Question regarding fuse needed for my cab-powering solution. 120V? 250V?

[quarterback]

A while back (a LONG while back) I bought this item to install into the back of my cocktail cab for a single (and removable, and with a switch) power cord solution.  The plan was to cut a hole in the cab, screw this thing in, wire the inside to my powerstrip and be good to go:


I'm finally getting around to doing it (or thinking about doing it) and realized that I need to buy some fuses because this thing needs fuses to work. 

My question is:  What fuses do I need?   I think I need 6amp 250v fuses, but I wanted to post the question before going out to look for them.  I'm also curious how tough it might be for me to find 6A fuses locally, but maybe it's an easy task.  I don't know, I've never tried.  Lowes?  Home Depot?  Wal-Mart?

In any case, the side of the unit looks like this:


It notes that the "switch rating" is "10A 250VAC"   So, at first, I thought I needed 10A fuses... HOWEVER, up at the top of the sticker (above the schematic) it says "6A/40C,120/250V ~, 50-60Hz"   So I realized while the built-in switch can handle 10A, it only wants 6A running though each leg.

This thing requires TWO fuses.  The ground goes directly through to the back, but both prongs of the plug/cable are set to run though 1 fuse each.    SOOOOOooo... QUESTION#1 Does this mean I need to find TWO 6A 250V fuses?  Or is it telling me that the total amperage should be 6amps?  (if you click on the pic, you should be able to see the schematic)

My guess is that I need two 6A fuses, but I just want to be sure.

QUESTION#2  120V or 250V?   I've always been a little confused when it comes to this.  I've been told that when buying fuses, it doesn't matter if it says 120V or 250V, either are okay... I find that difficult to believe (or, at the very least, difficult to understand)   But the shcematic says "6A 120V/250V"  So, does it matter?

Compounding my 120V/250V confusion is the writing on the FRONT of the unit (see larger version of picture #1) because it says "Use only with a 250V fuse"   As somebody who likes to follow instructions, I'm inclined to buy a 250V fuse but the sticker on the side implies I can use a 120V fuse.  Can anybody confirm or deny whether or not it will matter.

I think that's it for now.   Any helpful advice is appreciated.

[Fozzy The Bear]

It notes that the "switch rating" is "10A 250VAC"   So, at first, I thought I needed 10A fuses... HOWEVER, up at the top of the sticker (above the schematic) it says "6A/40C,120/250V ~, 50-60Hz"   So I realized while the built-in switch can handle 10A, it only wants 6A running though each leg.

You are confusing the maximum rating for the socket with the power rating you need to run your cabinet!! you're also confusing 240v and 110v supplies. The reason the unit handles both is that in the UK we use 240V at 50Hz  and in in the USA you use 120V at 60Hz.

You actually only need a 3Amp fuse for a cab on a 240Volt supply......  All of the full size cabinets I maintain at work are fused 3Amps.  This is the wrong rating for you in the USA though!! You need to properly calculate the maximum Ampage draw of all the equipment you are connecting to that socket then add 15% as a safety margin. You should also try and use a fast blow fuse.  You will probably find that a 4Amp fuse is more than enough.

I'd also strongly recommend that all cabinets should be plugged into a (Residual Current Device) "RCD Socket". Also known as an "Earth Leakage Circuit Breaker" socket. They switch off in times measured in Milliseconds if there is a fault on the circuit and save lives!!  In basic terms they switch off before the current has enough time to kill you!

Best Regards,
Julian (Fozzy The Bear)

[quarterback]

It notes that the "switch rating" is "10A 250VAC"   So, at first, I thought I needed 10A fuses... HOWEVER, up at the top of the sticker (above the schematic) it says "6A/40C,120/250V ~, 50-60Hz"   So I realized while the built-in switch can handle 10A, it only wants 6A running though each leg.

You are confusing the maximum rating for the socket with the power rating you need to run your cabinet!!

No, not really.  I have no real interest in determining how many amps my cab pulls. I'm just trying to determine what the manufacturers of this plug want me to put in it.   Frankly, I don't want the fuses at all.  I'd be happy enough to fill the holes with aluminum foil, but it seems a little ghetto and, since I've bought this nice little plug, I figure I might as well plug in the fuses. 

