Microwave trips main breaker???

[coffebreak]

have a TT 28ft with 30amp service... Have used the TT many times in the winter in vegas etc.. even with the A/C (13500) we were always able to use the micro with no problems. .... Last week our house A/C broke down (compressor) and we have been living in and still living in our TT in the back yard. Temps here in Az are about 115 daily and the A/C in the TT of course runs constantly. ....Now my question is that when we use the microwave now it runs for a few minutes and than the main breaker trips which it never did in the cooler weather... could this be happening because the temps are so hot now and the A/C is working constantly or maybe another reason? We use our coffee maker with no problem if that helps.
Thanks for any suggestions....

[road-runner]

CA Traveler wrote:
How does running the inside air circulation fan cool the outside compressor?

The evaporator and condenser fans are run by the same motor, and the some of the condenser airflow is routed over the compressor. Maybe they're not all the same, but that's how mine works.

[CA_Traveler]

How does running the inside air circulation fan cool the outside compressor?

[pianotuna]

Hi MrWizard,

Thanks for the information on the fan!

To me, that implies that running the fan constantly may be slightly better for the AC even when on shore power.

MrWizard wrote:
PT
Yes, running on fan removes heat from the compressor
So when done using the MW, just switch back to cool
No need to do the fan first restart delay
Standard practice for me when using a portable generator

[MrWizard]

PT
Yes, running on fan removes heat from the compressor
So when done using the MW, just switch back to cool
No need to do the fan first restart delay
Standard practice for me when using a portable generator

Right now with this RV, I've been using the 5kw Onan
And I can use the MW with one A/C running

[CA_Traveler]

Doug,

The NEC has the 80% rule for continuous loads which is defined as 3+ hours. Circuits and wiring can be rated for 100% but that is not common.

Since the OP has the problem with a few minutes of MW usage he could have low voltage or some other problem causing the CB to trip.

[coffebreak]

SoundGuy wrote:

coffebreak wrote:
Temps here in Az are about 115 daily and the A/C in the TT of course runs constantly. ....Now my question is that when we use the microwave now it runs for a few minutes and than the main breaker trips which it never did in the cooler weather... could this be happening because the temps are so hot now and the A/C is working constantly ...

Absolutely. As exterior ambient temps rise so too does compressor head pressure, which in turn means it's drawing more current than it would at lower temperatures.

Thanks,i was hoping that that might be the problem and not the microwave or a electrical problem.

[pianotuna]

Hi Doug,

I believe what you are saying is pretty much the same as what I am saying--except that I used watts rather than amps. I did make the assumption that the OP would realize he can not run the microwave and the roof air at the same time at those sort of ambient temperatures.

Is there a reason to run the Air Conditioner on high fan only as opposed to just turning it off?

dougrainer wrote:

pianotuna wrote:
At those temperatures my Dometic 13500 draws 1900 watts. Add the fridge (325 watts) and the microwave (1570 watts in my case) and the total is far more than 3600 watts

The OP's problem has to do with 115 temps. That means his roof AC is drawing 2 amps MORE than spec. Odds are his roof AC HI COOL is about 14 amps add 2 to 16 amps and other small amp draws(refer 3 amps) and then his M/W kicks in at average 10 to 11 amps and he goes over the 30 amp main breaker threshold. So, he needs to run the AC on Hi Fan only when operating the M/W. Then go back to Hi Cool after cooking. Doug

[coffebreak]

I do have a 30amp breaker in my pedestal next to the trailer and only using my power cord to the ped. to the trailer 25 ft. no extensions. as doug said I was hoping it was just the heat causing it. its 118 outside now and will be the same for another few days. I will have to wait for the temps to cool down , maybe in oct.LOL. to test it again. Don't want to mess with anything right now because if i screw anything up we really will have no place to stay. A/C is keeping the temps in the TT at about 89, 90 until the sun starts to set than it gets down to around 71 at night. hopefully A/C in house will be fixed by wed or thurs.Can u imagine had a brand new LENNOX 5 ton A/c / heat pump 6000.00 installed last summer and compressor already blew.And its taking them almost 2 weeks to get another one. House temp is around 120, already burned up my house refridge. lost all the food, had about 20cases of soda that blew destroying my carpet and walls. and Lennox could care less...... Thanks for all the help and hope ya'll stay cool......
thanks

[dougrainer]

pianotuna wrote:
At those temperatures my Dometic 13500 draws 1900 watts. Add the fridge (325 watts) and the microwave (1570 watts in my case) and the total is far more than 3600 watts.

A 30 amp service is intended to provide only 24 amps continuous. To translate that to watts multiply by 107 = 2568 watts. (the minimum safe voltage).

I have no idea where this wives tale came from. An RV 30 amp service is 30 amp continuous, NOT 24 amps. The OP's problem has to do with 115 temps. That means his roof AC is drawing 2 amps MORE than spec. Odds are his roof AC HI COOL is about 14 amps add 2 to 16 amps and other small amp draws(refer 3 amps) and then his M/W kicks in at average 10 to 11 amps and he goes over the 30 amp main breaker threshold. So, he needs to run the AC on Hi Fan only when operating the M/W. Then go back to Hi Cool after cooking. Doug

[downtheroad]

eHoefler wrote:
What kind of outlet are you plugged into, regular 30 amp, or 15 amp house hold outlet?? Any extension cords?? If you are plugged into a 15 amp outlet, and/or using extension cords, there is your problem.

This....

[pianotuna]

At those temperatures my Dometic 13500 draws 1900 watts. Add the fridge (325 watts) and the microwave (1570 watts in my case) and the total is far more than 3600 watts.

A 30 amp service is intended to provide only 24 amps continuous. To translate that to watts multiply by 107 = 2568 watts. (the minimum safe voltage).

[SoundGuy]

coffebreak wrote:
Temps here in Az are about 115 daily and the A/C in the TT of course runs constantly. ....Now my question is that when we use the microwave now it runs for a few minutes and than the main breaker trips which it never did in the cooler weather... could this be happening because the temps are so hot now and the A/C is working constantly ...

Absolutely. As exterior ambient temps rise so too does compressor head pressure, which in turn means it's drawing more current than it would at lower temperatures.

[eHoefler]

What kind of outlet are you plugged into, regular 30 amp, or 15 amp house hold outlet?? Any extension cords?? If you are plugged into a 15 amp outlet, and/or using extension cords, there is your problem.

[accsys]

I would assume you are using an extension cord to power the trailer? If so what is the length and gauge of the cord? There is a good chance the voltage dropping across the length of the cord is causing the A/C to pull more current and thus tripping the breaker when other items are used. Even if you have installed a 30 amp pedestal, that installation could prevent you getting a full thirty amps at 120V depending on the wiring and length from the house breaker box.

Measure your voltage at other outlets when the A/C and Microwave are running and see what your voltage is. I would guess it is dropping below 110V.