NH fuse in parallel?? aka NH knife blade fuse aka DIN NH blade fuse

[PyroRider]

THE NUMBERS ARE DEFINITELY CONFUSING.
the smaller size triple holder vs the much larger size single holder...
from my research the gG is the indication on some of the Siemens fuses that indicates the dual ac/dc rating..
I can't tell you anything on the fuse holders at this time... what it all means ac vs dc

I am definitely not looking to pull these fuses under load...
I do not have the expensive shielded fuse puller for them at this time either...

gG is not the dual rating for ac and dc but instead shows the tripping curve. gG is for standart uses, gL is slow-fast (sounds stupid but means that it is slow for low overcurrents and very fast for higher ones)
A proper NH glove costs ~35€ here in germany, for your 24V system a simple NH grip would be more than enough. The glove is there to protect you when you pull an NH fuse in the grid with 230/400V incase there is an arc flash.

 

[PyroRider]

the intent is to protect the inverter with the nh fuse....
large copper wires and tinned lugs are easy to assemble and bolt into place...
4/0 is the largest copper wire I have right now...
to be utilized with the fuses....to the inverter from the lifepo4 battery

4/0 is ~105mm2 so for 250A nominal you would need at least 2 of them in parallel for plus and 2 for minus (depending on the wire length). But you can easily use 2 cable lugs on the one Bolt, just put the 2 larger flat sides together when bolting them on.

 

[PyroRider]

-You have mentioned the fuses are rated for DC but the fuse holder does not appear to have a DC symbol on it. That may work fine but I'd probably avoid pulling them under load if you hadn't already thought that through.

View attachment 190222

The datasheet from siemens lists that model fuseholder for 440V DC

 

[michael d]

The datasheet from siemens lists that model fuseholder for 440V DC

thanks for explaining more of the Siemens' letters and numbers for NH fuses and their holders...
it does help me understand them a lot more...
it is my understanding that the NH fuses are better against exploding and are approved for insurance in the boating standards....
mine is strictly an off-grid stationary build....
the batteries and inverters will not be moving or jostled about as in cars and recreational vehicles...

 

[michael d]

As I am ordering NH compatible Siemens fuse bases it is still hard to tell what the size is, but the Siemens 355 Amp NH3-gG fuse fits the larger size base perfectly....
the fuse is being utilized as the catastrophe fuse in case of a major short to hopefully protect the inverter....
at least that is the intended application for my off-grid solar use...
here I have a picture of the large 355Amp fuse partially inserted into the fuse base...

 

[michael d]

gG is not the dual rating for ac and dc but instead shows the tripping curve. gG is for standart uses, gL is slow-fast (sounds stupid but means that it is slow for low overcurrents and very fast for higher ones)
A proper NH glove costs ~35€ here in germany, for your 24V system a simple NH grip would be more than enough. The glove is there to protect you when you pull an NH fuse in the grid with 230/400V incase there is an arc flash.

can you explain the gG vs the gL more for the tripping curve???
what would be the better one...???
It seems most of the ones I have purchased say gG on them...
again >>> a super thanks for all your informative replies....

 

[PyroRider]

As I am ordering NH compatible Siemens fuse bases it is still hard to tell what the size is, but the Siemens 355 Amp NH3-gG fuse fits the larger size base perfectly....
the fuse is being utilized as the catastrophe fuse in case of a major short to hopefully protect the inverter....
at least that is the intended application for my off-grid solar use...
here I have a picture of the large 355Amp fuse partially inserted into the fuse base...
View attachment 190373

They do fit, physically, but NH3 fuse holders (like the 3NH3430) have 2 brackets on either connector to carry the higher currents.
(Here is the NH2 for comparison: 3NH3330)

 

[PyroRider]

can you explain the gG vs the gL more for the tripping curve???
what would be the better one...???
It seems most of the ones I have purchased say gG on them...
again >>> a super thanks for all your informative replies....

