Mystery electrical problem

I have an electrical issue which just popped up and I am mystified.

Coach has been in storage for little while, picked it up last night and moved to a campground. Everything worked fine, heating with heat pumps. Ran a quick errand this morning and when I return I note that the heat pumps are not sound right, as-if the voltage is low. Look over at the volt meter and it reads zero. ?? Switch off heat pumps and start looking around. Plugs off, microwave off, fridge has auto switched to LP. Check shore power, all green lights on surge protector. All breakers good, flip them all anyway. GFIs good. Switch on inverter and power is restored to plugs but not microwave. It's as if I lost one leg of power.

I began to think maybe my new power transfer switch had failed (or perhaps a power lug had come loose), although (as I understand it) the inverter power doesn't run through there so even if it had failed everything should work fine on the inverter.

Very, and I mean very bad timing (isn't it always), so hoping someone has the easy answer. As I'm sitting here I can't think of what else to look at.

Thx

Just a few random thoughts.

You said everything was off.  Does that mean nothing worked including the heat pumps?

Can you unhook from shore power and run the generator?
That might tell you what works and what doesn't.

Your a/c heat pumps are not inverter powered either. If they were running at all, you had shore power. Maybe low voltage shore power, but some.

It sounds more like your inverters internal circuit breaker tripped. Most have a push button breaker right on the inverter itself.

Gary RV_Wizard said:

Your a/c heat pumps are not inverter powered either. If they were running at all, you had shore power. Maybe low voltage shore power, but some.

It sounds more like your inverters internal circuit breaker tripped. Most have a push button breaker right on the inverter itself.

Click to expand...

Heat pumps have at least some voltage (the fans run) but when I first noticed the issue it sounded like the voltage was low. I ran into this one time at a park where one leg of the shore pedestal shorted out and both ACs still tried to work.


Had a long talk with a local shop I really like (East Valley RV in Apache Junction, unfortunately everyone else likes them too, they?re booked until late January). They are also homing in on the inverter. The external breaker on the inverter is not popped. (I seem to remember reading something about resetting an inverter which involved totally unpowering it.)


Here?s what DOES work on shore power: ACs (at least partly), electric element for hot water. Here?s what DOESN?T work on shore power: battery charger, plugs (I think all but have to check), microwave, AC portion of Norcold fridge (seems to work fine on LP). When I start the inverter, the plugs work but not the microwave (which normally does work on the inverter).


One last thing to eliminate is the transfer switch. Although it?s new everything can break. I spoke with a mobile RV repair guy recommended by East Valley, and he said it?s possible the transfer switch isn?t passing both legs, so half the rig is unpowered. Although prohibited by the park I?m in I?m going to run the genset for 5 minutes and see if anything else changes.


Interesting side note, my solar is saving the day, without it I would have no battery charging. Pretty big deal since I?m fulltiming.

Very interested to hear the results of your generator test.

Kev

It could be a half-transfer switch failure, which might just be a loose wire.  And if the connection is just poor rather than totally gone, or if the problem is the neutral wire, you can get weird results.

You may have a separate small breaker box on the inverter output side, with breakers for the individual circuits powered by the inverter. It may be right along side the main breaker panel, or elsewhere. Check those breakers if you have it - that could explain why the micro isn't working on inverter.

There is not enough detail in the problem description to make a real solid diagnosis, but running the genset will help isolate it further.

Kevin Means said:

Very interested to hear the results of your generator test.

Click to expand...

No difference. With genset running and shore power disconnected, good power on both in and out lugs on transfer switch for both genset and control panel. With genset off and shore power on, same for shore power lugs and control panel.

Gary RV_Wizard said:

It could be a half-transfer switch failure, which might just be a loose wire.  And if the connection is just poor rather than totally gone, or if the problem is the neutral wire, you can get weird results.

Click to expand...

I wish this was the problem. Aside from test above, then moved downstream and tested both buss bar and lugs of all breakers in main panel - all good in and out. I do have the smaller breaker box, but TBH I couldn't figure out how to get the cover off and different trouble shooting eliminated those breakers as the culprit.

Also checked battery voltage at inverter with shore power off (good). Then removed positive lead and turned shore power on to test inverter output (none, which I anticipated at this point since inverter status light was not powered). Turned shore power off, then removed positive lead from inverter, along with battery temp and remote control cables; allowed unit to sit about 15 minutes. When positive cable was reattached, inverter briefly came on and indicator light showed green, then immediately went solid red for about a second, then flashed red twice, inverter clicked and (apparently) shut down, status light extinguished.

Manged to get a mobile repair company to come to my site (ASAP RV Service, pretty happy so far with the experience, the tech was very polite and quite knowledgeable). Agreed with previous opinions that the inverter had failed. Removed power leads and tied them together (I'm sure I'm not describing this properly, essentially he bypassed the presumed-dead inverter to allow shore power to power everything). He then removed the inverter and it is going to a Xantrex service center next week for bench testing.

Gary RV_Wizard said:

that could explain why the micro isn't working on inverter.

Click to expand...

Once the leads were setup to bypass the inverter, all AC power came to life in the coach (while connected to shore power). But... the microwave was still dead. Checked the receptacle used by the microwave and power was fine. So whatever event took out the inverter (or when the inverter just died on its own) also took out the microwave  When it rains it pours.

