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My Wine Fridge Ate Its Fuse

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Beth Stackpole
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Blogger
Overlooking the fundamentals
Beth Stackpole   7/30/2012 8:01:01 AM
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Nice catch--both for figuring out the fuse issue and for scoring a working wine fridge. Seems like a pretty basic case of specing the wrong part and overlooking fundamental design principles. You have to wonder if it's a case of oversight or a design choice caused by pressure to reduce costs. Either way, a pretty overavoidable design flaw.

notarboca
User Rank
Gold
Re: Overlooking the fundamentals
notarboca   7/31/2012 8:39:57 AM
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Yes, yes, a little practical engineering knowledge goes a long way!  What a sweet deal--2 operational wine fridges for next to naught cost.

warren@fourward.com
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Platinum
Re: Overlooking the fundamentals
warren@fourward.com   7/31/2012 9:45:22 AM
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In many ways, fuse ratings is an art form.  Inrush current, load current, spikes, motors starting up, and numerous other factors come into play.  You have to consider the steady state of the device, but what if all peripheral functions operate at the same time?  So rating a fuse can be tricky.  I assume the cooler design engineer was looking at the steady state current and not considering inrush from start-up.  But then again, running a fuse so close to steady state was foolish, unless he was forced to use wiring or other devices that could not handle much more current.  Then. that was just plain stupid, but cost effective.  Fused flex on start-up or an increase in current, so they will wear out if they aren't designed properly.  But, if there was no warranty, then who cares?

I wish I could find a Ferrari that someone threw away because of blown fuses.  I am sure I could find the fix...

Fuseman
User Rank
Iron
Re: Overlooking the fundamentals
Fuseman   7/31/2012 12:02:51 PM
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Fuses are not simple devices.  Standards agencies provide a very broad guideline regarding a device's current and voltage ratings.  However, differences between "equivalent" fuses from different manufacturers can cause trouble in precision applications.


Fuses can have an AC or DC rating, or both.  Each will likely have different levels of capability when it comes to interrupting the current.  There is also a very significent difference between a European fuse vs. a North American fuse for small fuses.  The different standards required make these two "mutually exclusive" when seeking a replacement.  If a European fuse is employed, it is designed to carry 100% rated current and typically at 250 Vac.  A similar looking North American fuse (UL) is designed to carry no more than 75% rated current to achieve a satisfactory life and safe operation.  These are typically rated 125 Vac. 


A North American application can use a European fuse if it is not able to be easily replaced by the consumer.  A soldered fuse meets this criterion.  The description given of a leaded fuse standing on end (typically referred to as "hairpin lead configuration) with a heat shrink cover is standard. 


I have worked in the fuse and protection industry for 30 years with my main responsibility being interfacing with manufacturers employing fuses and their engineers.  Much of my time was also dedicated to standards committees covering these components.

warren@fourward.com
User Rank
Platinum
Re: Overlooking the fundamentals
warren@fourward.com   7/31/2012 12:42:36 PM
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I always yield the floor to the pro.   Thanks for filling in the gaps.  As I said, and as they said in "Galaxy Quest," it is more of an art-form.

Cadman-LT
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Platinum
Re: Overlooking the fundamentals
Cadman-LT   8/2/2012 4:32:57 PM
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notarboca: I agree. Use that knowledge! Major score! Good for you! I got a 60" bigscreen TV that way once, it wasn't a fuse, but a $2 part. :)

Cadman-LT
User Rank
Platinum
Re: Overlooking the fundamentals
Cadman-LT   8/2/2012 4:35:51 PM
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That TV was about 10 years ago. It still works just fine. I've bought new stuff that doesn't last that long.

William K.
User Rank
Platinum
Wine refrigerators, and solid state cooler inrush???
William K.   8/6/2012 9:31:48 PM
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I don't think that an inrush current surge would exist with a thermoelectric cooler. That just does not make any sense. And, in the output circuit of a regulated switching power supply, I have a hard time imagining any surges big enough to pop a fuse. It seems that most switchers are regulated on the output side. I can easily imagine a cheap fuse failing mechanicaly, I have seen that kind of failure. In that application the fuse would be there to protect from a short circuit, not from an overload, and so the big question would be about what protection the supply needed. Probably the system would have been safe with NO secondary fuse. 

It is quite amazing the number of appliance type things that include a fuse that is obviously never intended to be replaced, and have no marking to indicate that they contain a protective fuse.

Ann R. Thryft
User Rank
Blogger
Easier to replace a fuse than 200 nails
Ann R. Thryft   8/7/2012 12:42:01 PM
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Another case of what one would think should be screamingly obvious to the design engineer. A carpentry parallel would be using the wrong size nail or screw. OTOH, my county has an overabundance of construction contractors and a (perhaps corresponding) overabundance of people who use the wrong screw, don't measure correctly, can't choose lumber correctly, and ad nauseum. It's a lot harder to retrofit the wrong nail or screw--thanks for letting us know that a fuse change may be all that's needed in this case.

tekochip
User Rank
Platinum
Re: Overlooking the fundamentals
tekochip   8/7/2012 2:16:25 PM
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Sometimes it's really tough to pick the right fuse, and it really is an art form.  In addition to all the fuse specifications you have to deal with agency requirements and how the device will respond to surges and faults on the line.  I too had a Phillips plasma that kept blowing its fuse for no reason.  The failure was amplified by having to remove the heavy appliance from the wall and removing more than a dozen screws to get to the fuse.  I changed the fuse to a different manufacturer and that has cured the problem.


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