I have the equivalent of an RV solar system installed in my home. (2- 260 watts solar panels, 40 amps MPPT controller, 2- 100 Ah deep cycle batteries and a 1000 watts inverter. Everything have inline fuses. I planed to connect a computer UPS to the inverter just for experimentation to have redundant protection for my computer system. When I connected the UPS, it did not worked, and reading about it, it seems that the system that I have been using everyday for more than a year, has a floating/ open ground.
My question is: Do I leave the system as is ? ( I've had no problems so far) , or I have to do something else to have a "real ground" on my system? Please consider that my inverter is not one used for homes, just a normal one that can be used on an RV. The inverter does not have an additional post for ground, just the positive and negative from the battery.
You are going to have to find out how the unit is intended to be used.
Is this an inverter with sockets for appliances to plug into directly or is it a unit that onlyhas terminals for permanent wiring to be attached? Units that have sockets are intended to have things plugged directly into them not be wired into a fixed system. If your device has both sockets and terminals there is a very good chance it is a socket only design that has had terminals bodged onto it at the factory and must be treated as if they are socket only units unless the manual explicitly states otherwise. A lot of Chinese inverters are bodged like this. There was a thread recently where this problem was discussed.
It's not only cheap Chinese inverters that are like this. Samlex has a line of 240V European inverters that are 'socket only' inverters with terminals for hardwiring too and they are designed like this too, but unlike the cheapies Samlex spells it out very clearly in manual what is going on and how the unit is intended to be used.
Socket only units/bodged terminals units typically do not have a neutral earth wire bond, there is no way to do it inside the unit itself, and actually doing it can damage the inverter. This is probably why your UPS is complaining, it can't see a neutral / earth bond. The two current carrying wires, hot/line/live and neutral are both at half voltage (120V for 240V inverter, 60V for 120V inverter) relative to the 'earth' pin on the socket. This is not leakage current, this can supply amps if called on. This offers protection from either of those wires breaking free and coming into contact with metal parts of appliances. A plug in RCD / GFCI can offer limited protection in the case that you manage to get yourself across either of the current carrying wires and the earth wire.
The earth pin on the socket may actually be joined to the chassis of the inverter. If this is the case and the inverter is screwed into the metalwork of the vehicle the RCD / GFCI protection will extend to cover you against coming into contact with either of the current carrying wires and being in contact with the vehicle metalwork or have low enough impedance (capacitive coupling) to the same too.
Note: I am not an electrician, what I have stated here may not cover all circumstances. If there is any doubt you should have the setup verified safe by an electrician.
If you want to make that work, you can put an isolation transformer on output of inverter. Use the isolated other winding to feed UPS, along with a ground wire, call one end of the isolated winding "neutral" and ground it.
Thanks for the answers. The inverter has sockets for appliances to plug into directly. By any chance, do you have the link for the thread that you mentioned?
Thanks for the answers. The inverter has sockets for appliances to plug into directly. By any chance, do you have the link for the thread that you mentioned?
Many threads mention "inverter" and +/- "60V" or otherwise talk about the issue of trying to connect neutral and ground to house wiring. Among those I found searching for those keywords:
I have this question about these inverters. I heard the hot is 60v and the neutral is 60v to make 120v. my AC output have two hot and 1 neutral. so if I buy two of these inverters and connect my 1 hot to each inverter and the AC output neutral to both inverters will it work ? or I will get two...
Sorry about that I misread the post.... You meant well. I was very fixated on inverters for the last few months while doing my due diligence research for my own system. Figures I ended up with the best.
My beloved UPSverter worked perfectly with my golf cart 48V FLA battery set. Later added solar panels to the cart which also worked perfectly with the battery set. Then tested the UPSverter while using the solar panels. Not so perfect. Whenever the battery climbed above 53V the UPS started...
diysolarforum.com
I would start by putting a voltmeter across neutral/ground. Then connect a lightbulb between them and check voltage again.
If it doesn't cooperate, could just use it for portable convenience (in conditions with no shock hazard) and pick up a better inverter for driving household loads.
