Class T details and specs

[Bluedog225]

I’m learning the hard way about class T fuse details.

Am I right in thinking the “B” dimension is exclusively determined by amp rating? I’d like to purchase the correct fuse for my blue sea holders. Buying the wrong stuff is getting expensive (chuckle).

JLLN and JLLS is a mystery to me. And the blue sea fuse holder spec on Amazon (and on the Blue Sea web site) doesn’t seem to specify which one it wants. But they have different B dimensions. I can measure the fuse holder (it’s up at the cabin) but feel like I’m missing something.

Any help appreciated understanding exactly which class T fuse to buy.

Thanks

 

[rmaddy]

The spec sheet you are showing the dimensions from shows the different specs between JLLN and JLLS on the first page. It appears that the primary difference is that the JLLS has a higher voltage rating and a different DC interrupting rating.

You do appear to be correct on the dimensions. The higher the current rating the bigger the fuse. This is why the Blue Sea site states the different fuse holders apply to different amp ranges.

The Amazon listing you show is for a JLLN fuse based on the 160VDC rating. The listing also shows that the holder is for 225A-400A fuses which matches the dimensions from the fuse spec sheet.

You need to buy the fuse with the needed current rating for your electric system. You then buy the correct holder for that fuse. You should not be trying to choose a fuse solely on what will fit in the holder you have.

 

[Bluedog225]

Thanks. Agreed. I was sizing this as a backdrop for my system. If all else fails.

That side, I’m curious about your saying it is JLLN since it is 160 volt. How do you know that? I’ve seen JLLN listed with other voltage ratings. Trying to learn here.

Thanks!

 

[rmaddy]

It's in the spec sheet. Here is the Class T fuse page from Littlefuse:

Class T Fuse - Industrial Power Fuses - Littelfuse

www.littelfuse.com

Click on the data sheet (which is probably what you already have since the fuse dimension table is in that spec sheet. At the top of the first page it shows the voltages for JLLN and JLLS.

The JLLN is actually either 160VDC or 125VDC depending on the amperage.

 

[Bluedog225]

Got it. I appreciate the help.

 

[Aakelley]

Ordered a 200A fuse and the wrong (larger size) fuse holder. Lesson learned. Trying to get the right sizes (smaller) fuse holder and coming up empty finding one anywhere. Any place you all have found that its in stock?

 

[rmaddy]

Trying to get the right sizes (smaller) fuse holder and coming up empty finding one anywhere. Any place you all have found that its in stock?

Try this one:

TFB1-200, 200A Class T Fuse Kit | DonRowe.com

The TFB1-200 offers 200 amps of over-current protection and provides safe operation of your inverter.

www.donrowe.com

 

[Bluedog225]

Hope that works out.

Lesson learned for me: Order the fuse and holder (sized to the wire) as a unit. The specs on sizing fuses (Class T) can get a little involved.

 

[Aakelley]

Everything sized to the wire. From what I understood there are two T fuse sizes? Large and small.

 

[GXMnow]

I ran into the same problem. I am running a 225 amp Class T Fuse. I bought the 300 amp fuse holder from Blue Sea and it didn't fit. Then I ran into a similar issue. I am using CNN fuses for the individual strings in my second battery bank. Tried 3 different fuse holders, none were the exact correct length. The higher voltage CNN fork lift fuses are just a little longer than "Mega" fuses. I know they do this o keep people from installing the wrong fuse, but it sure makes it a pain.

 

[timselectric]

Another option is to bolt the fuse between two bus bars. One bus bar to each end. Connect all battery connections to one bus bar. And, all load connections to the other bus bar.

 

[Aakelley]

So I have a Lynx power in that I can do this in. I thought the best practice was a type T fuse though, and the lynx only does Mega / ANL fuses.

 

[tigerwillow1]

there are two T fuse sizes? Large and small.

 

[tigerwillow1]

there are two T fuse sizes? Large and small.

I found about 16 physical sizes on the class-T data sheet. https://www.littelfuse.com/media?re...7d0-f4fe191d25b2&filename=jlln-jlls-datasheet

 

[Bluedog225]

Another option is to bolt the fuse between two bus bars. One bus bar to each end. Connect all battery connections to one bus bar. And, all load connections to the other bus bar.

Doh! That’s pretty smart. Thanks!

 

[Aakelley]

I found about 16 physical sizes on the class-T data sheet. https://www.littelfuse.com/media?re...7d0-f4fe191d25b2&filename=jlln-jlls-datasheet

Got it. Fuse sent back as well. Will buy them as a package. Guess I should pickup a spare as well since they seem hard to replace with same size.

 

[JRH]

Ordered a 200A fuse and the wrong (larger size) fuse holder. Lesson learned. Trying to get the right sizes (smaller) fuse holder and coming up empty finding one anywhere. Any place you all have found that its in stock?

I was told directly by blue seas tech support that the Blue seas class T fuse block 5007 series is for UP TO 200 amps and that the 5502 series was for 225 to 400 Amp . Neither come with a fuse as standard …You buy it Separately .. Both of the techs are cool guys and helpful. I bought 6 after speaking with them on Amazon and some other places.. ( 5502 type) .
The smaller fuses and Larger ones need the correct holder.. they are not interchangeable. They also can be hard to locate .. shop around …….

 

[filippomasoni]

I always read about class T fuses and most mentioned are blue seas, but doing a bit of research, at least here in Europe they are called HRC fuses and there are many different kinds, from reputable brands IEC approved at lower prices than blue seas.

Like this example:

TIS63M100 | Eaton 100A British Standard Fuse, A3, 660V ac, 73mm | RS

uk.rs-online.com

Or this:

3NA3142 | Siemens 224A NH Fuse, NH1, 500V ac | RS

uk.rs-online.com

This Siemens model is quite different, doesn't have holes to bolt it in, so I'm not really sure how to make the connection, but there's many versions and they are quite cheap, some even around 10 euro.

You can check out the spec sheet in the page,
I'm linking the UK site so everyone can read English but they are available all through Europe.

 

[filippomasoni]

Another option is to bolt the fuse between two bus bars. One bus bar to each end. Connect all battery connections to one bus bar. And, all load connections to the other bus bar.

That's exactly what I was thinking of doing since I have a 1.5m copper busbar that I got for free. 20x4mm so 80mm2. Basically eliminates a lot of connections between wires and lugs. It's probably fine for a stationary system, but that will make it very rigid and I'm not sure about it for my vehicle-mounted system, especially offroad.

 

[timselectric]

On a vehicle mounted system. You should check connections regularly, anyway. It's just a good habit to get into.