All this little unit is going to do is to bridge between my power strip and the wall.   As it stands, the power strip is plugged into the wall.  This is not going to do anything but make that connection neater.  I could have just as easily pulled a receptical out of an old power supply and wired it that way.  And that wouldn't require any fuses at all.

you're also confusing 240v and 110v supplies. The reason the unit handles both is that in the UK we use 240V at 50Hz  and in in the USA you use 120V at 60Hz.

I'm not really confusing that either.   I'm completely aware of the fact that the US is 120v and the UK is not.  There are plenty of fuses with "250V" stamped on them in the US.  And, as I said, I've had people tell me that it doesn't matter which you use.   My only confusion is that I don't understand why people would tell me that a 120V fuse is the same as a 250V fuse.  That, as I stated, seems odd to me.

You actually only need a 3Amp fuse for a cab on a 240Volt supply......  All of the full size cabinets I maintain at work are fused 3Amps.

My question#1 is about the specific markings on this plug.

Perhaps what you're saying  (in response to my question#1) is "it doesn't matter what the schematics say.  The only thing that matters is how much your cab is drawing"  Okay, I accept that as a logical answer, but not to the question I'm asking.   I'm really not concerned that my cab is going to pull so much power that the fuses will have to blow lest I burn my house down.

Or maybe what you're saying is "The info on the schematic isn't telling you what fuse to put in there, it's only telling you what the socket is rated for". But I find that hard to believe.  The switch is rated at 10A but the socket is only rated at 6A?  I guess it's possible, but I find that tough to believe.  I've got 99-cent power strips with chincy plugs that are rated at 10A and this thing is metal and heavy.  I guess that could be true, in which case, I'll just get some 6A fuses so I don't melt the socket.

And I still don't understand why it simply has a 6A rating.  Why doesn't it have different ratings for 250V versus 120V?  Is it true that I can just use a 250V fuse in my 120V appliances?  People have told me that and now the markings on this unit seem to imply the same thing.  That's where my confusion lies.
Thanks

[NickG]

How to decipher the markings: read the pdf

You only need one side of this DPST for 120V if you were actually going to use it as a circuit breaking switch.

[quarterback]

How to decipher the markings: read the pdf

Hey, thanks Nick!   

I guess it should have crossed my mind to search for a spec sheet... but it didn't      

Now maybe I can also figure out why the back has FIVE different terminals.

[Kevin Mullins]

[quote author=quarterback link=topic=58087.msg571966#msg571966 And I still don't understand why it simply has a 6A rating.  Why doesn't it have different ratings for 250V versus 120V?  Is it true that I can just use a 250V fuse in my 120V appliances?  People have told me that and now the markings on this unit seem to imply the same thing.  That's where my confusion lies.
Thanks
[/quote]

First off.... it says right on it to use a 250V fuse. (on the black plastic side)

Second..... most "appliance" fuses ARE 250V, even here in the US.
Just means they are more universal and the manufaturer can make more of the same type fuse to sell all over the world icluding the UK. The voltage rating simply needs to be equal to or greater than what is being applied to it. (in your case 120V) No fancy math there, that's it.
Kinda like choosing a replacemnet capacitor, the voltage needs to be equal to or greater than, but the actual capacitance is what needs to be exact.
In your case what I believe Fozzy Bear was also trying to say is that it is the AMPERAGE rating on the fuse that matters. Simply put if it is too low, it will consatantly blow.  The amp rating needs to be slighty above normal operating conditions so that if there were a sudden short or added draw of current THEN it would blow and act as a safety device.

6A 250V

[Fozzy The Bear]

  I have no real interest in determining how many amps my cab pulls. I'm just trying to determine what the manufacturers of this plug want me to put in it.

What the manufacturer of the plug is telling you is NOT what fuse to put in. They are telling you the MAXIMUM Load you can put through it!!

The only way to know the correct and safe fuse to put in, is to calculate how many Amps your equipment is ACTUALLY drawing.

