voltage on inverter

Roddick

Member
Location
Chicago
Recently I bought 24 V invereter (EDECOA 3000W dc 24V to ac 120V).I have a battery(6) bank and Solar Charge Controller .I got 8' long ground rod outside where is hooked up #8 wire from negative terminal of one battery and also #8 from body of the inverter.When I turned it on and made a test with my digital probe it shows me 120V between neutral and hot ,46 volt between hot and ground and 46 V between neutral and ground.I pluged portable AC for a few minutes.It was working fine(except a buzzing),but I was afraid to keep it working.That was just a test.The buzz was maybe caused because is modyfied inverter,I don't know.But my problem is with that voltage?Did I do anything wrong?Thanks for any help.
 

paulengr

Senior Member
Recently I bought 24 V invereter (EDECOA 3000W dc 24V to ac 120V).I have a battery(6) bank and Solar Charge Controller .I got 8' long ground rod outside where is hooked up #8 wire from negative terminal of one battery and also #8 from body of the inverter.When I turned it on and made a test with my digital probe it shows me 120V between neutral and hot ,46 volt between hot and ground and 46 V between neutral and ground.I pluged portable AC for a few minutes.It was working fine(except a buzzing),but I was afraid to keep it working.That was just a test.The buzz was maybe caused because is modyfied inverter,I don't know.But my problem is with that voltage?Did I do anything wrong?Thanks for any help.
Should be in the inverter wiring instructions. You need to connect the neutral to ground, too. Right now it is just floating.

Watch out though, if you intend on hooking it up to the main panel either as a grid tie (power can flow to utility) or not there are a couple different schemes with regards to how you bond the neutral to ground. Whichever method you use it should be grounded only in one spot. So if you bond everything to a common point so the inverter is sharing the utility ground/neutral make sure to remove a test jumper at the inverter.

Second inverters are designed for a certain minimum load or burden. If you don’t meet that requirement often they struggle to regulate the output. It is switching on for the minimum amount of time then right back off so the output is going to be very noisy and full of harmonics. Try a load like a window air conditioner, clothes dryer, air compressor. Something good sized. A cell phone charger is essentially no load at all unless the inverter is tiny.
 

GoldDigger

Moderator
Staff member
Should be in the inverter wiring instructions. You need to connect the neutral to ground, too. Right now it is just floating.

Watch out though, if you intend on hooking it up to the main panel either as a grid tie (power can flow to utility) or not there are a couple different schemes with regards to how you bond the neutral to ground. Whichever method you use it should be grounded only in one spot. So if you bond everything to a common point so the inverter is sharing the utility ground/neutral make sure to remove a test jumper at the inverter.

Second inverters are designed for a certain minimum load or burden. If you don’t meet that requirement often they struggle to regulate the output. It is switching on for the minimum amount of time then right back off so the output is going to be very noisy and full of harmonics. Try a load like a window air conditioner, clothes dryer, air compressor. Something good sized. A cell phone charger is essentially no load at all unless the inverter is tiny.
Danger, Will Robinson!
Some inexpensive battery powered square or modified square wave inverters connect their center tap to to ground (or indirectly to the battery ground and by design drive the "hot" and the "neutral" in opposite directions. Connecting neutral to ground on their output will either float the battery pack to 60V AC, it ungrounded, or let all the magic smoke out of the inverter.
By all means read the wiring instructions for the inverter.
Such inverters were once common in RVs and marine use and required a transfer switch that interrupted the neutral too when used with shore power.
The buzzing from the A/C is almost certainly the motor reacting to the square edges of the waveform and will probably correspond with a reduced motor life.
 

myspark

Senior Member
Location
SCV Ca, USA
Occupation
Retired EE
Danger, Will Robinson!
Some inexpensive battery powered square or modified square wave inverters connect their center tap to to ground (or indirectly to the battery ground and by design drive the "hot" and the "neutral" in opposite directions. Connecting neutral to ground on their output will either float the battery pack to 60V AC, it ungrounded, or let all the magic smoke out of the inverter.
By all means read the wiring instructions for the inverter.
Such inverters were once common in RVs and marine use and required a transfer switch that interrupted the neutral too when used with shore power.
The buzzing from the A/C is almost certainly the motor reacting to the square edges of the waveform and will probably correspond with a reduced motor life.
Inverters in RVs are not meant to run big loads with motors.

A 3000 watts inverter that derives power from a battery bank--can not support an A/C or even provide enough power to operate the unit for any discernible amount of time to offer comfort.

Have you tried running a small 5000 BTU A/C window unit with inverter using a battery?

Forget solar source with a miniscule power to even charge the battery bank to run the A/C.
My 13,500 BTU A/C unit won’t even start with the 3000W inverter.

For a 5000 BTU A/C unit, you can run it for about 3 minutes (if you’re lucky) and it will run down the battery in a hurry. It won’t even give you a chance to listen to the motor buzzing.
Forget the wave form of the inverter output.

Square wave or FAUX Sine Wave output-- won't save you--and allow you to run an AC unit with an inverter-- through a bank of batteries.
Location of neutral is irrelevant in the desired and expected operation of the inverter.

I run my 3000 W inverter only for powering my 32 inch TV and DVD player. (45 watts and 25 watts respectively)
It can only provide power to be able to watch one full length movie. After that one movie-- it will need help from the generator to recharge the batteries. . . but I have to wait.
 
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