Microwave Fuse?

Question

What value fuse shld I use for a Microwave which has power input at 120 volts a.c. 60 Hz 1450W, single phase with grounding and output frequency 2450 Mhz? It keeps blowing its fuse of 25 amps.

Answer 1

1450W @ 120V is about 12 A if you are blowing 25 A fuses you have a problem. Putting in a bigger fuse will help burn down your house. Typically house wiring is rated for 20 A maxand possibly 15A. Letting 20+ A go through will heat up the wiring and cause a fire.

FYI the microwave nameplate will give the full load amps so read it.

Get a new microwave and put the 15A fuses back in.

Answer 2

If the fuse you are talking about, is the branch circuit fuse, that is feeding the outlets in the room that the microwave is plugged in to - then stop immediately and establish what amperage the circuit is to be protected with.

The circuit breaker panel or fuse panel in the building should already have the proper breaker installed but if a older fuse panel box - I have often seen higher amperage fuses installed.
This is of course not at all safe by overfusing or pennies behind a fuse.

One house fire I investigated, had not only 30 amp fuses in the 15 and 20 amp positions but had pennies behind them also.
It wasn't such a bad place before the fire...That little 18 gauge extension cord really cooked with up to 30 amps available to it.....

Anyway - if the fuse you refer to is in a snap holder inside the microwave oven itself, then there ought to be a marking on a sticker or similar, somewhere, to indicate proper amperage.

I doubt it is to be any bigger than 15 amp and is frequently a ceramic ( white ) body type fuse. It may have a slo-blo fuse specified but if that fuse continues to immediately blow - then you may at best have a shorted HV rectifier but more likely the magnatron tube has an internal short and the cost of replacing that mag tube usually exceeds the value of the appliance.

Replacing mag tubes is not for an inexperienced person. Microwave energy is not a joke or a play toy.

Deric

Answer 3

1450W divided by 120 V = 12 amps. I surmise there could be a normal starting spike that would prevent the use of a 15 amp fuse over time. You should be using a 20 amp fuse. My first thought regarding your experience with blowing 25 amp fuses is that the microwave is defective. The second likely possibility is that the outlet is tied in with another load. Combined they blow the fuse. (Refrigerator, toaster, even another room if it is an older home.) Nothing to do with your microwave: If your wiring is only 14 ga don't go larger than 15 amp. 12 ga is limited to 20 amp.