Me again,was told to buy a 30 amp disconnect for air conditioning unit.purchased an eaton/cutler hammer # 1 dpf221rp.it says it accepts class h fuses.cant seem to find anyone who knows what a class h fuse is.been to ace and home depot,can anyone help?? :confused:

Give me the model nimber of the switch. Class H is a renewable fuse, and there are code restricitions on their use. There are other classes of fuses that this switch must work with.


Never mind I just saw the number in the post, be back at you later.

OK See the attached product sheet, you want a Bussman # NON-30, assuming a 30 amp fuse. It is a 250 volt no renewable fuse, 2 " long, and goes up to 30 a.

This is your plain vanilla everyday general purpose fuse that should be easily found at electrical supply houses.

Disreard my previous comment on code restriction, I first saw "renewable" and that is what has code restrections, not the Class H.

Much Thanks Tk

Pardon my curious ignorance, but what is a "renewable" fuse?

A cartridge fuse that has screw cap type ferrules and the metal fuse links.

Links come several in a box, if a fuse blew, pull the fuse out , open the cap and thread through another link. The cases are reused.

These are restricted to places under direct supervison, such as large industrial, they use them to save money due to large quantity of fuses blown.

In the hands of the public, you could have 100 amp links in 30 amp fuse. Would look like when Chicago burned.

Aha. Thank you for the explanation.

Back to the restrictions for renewable fuses. Where can I read more on the restrictions.
Thanks

The NFPA 70 National Electric Code 2005 Edition.

A class H fuse is simply a one time fuse or a renewable element fuse. It is of the least expensive type fuse available. It is not necessary to use a class H fuse in your disconnect. You can use a RK5 fuse or an RK1. Basically this determines the interrupting rating of the fuse. The higher the interrupting the better the fuse.
I would recommend a Littelfuse FLNR(amperage). This is a RK5 fuse and will suit your application.

National Electrical Code. 2012 page 97
Article 240 - Overcurrent Protection - Section VI Cartridge Fuses and Fuseholders 240.60 (D) "Renewable Fuses. Class H fuses and fuseholders of the renewable type shall be permitted to be used only for replacement in existing installations where there is no evidence of overfusing or tampering.