Bolt-on vs. Spring Clip Fuses

DrSparks

Senior Member
On our recent thermographic study, we discovered that many of our fused disconnects in the plant are heating up at the spring clip fuse holders. Also at our lug terminations as well. We've begun rectifying the latter problem by investing $5k in a hydraulic crimper and a full set of dies, but does anyone have any pointers on mitigating the former issue? I was looking into switch to class L bolt-on fuses, but my supplier says they start at 600-amps. However, a simple Google search tells me that Littelfuse has their LDC series, which goes down to 150 amps.

Thanks for your help!

P.S. Anyone ever hear of bolt-on fuse holders in I-Line bus duct disconnects?
 

zog

Senior Member
Well there will be some heating, how much are we talking about? Was the IR scanning done by a certified thermographer?
 

zog

Senior Member
Yes, it was a certified contractor. I think the highest was 190F
Certified contractor or thermographer? Plenty of contractors out there with IR guns with no idea how to use them. A single temp doesn't tell you much, it is your delta T's that matter.
 

pjones

Member
Certified contractor or thermographer? Plenty of contractors out there with IR guns with no idea how to use them. A single temp doesn't tell you much, it is your delta T's that matter.
A customer of mine was shocked when I told them they had a bad connection inside their panel. They were shocked because they JUST had it thermal scanned the week before. Turns out the person scanning didn’t turn the loads on before scanning so there was no heat to be generated... I think they just had a new tool and were excited to use it.


Sent from my iPhone using Tapatalk
 

pv_n00b

Senior Member
IR is a skilled job task, so make sure the person has training and did not just order a tool to add to their list of things they can do. It's not point and shoot.
 

Jraef

Moderator
Staff member
Switching to bolt-in fuses will also likely introduce additional down time issues as well. The fuses are not easily available in stock and the act of working in the disconnect with tools will require more time and maybe more precautions depending on the circumstances, compared to using a standard fuse and standard fuse puller.

One problem I've always had with fused disconnects is that every time a fuse blows from overload (as opposed to short circuit), there is a lot of heat in the fuse, and that heat sometimes weakens the spring clips. So we probably SHOULD be replacing the spring slips when we replace the fuses, but NOBODY does that. I've used those Bussman clamps to good effect but every time I have recommended them, people get excited about the added cost.
 
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