Community Forums

sirpurrcival · 07-15-2010, 12:17 AM

Hi Everybody. I have a Generac Q-55g (5500 watt) generator in my National Motorhome. This generator has 2 circuit breakers on the Generator itself, a 20 amp and a 30 amp. The 20 amp breaker keeps popping when I run the Microwave. It runs on house current just fine (15 amp breaker). I thought maybe the breaker was bad so I temporarily wired in a 20 amp breaker from a house while waiting for a replacement breaker I ordered. It seemed to work fine so I was convinced that the original breaker had been the problem. When the replacement arrived, I installed it and I am back to the same problem. I can't think that there is much in the way of hidden loads. Battery charger is all I can think of and even so, if it was a load problem, then my temporary breaker fix should have had the same problem. It is a GE Convection Microwave but I am just trying to heat a cup of water. It will pop after about 1 minute. Anybody have any ideas what might be the problem. I am loath to remove the microwave for additional testing but I may have do so if I can't figure out anything else.

Thanks in advance

RV Wizard · 07-15-2010, 03:01 AM

There can be a couple or maybe more scenarios. I would recommend you go to the transfer switch and disconnect the circuit conductor that is fed by the 20 amp breaker on the generator. Usually this breaker is for a second or rear air conditioner but not always. Start the generator with the removed conductor safely isolated from any ground source. Reset or make sure the 20 amp circuit breaker is turned on and check for voltage at the transfer switch side. If you have voltage and the breaker holds, this will eliminate the conductor having a problem between generator and transfer switch. Now go to the AC voltage distribution panel and remove the cover. Check the circuit breakers for voltage and list which ones are live and which are not while the 20 amp circuit is not connected to transfer switch. You want most all of your circuit breakers to have voltage at this point. I have seen where a generator was serviced and when reinstalled the technician got the 20 and 30 amp conductor circuits reversed. Turn off the generator and reconnect the 20 amp conductor to the transfer switch. If you only find one or two circuits are powered from the 30 amp breaker on the generator, you will want to reverse the conductors on the circuit breakers coming from the generator. Usually there is a junction box that is near the generator and technician remove these connections when pulling the genset out. This is where you want to make certain that the 30 amp circuit feeds a #10 conductor and the 20 amp breaker feeds the #12 conductor. You do not want to be connected to shore power during any of these tests or repairs.
If the microwave works properly on shore power, the microwave is not the problem when you try to operate it with the generator. Do these tests and reverse the conductors at the junction box if need be and get back to us as to what you found.

NeilV · 07-15-2010, 04:31 AM

We had that problem when we first purchased our current coach and as Mike has mentioned our problem was that the 20 and 30 amp circuits had been swapped at some time by the previous owner either when servicing the generator or possibly the transfer switch.

If you shut off the 30 amp House Breaker at the RV Main Panel does the microwave stop working? If so them the 20 amp side of the generator is wired to the 30 amp House Breaker and is backwards.

When you shut down the 30 breaker at the generator does only the second AC stop working. If so then again it would lead to believing that the generators 30 and 20 amp outputs have been swapped.

Before I started disconnecting the transfer switch I would test for the generator circuits being swapped to carry the wrong loads.

dieselclacker · 07-15-2010, 07:00 AM

Not to steal this thread, but along these same lines.....

The 20 amp circuit breaker on my Onan generator will pop when running the rear A/C, the microwave, and the water heater on electric. Discovered this last summer while parked at my SIL house for a visit. I normally do not run the water heater on 120 volt power, wife had unknownly turned on the switch for it while cleaning. Is this how the three circuits mentioned are normally wired? I have an Allegro with 50 amp service.

Dieselclacker

sirpurrcival · 07-15-2010, 10:36 AM

Thank you everybody for all your helpful responses

The first scenario seems somewhat likely as the last Owner was a "do it yourself'er" who did work on the electrical at points. However, based on some some of the other "do it yourself" projects that I have had to remedy already, I haven't got the highest confidence in his skills. Since I don't want to go down the same road (metaphorically) and since only unasked questions are dumb ones, where should I be looking for the transfer switch? would this likely be in the area of the converter? Sorry to be so rudimentary but I am still finding things and tentatively identifying them.

Always-RVing · 07-15-2010, 11:25 AM

Another Possibility: The Microwave could be generating noise spikes on the AC Line causing the breaker to trip. The generator could be sensitive to noise and spikes like you might see when running a compressor motor or vacuum cleaner.

Gary RVRoamer · 07-15-2010, 04:21 PM

Clacker... there is no "normal" for RV wiring, but with 50A shore power the appliances will be more or less distributed over the two available hot feeds that 50A provides. 50A shore power has 50A on each of two feeds. If your genset only suppies 20A on one of the two feeds, then yes you may trip breakers if too many things are running. Same thing on the other hot leg, which is probably 30A. that's far less than shore power provides, so you will need to be cautious about extra power draws when the front a/c is running.

Basically, your generator is a bit underpowered for a 50A rig. My generator provides 32 amps on each hot leg and I can still pop a breaker if the clothes dryer runs with the rear a/c and water heater too.

dieselclacker · 07-15-2010, 06:06 PM

Thanks for the reply Gary, makes sense. Will try to remember not to over load that 20 amp generator circuit.

Dieselclacker

sirpurrcival · 09-01-2011, 01:22 AM

PostScript

First, thank you for all the troubleshooting suggestions. I finally figured out what my issue was (I know I have many

).

As it turns out, there was a hidden draw on the circuit that I was unaware of. Twould seem that at some point, I was completely oblivious to the fact that my water heater is a combination unit. Low and behold, so it is. There is a cut off switch for the electrical side of the heater but it is nicely located on the water heater itself (not in view) and hidden behind a piece of plywood that is screwed in under my sink for good measure (nice engineering there). Once I discovered this and switched it off, my 20 amp breaker popping problem disappeared when using my convection oven. So in the end, it wasn't the generator, it wasn't my transfer switch (I actually don't have one of those), it was simply too much load on the circuit at one time and one naive RV'r who is a little wiser for the journey.