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bcbowers · 05-23-2022, 02:44 PM

I have an interesting loud HUM coming from our Xantrex SW2000 inverter/charger. For years we kept hearing a loud HUM come & go always in the morning around 6 to 9 AM. It hums for less than a minute, goes away for a while then repeats that pattern. It’s taken us years to finally associate the hum with using a ceramic space heater and a Keurig coffee maker. But no other A/C appliances cause the HUM which includes water heater, refrigerator, and clothes dryer.

I called Xantrex Tech Support last year who blamed the shore power as the possible source but didn’t explain the HUM. Since we’ve been in multiple campgrounds over the past years that really doesn’t fit.

Any ideas why it’s HUMMING?

We can quit using the space heater (just using it to save on propane) but the wife MUST have coffee maker. I just don’t understand how they’re causing a problem.

On a side note …. we plug the space heater into the PS of the coach which is NOT on the same leg of the 50amp circuit as the charger whereas the Keurig is in the same leg. The SCP displays the “Load” and “AC In” which increases when the Keurig & the space heater are ON. Seems like only Keurig should cause it to increase. Am I missing something?

I’m waiting to get a call from Xantrex Tech Support but I’m not expecting much help based on previous calls. They’ll probably say “Quit using the space heater & Keurig”.

Kid Gloves · 05-23-2022, 05:19 PM

Are you inverting while on shore power?

Old Scout · 05-23-2022, 05:35 PM

Unless its a hybrid inverter--I dont think inverting while on shore power is possible? Not all outlets and appliances are wired thru the inverter but it does sound like the points on the inverter by-pass circuit contactors are chattering with high amp draws from appliances with heating elements???

bcbowers · 05-23-2022, 10:34 PM

No … not inverting power … strictly shore power.

Xantrex called …. I changed the “Power Share” setting from 20amp to 30amp. Also, I’ve discovered that the outlets I’m using on the PS is actually on the same leg as the charger which is where I was plugging in the space heater. I’ll try it tomorrow with the new setting and report.

Old Scout · 05-24-2022, 07:57 AM

Guess I am missing the point here--so if you are on shore power:
1- inverter function is not in the equation.
2- unless batteries are depleted, charger is drawing low amps, so rating or de-rating [power share] the charger really isnt going to help.
3- Not sure how the inverter/charger sharing a 50 amp leg/circuit would be an issue, unless you are running a high amp appliance thru the by-pass. Then, not sure "power share" has any impact on the by-pass circuit?

If you are running one or more high amp appliances thru the by-pass circuit, then I am back to a potential issue with the internal by-pass contactors in the inverter/charger.
Example: the AC contactors in some RV transfer switches tend to "hum" more as they get older--that is why the better ATS's use DC contactors.

bcbowers · 05-24-2022, 08:15 AM

OS … I would agree but the hum is not constant and only occurs when the 2 small appliances are on.

Today, the hum dud not occur while the space heater was on. However, it came on after turning on the Keurig (space heater turned off) and after the “Heat” cycle. The hum sound was not as loud and seemed to go on & off in shorter cycles. Not very conclusive but seems to be better.

Alpine36 · 05-24-2022, 09:09 AM

The 120v outlet by the front door, pass side, should be wired to the main breaker panel and not go thru the inverter. I suspect something in the inverter pass thru circuit is weak. Our 2000 did the same thing when using the convection/microwave oven or coffee maker on shore power. Note, our inverter is the old Freedom 458 series and the pass thru circuit finally failed. After repairing the inverter I did a work around and fed the sub panel thru the unused washer dryer breaker in the main panel. The inverter is now only feeding one 15a breaker in the sub panel that serves the TVs, kitchen overhead light and the bedroom outlets. We only use the inverter for TVs and bedroom cpap now. Why they wired the convection oven and nearly every outlet thru the inverter baffles me.

Old Scout · 05-24-2022, 09:10 AM

Not sure how the Keurig works but most heating element appliances tend to cycle the element, eg crock pots. Seem to recall reading about owners having "issues" with these types of appliances as they get older, but dont recall hearing about any root causes.

Old Scout · 05-24-2022, 09:18 AM

Agree-- never felt comfortable running the microwave on a 2000w inverter [with 4 or 6 bats], for an extended length of time, but 30-40 seconds for a cup of coffee or a sandwich--priceless [smile].

Alpine36 · 05-24-2022, 09:34 AM

Quote:

Originally Posted by Old Scout

Agree-- never felt comfortable running the microwave on a 2000w inverter [with 4 or 6 bats], for an extended length of time, but 30-40 seconds for a cup of coffee or a sandwich--priceless [smile].

Agree, that was a nice feature, but if you look at potential load share it could become problematic. In our case the inverter pass thru failed one cold fall day. Space heater, coffee pot, biscuits in the oven and hair dryer took it out while on 50a shore power. If we're off grid I fire up the gen for a couple hours in the morning and do our coffee and breakfast during battery charge time. 80% of the time were on the shore cord anyhow.

Old Scout · 05-24-2022, 09:42 AM

Your comment on the by-pass circuit is exactly what I was driving at regarding the OP's "humming" issue. Regardless of shore power, you only have 30 amps to work with going thru the inverter by-pass circuit. If you dont divide up the draws between inverter by-pass and non-by-pass circuits in the coach, you can easily over-load the inverter circuit--usually means you will trip the 30-amp breaker or the reset-fuse in the inverter, if so equipped.

bcbowers · 05-24-2022, 10:57 PM

The SCP displays the "Load" and "AC In" which ultimately monitors the pass through current. It typically shows 1-3 amps with no appliances turned on. The Keurig will add around 10 amps while initially heating & pumping water. However, this morning the hum started AFTER the water heating and pumping stopped. Weird!

I'll see what it does tomorrow. At least it's not humming as much now.

paul65k · 05-25-2022, 06:30 AM

Well I am pretty sure that the Keurig causing the hum is due to the fact that they don't play well with Modified Sign Wave inverters...... the same thing happens when you run the microwave I would think.....all humming went away for us when we upgraded to a Pure Sine Wave inverter...... friend had the same issue trying to run a Nespresso coffee machine (actually would not run at all on MSW), they went PSW and had no issues.

Just a single data point and all the comments about pass-through are also spot-on, sounds like your 20-year-old inverter is probably feeling the effects of time....... like we all do eventually

bcbowers · 05-25-2022, 10:07 AM

Xantrex Freedom SW2000 is a pure sine wave inverter. We replaced the old Freedom 458 in 2014 when the 458 “lost its magic smoke”.

The same results today as yesterday. Some humming after the Keurig finishes heating & pumping water right after turning it on. I don’t what the exact answer is but the hum is much softer sounding so I think we’ll just live with it. If someone comes up with an absolute answer or even an idea, I’ll stay engaged with this issue. Thanks!