I have the equivalent of an RV solar system installed in my home. (2- 260 watts solar panels, 40 amps MPPT controller, 2- 100 Ah deep cycle batteries and a 1000 watts inverter. Everything have inline fuses. I planed to connect a computer UPS to the inverter just for experimentation to have redundant protection for my computer system. When I connected the UPS, it did not worked, and reading about it, it seems that the system that I have been using everyday for more than a year, has a floating/ open ground.
My question is: Do I leave the system as is ? ( I've had no problems so far) , or I have to do something else to have a "real ground" on my system? Please consider that my inverter is not one used for homes, just a normal one that can be used on an RV. The inverter does not have an additional post for ground, just the positive and negative from the battery.
What do you mean the UPS doesn't work? The UPS refuses to turn on? O just gives a warning about open ground?
The UPS should work regardless if there's ground or not, if it in fact doesn't want to work it would mean that the UPS cannot be use in old houses that were updated to open ground receptacles with GFCI protection. (Completely safe and allowed by the code).
You are going to have to find out how the unit is intended to be used.
Is this an inverter with sockets for appliances to plug into directly or is it a unit that onlyhas terminals for permanent wiring to be attached? Units that have sockets are intended to have things plugged directly into them not be wired into a fixed system. If your device has both sockets and terminals there is a very good chance it is a socket only design that has had terminals bodged onto it at the factory and must be treated as if they are socket only units unless the manual explicitly states otherwise. A lot of Chinese inverters are bodged like this. There was a thread recently where this problem was discussed.
It's not only cheap Chinese inverters that are like this. Samlex has a line of 240V European inverters that are 'socket only' inverters with terminals for hardwiring too and they are designed like this too, but unlike the cheapies Samlex spells it out very clearly in manual what is going on and how the unit is intended to be used.
Socket only units/bodged terminals units typically do not have a neutral earth wire bond, there is no way to do it inside the unit itself, and actually doing it can damage the inverter. This is probably why your UPS is complaining, it can't see a neutral / earth bond. The two current carrying wires, hot/line/live and neutral are both at half voltage (120V for 240V inverter, 60V for 120V inverter) relative to the 'earth' pin on the socket. This is not leakage current, this can supply amps if called on. This offers protection from either of those wires breaking free and coming into contact with metal parts of appliances. A plug in RCD / GFCI can offer limited protection in the case that you manage to get yourself across either of the current carrying wires and the earth wire.
The earth pin on the socket may actually be joined to the chassis of the inverter. If this is the case and the inverter is screwed into the metalwork of the vehicle the RCD / GFCI protection will extend to cover you against coming into contact with either of the current carrying wires and being in contact with the vehicle metalwork or have low enough impedance (capacitive coupling) to the same too.
Note: I am not an electrician, what I have stated here may not cover all circumstances. If there is any doubt you should have the setup verified safe by an electrician.
Do hardwire inverters actually bond their output to their metal chasis? That can't be right. It would mean that if a transfer switch were to be used it would need to switch the neutral and you could not use it with an interlock either, it would create what is known as objectionable current.
You can threat most inverters as a isolation transformer, whatever the output voltage is, it is not referenced to ground (the mains at your house it is referenced to ground because they connected the neutral to the actual earth) the proper name of neutral is grounded conductor.
Either way, you can do the bond no issues without damaging the inverter (though it makes little sense to do it, it is better to have an isolated system and some european countries have the option to provide you with one).
And btw, that disclaimer of yours, FYI 90% of electricians and even electrical inspectors don't understand the difference between grounding and bonding (what we are talking about) Mike Holt has several hours long videos explaining all of this and even several several cases of people that were killed because the electricians, inspectors and even equipment manufacturers think that by putting a ground rod instead of running an EGC it will protect you againts electrical shock (it will fucking not).
You don't understand the problem with these inverters. It's been covered enough on the forum for there to not be a need to repeat what has been discussed previously. Please make use of the forum search if you want to see those discussions.
