What size Fuse to Use??

Old 02-20-05, 10:57 AM
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What size Fuse to Use??

I have a little rental home that still has an a box with screw in fuses and cartridges.

My question is what is the right fuse to use as I think the tenant is putting the wrong size fuses in.

3 lines going to a kitchen specifically. One has a 15amp and other has a 30amp and another 20amp fuse. I'm pretty sure I don't have 30amp circuits.

So, should I base it on the wire size(read it somewhere) or can I just say go with a 20amp fuse for at least those lines.? What is the danger of putting a 20amp on a 15amp? Is there a test or does wire size essentially determine this?

Old 02-20-05, 11:27 AM
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It is wire size alone that determines the size fuse. With 14 AWG cable, you use a 15Amp fuse; with 12AWG cable you use a 20Amp fuse.

With a rental unit, you probably should upgrade to a circuit breaker panel to eliminate the temptation of overfusing. An alternative is to find what is called S-type inserts that prevent inserting fuses of a higher rating.

Mr Fixit eh
Old 02-20-05, 12:30 PM
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The 30 amp fuses are most likely too large. If they are too large, they represent a fire hazard.

Branch circuits in a residence are 15 or 20 amp size. it is against code to have a normal branch circuit any larger than 20 amp.

Go by the wire size. If any portion of the wire is 14 gauge, then use 15 amp fuses. If all of the wire on a circuit is 12 gauge then go with a 20 amp fuse.

Do not use a 30 amp fuse. A 30 amp fuse could only be used for a subpanel or a special load, such as a dryer.

I go agree Mr. Fixit. Set this up so that the homeowner cannot insert the wrong size fuse. Better yet, bite the bullet and have the panel replaced with a circuit breaker panel.

In the mean time, make sure that your fire insurance is paid up.
Old 02-20-05, 03:28 PM
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I agree that this is a potentially dangerous situation. You have an older house built with a minimum of circuits. Now you have a tenant who may have a microwave, toaster oven, coffe pot, and a hair dryer all going at the same time!

I do strongly suggest that you get the special inserts which prevent screwing in the wrong amperage fuse; or have the panel updated.

Your tenants will feel inconvenienced by the lack of a modern electrical service. At some point, it would make sense to upgrade the service and have 1 or 2 new dedicated circuits installed, at least in the kitchen.

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