They do not necessarily have to be the same. There may or may not be a legitimate reason for the difference. But my guess is that the more likely explanation is that one of the 40 amp fuses failed and a 60 was substituted. The 60 would be more easily found in most retail stores.You need a pro to determine the proper size.
The NON means that the fuse is a quick-blow non-replaceable element. Fine for ranges and water heaters. NON is a poor choice for motor loads such as air conditioners and heat pumps. FRN is the better choice for heavy starting loads.
Fuses are by no means inferior protection, but they are more subject to tampering and use of wrong size.
Your heading says "murphy". Did you mean to say that the panel is a Murray?

This post was edited by bus_driver on Sun, Jan 19, 14 at 22:28

Whoops,

My mistake, yes, the panel is a Murray. The sticker inside says it is a 100 amp service. Thanks for your input bus_driver.

That panel probably dates from the early 1950s to the mid 60s.
One pullout protects all the plug fuses plus the subfeed lugs while the other pullout protects the range. There is no main disconnect ahead of the range pullout. Both pullouts must be removed to shut off the panel as much as is possible from that location.

Thanks again,

Do you think that the dimming lights would be consistent with one of the two cartridge fuses in a pullout being blown? Also, if the pullout contains a 60 and a 40, is it still 40 amps or does the rating change?

Thanks again,

Do you think that the dimming lights would be consistent with one of the two cartridge fuses in a pullout being blown? Also, if the pullout contains a 60 and a 40, is it still 40 amps or does the rating change?

Tighten all the connections in the panel. The lugs where the wires are connected. Do not delay in doing this.

The dimming lights have nothing to do with the fuses. You need to find out what the proper fuse is. If it's supposed to be 40, then yes putting a 60 even on one side *IS* a big deal.

Now, if there is no path to ground, the 40A fuse ought to blow prior to the 60, but given a path to ground (either 120V loads or a fault somewhere), the oversized 60A fuse can indeed allow too much current to flow.

Thanks guys,

let me try to describe the condition once more.

several times now we have experienced a condition where it seems like we are getting partial power. Plugged appliances operate slowly and lighting is dim. This only applies to the fixtures and receptacles that are fed from the pullout fuse block that has a 60 and 40 in it. the 40 is always blown and replacing it temporarily fixes the problem.

Are you playing games with us?
If you are telling the truth, the panel probably already has heat damage to the spring prongs that contact the fuse holder legs. If so, replacement of that panel is the only solution.
Replace the 40 with a 60 and get someone who knows that they are doing to tighten the connections in the panel.

Thanks guys,

let me try to describe the condition once more.

several times now we have experienced a condition where it seems like we are getting partial power. Plugged appliances operate slowly and lighting is dim. This only applies to the fixtures and receptacles that are fed from the pullout fuse block that has a 60 and 40 in it. the 40 is always blown and replacing it temporarily fixes the problem.

I think I missed something....

Sorry, I am not playing games with you. Actually, I'm not even sure what part of that led you to believe that. I promise that the condition I'm describing is as close to accurate as I can figure out how to explain. It seems like you're pretty alarmed by this. Is that because this is unusual? I just replaced the blown 40 amp fuse with a fresh 40 and everything seems to be okay again. I feel a bit nervous about your last post. What made you think that I might not be telling the truth?

This is strange,

I'm not sure what happened here....

I think the summary is that you perhaps have a loose ground or some other connection problem. Replacing fuses over and over is just fixing the symptom but not the disease. I think you need to bring a real electrician onsite to check it out.

No, the real problem is that this person ignores what he/she is told. Why offer additional comments? More to be ignored?
The original post was skimpy on information, so to the response was equally lacking, but as complete as possible under the circumstances. The photos made the info complete. Both fuses are supposed to be 60 amp. And that is already posted. And already ignored.