You don't understand the problem with these inverters. It's been covered enough on the forum for there to not be a need to repeat what has been discussed previously. Please make use of the forum search if you want to see those discussions.
When testing, all my outlets report Open Ground. My inverter is properly grounded to a grounding rod outside, but I believe the reason for the Open Ground, is because inside my inverter the Ground & Neutral wires are not bonded. I'm wondering if there is a shock risk, if there was ever a short...
diysolarforum.com
In the vid, the very first inverter that he tested has a split phase configuration with 60-0-60 and to get 120V you would need to go between 60 and 60, this is very common configuration in the UK for construction sites btw.
However the 0V cannot be called neutral yet, for it to be neutral, it would need to be bonded to the metal chasis of the inverter, the proper name of neutral is the grounded conductor per the NEC. And just in case, no you don't drive a ground rod for the inverter if you're connecting it to a system that already has a ground rod (your house panel).
At worst if the 0V was bonded to the metal chasis of the inverter and you tried to then bond what would now be 60V to ground it would just short circuit the inverter and it should just turn off, if the inverter gets damaged by this it means that the thing has no short circuit protection and even some appliances that draw huge current spikes at start up could damage it.
And if you instead bonded one leg of the 120V to your house panel without joining the inveter to the EGC (Equipment grounding conductor, the bare or green wire) if you were to measure the inverter it will be 60V live in reference to the earth and will give you a shock if you touch it (though I would not call it much of a hazard since it is 60V) but it is incorrectly installed. This is fact covered in the video that I linked when people drive ground rods to individual circuits without bringing and EGC. This is what I think the guy in the video refers to as ''live ground''. (That's a contradicting term btw).
To ''fix'' that ''problem' 'you would need to open the inverter and change the bonding inside. But then another person comes and makes an incorrect comparison with bridging amplifiers which are more expensive than regular amplifiers.
And to top if off recommends instead adding an isolation transformer, but the whole inverter already behaves like an isolation transformer xd, and even if the inverter doesn't use high frequency transformers for the step up (that is it is truly not input to output isolated), the whole inverter with batteries and panels is still an isolated system. If the case of your inverter was bonded to the battery negative and one of the inverters output, you would need to also remove the battery negative bond to the inverter chasis. But I don't really think you will ever run into a non input-output isolated inverter, those things are rare, and either way you can check it with your voltmeter with a small load in parallel (some inverters connect the secondary and primary thru class Y capacitors, so just voltage measurements with the high input impedance of a voltmeter are not enough, you need like a 1K Ohm load in parallel while measuring.
If you have non isolated inverter with boost converter instead of transformer (That is non isolated) and it is also split phase, if you were to redo de bonding to have 0-60-120 instead of 60-0-60 the battery negative will now be at 60V in reference to the EGC.
But I don't even know if such thing even exists, non isolated inverters are rare. It would be cost prohibited to make a non isolated 60-0-60 Inverter because they would need to use a voltage inverter (this is something that takes 100V and spits -100V instead of using a center tapped transformer or two independent transformers.
The likely reason the inverter was made that way it is because with minimum changes to the design they can work with 230/400V european appliances.
Really watch the video grounding video of Mike Holt I beg you. People don't really understand the difference between grounding and bonding, including those that should know.
Edit: And in the end someone else ended changing the bonding of the inverter without issues, it is as simple as changing a wire inside the thing.
But now it gets worse xd:
You can only have one bond between Neutral and the EGC, that is if your inverter is ''correctly'' wired and it has only two terminals of 120V in between and one end is connected to the chasis to the inverters EGC, YOU CANNOT connect that inverter to a house panel that also has another bond of neutral to its EGC. It creates something known as objectionable current. Basically the neutral and earth wires going to your inverter would be in parallel, you would either need to remove the bond (and use a floating ground which what you should do (it will still be bonded at the panel)) or use a transfer switch that switches the neutral as well, not even an interlock would work in this case.
