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#187496 06/28/09 11:29 PM
Joined: May 2004
Posts: 24
T
thiggy Offline OP
Member
I have an old family farm house with a 125 amp Square D breaker box. The service disconnect is a 100 amp Square D cartridge fuse. I have never had the main blow, but I decided that I better have a spare pair of fuses on hand just in case, as in this rural area it would be difficult to locate one in a hurry. I drove to the nearest city and located fuses at Lowes, but I am not sure which one of the two types they had should be used for my application. The heavy-duty time-delay one said it is "for motor and main panel protection. (FRN-R)" It indicated that "for lighting or electric heating circuits use general purpose fuses.(NON)" I use window AC units for cooling, and 1500 watt portable heaters for infrequent use in winter heating. Water heaters are also electric. (This is generally just a week-end house.) Which type of fuse would be the most appropriate for my use?

Joined: Jul 2004
Posts: 9,643
G
Member
I would go with the FRN.
That will tolerate a short time spike in current.
The biggest opportunity for a spike in current is when you have a power glitch and the service would see locked rotor from every motor that was running at that time.


Greg Fretwell
Joined: Jul 2002
Posts: 8,407
Member
Yeah,
I agree with Greg.
You really need something with a bit of time delay on it for a main fuse.
After all, the fuse/CB that is electrically closest to the fault (ie, a sub-circuit fuse/CB) should operate first, in any electrical system.
Anything less is poor design.

Joined: Dec 2000
Posts: 4,287
Member
You answered your own question.

Quote
The heavy-duty time-delay one said it is "for motor and main panel protection. (FRN-R)"

Joined: May 2004
Posts: 24
T
thiggy Offline OP
Member
Thanks for the responses. I shall go with the time delay fuse. (I actually bought two of both types with the intention of returning one pair after I determined which type I should use.)

Joined: Jul 2001
Posts: 599
J
JBD Offline
Member
There is almost no reason to ever install an NON fuse. For all intents NONs are old technology, and are almost always sold based on price only.

Joined: Jul 2004
Posts: 9,643
G
Member
We used NONs to protect electronics and there was even a faster blowing fuse that we used for the input to switcher power supplies way back when they were a big cabinet full very expensive parts.


Greg Fretwell

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