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Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
I'm trying to figure out what is the best rated resettable fuses to get, to replace my variacs fuse. I have a 0-140V, 7.5A rated variac, and it came with a 8A glass fuse. I wanted to replace this fuse with something that can reset. I was told it's best to get both thermal, and magnetic. But what ratings might be best?
Wasn't sure if it would be best to get a 8A rated thermal, or do i want it lower..Not a clue, I see newark sells a lot in that body type, where its a easy fire into my variac, with the rounded screw end, just pops right into the old fuse hole.
Please help, Just looking for a way to protect my variac against shorts and over heating somehow due to well, you know...Thus getting a thermal fuse.
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638
A thermal one should be fine provided there is no chance of you shorting out turns with debris. Magnetic breakers tend to be larger then thermal ones and I doubt you will find one that small, if you really wanted the over load and dead short protection you could buy a separate magnetic breaker and put it inline with your variac's cord.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Nik wrote ...
A thermal one should be fine provided there is no chance of you shorting out turns with debris. Magnetic breakers tend to be larger then thermal ones and I doubt you will find one that small, if you really wanted the over load and dead short protection you could buy a separate magnetic breaker and put it inline with your variac's cord.
Yeah thats what i ment, I figured with the magnet breakers, my house is 15A, so anything below 15A, should kick in before my houses.
If i did this, and say turns were shorted by debris, would magnet breakers protect against this? I did have plans to get both types. I just wasnt sure how many amps for that thermal one, unless the one i listed, is good.
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Hmm. Well, I thought at first someone told be breakers, say 4A, wouldn't trip until 8A. But to that site, 4A trips 4.25A. I guess i'll hVe to get a 8A if that's the case. Since the fuse I have is 8A, and it's a 7.5 variac. I'm just scared if I did that, the powe start would trip it. So far my house 15A won't trip when I turn it on. I'm sure if I put the breaker before the variac, it would. But after, the output, maybe not.
Registered Member #53
Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638
Magnetic breakers are generally over current protection which are only to protect your house wires from melting when you run over a cord with the lawn mover or drop a screw into a transformer case. Thermal breakers are generally over load protection which protect what ever device you have on the other side of it from being melted due to excessive but not incredibly high current. I would say stick with the 8amp pop breaker, it should react slow enough to not go from inrush current but it will protect you from melting your variac. Your house breaker will protect your house and self from fire and explosion (mostly).
TLDR: Magnetic breaker would be over kill for your application, 8amp thermal is ok.
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Help with replacing variac fuse type