This is the exact issue I am having. I have a generator transfer switch already wired into my home that looks
like it was used with a gas powered unit. I'd like to use an inverter but my switch is hot leg only and it seems
like any inverters I can find are all as stated above. I'm down to getting something like a Goal Zero unit with add on battery tanks. Their integration panel is exactly like the one installed already and should work just fine.
It's frustrating that this is so difficult to resolve easily. Where I live, code is king and they DO check everything.
I was told many times, anything not to code that results in damage, fire etc. is on your dime, insurance won't
cover it....
Any decent size inverter will have hot and neutral which can be grounded. The light weight or smaller all-in-one may not.
If you have ANY AC source not compatible with your desired grounding situation, whether a cheap +/-60V inverter or a 208 Y source, you can adapt the voltage and create the grounding you want.
For some inverters like 120V output that doesn't have funny grounding inside, a 120/240V auto-transformer would give the voltages you need.
For that cheap inverter with funny grounding, an isolated 120V to 120V transformer, or 120V to 120/240V transformer could have the secondary grounded as desired.
For a 208V source (e.g. two legs of a 3-phase generator), a 208 to 120/240V transformer would produce the desired voltages and permit grounding of the centertap.
I would get a good inverter that is already compatible, and that has a separate generator input. Then you can also use a generator if needed on cloudy days.
The transformer probably costs more than the inverter...
The scary part about people opening up these cheap inverters and hacking wires off is that it is often done without any understanding of the design of the unit. There are examples where people have not understood their particular inverter, modified wiring to stop the unit self-destructing and as a result left their battery system with mains / grid voltage between the terminals and the ground they stand on. This too has killed people.
The transformer costs less than the wrongful death lawsuit.
I recommend an inverter that meets your needs.
Originally I was going to use one Sunny Island, which has 120V isolation transformer inside, and add 120/240V autotransformer outside. Back when inverter cost $5k and transformer was $500.
Liquidation prices, and I've installed multiple Sunny Island for split-phase.
Yes, yes. We can always find an argument for costs, but let's keep it sensible please. It's obviously a discussion about the technicalities not the liability.
And therefore, I suggested a transformer. It fixes the technical problem.
I saw a few toroids on eBay in the $250 to $500 range, several kVA.
If someone is trying to use a 1 kW or smaller inverter, of course a smaller transformer would work.
My budget tends to be in the range of $5k a pop, but someone else may need to make something work for a few $hundred.
Decent new or used inverters would probably fit the bill, except to start larger induction motors.
I take some care to provide slow transfer between sources if the item has an issue with out of phase power (SMA says switch should be off 5 seconds before connecting inverter to a different AC input.)
And I make sure nothing has dangerous voltages accessible, especially metal exterior.
I started to design a surge arrestor with LEDs to show condition (like Midnight's) and realized I would have an LED's molded plastic holding off 120 VAC, which didn't seem like a good idea.
This is the exact issue I am having. I have a generator transfer switch already wired into my home that looks
like it was used with a gas powered unit. I'd like to use an inverter but my switch is hot leg only and it seems
like any inverters I can find are all as stated above. I'm down to getting something like a Goal Zero unit with add on battery tanks. Their integration panel is exactly like the one installed already and should work just fine.
It's frustrating that this is so difficult to resolve easily. Where I live, code is king and they DO check everything.
I was told many times, anything not to code that results in damage, fire etc. is on your dime, insurance won't
cover it....
Automatic transfer switch? Are you sure it only switches the hot?
If you have a non bonded inverter (check the continuity between its output terminals either way), if the transfer only switches the hot you should not have an open ground because one conductor of the inverter will connect directly to the neutral busbar of your panel (therefore to your EGC and GEC).
You haven't exactly say what happens with the UPS, some UPS refuse to work with some inverters because they are too noisy.
Automatic transfer switch? Are you sure it only switches the hot?
If you have a non bonded inverter (check the continuity between its output terminals either way), if the transfer only switches the hot you should not have an open ground because one conductor of the inverter will connect directly to the neutral busbar of your panel (therefore to your EGC and GEC).
You haven't exactly say what happens with the UPS, some UPS refuse to work with some inverters because they are too noisy.
