Microwave and converter fried at campground

[Mike_Schriber]

Just got set up at a campground in Colorado Springs and I have a big problem. Everything seemed to be working correctly electrically initially but when we came back to camp I found the front air conditioner breaker blown, the microwave off and the battery not charging. I reset the AC breaker and the unit seems fine.
I then checked the outlets for the microwave and converter (each on a separate breaker) and they had power. The converter smells fried and is not putting out any power and the microwave appears to be history.

Doing more testing, I used a circuit checker to test the other outlets. One circuit showed that the hot and ground were reversed (the laptop plugged into that circuit also stopped charging). I switched from the 50 amp plug to the 30 amp and the circuit showed good. I'm now figuring that one leg is wired wrong at the pedestal on the 50 amp outlet. However, I switched back to the 50 amp circuit to double check and now the circuit shows normal.

I'm really stumped. I know it's not anything on the motorhome side but I can't explain the shifting readings. I plan to have some words with the campground management in the morning and I'd love to have some idea what's going on with their power before I do.

Any thoughts?

Thanks!

[wa8yxm]

Electric systems can be compared to water systems

Imagine two tanks of water.. One has a pipe coming out of it goign to a pump, this pump pumps water into the other tank but there is a "T" fitting and connected to the other side of the "T" is a 2nd pump pumping water BACK into the main tank.

THe pumps are L-1 and L-2 the 2nd tank or rather the pipe connecting it to the :"T" is the "Neutral".

So long as both pumps are running exactly the same current (Gallons per minute) There is NO water flowing in the "Neutral" pipe it's just going around in circles.

But shut one of the pumps off and the "Neutral" line is now carrying whatever trhe other pump is pushing up to 50 GPM,

And that is how it works. Pressure (Between neutral and L-1/L-2) depends on if both pumps are running..

Now,,, Imagine the "neutral" pipe is clogged.. The running pump is going to create quite a bit of pressure (or vaccum) at teh "T" fitting.

[time2roll]

Bobbo, dedicated neutral and circuit you are right. And most RV parks have a shared neutral. Depending on the location of the issue you can most certainly have high voltage on 30 amp. Seen it 137 when my ems cut power. No time for issues so I was on inverter the rest of the night.

[pianotuna]

Bobbo,

See wa8yxm's explanation.

Think about how a duplexed outlet works in a Kitchen.

[MEXICOWANDERER]

That's called

TOUCH THE SKIN OF THE RIG AND NO NEED FOR MORNING COFFEE

[Bobbo]

pianotuna wrote:
I wish that were so--but the 30 amp shore power can be on either the high or low voltage side of a neutral.

Correct me if I am wrong, but on a 30 amp circuit, you have a HOT and a NEUTRAL. If the NEUTRAL loses connection (which is what happened to fry his stuff) you have NO CONNECTION. You can only have the 0v and 240v (or low voltage/high voltage) difference if you have both HOTs connected with no NEUTRAL.

Of course, if the pedestal is miswired (e.g. a HOT/NEUTRAL reverse) all bets are off.

wa8yxm wrote:
Longer anser
On a 30 amp RV it may well work out the same way only now you and a neighbor share a "Neutral" (The neighbor may be some distance away) so either NOTHIGN works (That's safe) or you see the same thign happening to your RV when HIS A/C kicks in.

Question. If you and a neighbor are sharing a NEUTRAL, and you (or he) loses the NEUTRAL on a 30 amp system, what is the return path that allows the current to flow into your HOT wire at 240v (ish)?

[wa8yxm]

Sort answer: I will assume you have a 50 amp RV (The long answer covers 30 amp)

YOu have an open neutral. NOW it may be the park's fault, or yours, but this is why you really need a Progressive Industries HW-50C installed in your 50 amp RV (HW-30c on 30 amp RVs)

50 amp service is 240 volts divided into two 120 volt "legs" but leg to leg is 240.... NOW.. if both legs are drawing identical current. THe neutral is idle, nothing flows.. But if, for example, your REAR A/C kicks in and the neutral is open.. The "Front" leg is going to see 200 volts or more, also the A/C will see, what's left, so it will trip its breaker while all the electroncs on the other leg fry.

Exactly as you describe.


Longer anser
On a 30 amp RV it may well work out the same way only now you and a neighbor share a "Neutral" (The neighbor may be some distance away) so either NOTHIGN works (That's safe) or you see the same thign happening to your RV when HIS A/C kicks in.

[MEXICOWANDERER]

Ratz!
Well it was worth a look I suppose. My commercial 1,875 watt LG has two fuses and a disconnect breaker. The unit has to be unplugged to reset the breaker which is rated 5 amperes less than the main power fuse. Just as a note it takes three separate programming steps to exceed 1,200 watts power. It will boil a liter of water somewhere in the neighborhood of 60-seconds. it demands a 20-amp receptacle. Which do not exist down here. The 15-amp pictogram with red circle and bar showing a standard 15-amp receptacle is how the unit was discounted to me. I picked it up brand new for around $108. Stainless steel cabinet and membrane touch pad. It has a built in 2032 three battery memory retention.

[Mike_Schriber]

Just reread the service manual. No additional fuses. Troubleshooting flowchart indicates a bad thermostat. Not gonna bother messing with it.

[pianotuna]

Hi Mike,

I wish that were so--but the 30 amp shore power can be on either the high or low voltage side of a neutral. It is rarer, but not impossible. That is why I always check voltage and polarity under load before I plug in the RV.

BTW I'm not a surge protector believer, but rather an energy management believer. Mostly low voltage is what causes slow but progressive damage to items such as the air conditioner. That is why the first line of defense is measurement under load, before plugging in the RV. The second line is a Sola Basic autoformer which does 3 layers of boost and 1 layer of buck.

Mike Schriber wrote:
Assuming that it may be my plug that's defective, if I continue to only use the 30 amp adapter that should prevent a similar overvoltage from happening again right?

[Mike_Schriber]

I found the power supply fuse but didn't see one on the controller board unfortunately.

[MEXICOWANDERER]

Many microwaves TWO FUSES

One for power usually 10-15 amp slo-blo

Other is for circuit board control 1-3 amperes

I have never seen a board with both fuses in close proximity to each other.

[Mike_Schriber]

Actually just had some downtime so I pulled the microwave and checked the fuse. Fuse is fine so the microwave appears to be toast. Bummer.

Now to try and find something that'll fit in the opening.

[Mike_Schriber]

I bought and installed a new converter and the campground has already paid me for it. Microwave will have to wait until we're home but they're going to cover that too.

Thanks again for the assistance in nailing this down.

[MEXICOWANDERER]

SPST 120 coil relay

L1 or L2 through piezo annuniator to earth ground. Use NC contacts

L1 or L2 through RELAY coil then to L0 neutral

No connection relay coil no function. Contacts are closed but no alarm power

Connection with neutral. Contacts pull open breaking piezo circuit.

Disconnection from neutral but valid line connection. Relay contacts close enabling piezo annunciator.

Extremely low power device. Long-life relays are inexpensive. Unlimited power available from line to earth for annunciator. Searchlight. Air Raid Siren.

BTW a power management center or any surge suppression circuit can only protect in an extremely low-order lightning strike event. Even modest events will vaporize the most expensive consumer devices on earth. Spoken from practical experience.

[cyntdon2010]

we had a lighting strike at home. converter was fried and A/C relay and thermos burn up...... I purchased a surge protector....