Hey all,

 

So I purchased some Onesto Fuse Disconnectors and then Onesto Fuses for when I install my batteries, I assumed they were for batteries and were for DC voltage.

When I received them, I noticed that the fuse seems as if it is for AC and not DC - although I see other websites are advertising it as a battery fuse: 

https://diyshop.co.za/products/general-protection-fuse-for-battery-disconnect-onesto?variant=44250923925754

https://diyshop.co.za/products/battery-disconnect-fuse-box-onesto

 

I assume the Onesto fuse holder would work fine as a battery disconnector provided an appropriate DC fuse were to be used?

Although I also noticed that some fuses seem to be rated for both AC and DC, although just different voltage ranges? Like this Mersen fuse here:

https://www.inverter-warehouse.co.za/products/fuse-mersen-nh-size-00-80amp?variant=36493224509592&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwoeemBhCfARIsADR2QCtGvRqrQMLSAXUUeEJWJgLYLbkt7hNtSqwRcfFQHZUhoagSwmKmWWQaAjFIEALw_wcB

 

 

So now I am very confused and am wondering if there is something I am missing or not understanding. I was under the impression a fuse is specific for AC voltage or DC voltage?

So I just want a bit of clarity, could I keep the Onesto fuse holder and use that safely? Do you think it is just the fuses I need to return and get DC rated fuses or is there a chance that these Onesto fuses are DC rated as well and are safe to use?

 

I cannot find much info on the Onesto website either for the fuses: https://www.onesto.cn/product/NH-00-335.html

However on the fuse itself it it has 500V~ or 690V~ and to me that indicates AC and not DC.

The fuse holder is rated for 440V DC.

The fuse *might* have a DC rating, but you will need to ask the supplier for a datasheet to confirm (you need a password to get tech docs directly from Onesto).

11 minutes ago, JustinSchoeman said:

The fuse holder is rated for 440V DC.

The fuse *might* have a DC rating, but you will need to ask the supplier for a datasheet to confirm (you need a password to get tech docs directly from Onesto).

Thanks for the confirmation on the fuse holder rating.

 

I did reach out to the supplier, they think the fuse is DC rated and I have asked them for the data sheet or some sort of confirmation. Let's wait and see, I will give feedback here, the pricing on these Onesto fuses and holders is pretty good and they currently seem common in SA so I suspect we may see more of these for new installations.

 

Weird that one requires a password to get the technical docs from Onesto.

5 hours ago, PsyCLown said:

Hey all,

 

Although I also noticed that some fuses seem to be rated for both AC and DC, although just different voltage ranges? Like this Mersen fuse here:

So now I am very confused and am wondering if there is something I am missing or not understanding. I was under the impression a fuse is specific for AC voltage or DC voltage?

So I just want a bit of clarity, could I keep the Onesto fuse holder and use that safely? Do you think it is just the fuses I need to return and get DC rated fuses or is there a chance that these Onesto fuses are DC rated as well and are safe to use?

A fuse is a fuse. Just that. The voltage range differs between AC and DC though.

You can safely use those Onesto fuses in that disconnector. 

Just take care to press that square button on the side of the holder to mount the 2 fuses.

Iow, press and hold the button, insert the fuses and release the button.

3 hours ago, Virwat said:

A fuse is a fuse. Just that.

10 hours ago, PsyCLown said:

Hey all,

 

So I purchased some Onesto Fuse Disconnectors and then Onesto Fuses for when I install my batteries, I assumed they were for batteries and were for DC voltage.

When I received them, I noticed that the fuse seems as if it is for AC and not DC - although I see other websites are advertising it as a battery fuse: 

https://diyshop.co.za/products/general-protection-fuse-for-battery-disconnect-onesto?variant=44250923925754

https://diyshop.co.za/products/battery-disconnect-fuse-box-onesto

 

I assume the Onesto fuse holder would work fine as a battery disconnector provided an appropriate DC fuse were to be used?

Although I also noticed that some fuses seem to be rated for both AC and DC, although just different voltage ranges? Like this Mersen fuse here:

https://www.inverter-warehouse.co.za/products/fuse-mersen-nh-size-00-80amp?variant=36493224509592&currency=ZAR&utm_medium=product_sync&utm_source=google&utm_content=sag_organic&utm_campaign=sag_organic&gclid=Cj0KCQjwoeemBhCfARIsADR2QCtGvRqrQMLSAXUUeEJWJgLYLbkt7hNtSqwRcfFQHZUhoagSwmKmWWQaAjFIEALw_wcB

 

 

So now I am very confused and am wondering if there is something I am missing or not understanding. I was under the impression a fuse is specific for AC voltage or DC voltage?

So I just want a bit of clarity, could I keep the Onesto fuse holder and use that safely? Do you think it is just the fuses I need to return and get DC rated fuses or is there a chance that these Onesto fuses are DC rated as well and are safe to use?

 

I cannot find much info on the Onesto website either for the fuses: https://www.onesto.cn/product/NH-00-335.html

However on the fuse itself it it has 500V~ or 690V~ and to me that indicates AC and not DC.

The fuse rating is for general purpose use and is not rated for DC. Look at below 2nd picture your fuse marked gG it should be gS for battery use and gPV for solar use.

8 hours ago, TaliaB said:

your fuse marked gG it should be gS for battery use and gPV for solar use

Thanks Talia. Are you suggesting that the Eaton Bussman and Jean Müller fuselinks commonly sold with the disconnectors are not appropriate for use between inverter and battery? They're rated gG/gL but not gS...

8 hours ago, TaliaB said:

The fuse rating is for general purpose use and is not rated for DC. Look at below 2nd picture your fuse marked gG it should be gS for battery use and gPV for solar use.

