Class T vs NH00 Fuse

[RSahan]

Hi,

I live in Australia and there is no choice here for class T fuses except the blue sea systems ones starting from 225A.
My solar system consists of Deye 5kw inverter + 280ah x 16 CATL cell battery. I'm looking to buy a proper fuse. According to my research 225A from blue sea systems is a bit too high for my system.

In Australia, most people seem to be using these NH/FH00 style fuses, and it's pretty affordable when considering I can get the following with 3 included 125A fuses. (125A because these fuses seem to be slow blow style) - https://www.solamart.com.au/product/battery-fuse-holder-disconnect-160a-fh00-with-fuses/



Should I get one of the above or pay more to get a single 150A JLLN Class T fuse from shunts.com?



No UL conformity is needed.


Thanks in advance

 

[upnorthandpersonal]

NH/FH00

Those are, in my opinion, way too slow. Fast acting fuses have the advantage that they can also be used to protect the silicon (semiconductor protection fuses, limiting the I2t peak let-through current), not just the wiring.

If not Class T, you could go for BS88 British Style fuses - they should do (from datasheet info), although I have not tested them yet. Class T is my go-to fuse for these things, and I have tested them extensively.

 

[BiduleOhm]

I like NH fuses, far cheaper than class T but they're more bulky tho.

There's fast acting ones, for example: https://uk.rs-online.com/web/p/tag-fuses/2213688

Also, even fast acting fuses are usually to slow to protect semiconductors. Someone I knew was always saying a fuse doesn't protect a transistor but a transistor protects a fuse very well...?

 

[RSahan]

you could go for BS88 British Style fuses

Thanks for your input. What do you think about this? https://www.eaton.com/us/en-us/skuPage.160LET.html

I found a local place to get the 160A BS88 and the base for AU$72 shipped.


I cant seem to figure out the interrupt rating and the time to blow by looking at the graph in datasheet though ?

 

[upnorthandpersonal]

Also, even fast acting fuses are usually to slow to protect semiconductors.

There are specific fuses built to protect semiconductors - the BS88 ones for example. Look for this symbol:

Thanks for your input. What do you think about this? https://www.eaton.com/us/en-us/skuPage.160LET.html

I found a local place to get the 160A BS88 and the base for AU$72 shipped.

I'm actually in the process of buying 10 of those for testing.

 

[JoeHam]

The fuse holder pictured above says it’s rated for 75 Amps.

I assume they have another for the 160A fuse ?

If I’m reading this right it’s interrupt rating is good :

160FEE

BUSSMANN 160FEE • Volts • 690 Vac/500 Vdc (IEC) • 700 Vac/500 Vdc (UL) • Amps 160 A

bussmannpower.com

 

[BiduleOhm]

There are specific fuses built to protect semiconductors - the BS88 ones for example. Look for this symbol:

I'm actually in the process of buying 10 of those for testing.

The problem is that unless the semiconductors are way oversized or particularly robust, they fail before the fuse.

Just because there's semiconductor on the fuse label doesn't guarantee it will protect all devices in all cases.

 

[upnorthandpersonal]

The problem is that unless the semiconductors are way oversized or particularly robust, they fail before the fuse.

Just because there's semiconductor on the fuse label doesn't guarantee it will protect all devices in all cases.

Sure, absolutely agreed. Fuse should be sized appropriately for this purpose.

 

[upnorthandpersonal]

They arrived. Let's see when I will find time to run some tests...

 

[aentrop]

Any updates on testing?

 

[Pappion]

There are specific fuses built to protect semiconductors - the BS88 ones for example. Look for this symbol:

I'm actually in the process of buying 10 of those for testing.

Rated voltage DC 150 V
Interrupt rating 200 kA RMS Sym, 50 kA DC at 150 Vdc

ANL fuses have an interrupt rating of 6000 Amps, which by the ABYC standards, allows them to be used as the primary circuit protection for lead acid batteries.

 

[upnorthandpersonal]

Any updates on testing?

So far, so good. I did a few short circuit tests with a BMS in line. BMS survived. I'm waiting on some better weather, since I want to build a different enclosure for my batteries (optimize some space) and I will do more testing then - I'm putting these on two of my production batteries to see what happens over summer.

A Class T fuse is a fast acting, current limiting, fuse that is rated to interrupt a minimum of 200,000 amps. @ 125V DC

Most class T fuses are 20k Amp DC and 200kA AC - where do you find a 200kA DC class T fuse?

 

[Pappion]

So far, so good. I did a few short circuit tests with a BMS in line. BMS survived. I'm waiting on some better weather, since I want to build a different enclosure for my batteries (optimize some space) and I will do more testing then - I'm putting these on two of my production batteries to see what happens over summer.



Most class T fuses are 20k Amp DC and 200kA AC - where do you find a 200kA DC class T fuse?

Bad source, tried to edit it last night

 

[Pappion]

https://diysolarforum.com/threads/do-not-discard-a-dead-victron-mppt-100-30-or-its-kind.23289/page-4
Page 3 has a pic of fuse in victron mppt.

"I replaced it with Bussmann 80LET 80Amp LET 150VDC Fast-Blow Cartridge Blade, which is same kind as the original fuse."

 

[upnorthandpersonal]

I did not know Victron uses them - I'm somewhat surprised they didn't design their Lynx Distributor around them instead of Mega fuses, but I guess they wanted something that is more readily available...

 

[John Frum]

I did not know Victron uses them - I'm somewhat surprised they didn't design their Lynx Distributor around them instead of Mega fuses, but I guess they wanted something that is more readily available...

I think the problem is the LET fuses are not all the same physical size.
I guess the generic name is BS88.
Also the ratings are not in round numbers.
There are no 150 amp, 300 and 350 amp versions.

 

[upnorthandpersonal]

I think the problem is the LET fuses are not all the same physical size.
I guess the generic name is BS88.

Yes, BS88 (British Standard) is the generic name, LET/EET/.. are the types within the standard and those can each have different physical sizes.
So yeah, the engineering to accommodate them would be a lot more complicated compared to Mega fuses.

 

[silverstone]

Sorry if I hijack this thread, but wanted to raise a concern.

From EATON catalog, these are "aR" operating class fuses. Meaning they can ONLY be used for short-circuit protection. Not for overload protection !

Do not operate at overload (or even nominal for that matter) for extended periods of time. aR fuses turn into bombs if you do that !

 

[upnorthandpersonal]

Meaning they can ONLY be used for short-circuit protection. Not for overload protection !

Yes - but since you size them based on the inverter, you tend not to be able to create overload situations.

 

[silverstone]

In principle yes, but depends on the fault impedance. You hope to get a hard short in order to blow the fuse. And hope your battery soc is high enough that the resistance of your battery pack is low enough. In most situations it will probably be just fine. But in some it might not