Circuit Breaker Fries......and A/C Power Question

[Fizzban]

Hello...

I have a 2004 Tioga Class "C"...if I run my Microwave, and A/C at the same time it Kills a 30/20 breaker....DOESN'T just trip it, it kills it.  I have several replacements now, but does anyone know why that happens?

ALSO

Is it okay to run the A/C from a 20 amp sully from my house?  I have heard that perhaps it can kill the A/C compressor by not getting 30 amps.

Thanks for your thoughts!

Fizzban in Memphis

 

[Carl L]

Dunno about the breaker except to say you have a major problem that needs professional attention.  In the meantime, disconnect the microwave.

20 amps is not the issue, volatage drop is.  If your voltage drops below 110VAC it is time to turn off the A/C.    If the voltage drops below 105VAC, your A/C is getting into trouble.  Use a plug in voltmeter in a covenient outlet in the RV to monitor voltage.  (Check calibration with a multimeter). 

 

[Gary RV_Wizard]

Don't know about Tiogas specifically, but it is common in Fleetwood Rvs with 30A power to have a two-position switch that prevents the AC and the microwave from operating at the same time. There generally is not sufficient power to do so in a 30A system, so they put in a switch that routes power to one or the other but never both. If you have such a switch, I'm wondering if it has failed or if somebody (a prior owner?) may have disabled it or replaced it with an incorrect switch.  Do you have such a switch? Or a switch you don't know what its for?

Unless you have some experience with diagnosing electrical power systems, you are probably going to need some professional help with this.  I would be uncomfortable giving an inexperienced person directions on trouble-shooting this sort of problem, since sometime is clearly seriously wrong.

 

[John From Detroit]

There is basically nothing that should fry a circuit breaker other than long term abuse or age.  If you have replaced it more than twice in a decade something is wrong

 

[woodartist]

Could you amplify on the

DOESN'T just trip it, it kills it.

Is there an odor or smoke? As John implied, a circuit breaker should not be destroyed by an over current condition, and certainly not a replacement...if you did change it. I know of AC's that almost had a short and the breaker just popped, as it should....

 

[John From Detroit]

Oh, I do remember a couple of things that will fry breakers rather quickly

1: Direct hit by lightning on the radio tower powered via said breaker (happened where I used to work, breaker survived though, believe it or not,  Needed replacement later as bits were blown out the box, but when the Sgt reset it power went to the tower.  Tower survived too, save for 1/2 of a battery charger (they never found it, just the burnt other half)

2: High tension power line across your house drop.  Believe it or not this did much more damage to the neighbors of a friend of mine.

Said friend spent most of the day of an ice storm cussing and cutting up a tree that fell across the power drop to his house blacking him out (He used the wood in fireplaces inside the house for heat)  Then along about 4:30 one of the high tension lines snapped under the strain and dropped actross a neighbor's drop  Thousands of volts where only a bit over 100 belong.  Breakers were blown right out of  boxes, Fuses blown through quarter inch thick steel cabnet doors.  Range elements shatterd, Antique light fixtures shattered, Houses set a-fire by the force of all that electricity.

My friend however had no damage., that lovely tree be praised, You see, since the drop to his house was seperated from the rest of the neighborhood.. There was no path for the over voltage

 

[Gary RV_Wizard]

Common brakers have either an electromagnet or a bimetallic strip in the overcurrent trip mechanism.  If hit with a really fast, high spike, it is entirely possible to burn that out before the circuit opens, destroying the circuit breaker.  A microwave generates that sort of power spike a couple times a second, but it of course should not be pushing that spike back into the power circuit. But who knows...? In any case, it's not someting for a novice to mess around with.

 

[woodartist]

I've seen shorted magnetrons and the breakers tripped fine. Can't remember the response time of AC breakers. I'd like to know the details of what happened because if he did replace the breaker and the new one "fried"...whatever that means, it would be interesting to see what the cause was. Just never saw that before. Even playing around with some high powered stuff, with a great di/dt, never saw a breaker fried. Just want to learn something new

 

[Gary RV_Wizard]

I've seen shorted magnetrons and the breakers tripped fine.

Yeah, merely shorting out the magetron should not bother it.  But the output pulse from the high voltage transformer that feeds the magetron could, if shorted back into the input power line and hence to the breaker.  But then I doubt if the microwave would be working either.

About the only thing I can think of that can "fry" a breaker is a high voltage, low current, electrical surge.  The breaker is sensitive to high current and trips on high curent, but does not react quickly (or at all) to extreme voltages with low current flow. Lightning, for example.

 

[Fizzban]

Thanks for all the responses.  I have been unable to check this site until today.  The breaker in question is a two pole 30/20.  I had a similar problem in a TT.  You could not run the A/C and Microwave at the same time.  It would trip the breaker.  In this case, the breaker trips...and won't reset.  There is no sign of burn marks, but the breaker is useless after that.  I have taken to not running both at the same time, and keeping spares just in case.

I understand how it might trip, but don't understand why I can't reset it.  BTW, it is the 30A side that won't reset.

Thanks for your thoughts...

Fizzban

 

[Ned]

When a circuit breaker trips, you can't just turn it back on, you have to turn completely off, then back on.  Is this possibly what is happening?

 

[Fizzban]

Good thought....but one I thought of too.  I sometimes have breakers trip in my home, and over the years have learned that.  Thanks for the input anyway.

Fizzban

 

[Gary RV_Wizard]

You could not run the A/C and Microwave at the same time.  It would trip the breaker.  In this case, the breaker trips...and won't reset.  There is no sign of burn marks, but the breaker is useless after that.  I have taken to not running both at the same time, and keeping spares just in case.

As you have discovered, you generally do not have enough power available on a 30A hook-up to operate both a micorwave and an a/c at the same time. Best to avoid that altogether.  And as I stated previously, I'm surprised there is not a double-throw switch that prevents operating both at the same time - most 30A RVs ae equipped with such a switch.  I've never seen a Fleetwood 30A Rv that did not have one.  I'm wondering if somebody removed or disabled the switch in the past and screwed up the wiring somehow when doing so?

But tripping should not fry the breaker.  I gather that replacing the breaker solves the problem and you are OK until the next time you run bith and trip it again?

 

[Fizzban]

Roamer...

You are exactly right.  As long as I don't run the A/C and Microwave at the same time everything is fine.  Only when they both run at the same time do I have a problem.  I don't THINK that the breaker was replaced with something else.  I THINK I remember checking the literature and seeing that the amperage is what is there now.

I suspect that only when the compressor is running, and the microwave is hitting full power, does it trip.  I know the last time that happened, it didn't happen right away.  The microwave was running for a couple of min  before it tripped.

THANKS

 

[Carl L]

Seems like the simple solution here is to turn off the A/C compressor and run the unit on fan only while the microwave is in operation.  That way you avoid the impedance load of that compressor cycling on and off.

 

[Karl]

The single pole double throw switch on my Bounder switches the microwave and the washer/dryer; nothing to prevent one or the other to be used with the a/c. The load shedding control will shut down the compressor if it gets too near the 30A limit. Maybe his load shedding isn't working or there is none?

 

[woodartist]

FWIW, I have a 5th and travel trailer that both have a switch where you can apply power to the microwave...or the AC. Not both. 30 A service.

 

[Shayne]

It's the same on our Pace Arrow MH  1 switch and either 1 or the other

 

[Fizzban]

Hummm.....A switch huh?  Maybe there is one there, and I don't know about it.  I'll have to look.  I have just been turning the A/C completely off, but then I don't use the microwave much anyway.....Heh...

Fizzban