Half of 120 volt buss is dead

[PmsPks]

I have lost the power to half of the 120 volt power buss. I have checked the main 50 amp breaker and it is good. Both L1 and L2 incoming are hot. Half the breakers are hot, the other half of the breakers are not. I can usually figure these things out, but this one has me baffled. Appreciate any ideas.

[westernrvparkow]

PmsPks wrote:

lanerd wrote:
I would first check the transfer switch output lugs to make sure you have 120 on both L1 and L2.

I have checked the voltage on both L1 and L2 wires coming into the 50 amp breakers and they are both 120v.

There should only be one 50 amp main in your rig. Check the voltage coming into that breaker, and check the voltage coming out. If there is power entering into the breaker and none coming out, the breaker is tripped or bad, end of story. If there is not power coming into the breaker on both legs, most likely issues are either a bad leg on the shore power (but you checked that) a bad wire in your cord (but you checked the power entering the transfer switch) or a bad relay in the transfer switch (my vote). I have "fixed" several customers problems by loaning them a rubber hammer and showing them where to tap (on the transfer switch itself). A transfer switch is nothing more than an electromagnetic switch that swings a lug when power is present. The lug can get stuck, for lack of a technical term. The generator's output does not go thru the transfer switch, so you would have full power on generator, while only half if the problem is the transfer switch or any of the other issues upstream to and including the pedestal.

[PmsPks]

Thank you all for your comments and suggestions. I haven't made it back to the MH to continue my testing. I will report back on what I find.

[RCMAN46]

I believe it has been asked but do you have 240 volts across the input to the 50 amp breakers in the coach.

[lanerd]

PmsPks wrote:

lanerd wrote:
I would first check the transfer switch output lugs to make sure you have 120 on both L1 and L2.

I have checked the voltage on both L1 and L2 wires coming into the 50 amp breakers and they are both 120v.

Sorry, you didn't read my question correctly. I asked if you have 120 on both "output" lugs (terminals)....not the input. And for further info, I'm speaking of the "relay" inside the transfer switch...not the breaker box.

Ron

[Mile_High]

Are you sure you have lost 1/2 of the panel, or just some major breakers. If you have power to both sides of the buss in the panel after the 50A breaker, then it should be relatively easy to start tracing it down the bus to each breaker.

Neutrals? Perhaps you lost a batch on the neutral bus?

[tinkerer]

If you have an inverter check the the reset buttons on the inverter.

[wa8yxm]

Most people think that dual 50 amp breaker .. .if one trips. both trip.

NOT TRUE. it is not a dual breaker, it is two breakers, both in the same case, with a piece joining the handles.

But each breaker is independent of the other.

One can trip and the other remain "Set"..

Turn them off, press HARD to the off position and then restore (Turn back on) them. See if that works.. Following that is replacement of said dual breaker.

Also... Have seen this in campgrounds. never in an RV. but make sure they are fully SEATED (Push back/in on the top of the breaker)

[RoyB]

This is a VOLTAGE CHART showing what BUD is suggesting to look at... As with all high AC Voltages use extreme care with the meter probes when making voltage measurements.

50A SERVICE at the Pedestal

NO SHOCK ZONE image

This is a simplified pictorial for the 50A Dual Zone Distribution layout...


Google Image

Roy Ken

[Bruce_Brown]

RoyB wrote:
Be sure to double check all of your GFCI breakers.. Do a reset on them...

When we lost 1/2 of the circuits in our MH this was the reason. We replaced the GFI and regained everything.

[enblethen]

Do you have 240 volts between L1 and L2?
You could be reading backfeed if 240 is not present.

[pianotuna]

When you reverse the legs does the problem remain the same--or does it swap sides?

[PmsPks]

BB_TX wrote:
You say you checked both L1 and L2 on the main 50 amp breaker and have 120 vac incoming on both. But did you check the load side of the main 50 amp breaker to make sure you have 120 vac coming out of the breaker to the distribution panel. Main breaker could have a bad leg.

I have replaced the 50amp main breaker(s), still have the same problem. This problem just doesn't make sense. I guess it is time to take one thing at a time from plug to buss.

[accsys]

Do both of your ACs work? If so, check your inverter breakers and make sure none are tripped.

[MarkTwain]

PmsPks wrote:
I have lost the power to half of the 120 volt power buss. I have checked the main 50 amp breaker and it is good. Both L1 and L2 incoming are hot. Half the breakers are hot, the other half of the breakers are not. I can usually figure these things out, but this one has me baffled. Appreciate any ideas.

Unplug your main electrical cord coming from the shore power to your RV and then make sure you have it fully and securely plugged in.