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I keep blowing 400 amp t-fuses when charging at 240 amps

EATON HEINEMANN 250 amp GJ series breaker. A Canadian company. Very old school and very industrial quality. Maybe one each per inverter to bussbar and a seperate similar breaker for the Coach 12 volt system. The only thing lacking is the "cheap" part.

Given the price of the Class T fuses, the price of that breaker isn't that bad. I found them for as low as $83.

A quick search didn't turn up a datasheet. I would like to see the specs for that breaker. It looks similar to one I saw on the Midnite Solar site.
 
EATON HEINEMANN 250 amp GJ series breaker. A Canadian company. Very old school and very industrial quality. Maybe one each per inverter to bussbar and a seperate similar breaker for the Coach 12 volt system. The only thing lacking is the "cheap" part.
I do love the breaker idea, but not sure how I would even mount such a breaker lol.
 
I beleive the conclusion I am coming too is the connection is not as good as I thought it was. I really appreciate all the help. I am going to simply try to change the fuse block to a lug on type and stick with one 400 amp t-fuse. I will definately be monitoring it for heat. The other solutions I see here are great but require more work and more expence. Worse case scenario is I still blow another fuse and try something else. Best case scenario is the issue is resolved.
 
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Need studs?
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https://www.bestconverter.com/Class-T-Fuse-Block-400-Amp_p_220.html#.YeuGmi-B0h8
 
It sounds like your T fuse is a long way from your batteries. Keep in mind that the purpose of the Class-T is to protect the wires from the huge current that can be supplied from the battery in case of a dead short somewhere in the system.
 
From the battery there is about a 12 inch cable to the switch then a 3 inch cable to the T fuse
 
If the fuses are not blowing when the inverter/chargers power on then its not capacitor in-rush.
Is that what is happening?

Unless fuse integrity was compromised by partial melting from inrush.

Perform a precharge before completing circuit when next new fuse is used.

I beleive the conclusion I am coming too is the connection is not as good as I thought it was. I really appreciate all the help. I am going to simply try to change the fuse block to a lug on type and stick with one 400 amp t-fuse. I will definately be monitoring it for heat. The other solutions I see here are great but require more work and more expence. Worse case scenario is I still blow another fuse and try something else. Best case scenario is the issue is resolved.

How about a photo of the fuse/holder/wires in exact configuration where the problem occurred?
Simply having a nut under the fuse or cable could be sufficient to cause overheating.
 
Unless fuse integrity was compromised by partial melting from inrush.

Perform a precharge before completing circuit when next new fuse is used.



How about a photo of the fuse/holder/wires in exact configuration where the problem occurred?
Simply having a nut under the fuse or cable could be sufficient to cause overheating.
Actually the wire lengths are shorter than I estimated. I don’t think precharge is required as it can run for several hours before blowing the fuse.

Gary
 

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Unless fuse integrity was compromised by partial melting from inrush.

That could lead to blown fuse. But it would not explain melted fuse holder.
Poor electrical connection (or high resistance conductor like a nut or washer in the current path) is most likely.

Actually the wire lengths are shorter than I estimated.

Wire length doesn't generally relate to blown fuses. It is just more wire that might contact something and short if insulation damaged.
We like fuse located such that no short before the fuse is physically possible.
 
Actually the wire lengths are shorter than I estimated. I don’t think precharge is required as it can run for several hours before blowing the fuse.

Gary
Pre-charge protects the fets in a fet based bms.
If you don't have a bms then its not required.
 
2 multiplus 3000 wires in split phase.

400 amp t fuse

What gauge wire?
You could fork from battery positive to two (smaller) fuses, one for each inverter.
Doesn't help with the blowing/melting issue you're having, but might be better system protection.
It takes a pretty heavy wire for 400A fuse to be correct size.
 
When you run the current backwards through a breaker it will start a fire.
The short solution is to charge at a more reasonable rate and downsize that 20 hp generator to save fuel. Is the generator 3 phase. Are you tapped 120 Phase angle? Also the PFC circuit in the charger does it say it is ok to hit it with a Generator?? Probably not. Redesign in order.
 
That could lead to blown fuse. But it would not explain melted fuse holder.
Poor electrical connection (or high resistance conductor like a nut or washer in the current path) is most likely.



Wire length doesn't generally relate to blown fuses. It is just more wire that might contact something and short if insulation damaged.
We like fuse located such that no short before the fuse is physically possible.
I only mentioned wire length as it is different in the picture than what i mentioned earlier. The fuse holder may have been ok if i alllowed the fuse and holder to cool before removal. But i did not and when i went to rachet out the nuts the bolts turned and partially spun in the holder.
 
What gauge wire?
You could fork from battery positive to two (smaller) fuses, one for each inverter.
Doesn't help with the blowing/melting issue you're having, but might be better system protection.
It takes a pretty heavy wire for 400A fuse to be correct size.
Wire is 4/0 wielding cable.
 
When you run the current backwards through a breaker it will start a fire.
The short solution is to charge at a more reasonable rate and downsize that 20 hp generator to save fuel. Is the generator 3 phase. Are you tapped 120 Phase angle? Also the PFC circuit in the charger does it say it is ok to hit it with a Generator?? Probably not. Redesign in order.
Generator is 10kw and part of the Coach when they built it.
 
When you run the current backwards through a breaker it will start a fire.
Not when you use the correct breaker.

Square D QO, QOU and QOB breakers NOT HOMELINE!! are are also bidirectional and rated up to 60vdc and 60 amps.
 
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