I've read a bit more, so gL is an old curve (for cables) replaced by gG (for general purpose).
The first g is for "general purpose", there could also be an a for "accompanied fuse")
the second letters could be:
G - general purpose
M - electric motors
R - semiconductor protection
B - mining
Tr - transformers

I am going to look into gR fuses for my system for long term as they are very very fast tripping to protect semiconductors (the inverter i.e.) against shorts or overloads.
For high voltage dc systems (PV systems) there are also gPV fuses for 1000Vdc / 1500Vdc

 

[michael d]

I ordered some DC-rated PV 1100-volt 160 Amp NH fuses and they were totally huge >>> super long; >>> so what I thought was a good price ,,,, I ended up having to order the extra long fuse holder of that same brand ..... waiting on them now.... I will post pictures of them later when they arrive next week???
but still only slightly more than 26 dollars delivered ((for the fuse and fuse holder.....))
the class t fuse prices have gone sky high with the current inflation...(January 2024) in the USA.

 

[michael d]

this is the PV fuse i bought



the fuse holders are suposed to arrive on Monday ....hopefully the correct ones....

 

[michael d]

They do fit, physically, but NH3 fuse holders (like the 3NH3430) have 2 brackets on either connector to carry the higher currents.
(Here is the NH2 for comparison: 3NH3330)

I bought 3 of the italweber fuse holders and they have two of the retaining clips on each side but are so tight I am not sure how to put a fuse into them...but perhaps they are designed for a slightly different fuse....????


these have some sort of electrical relay which i do not need but the fuse base has the two clips on each side???
the electrical relay part can be taken off as it is attached by a screw...

 

[michael d]

italweber with relay pic


perhaps >>once the ital weber fuse base is securely mounted the fuse would be insertable with a lot of force???
or else it needs only italweber fuses to fit it correctly???

the grow light gives the photos a reddish color... in my photos

 

[michael d]

the siba pv fuse is quite long and needs a longer fuse holder...

 

[A.Justice]

While paralleling fuses can be done, it is not usually recommended. I saw this question answered a while back on here, and somebody demonstrated how the failure of a single fuse can create problems with the others.

 

[PyroRider]

I bought 3 of the italweber fuse holders and they have two of the retaining clips on each side but are so tight I am not sure how to put a fuse into them...but perhaps they are designed for a slightly different fuse....????

View attachment 191592
these have some sort of electrical relay which i do not need but the fuse base has the two clips on each side???
the electrical relay part can be taken off as it is attached by a screw...

It is on purpose that the clamps have such a tight grip, those 4 "tiny" clamps need to be low resistance enough to handle currents of up to I think it 3000A (3000A on a tenth Ohm of resistance would be 300W of heat on the terminals)
Those relay are for fuses with a special pin that comes out when the fuse is blown to enable remote monitoring or shutdowns once a fuse is blown

 

[PyroRider]

View attachment 191621
italweber with relay pic

View attachment 191622
perhaps >>once the ital weber fuse base is securely mounted the fuse would be insertable with a lot of force???
or else it needs only italweber fuses to fit it correctly???

the grow light gives the photos a reddish color... in my photos

You just need A LOT of force

 

[PyroRider]

View attachment 191628
the siba pv fuse is quite long and needs a longer fuse holder...

Well, it is technically an NH1 fuse, but you actually an NH1 XL (for the extra length)

 

[PyroRider]

Whats you String Voltage that you chose the Siba PV fuse? The normal "small" NH00 from siemens can already handle 250Vdc if I remember correctly

 

[PyroRider]

Just as a sidenote, before buying anything else, please show me what you want to buy and what you want to do with it so that I can tell you if its the right thing or not

 

[michael d]

I plan to utilize the NH fuse-links between the high amp lifepo4 battery and the inverters...
I thought the PV fuses would be a step up in protection in case of catastrophe....

the price of class T fuses and fuse holders has increased significantly in the past year....
I was reading that the NH fuses are better (ie they do not explode ) at least the idea is to improve the system's safety...

I have 3200-watt inverters, 5000-watt inverters, and up to 15000-watt inverters hooked to 4 separate lifepo4 battery builds....
I also have some prebuilt lifepo4 batteries ...

at any rate, the primary purpose is to utilize the NH fuse between the inverters and the lifepo4 batteries...

The DC disconnect is another part I still need to improve in the system...
all is done off-grid with no connection to the grid....
more later,