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Inverter Function When Connectd to 50 amp Shore Power

May 17, 2018, 08:56:26 am

I normally leave main inverter on when connected to campground utilities...no particular reason, just never though about it.

This morning when we turned the toaster oven on there was a significant hum from the inverter which ended when I put the inverter into Standby. Toaster oven continued to operate as Inassumed it would. And, obviously after toasting the hum did not recur when I put the inverter back online.

Maybe I can get a better understanding of how the inverter functions when on shore power and best practices for its operation on shore power.

Thanks

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #1 – May 17, 2018, 09:18:24 am

Need to know what inverter you have for a more specific answer from a member with the same equipment.

Our inverter (Magnum MS2812) has two operating "modes".  When we are plugged in to shore power (or when generator is running), it automatically switches to "battery charge" mode.  When I disconnect from shore power (or shut down the generator), it automatically switches to "inverter" mode and starts pulling power from the batteries.

I leave our inverter on 24/7 and let it decide what mode is appropriate...which it does without any (noticeable) problem.  In fact, the transition from "charging" mode to "inverting" mode is absolutely transparent - I never see any indication in any coach appliance when the switch is made.

SO, IF your inverter operates the same way, and IF there was no problem with the shore power connection at the time you turned on the toaster oven, then I would say your inverter should not have reacted to turning the oven on.

If, for some reason, your inverter was "inverting" at the time you turned the oven on, then it might react to the sudden large power draw of the toaster oven with a humming noise?  Just guessing...

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #2 – May 17, 2018, 09:18:31 am

Randy, do you have the original inverter and two transfer switches?  Maybe only one?  Do you have the big FT book? Look in the back for a schematic of how this is connected.

Generally if you are connected to shore power the only thing the inverter is doing is battery charging.  The 120v output from the inverter side is not connected due to the second transfer switch. 

See VICTRON Multi - install advice/opinion

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #3 – May 17, 2018, 10:19:29 am

Randy,

When on shore power (and, critically, they receive 120 VAC from the main breaker panel) , MOST inverters "pass through" the shore power.  Said another way, they do not "invert". Yes, some coaches have  a second transfer switch rather than relying on the transfer switch built into the inverter.

Wonder if you lost 120 VAC to the inverter and turning on the over caused it to invert and that is what you heard?

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #4 – May 17, 2018, 03:14:02 pm

Sorry for the delay. Travel day. Xantrex 3012. Not sure about transfer switches except that MOT replaced a loud one when we bought the coach.

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #5 – May 17, 2018, 03:54:22 pm

Check in the "electrical area" under the foot of the bed.  You will have either one or two ATS's.

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #6 – May 17, 2018, 04:09:46 pm

The Xantrex 3012 has a ACIn setting that qualifies the AC input. If the input falls below a certain setting, the inverter will switch from AC input to inverting. It is unlikely that with a 50 amp service the AC input would fall low enough to trigger that function. However, if you are in a campground with iffy shore power and the ACIn setting is set to its max setting, 115 VAC, it would be possible. Running all air conditioners, electric water heater, etc. and then turning on a high amp appliance like a toaster may do it. It is something easy to check. Just go into set up and check the setting. Default is 95 VAC.

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #7 – May 17, 2018, 04:16:33 pm

And 95 VAC is BELOW any safe voltage for any of your appliances.

108 VAC is the lowest you will want to run.  So, if the inverter started inverting based on voltage reaching 95 .....

Note: I have no first hand experience with this inverter, so not vouching for the "starts inverting at 95 VAC".

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #8 – May 17, 2018, 07:03:38 pm

Our current coach, which is not a Foretravel, has an inverter that picks us the AC load anytime the 120 Volt shore power VAC is lower than 105 VAC. Our coach has a 30 amp service. When rv park shore power is iffy, and the air conditioner comes on, the VAC sometimes drops below 105 VAC for a split second and the TV and Satellite receiver turns off. When the Inverter is turned on, the inverter turns on and supplies AC voltage to the TV and Satellite receiver which keeps them from turning off.  When shore power VAC returns to above 105 VAC the inverter turns off. The Inverter does not have the Air Conditioner and electric water heater on the Inverter circuit.
BTW, our Foretravel had the Xantrex SW 3012 Inverter.

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Re: Inverter Function When Connectd to 50 amp Shore Power

Reply #9 – May 20, 2018, 06:38:25 pm

Floridarandy,
After you post have you come to a better understanding of how your inverter functions?

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