Fuses vs breakers

Now I'm working on rewiring the buildings a bit - everything was one or 2 fuses running a couple lights and an outlet or 2 for the most part.

So, I have a big 110v Craftsman air compressor.

Works great on the old 20 amp fuse in the old buildings.

I've used it on a different farm, and on my own in a couple of buildings that have 20 amp QO Square D breakers. Mostly it will snap the breakers more often than not.

Huh????? ?

All was in summer temps (not now!), no extension cords involved, wiring on the 20 amp breakers is to code 12ga., one was a very short run, only thing on the circut was this one outlet. I can't think of any 'duh' thing that would be different....

I've run the compressor a lot more on 2 different buildings on my farm with 20 amp fuses, and never a problem.

What does that mean for my future use of this compressor???? Or converting over to breakers?

--->Paul

A quick look at the compressor, Craftsman 2.0 running hp, 120v, 15 amp. (Yea I know that doesn't add up.) Too cold & dark to look at the motor itself....

It is a year old, & I haven't used it all that much yet. I believe I can hear the unloader valve unload. But it would rather trip a 20 amp breaker than power up if there is any pressure in the tank. Once running, it runs & runs just fine. It is the starting inrush that takes out the breakers.

Since it has tripped several breakers in several locations all 20 amp setups, I'm thinking it isn't just a bad breaker. More to the story than that.

It works fine on my old chickenbarn setup with fuses, wiring to a light plug with a plug adaptor in it, and a 25 foot 14ga extension cord. _This_ works with never a problem.....

Yes, I know not an idea setup, I wish to change this to a much better setup.

However, my problem - it seems to trip breakers, and work fine with the fuses & sub-par wiring. So now I'm not in a hurry to change to the breakers, if they can't handle it?

My farm buildings are spread over 700 feet or more in 2 directions, my plan was to take this portable compressor to different buildings. So I'd not like to set up a dedicated 30 amp breaker - tho I understand the thinking behind that.

It is supposed to be a 120v compressor 'off the shelf', so I'm puzzled that it doesn't want to work with a good 20 amp breaker install.

Perhaps the unloader valve need more looking into.

I also have a microwave in the house that worked fine on fuses; but it likes to trip the breaker fairly often now that I upgraded the house.

I'm not so sold on the 'toss out fuses, get breakers' thing any more.... ;)

--->Paul

Other brands are not designed this way. I have welded with soid 12 gauge wire shorted out to a junction box trying to trip a breaker and it would not trip. SqD will trip everytime easily. Once you get up to 30 amp and 220vac breakers SqD does not have a seperate breaker for motor loads like it does for 120vac 15 and 20 amp breakers
Ron

That eliminates the portability that I was looking for.

--->Paul

Thanks all. I don't usually throw such a fuss, but Craftsman sells a ton of these 110v compressors, would think they would work if one follows the rules. :)

--->Paul

1. What is the hp of your motor?

2. What is the full load amps of the motor?

3. What is the service factor of the motor?

All this information is on the motor nameplate.

Once we have this information then we can look in art. 430 of the NEC and we will have our answers.

You can still use a circuit breaker you may have to bump it up a size or two, say to a 30 amp breaker and see if that lets her start????? The circuit breaker is to protect against short circuits in the motor branch circuit while the motors thermal overload protection device, be it internal thermal protection or an external motor starter, is to protect the motor windings from over current and overheating. Thats how n why the NEC allows a bigger then otherwise normal circuit breaker on a motor branch circuit so as to allow the motor to start without tripping the breaker.

As far as the fuze, it may be a dual element time delay (slow blow) which allows the motor to start when it draws heavier then normal run current.

I would insure the motor has thermal overload protection, it may be a red overload push to reset button if its internal or a remote starter with thermal protection, and then try a 30 amp breaker n see if it will start. If you use a fuze, then try a 20 amp dual element time delay slow blow n see what happens NOTE the 20 amp figure is based on your post, it really needs to be sized in accordance with the motors amperage, of course.

let us know

Best wishes n God Bless

John T (Long retired EE n a tad rustyyyyy y)

There's more than one type of fuse, a slow blow as there named for motor starting. This allows for the starting current rise without nussiance blowing the fuse. As far as I know, they don't make the same equivilant in a breaker.

If your compressor motor has a start cap then you might change the capicator as it may be getting weak. 90% chance that this won't help or that has been my experience but capacitors are cheap so worth a try.

Could be your start switch is hanging slighty dropping out the start winding causing a tad high inrush current as the motor try's to start. This may be slightly too much current for a breaker but ok for a fuse.

T_Bone

I was afraid of what you have to say. Looks like I'll have to keep a few fuse boxes around? How else can I use this? 220 is the other answer I don't want....

Wish there was a breaker that dealt with this.

--->Paul

I've just been out of the loop to long Paul to make too many suggestions. I'm even fighting trying to remember therory. When another 10yrs goes by, I should just about be empty... LMAO I assumed you have this recepitical sized correct for the motor load requirement? 125% of RLA, True? then I'd be looking at the start swtich hanging.

230vac not so bad and it's really more efficent to add 3/8" air line when needed than running a 115v extension cord. HF has 3/8"x50ft Gates air line for $15 on sale

T_Bone

Grainger Catalog page 396,Circuit Breaker, 20 amp, Square-D QO HIgh Magnetic.

I had a table saw that was acting just like your air compressor, at startup it would trip the 20 amp breaker 3 out of 5 times,this high magnetic breaker solved the problem at a very low cost,and you will still have the 20 amp over current protection.

But that wire will affect the motor currents. The long run will lower the starting current but will lengthen the time to get up to speed. That may cause the breaker to trip more often because of the longer time for starting. That long run will increase the motor run current because it lowers the motor supply voltage and it takes watts to turn at near synchronous speed and supply the load at that speed.

Gerald J.