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

[michael d]

What are NH Fuses? NH fuses (also known as NH Knife Blade Fuses or DIN NH Blade Fuses) were defined in the German DIN standard 43620 around 1944. They were primarily designed as general purpose fuses for the protection of conductors.

my question is: >>>> I purchased a 3 fuse holder that is rated at 160 amps made for the NH style fuse.... can these fuses be connected in parallel and if so does that effectively increase the amperage ability of each 160 amp NH fuse as a whole to 480 AMPS????

maybe a novice question but I would like to get a response... or at least get a discussion going as to why and why not

solar panels in parallel >>>> the amps add up
battery cells in parallel >>>> the amps add up

what about fuses in parallel????

the 355 amp NH style fuse I bought was huge and requires a much larger fuse holder >>> but the 160 Amp are physically smaller and I believe the same physical size as the 200 amp and 250 amp fuses in the NH style fuses I bought....

they are all Siemens brand NH fuses.... and all are rated for use with DC...

I have cnswipower 3200-watt and 6000-watt HF inverters in the 24-volt version that I am fusing.....presently w/o fuse externally to protect the wire >>> but presently only powering very light loads.

it may be in the forum someplace but I could not find the answer in another thread so I posted this one here about fuses in parallel ????

 

[michael d]

the above photo was off the internet,,, but the fuse holder for 3 NH fuses looks like that but better condition...

 

[michael d]

the 200 amp 250 amp and 355 amp are the same lengths but the blade is physically bigger on the 355 amp one... so may require a different fuse holder (the 355 amp Siemens NH fuse)
without even measuring it is quite obvious the 355 amp fuse is a lot wider and would never fit in the 3 place holder with any other fuse...

but that still does not get to the question /answer/ solution >>>> Can the 160 amp NH fuses be connected in parallel or any other size for that matter???

 

[michael d]

the bolt-down NH fuse holder ( probably screws or bolts would function to secure them in place) so could be mounted inside an enclosure if one needed to for extra safety (from innocent fingers)...

 

[PyroRider]

Hi, as a german electrician with NH-Fuse switches from Wöhner in my 48V pv system I might be able to answer your questions.
The fuse holder you have is for the size NH000 and NH00 (Gr00). It goes up to 160A per fuse. The larger fuses (200A, 355A) are likely NH1, NH2 or NH3 (bigger holders).
You can put all 3 nh terminals in parallel (i.e. with a copper busbar), but then make sure that your cable is rated for 480A.

 

[PyroRider]

I would recommend getting a larger fuse size (6000W/24V (excluding conversion losses) is 250A, so at a minimum I'd use a single NH1 holder (up to your mentioned 355A).

 

[michael d]

Hi, as a german electrician with NH-Fuse switches from Wöhner in my 48V pv system I might be able to answer your questions.
The fuse holder you have is for the size NH000 and NH00 (Gr00). It goes up to 160A per fuse. The larger fuses (200A, 355A) are likely NH1, NH2 or NH3 (bigger holders).
You can put all 3 nh terminals in parallel (i.e. with a copper busbar), but then make sure that your cable is rated for 480A.

thanks that helps me some for sure,,,, as trying to get an interpretation from the datasheets seems to be plus and minus... thanks

 

[PyroRider]

I need to correct myself at least for Siemens NH fuses, Siemens makes NH1 fuses only up to 250A so maybe consider getting an NH2 base

 

[michael d]

I would recommend getting a larger fuse size (6000W/24V (excluding conversion losses) is 250A, so at a minimum I'd use a single NH1 holder (up to your mentioned 355A).

I bought some single fuse holders also, hope they are the right size for the 250Amp NH style fuse...
I will have to do some more comparison.... and sizing..
even the holders are not even labeled very clearly >>> at least for my comprehension... at this time...
I sure appreciate the reply...

 

[PyroRider]

This would be an NH2 fuse with 300A from siemens: 3NA3250
Edit:
Or the 3NA6250 if you like the fuse to have another "tripped-flag" on the front facing you (useful when used in NH switches where you cant see the flag on top of the fuse)

 

[PyroRider]

I bought some single fuse holders also, hope they are the right size for the 250Amp NH style fuse...
I will have to do some more comparison.... and sizing..
even the holders are not even labeled very clearly >>> at least for my comprehension... at this time...
I sure appreciate the reply...

Share a photo or the text from the holder, I might be able to tell you the NH size

 

[michael d]

I need to correct myself at least for Siemens NH fuses, Siemens makes NH1 fuses only up to 250A so maybe consider getting an NH2 base

yes, I still need to compare the base to the fuse sizing.....

the 355 amp is definitely a lot larger blade depth than the 200 and 250 amp Siemens NH fuse...

 

[michael d]

Lot Of 3 Siemens 3NH3 330 Fuse Holders Fuse Block 400A 690V #08B32 (

one was missing a retaining ring so I really only received 2 functional ones in this size...
it says size 2/3NA 400 amp on the picture on the internet... the holder is out in the solar power shed.
I will go see if I can get a better picture of it...

 

[OzSolar]

I have cnswipower 3200-watt and 6000-watt HF inverters in the 24-volt version that I am fusing.....presently w/o fuse externally to protect the wire >>> but presently only powering very light loads

A couple things I'd add to the discussion:

-Light loads? Fusing is more about protecting your property against catastrophe should something go wrong. I see people say things like this and it concerns me. EG: "my system is small so I don't need breakers or fuses." can be a very dangerous assumption.

-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.

 

[michael d]

NH fuse 355Amp, 250Amp, 200Amp and 160Amp fuses, and a single holder for NH fuse pictures

this much larger fuse holder says:
SIEMENS
Gr.2 - 400A
~690V
VDE 0636/IEC M269
MADE IN GERMANY
400A/600V
FOR HRC II-MISC
FUSES TYPES
SIZE 2/3NA

 

[michael d]

A couple things I'd add to the discussion:

-Light loads? Fusing is more about protecting your property against catastrophe should something go wrong. I see people say things like this and it concerns me. EG: "my system is small so I don't need breakers or fuses." can be a very dangerous assumption.

-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

that was the smaller triple fuse holder it is outside now. I will try to get a better picture of it later

 

[michael d]

A couple things I'd add to the discussion:

-Light loads? Fusing is more about protecting your property against catastrophe should something go wrong. I see people say things like this and it concerns me. EG: "my system is small so I don't need breakers or fuses." can be a very dangerous assumption.

-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 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...

 

[michael d]

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

 

[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 holder is jsut a holder, not a switch but to calm you down, at 24V you can use the holders with no problem, even at 48V you wont get giant arcs flashing around

 

[PyroRider]

NH fuse 355Amp, 250Amp, 200Amp and 160Amp fuses, and a single holder for NH fuse pictures

this much larger fuse holder says:
SIEMENS
Gr.2 - 400A
~690V
VDE 0636/IEC M269
MADE IN GERMANY
400A/600V
FOR HRC II-MISC
FUSES TYPES
SIZE 2/3NA

Thats an NH2 fuse holder up to 400A

 

[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...