In your case what I believe Fozzy Bear was also trying to say is that it is the AMPERAGE rating on the fuse that matters. Simply put if it is too low, it will consatantly blow.  The amp rating needs to be slighty above normal operating conditions so that if there were a sudden short or added draw of current THEN it would blow and act as a safety device.
6A 250V

Spot on!!!! Thanks Kevin..... That's exactly what I was saying.... Although I could have worded it a bit better.  It's the Ampage Draw that blows fuses.

SO... Like I said, he needs to calculate the exact ampage draw of the components he's connecting then add 10% and fit the nearest fuse to that rating. Which in this case should also be a fast blow fuse.

The numbers on the socket ONLY indicate the maximum load the socket can take. Not the type and rating of fuse that you should fit. The rating of fuse you fit is totally dependant on what you are connecting to it.

Best Regards,
Julian (Fozzy The Bear)

[quarterback]

  I have no real interest in determining how many amps my cab pulls. I'm just trying to determine what the manufacturers of this plug want me to put in it.

What the manufacturer of the plug is telling you is NOT what fuse to put in. They are telling you the MAXIMUM Load you can put through it!!

And while I know this is hard for you guys to believe, but that is ALL I wanted to know.

The only way to know the correct and safe fuse to put in, is to calculate how many Amps your equipment is ACTUALLY drawing.

No, that is NOT the only way to know the 'safe fuse to put in'.   The question is "safe for WHAT?"  I wanted to confirm "What is safe for this power input block"  That's all.  You're thinking "safe for all the items in my cab" or "safe for my household wiring" but that is NOT what I wanted clarification on.

Listen, let's go step by step through this because you guys clearly don't understand the information I was looking for  or why I wanted clarification.

(1) The purpose of a fuse it to protect equipment.
Can we all agree on that?   Okay:
(2) The power-input-block that I have has certain ratings.  It has a rating for the switch and has a rating for the device.  These ratings tell us how much power can safely go through these items.
Do we agree on that?
(3) You suggested that, since an arcade cab only draws about 3A, then the " the correct and safe fuse to put in" would be a 3A fuse (+15% safety margin).  You reiterate that train of thought again in your last post, saying "The only way to know the correct and safe fuse to put in, is to calculate how many Amps your equipment is ACTUALLY drawing"   
This is where we diverge.

I would ask you "Why?  Why do I even care how much the cab is drawing?    What are you imagining these fuses protecting?   My household wiring?   Are you worried I'm going to try and pull 40A through my household wiring?   I'm not.  I'm not worried about that at all. 

My cab is NOT going to pull 40A  and, if somehow it DID pull 40A, my household breakers would trip.  That's why they're there.   And, as I stated in an earlier post, I COULD do exactly what OTHER people do which is to use a completely unfused plug all-together.   If there really is some danger of everybody's cabinets suddenly drawing 1000A, then I think there'd be more stories of spontaneous-cab-combustion on this board.

So, the question is: if I don't need these fuses to protect my household wiring, why DO I need these fuses?  What exactly are they protecting?   The internals of my cab?

If my speakers needed to be fused, they'd have a fuse built into them or some kind of warning about why you shouldn't plug them straight into the wall.  They don't.  They're intended to be plugged straight into the wall, no additional fuses required.

If my computer needed to be double-or-triple fused, it would have instructions for me to run its power through a fused powerstrip and then through an additional fused connector (like the one we're discussing).  It doesn't.  People plug their PCs into their wall outlets all the time.    Additionally, I DO have everything running through a power strip (as stated in a previous post) and that power strip has a fuse in it. 

So what exactly do you think I need these fuses for?  What part of my cab do you think needs more protection than any of the other cabs on this board?

As I said before "All this little unit is going to do is to bridge between my power strip and the wall."  That's all.  It's as if I'm just adding a very short extension cord.  If you were going to add a 1" extension cord to your cab, would you also wire fuses into it?  My guess is "No"    The ONLY reason I'm putting fuses in this thing is because it HAS to have fuses for it to operate.  I'm NOT using those fuses to protect ANYTHING except for the POWER INPUT BLOCK ITSELF.