So my current status is good 120V throughout while on shore power, but no battery charger or microwave. Fortunately I have the solar so just have to be in "dry camp mode" re power usage and I should be fine, allowing the solar to recharge the batteries. I have shore power at my next stop next week, so should be OK until the inverter is fixed/replaced.

A $10-$20 simple battery maintainer/charger from Harbor Freight or Walmart will keep the charge up if the sun isn't shining. It replaces enough power overnight to compensate for what gets used.

Was gonna suggest the same thing. Anyway, I?m sorry it turned out to be the inverter and not just a loose wire or connection, but I?m glad you got it figured out Scott.

Kev

X3 on the battery maintainer.  Glad you figured it out!

Thanks everyone for the suggestion. I had thought of it earlier but would have forgotten to pull the battery charger out of hiding where it was stored. And good timing, today was a pretty cloudy day here in the Phoenix area. When I got back to the rig a few minutes ago I checked and the solar only got me back to 12.4 volts. On the charger now.

Battery Tenders come in assorted sizes. when my converter died. I could not get one right away (Sunday) so I dropped 100 bucks on a Deltran Battery Tender Delux.. This thing not only is a 1-2 amp "Smart Tender" But you can MANUALLY set it to 20 amps. it will auto exit when the batteries are up to 14.1 volts. or either 70 or 75 amps (For jump starting)  WI-Fi to your smart phone for adjustment or do it from the control panel..  Well worth the cost.

So the plot thickens. Ran a quick errand and when I came back I heard from the outside that the fridge had switched to LP. Went and looked at the pedestal, all green on the surge protector. Went inside and looked at the plugin digital voltmeter in the kitchen, 237!! Ran in to the bedroom and checked the analog, pegged high. Ran outside and switched off and unplugged.

Obviously I'm now thinking the park power fried my stuff, and I will have to deal with that. But how can that happen? I know about miswired 30 amp plugs, but how does a 50 amp receptacle, which has been fine every time I looked at the voltage from inside (running around 119v) suddenly double?

I test L1 and L2 at the pedestal and it's reading 237, so the voltage at the pedestal does seem normal. So I guess the real question is, how did it double in the coach?

I then adapted down to use the 15A receptacle (thinking that way there's no way to get high voltage in the coach since there's only one leg), and although I was getting all green on the surge protector I  had no AC in the coach. (Recall that the inverter has been removed for testing and bypassed.) Breakers are all good. I then removed the surge protector, still adapted down to 15, and now I have AC in the coach. So I'm now wondering if the surge protector somehow caused this. ???

You are describing an open neutral.  One of the conditions a Progressive Industries HW-50c is designed to protect against.. Issue could be at either side of the park/RV cord interface without further testing i can not be sure.

I recently had a lead failure in my plug. Thankfully NOT the neutral.

50 amp sockets have two hot lines. Between each line and neutral you should read 120 volts, between one hot pin and another is 240 volts.


    |------- 240 volts -------|
    |--- 120 ---|--- 120 ----|
    L1        Neutral          L2

The neutral stays at 0 volts but don't confuse neutral and ground.  Ground (on the round 4th pin) is for safety, to make sure exposed metal parts don't carry voltage.  Neutral is the vertical pin between the two hot pins that carries the return current to keep the two 120 volt circuits stabilized.

If the neutral opened up, due to a bad connection in either the RV or in the shore power, the voltage on each of the 120 volt lines will vary according to the load on them. A balanced load will maintain 120 volts on each circuit, but if one draws more current than the other you can get up to 240 volts on the lightly loaded side and and as low as 0 volts on the other side.

It's possible the park pedestal could have a bad neutral, or it could be in either the rig's power cord or in the transfer switch. The surge protector only monitors the voltages between the hot lines and ground, it may or may not detect a bad neutral.  That's where a load management system like the Progressive Industries comes into play.

Yes, that kind of voltage on 50A shore power is almost surely an open neutral.  I'd be looking closely at the plug on your shore cord - it gets a lot of flex wear & tear and sometimes a wire breaks loose where it connects to the plug. If its the neutral, You can get the problem yuu see. Doesn't have to be completely broken off - just mostly. Sometimes a simil;ar problem arises at the transfer switch, due to road vibration of just plain sloppy installation.

I'm back at the rig following the last of my move to fulltiming (yes, this is perfect timing  :-\ ) Did some more testing:

At the pedestal, 50A receptacle: L1/L2 = 237, L1/neutral = 120, L2/neutral = 120, neutral/ground = 0.

With SurgeGard plugged in to the 50A receptacle but no shore cord plugged in to SurgeGard, all green lights, specifically not indicating an open neutral (however reliable that indication is, are these SurgeGards worthless?)

With SurgeGard installed and adapted down to 15A using 15A receptacle, testing power cord lugs at transfer switch: L1/neutral = 0, L2/neutral = 0.

With SurgeGard not installed and adapted down to 15A using 15A receptacle, testing power cord lugs at transfer switch: L1/neutral = 120, L2/neutral = 120.

As a layman this makes me very suspicious of the surgegard. If there is any chance this is a problem with the receptacle, I need to know this ASAP because that means the park  will have fried at least a couple items. But Lou, I'm concerned about your comment that an open neutral might only show up with an unbalanced load, as I doubt the park will do anything other than a test equivalent to the the indications shown on the SurgeGard (or do they load test?) No way I'm plugging the coach in to provide a load.