High Voltage from Inverter

[tcolburn]

Our coach is equipped with a Xantrex Freedom 458 inverter/converter. I've rarely used the inverter function. Yesterday I turned it on to test my TV antenna cable and noticed that my digital plug-in voltmeter was reading 157 volts at the inverter-powered outlets!! Kinda scary, so rather than damage anything I shut off the inverter and used the generator instead (voltage reading was the normal 120 volts, so it's not the voltmeter). Is this a symptom of a failing inverter, or might there be an incorrect setting that I can access to get the inverter output voltage down to the right level?

Thanks for any guidance.

--Tim C.

[abyrd]

If your inverter is a modified sine wave inverter and you are using a digital volt meter you make getting a incorrect reading.  When reading AC voltages you can get incorrect reading if you don't have a true sine wave.

Jim

[BillAdams]

The Freedom 458 is a modified sine wave inverter and your meter is reading incorrectly.

[dickandlois]

Tim, Does your meter have a setting that says True RMS Reading on it? If it does see what the meter reads an let us know.

RMS stands for Root Means Squared.

Like Bill and Jim mentioned your style inverter pouts out a Modified Sine wave not a pure sine wave

So you reading the peak to peak reading.

Rich.

[tcolburn]

Ah, I forgot about the modified sine wave. No, none of my meters has a "True RMS" setting, but if I can find one that does I'll try it and report my results. Meantime it sounds like the inverter's probably working all right. When I've used it before I never bothered to check the output, but the TV and microwave always worked.... Thanks!

--Tim

[dickandlois]

2 hours ago, tcolburn said:

Ah, I forgot about the modified sine wave. No, none of my meters has a "True RMS" setting, but if I can find one that does I'll try it and report my results. Meantime it sounds like the inverter's probably working all right. When I've used it before I never bothered to check the output, but the TV and microwave always worked.... Thanks!

--Tim

Tim, there has been a little conversation going on in the background of your post regarding the reading you got, so check the readings with a second meter before running the inverter. It is always good to know if a different meter gets a different reading. Inverters can go south and the same is true regarding meters. You did mention (voltage reading was the normal 120 volts, so it's not the voltmeter). When the Generator was running.

The key to the conversation is no one can say that we got a reading as high as you posted.

Rich.

[tcolburn]

Thank you Rich (and everyone else!), for the warning and explanation. The meter I was looking at is one of those digital plug-in ones. I'll take my other DVM over tomorrow and see what I can discover.

--Tim

[tcolburn]

Update... so I went out and found a "true RMS meter" and tested the inverter output with it. First photo shows the result: "generic" voltmeter= 158 VAC; RMS voltmeter= 147.7 VAC. Still too high, I think... (Incidentally, the RMS meter does show that the current is 59.99 Hz, so the frequency appears to be OK.)

Second photo, just for reference, shows house current at my home: 124.3 VAC.

For what it's worth, the TV works on this high voltage! But I'm not going to use the inverter till I can get a complete diagnosis. Probably will call Xantrex next week to see what they say. Thanks again to all who have been following this thread and offering your advice and opinions. I'll keep everyone posted....

--Tim C.

[abyrd]

Did you have any load on the inverter when you tested? Might test it with a 500

watt heater as load and see what you get.

 

 

 

Jim

[manholt]

Or, shut off the breaker on inverter, then turn back on.  

[BillAdams]

I highly doubt that the inverter is actually putting out voltage at the rate you are reading.  Please keep us informed about what you find.

[manholt]

I have a built in surge protector and also a portable one, plug in portable, turn on breaker, if good then you have all green lights.  mine will also check for reverse polarity.  I use it every where, even at house and my camp!  I have never heard of what I just saw a picture off!  Dumbfounded..

[BillAdams]

The surge suppressor would not look at inverter voltage, only voltage coming from the park power pole.  The OP has no issues with shore power.

[manholt]

I just re read his OP and subsequent reply's.. he has no issue on generator, but he's testing 120V outlet in coach and in house, I think, granted he's not said so, that he's hooked up to shore power at his home.

Could be wrong...not the first time.

Carl

[tcolburn]

Carl, I'm not hooked up to shore power at home. That photo was just to verify that the meter is working all right on a known-good power source. Now, the idea of checking inverter output with a surge suppressor (I have a portable Progressive 50A EMS) is interesting. Seems like I should be able to plug it into one of the outlets served by the inverter with suitable 50-30-20A adapters, and get a reading, just as I do when I plug into shore power at a campground or my garage outlet at home. Of course, if the EMS doesn't like the modified sine wave, I wonder if I could end up damaging it... So my next step, when I get home, will be to try calling Xantrex, then go from there.

The adventure continues! --Tim

[manholt]

Should not hurt EMS.

[tcolburn]

OK, I'm back, with good news! 

I spoke to tech support at Xantrex in Elkhart. The young man I spoke with suggested that I should add a resistive load and check the reading again. He said if I saw 134 VAC or less I should be fine. So, I plugged in a trouble light with a 75W bulb and checked the voltage again: voila--126 VAC! Apparently there is nothing wrong with my inverter after all.

I learned a lot from this episode, and I want to thank you all for helping to get me pointed in the right direction. Hope to meet in person one day.

--Tim C.

[mrlitwiller]

I had the same problem with my Xantrex Freedom 458 2000; high voltage on a cheapie meter verified by my Fluke True RMS. Since my coach had indications of voltage issues before I purchased it, I wasn't surprised. Fortunately, my "stuff" is stored in Portland, OR -- one of the few locations of a Xantrex authorized repair center, so on a pass thru to fondle the stuff in storage, I dropped it off last fall.

DC board was defective, tech advised replacing the AC board as well since it has a history of failure.  The repair was roughly half that of new, the magic threshold, but it's still a current model; so opted for repair since it's not in regular use. Unit was only in the shop overnight. I'd question whether a non-authorized shop would be efficient enough to avoid racking up labor charges -- I paid the minimum.

Not sure this helps, but I'd recommend finding an authorized repair center -- I feel it paid off for me. Surge protector is not an issue in your case, voltage regulator would be. Calling Xantrex will probably be marginal help. Call a repair center.

[kaypsmith]

The resistive load is the key in his case, I got in a little late for the discussion, but an old fashioned analog meter is also a better measurement for a MSW inverter, it is not as sensitive to the abrupt rise and fall of the sine wave. An osciliscope is the best possible means for an accurate measurement, but few these days even know what that is much less how to read it.