Again:  The only thing I'm concerned about, in this setup, is the plug itself.



My actual question, and the reason I wanted clarification was just to be safe and because I found some of the markings on the block to be contradictory.  That's all.   I found it odd that one part of the power-input-block had 250v and 120v ratings BUT another part specifically said 250V only.  That seemed odd to me.  That seemed odd enough for me to open this thread.

Additionally, it says it's rated at 6A, but requires two fuses.  As I stated in my very first post, my assumption is that I could put two 6A 250v fuses in there and be within the safety range of this unit itself.  But, just to be sure (since there are TWO fuses) I thought I'd ask for somebody to confirm this.  That's all.

My assumption has been confirmed.    I'm sorry if this seems like a rant, but you guys are telling me things that I don't need to know and it's making me crazy.  All I wanted to know is what as safe for this little power-input-unit.  That's all. 


If you're still not sure why I am not interested in selecting a fuse based specifically on what my cabinet is pulling, the try this analagous situation:

Just pretend for a minute that this power-input-unit is a powerstrip with a fuse (because effectively that's all it is).   Pretend that I found a fused powerstrip but the fuse was missing.  On the power strip next to the place where the fuse goes it said "10A".    When the power strip was purchased, there was a 10A fuse in it.  What I want to do is to put a 10A fuse back into it and be on my way.  What you guys are telling me is that I shouldn't do that!  That's not the way it works!  Putting a 10A fuse into that powerstrip would be a bad thing!  You're telling me that what I really need to do is to look at the draw of everything I might plug into that powerstrip and then select a fuse that is appropriate.

I say "hogwash".  Nobody on this board buys powerstrips and then reverse engineers them (and their fuses or breakers) to match exactly what is plugged into them at any given time.    I have all kinds of powerstrips with 10A fuses or breakers in them.   Would you really suggest that, if I'm only drawing 3A through them, that I go in and replace the factory parts so I can use a 3A (+15%) breaker or fuse?    Because that's effectively what you're suggesting I do with this unit.

If I find a powerstrip that's missing it's 10A fuse, I'm going to replace it with another 10A fuse.  And frankly, I don't think that's crazy at all.


If, after reading this post, you still feel like I'm completely insane, or an idiot, or I don't understand that the US is a 120v system and the UK is 240v, or whatever, then explain to me, specifically, why putting 6A 250V fuses into this unit would be a bad thing.    If there is some reason that putting two 6A fuses in here and wiring it to my power strip is going to be any worse than simply using my powerstrip plugged into the wall, then make an argument for that.

[Fozzy The Bear]

If, after reading this post, you still feel like I'm completely insane, or an idiot, or I don't understand that the US is a 120v system and the UK is 240v, or whatever, then explain to me, specifically, why putting 6A 250V fuses into this unit would be a bad thing.    If there is some reason that putting two 6A fuses in here and wiring it to my power strip is going to be any worse than simply using my powerstrip plugged into the wall, then make an argument for that.

We already did, and you ARE clearly insane!! LOL   

You are creating extra wiring here! that wiring in itself could go into a fault condition and leave some part of your cabinet or something in contact with it LIVE! and however unlikely you think that might be, it could still kill you!!... less than 1Amp is enough to kill you!!! 

You are getting annoyed here because we didn't give you the answer YOU wanted to hear!!

(1) The purpose of a fuse it to protect equipment.
Can we all agree on that?   Okay:

WRONG!! The purpose of a fuse is to protect YOU! Not to protect the equipment!!!  Equipment can be replaced, life can't!!

You are very clearly NOT an electrician, and when you get an answer from at least two people who are electricians, then rant and shout because you don't like the answer you got, and would rather go ahead and do it your own way, WHY BOTHER ASKING THE QUESTION!!!

I have nothing else to say about this... and you won't get another reply. Go ahead do whatever you want!! sounds like you'll ignore any qualified advice given to you anyway, if it doesn't fit with the way you want to do it.

For future reference... when somebody tries to help you, you might try saying Thankyou, instead of ranting at them because you got a qualified answer that you didn't like! 

Regards,
Julian (Fozzy The Bear)