Fuses

[Davebones]

Have some heater control panels that will feed imersion type tank heaters .Due to space limitations we are using class J fuses .Littlefuse calls for a JLS fuse for heater circuits . Is there any reason we can't use JTD fuses? We can get the ID type fuses in JTD but not in JLS.For safety we want the ID type . They are both current limiting but the JTD are time delay ?

 

[petersonra]

Have some heater control panels that will feed imersion type tank heaters .Due to space limitations we are using class J fuses .Littlefuse calls for a JLS fuse for heater circuits . Is there any reason we can't use JTD fuses? We can get the ID type fuses in JTD but not in JLS.For safety we want the ID type . They are both current limiting but the JTD are time delay ?

Heater circuits don't have an inrush so no need for time delay on them.

I don't see why you could not use TD anyway.

 

[Davebones]

Only reason we want to use JTD is for safety .We can get the JTD with the indicator window. Can't find JLS fuse with indicator !

 

[petersonra]

Only reason we want to use JTD is for safety .We can get the JTD with the indicator window. Can't find JLS fuse with indicator !

I don't get how the indicator makes it any safer.

 

[LarryFine]

I don't get how the indicator makes it any safer.

Safer to see if a fuse blew. :roll:

 

[jdsmith]

For class J fuses up to 60 amp you can use a fingersafe tilit-out type fuseholder with a blown fuse indicating light instead of the little indicator window. The Shawmut US3J/US6J series is the best, Bussmann also makes a similar product that isn't as nice as the Shawmut.

As long as the NEC overcurrent protection rules allow it, there is no technical reason that a class J time delay fuse cannot be used when a class J fast acting fuse is called out. Class J time delay fuses are designed to withstand 500% of rated current for 10 seconds without blowing. They are dual element type, which also means they cost somewhat more than a single element fast acting class J fuse.

I use a lot of class J fuses for switchgear control circuits, medium voltage motor starter control circuits, and UPS power branch circuits - none of these uses require me to go above 60A, which is why I standardized on the Shawmut fingersafe holders with LED blown fuse indicating lamps.

 

[petersonra]

Safer to see if a fuse blew. :roll:

How do you figure it is safer though. You still have to go through the exact same safety issues to open the door up to look at the indicator as you would to measure the voltage across the fuse to see if it had blown.

Unless you went to the trouble to cut a window in so the indicator was visible from outside, but its not like they are all that easy to see anyway.

 

[iwire]

How do you figure it is safer though. You still have to go through the exact same safety issues to open the door up to look at the indicator as you would to measure the voltage across the fuse to see if it had blown.

You do not have to contact potentially live parts, that makes it safer than contacting live parts.

Unless you went to the trouble to cut a window in so the indicator was visible from outside, but its not like they are all that easy to see anyway.

You laugh but they are selling windows for enclosures for various reasons to avoid the hot work issues.

 

[petersonra]

You do not have to contact potentially live parts, that makes it safer than contacting live parts.




You laugh but they are selling windows for enclosures for various reasons to avoid the hot work issues.

I have to say that actually seeing the blown fuse indicators that are part of these kind of fuses through a door mounted window is a pretty iffy thing. The blown fuse indicator lights built into the fuse blocks are a better choice if you want to be able to see the indication through a window.

I wouldn't laugh about it. It was pretty common spec 20 years ago to put the windows in place so you could see the I/O status lights without opening the doors. That kind of went by the wayside along the way for some reason. It would be a good thing to bring back though.

 

[zog]

I wouldn't laugh about it. It was pretty common spec 20 years ago to put the windows in place so you could see the I/O status lights without opening the doors. That kind of went by the wayside along the way for some reason. It would be a good thing to bring back though.

Americas Walmart metality took over the switchgear industry too.