Fuse rating for AC

[RayB]

I am in my final wiring stages and wish to know what rating of fuse I should use to go between the plug that goes out to the wall socket, and my on/off switch.

I live in North america, so we're talking 110/120v.

I found a fuse holder and fuse I pulled from a very poorly wired generic JAMMA cab, and it's rated 5A 250. Is this the correct amperage?

[RayB]

Found the info on Bob Roberts' site. He says 3A 125v. So looks like my fuse is too high.

[Nipedley]

It does change from cab to cab, Bob Roberts information is likely intended as a guide - my Terminator machine wont run on anything less than a 5A fuse - and that is also what is stated in the manual, so whatever works for you I guess!

[ChadTower]

Yeah, it's definitely an individual thing.  You're going to be best served by summing up the amperages drawn by each component in the cab under max load.

[RayB]

Yeah, it's definitely an individual thing.

[ChadTower]

You never need a fuse, technically.  It's a safety measure.

I would think you would sum the amp draws, since they are all drawing individually.  If you have 4 items that draw an average of 1.5A, then you are drawing a total of 6A most of the time, yes?

I could be wrong, as I'm still learning EE stuff, but this one just seems common sense.

[Minwah]

Would I add them up or average them?

Add them up and make sure your fuse is just above the total max current.

Not sure how it is in the US but in the UK (practically) all appliances have their own fuse in the mains plug so you don't generally have to worry.  Multi-way extension leads tend to have a 13A fuse in them as this covers everything.

[2600]

Just remember you want to sum the AC current, not the DC current.  Also, you may have to worry about about the initial draw of current which may be higher then the sums you added.  This will cause you to blow your fuse everytime you flip your switch.



Personally, I would just add a surge protector for your situation.


Edit: Rayb, I always read about your project, but still get confused on what you are doing.  Like this example, you are looking for a fuse rating for a JAMMA cab, but you are building a MAME cabinet.  Correct?

[RayB]

Edit: Rayb, I always read about your project, but still get confused on what you are doing.

[ChadTower]

h may be higher then the sums you added.

[2600]

h may be higher then the sums you added.  This will cause you to blow your fuse everytime you flip your switch.

That is why we both told him MAX draw, not average draw, for the fuse.

You said max load.  Then you said average draw most of the time.

I'm talking about initial current rush.  There is a difference. 

For example, if you have 8 cabs on one circuit breaker.  If you turn them all on at once, the circuit breaker trips.  If you power them all on individually, the breaker does not trip. 

[ChadTower]

Initial draw <= max draw

Always.

It could be that initial draw actually IS max draw, but it may not be max draw.

[2600]

Chad - I'd argue, but I'm afraid it would be fact vs. opinion which would never end. 


RayB - Look at it this way, you now have an optipac for future expansion.