Size of Generator Circuit breaker?

[TheBishop]

I have an old old 1960s military generator. It's an electric start and about 3-4kw power. It still runs good and the output is good.

The circuit breaker has failed, I think from age. I need to replace it but I can't find the AMP size.

What should it be minimum or recommended.

I'll try a few pics

Thanks

 

[uniquify]

Is there a data plate on the generator with model and output ratings?

 

[Tinstar]

The circuit breaker should have an Amp number marked on it somewhere.
But being it’s that old, who knows.

 

[TheBishop]

No plate readable. Painted over several times on the whole generator. Engine size only = 3.5kw.

The on board circuit breaker has triped on one side from age. If I strap the circuit like seen in the photo, I get 220V or two good 110s. I found a look alike breaker that matched perfectly last year online that I missed.

I need the average amp load breaker size for a +/- 35kw. 10amp, 15amp or 20 amp?

 

[TehTDK]

I would say a 20 Amp, because at 15 amp you are completely maxing it out if you are trying to draw full power from the generator.

 

[Zed254]

3,500 watts/.8 (military de-rating)=4,375 max watts/240 volts=18.2Amps. Looks like 20 amps to me, too. My house and generator are 240/120 volts.

I am assuming this generator is de-rated like my MEP803A.

You indicate a 220 volt reading. If so 4,375/220 = 19.9 amps. I forget how accurate the trip setting is on circuit breakers, but if you are putting out 220 volts you are getting mighty close to a 20 amp breaker's capacity.....may want to go with a 25amp. If your generator is not de-rated then you are back to 20 amps (3,500/220 = 15.9).

 

[uniquify]

Can you tell what the wire size is going to/from the breaker? That could give a hint, too.

14 Awg --> 15 amp
12 Awg --> 20 amp
10 Awg --> 30 amp

 

[Chainbreaker]

Also, in addition to the above suggestions...since its bad I would take it out. You then might see a rating on it that's obscured when mounted. You could then also take it with you to an electrical supply business and they can probably determine its rating.

 

[TheBishop]

If you can look at the back of the Circuit breaker in the photo the lower wire looks very heavy gauge. But back in the 60s they might have made all wires heavier than they needed to be by the military up to the breaker.

It will be a while before I can remove the breaker for a closer inspection. My first thought was just to have a standard replacement in hand when I do. I didn't think there would be a problem with a stock amp size.

 

[LEOK]

Take that breaker out and carefully clean it with plain water and soft brush, should find more info. From the photo I can't say ten or 12 gauge.