Any idea where one could actually source a 160A NH00 gS fuse which is DC rated?

Seems to be a lot more challenging than one might think, lots of solar retailers selling gG fuses only.

10 hours ago, TaliaB said:

The fuse rating is for general purpose use and is not rated for DC. Look at below 2nd picture your fuse marked gG it should be gS for battery use and gPV for solar use.

I doubt there is a single installation in SA with gS fuses. Is every retailer selling gG battery fuses wrong?

Fortunately, SANS10142 only requires fuses for conductor protection (not device protection), so gG should meet the legal requirement. I have never seen gS or gR anywhere in South Africa (technically the outside facing part of the battery is the BMS, so gR would be more appropriate - gS would be for LA batteries).

For DC fuses, GC Solar is showing stock. Lite-Glo is not showing stock, but if you pop them an email, they will generally source whatever you need in a day or two.

 

1 hour ago, PsyCLown said:

Any idea where one could actually source a 160A NH00 gS fuse which is DC rated?

Seems to be a lot more challenging than one might think, lots of solar retailers selling gG fuses only.

I understand what you guys are saying most suppliers don't sell the correct NH fuses for dc. I get my fuses from ElectroMechanica or i import the correct NH dc rated fused. Look using NH fuses with gG rating on 48v batteries are not that crucial but beware of high voltage solar arrays. Below link of NH fuses available(or not) from Electro Mechanica.

https://www.em.co.za/site/img/Supplier catalogues/DF photovoltaic-fuses-and-bases.pdf

44 minutes ago, JustinSchoeman said:

Fortunately, SANS10142 only requires fuses for conductor protection (not device protection), so gG should meet the legal requirement. I have never seen gS or gR anywhere in South Africa (technically the outside facing part of the battery is the BMS, so gR would be more appropriate - gS would be for LA batteries).

For DC fuses, GC Solar is showing stock. Lite-Glo is not showing stock, but if you pop them an email, they will generally source whatever you need in a day or two.

 

Here is the international standard for low voltage fuses. IEC 60269-6

IEC-60269-6-2010.pdf

3 minutes ago, TaliaB said:

Here is the international standard for low voltage fuses. IEC 60269-6

IEC-60269-6-2010.pdf 1.15 MB · 0 downloads

Where is the standard which says gS fuse has to be used for Lithium Batteries in SA?

2 hours ago, PowerUser said:

Where is the standard which says gS fuse has to be used for Lithium Batteries in SA?

We as installers and electricians has the responsibility to use the correct components for installations. We as installers should know the diffrence between correct and incorrect without referring to standards. Standards are there for guidelines. In all my installations i will not use fuses or curcuit breakers on dc that is not dc rated.

Incorrect fuse for dc applications:

Correct fuse for dc applications:

10 minutes ago, TaliaB said:

We as installers and electricians has the responsibility to use the correct components for installations. We as installers should know the diffrence between correct and incorrect without referring to standards. Standards are there for guidelines. In all my installations i will not use fuses or curcuit breakers on dc that is not dc rated.

Incorrect fuse for dc applications:

Correct fuse for dc applications:

 

Are ALL gG fuses wrong for DC applications?

Can one assume all fuses with blown fuse indicator with no AC or DC marking to be for AC use? 

From your IEC-60269-6-2010 document, which defines the gPV utilization category:

"1.1 Scope and object
These supplementary requirements apply to fuse-links for protecting PV strings and PV arrays
in equipment for circuits of nominal voltages up to 1 500 V d.c."

gPV is specifically for protection of solar panels.  The question at hand is with regards to battery fuses:

DC rated but with gG utilization category.

 Explanation for NH fuses:

https://www.swe-check.com.au/editorials/nh_fuses.php

35 minutes ago, TaliaB said:

 Explanation for NH fuses:

https://www.swe-check.com.au/editorials/nh_fuses.php

From you document:

gS is a very fast acting fuse.

gG is a fast acting fuse.

 

Where in that document is anything which prohibits gG in DC applications?

Edited August 15, 20232 yr by PowerUser

42 minutes ago, PowerUser said:

From you document:

gS is a very fast acting fuse.

gG is a fast acting fuse.

 

Where in that document is anything which prohibits gG in DC applications?

I believe there is no reason why gG fuses cannot be used in a DC application, provided the fuse is DC rated.

The fuse speed rating is what was pointed out by @TaliaB that the gG fuses are perhaps not the correct / ideal fuses to be used the way we generally use these fuses (between a battery and inverter).

My initial question and concern was that the Onesto fuse does not state anything about being DC rated and nobody is able to provide me with any documentation which states it is DC rated - I spoke to the supplier and they will swap it out for me with a Chint fuse (gG) but it at least states it has a DC rating and I prefer this and feel more comfortable with it.

 

https://www.asbeam.com/news/nh_fuse_cross_reference-cn.html#:~:text=NH fuse class gG which,times of the rated current.

This article states that the gG / gL fuses will blow within 2 to 5 seconds at 5x their rating.

So a 160A gG fuse will blow within 2 to 5 seconds when 800A is being passed through it. It would only make sense that the gS fuse would blow quicker and therefore potentially offer more protection? I guess it depends on what you are trying to protect as well, if the device and/or cable can handle such a burst of current its not a problem and the gG fuse would suffice.

 

If one wanted to use the fuse to not only protect the cable but also protect the inverter, then I think the gS fuse may be the better or safer option?

For protecting just the cable, perhaps gG is sufficient?

EDIT: I found this under the Battery Protection link.

https://www.swe-check.com.au/catalog/65.pdf

At the bottom it basically states why go for the gS fuse over the gG fuse and it is to do with how quick the gS fuse reacts compared to the gG fuse.

Edited August 15, 20232 yr by PsyCLown
Added another link