Hybrid inverter grounding floating.

aby

Good day. I have a grounding floating problem with my hybrid inverter. It is a MUST brand 3kVA. On this inverter there is 8 terminals. 3 terminals for grid input (hot + neutral + ground), 3 terminals for AC inverter output (hot + neutral + ground), and another 2 is battery input (+ve & -ve). When there is grid supply as a primary source, the load will received completed circuit (by using socket tester all indicator hot + neutral + ground are lit). The poblem is when the grid supply cutoff, the battery source will take over and run inverter AC output, but at this time the socket tester indicator only shown hot & neutral lit and no ground indicator. Why is the grounding floating when run inverter from battery but ok by using grid supply. For information the grid grounding and inverter output grounding is tap at the same point. Any body can help me or had any same issue. Thanks in advance. Very appreciate on that.

BB.

Welcome to the forum Aby,

Do you have a link to the product? Is this it?

https://www.mustpower.com/pv1800-pro-series-high-frequency-off-grid-solar-inverter-3-5kw/

Are you disconnecting the AG grid (hots/neutral) or just the hot leads, and leaving the neutral connected?

-Bill

aby

BB. said:

Welcome to the forum Aby,

Do you have a link to the product? Is this it?

https://www.mustpower.com/pv1800-pro-series-high-frequency-off-grid-solar-inverter-3-5kw/

Are you disconnecting the AG grid (hots/neutral) or just the hot leads, and leaving the neutral connected?

-Bill

Yes sir....it's the same hybrid as your attachment..

The situation: 

When grid supply available it will sourced to the inverter then to the loads and same time charging the battery. If grid supply not available, Inverter will auto switching to take source from battery. In this condition neutral from grid will also not connected to the Inverter automatically. Can refer my drawing attached. 

aby

Sorry the picture upside down..

BB.

I am guessing you are in Malaysia and have 240 VAC @ 50 Hz.

Everything I type below is Internet searches and guesses on my part... You need to confirm your location/wiring standards/and common practices in your country. In many countries, only licensed electricians may do this type of work (transfer switches in home wiring, etc.).

Generally you should have Hot/Neutral/Ground wiring to a residential outlet. And since the British standard uses a 3 or 13 amp fuse in the plug to protect the "hot lead", I would guess your outlets are polarized:




In the US, when we have transfer switches for our 120/240 VAC split phase power (two Hots, one Neutral, and one ground), we generally do not switch the neutral (or the ground).

So, in your case, If this is a "simple" connection from AC mains to AC Inverter to "Protected" panel (your loads you want to run from AC inverter)--Normally I would suggest you simply wire the neutral wire across the input/output neutral connectors on your inverter (you probably need to have one or two neutrals connected to the inverter too for it to properly function). It is possible that there is a "neutral jumper" inside the inverter that you can configure.

Assuming:

1. Your AC mains are "polarized" (you always know which is neutral and which is hot for wiring/plugs/etc.)
2. Your AC mains panel has the "brown wire" connected to your fuses/breakers. The "blue wire" Neutral is not fused and connects to a  neutral bus bar--Which also may be grounded in the main panel
3. Your AC inverter is a PSW/TSW (pure/true sine wave) AC inverter that supports ground bonded neutral operation (MSW--Modified sine/square wave inverters do not, generally, have isolated outputs--If you ground bond an AC output wire and ground bond the negative battery bank terminal, you will get a short circuit).
4. You are not running a backup AC Generator (at least without more research/thought).

I could not find a manual for your AC inverter--So I cannot review what this recommend for connections (generally, the place to start is the installation manual). Do you have a link for your manual you can post?

Some transfer switches are configurable so that they proved a ground bonded neutral when needed... Sort of common requirement for Recreational Vehicles that plug into "shore power" and have AC inverter/AC gensets on board. Having "switchable" ground bonding for the RV neutral is a requirement.

-Bill

aby

Yes... you're right sir. I'm from Malaysia which had 240VAC 50Hz. Will try your recommendation to loop the grid neutral input wire to the inverter neutral output wire. Really appreciate on your clear explanation. 

aby

Will attach also the operation manual for this model for your reference. So the expert like you can interpret more. Thanks sir.

aby

Here you are sir....as requested, the operation manual for the Hybrid Inverter that i'm using. 

BB.

Aby,

You are correct... The installation manual says almost nothing useful about the AC power connections.

What are the markings on the AC power connections of the AC inverter? Photograph? You show 6x connectors (3x AC in, 3x AC out). The documentation shows 5 connectors (2x AC in, 2x AC out, 1x ground)--From that I can tell.

If you are connecting utility power to AC inverter => your "protected" AC loads... I don't see how bonding the AC Input Neutral (from utility) to AC Output Neutral.

Check with a voltmeter that your AC input (from utility power) is properly wired (i.e., Brown~240 VAC, Blue~0 volts; when measured with Green Wire/Ground).

One thing to watch for--Inside your "Black Box" (the AC inverter), the engineer can measure your AC input and output current ether with the Brown Wire (hot) or the Blue Wire (Neutral)--From the engineer's point of view, either is fine (and the neutral current hardware can be "safer" because it is always near zero volts)... Check the LCD display and see if your AC Current readings make sense or not (i.e., the jumper will carry current "around" a neutral based current transformer).

-Bill