
Location: Powell River, B.C.
Posts: 27,894
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If you'll get onto Newmar , maybe with multiple customer complaints they'll change suppliers of the fuse holder . 
__________________
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.
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10-18-2020, 06:33 PM
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#13
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Senior Member
Join Date: Nov 2012
Location: WATERBURY, CT.
Posts: 1,194
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Quote:
Originally Posted by Skip426
If you'll get onto Newmar , maybe with multiple customer complaints they'll change suppliers of the fuse holder . |
I formed a letter to Newmar with links to this and my thread.
Hopefully they take it seriously and look at this and come up with a solution or use my solution.
Ted.
__________________
My name is Ted, My coach 2019 NEWMAR Ventana 4369 (Vickie) Cummins L9 451 Horsepower.
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10-19-2020, 08:19 AM
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#14
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Senior Member
Join Date: Jun 2011
Location: FL
Posts: 10,794
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A nut and washer on first, then the fuse, then the rest of the hardware would allow the connections to be properly tight and provide a bit of extra heat sink. There should be little heat build up there of course.
I have replaced thousands of fuse blocks in my business over the years and it usually comes down to finding a loose connection on one end.
Yes there are better built fuse blocks and we always looked for top of the line products.
__________________
Certified Senior Electronic Technician, Telecommunications Engineer, Telecommunications repair Service Center Owner, Original owner HR 2008
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