fuses

[sthobe]

will any15 amp do or do i need to order from light o rama

[Don]

sthobe wrote:

will any15 amp do or do i need to order from light o rama

See previous thread.

However, you need only purchase 15amp fast acting ceramic fuses. Where you get them does not matter.

[Brian Mitchell]

The big box stores may call them Microwave Oven fuses.

[Max-Paul]

Don,

Being a electrician myself I should not need to ask this, but I think age is slowly catching up with me. I am trying to remember the purpose of the ceramic fuse body. Is it to keep from cracking the glass body an becoming an arc problem?

[LightORamaDan]

Max-Paul wrote:

Don,

Being a electrician myself I should not need to ask this, but I think age is slowly catching up with me. I am trying to remember the purpose of the ceramic fuse body. Is it to keep from cracking the glass body an becoming an arc problem?

The get pretty hot when run at 100% which may be part of the reason and they really pop (internally) when they go so the ceramic may provide additional strength to prevent the fuse from breaking. It is difficult to find a fast acting 15 amp fuse rated at 250 volts that is not ceramic.

The main reason we always mention ceramic is that it pretty much guarantees that people do not get regular or slow acting fuses and/or car fuses (which are generally rated at 32 volts).

Dan

[Dave Batzdorf]

per Wiki:

While glass fuses have the advantage of a fuse element visible for inspection purposes, they have a low breaking capacity which generally restricts them to applications of 15 A or less at 250 V_AC. Ceramic fuses have the advantage of a higher breaking capacity, facilitating their use in circuits with higher current and voltage.

[ErnieHorning]

The ceramic is tougher then just glass and is used to protect the user from a possible violent explosion. If the current is excessive (i.e. a dead short) the rate of heat expansion could cause injury to a near by person.



I can’t see a fuse getting old unless we’re talking antique, though I don’t think LOR qualifies yet. I can see it being weakened by repeated current near its limit though. It’s supposed to melt but there is a point where it will start to glow red but not open. I’ve experience this myself. The fuse becomes more resistive and won’t pass nearly as much current.

[R Weiland]

Max;

Age hasn't caught you yet!, you were pretty much on target as to the glass vs ceramic barrels in fuses. Heat is the issue. Glass expands an order of magnitude more than ceramic when heated, and if heated or cooled too rapidly it will thermal shock, ie crack and shatter into pieces whereas the ceramic barrels under the same temperature change will not.

[George Simmons]

Is there any way to visually determine if a ceramic fuse is blown?

[Dave Batzdorf]

Nope. If your do not have a volt-ohm meter, use a battery and mini or even a 9-v piezo buzzer with a set of alligator clips (very crude setup but works). Best bet is to always have a volt-ohm meter. I also have a clamp-on amp meter that has the other two items built in.

[-klb-]

Not visual, but the fastest way I know of, and I would never recommend this, but in theory, unplug the controller, (both sides!!!) remove the insulating caps. Plug the controller back in. Use a VOM to read the voltage across the fuse. Should be zero. Anything more than a fraction of a volt is likely a failed fuse.