V-0-V Generator?

[Ingo]

Hi Guys,

I admit I have a portable generator wired to my system as a backup during extended grid failures. But, common sense has prevailed and I am going to remove it due to legal and safety issues unless there is a way to safely change the nature of the generator feed to my house. I was thinking of two options, and if I didn't already have a Honda EU30iS Inverter Generator, I would never consider these due to overall cost. I would have bought a proper backup generator instead.

Option 1: Connect an Isolation Transformer (3600W) between the Generator and one of my Quattro inputs. This will separate the generator earth from the 'house' earth and allow me to tie the output Neutral to my house grid earth which enables all the safety devices and surge protection to work correctly. See the Shore input as Generator and Ship as the House.

Option 2: Connect the Generator as-is to a Skyla TG 48/50 and use it as a power supply. My generator can supply enough power to max the Skylla at 50A which is enough to drive the house critical loads.

Would any of the above be considered a legal way to connect a portable generator? Are the two options possible or am I smoking something?

Ingo

PS. Option 3: Sell the generator 

[___]

I assume the issue is that you cannot bond the earth and neutral on this (cheap?) generator? Are you sure you can't? :-)

[Ingo]

Correct. I briefly tested it but you could hear the generator taking strain even at no load. The casing of the (enclosed) inverter module seems to be internally wired to the generator earth, no amount of effort is going to change that (well, not that I can see anyway).

[Gabriel_2018]

1 hour ago, Ingo said:

Hi Guys,

I admit I have a portable generator wired to my system as a backup during extended grid failures. But, common sense has prevailed and I am going to remove it due to legal and safety issues unless there is a way to safely change the nature of the generator feed to my house. I was thinking of two options, and if I didn't already have a Honda EU30iS Inverter Generator, I would never consider these due to overall cost. I would have bought a proper backup generator instead.

Option 1: Connect an Isolation Transformer (3600W) between the Generator and one of my Quattro inputs. This will separate the generator earth from the 'house' earth and allow me to tie the output Neutral to my house grid earth which enables all the safety devices and surge protection to work correctly. See the Shore input as Generator and Ship as the House.

Option 2: Connect the Generator as-is to a Skyla TG 48/50 and use it as a power supply. My generator can supply enough power to max the Skylla at 50A which is enough to drive the house critical loads.

Would any of the above be considered a legal way to connect a portable generator? Are the two options possible or am I smoking something?

Ingo

PS. Option 3: Sell the generator 

I prefer option 1 because is cheaper and more efficient than option 2. 

I think that kind of softstar is not neccesary. It is enough run generator and wait a pair of minutes to conect loads.

Edited January 5, 2019 by Javi Martínez

[phil.g00]

I admit I haven't delved into the detail of generator connection aspect of my system, but I certainly was considering an inverter generator for the quality of sine wave in the future.

So I am interested.

2 hours ago, Ingo said:

PS. Option 3: Sell the generator 

But seriously,

I'll have to rely on first principles, because I don't have experience with small generators.

( Caveat: this does not imply legal conformance).

V-0-V,  would imply to me that you have a 110V - 0V -110V arrangement, with the full 220V only across both hot legs. 

1 hour ago, Ingo said:

The casing of the (enclosed) inverter module seems to be internally wired to the generator earth

Most (all?) inverter generators would have a floating ground.

Bonded to the case - I doubt it, I'd reason that the casing is not bonded to the center-tap, and you can earth the case directly and separately  to an external earth point. - It's important to prove this, otherwise you'll get a shock from your  gen casing. (Which is why I doubt, they'd make it like that).

 When used as a portable generator connecting an  external earth at the centre tap would mean that the highest voltage from earth is 110Vac, (stands to reason, good for safety in that application).

However, when using it in parallel to the grid, I'd expect the wiring to be such that the centre-tap to remains floating (unconnected), and one of the hot legs to be earthed through the grid, (by virtue of connection).

How are you wiring this?

 

 

 

[Ingo]

The generator chassis-earth is connected to the output earth, this was confirmed with a simple resistance check. Next, as you said, the output is 110V on each leg using the chassis-earth as the reference for that safety feature mentioned.

Connecting it to my Inverter I disconnected the centre-tap earth from the generator going to the inverter. That said, my Inverter is not a parallel connected unit, I have a complete separation from utility through my unit meaning Critical loads and AC loads run through the Inverter (AC Out 1 and AC Out 2). Connected like this everything works perfectly.

I am concerned that a certain legal interpretation could mean that even though I never have my generator's L & N ever touch the Grid they can still fall back to say V-0-V must never be connected to a DB. If something does fail somewhere I might be liable to whatever book they try throw at me.

Edited January 5, 2019 by Ingo

[phil.g00]

You do realize that your problem was that you were trying to parallel 110Vac -E and 220Vac-E together?

Your generator casing is still earthed right, just that you are now using a two-wire connection through to the inverter?

Legal compliance is rooted in safety, your system is not inherently unsafe.

But legality is fickle, and also has geographical refinements, the internet is not the place for that advice.

 

[Gabriel_2018]

I was asking myself how is possible skylla is so expensive. Watching specs, it seems a full PFC+Full bridge SMPS whit current limit.

Do you know a special feature? @plonkster

[___]

55 minutes ago, phil.g00 said:

You do realize that your problem was that you were trying to parallel 110Vac -E and 220Vac-E together?

I was thinking the same thing now. It seems like the generator is wired according to the US method, where you have two legs 180 degrees apart and earth in the middle. The two legs are both considered "hot" (ie one side is NOT neutral). Your 240V appliances connect across the two legs.

The correct way to deal with this is to use an isolation transformer. It would also be more efficient than using a battery charger. The isolation transformer isn't exactly cheap though, if you're going for the blue model it costs about the same as a Skylla charger, around 750 Euro.

7 minutes ago, Javi Martínez said:

Do you know a special feature?

I'm not sure. I suspect it's just because the primary target is the marine market. It has the whole NMEA2000 canbus thing built in.

[Ingo]

58 minutes ago, phil.g00 said:

You do realize that your problem was that you were trying to parallel 110Vac -E and 220Vac-E together?

Your generator casing is still earthed right, just that you are now using a two-wire connection through to the inverter?

Legal compliance is rooted in safety, your system is not inherently unsafe.

But legality is fickle, and also has geographical refinements, the internet is not the place for that advice.

 

Yes, that was the quick test under no-load. And Correct again, only a 2-Wire connection to the Inverter.

The generator chassis is not earthed at all - well... it has the centre-tap winding connected to the chassis so it's at 0V when looking at the generator itself. The house wiring is earthed to the utility earth but if someone touches the Neutral wire it will not trip the E/L (Danger!!) right?

If I connect the generator N to Utility earth then the generator chassis becomes live with 110V with reference to the Utility Earth - Hence Option 1 to keep Generator Chassis happy and have proper 0-220V on the Inverter side of the isolation transformer with no voltage on the N line.

Is my thinking correct, safety wise, Legalities aside?

[phil.g00]

If you use an isolation transformer then you can have different earth references, yes.

If you cant break the connection between the centre-tap and the gen chassis earth then you're gen chassis will be sitting 110Vac from earth and it will shock you if you are between it and actual earth.

Are you sure there is no way of isolating the chassis from the centre tap?

If there isn't then an isolating trafo is your only option.

[___]

5 minutes ago, Ingo said:

Is my thinking correct, safety wise, Legalities aside?

Yup, your thinking seems accurate. The generator body is floating, and if you earth the one leg then the generator body sits at 115V (ish).

About option 3: How much is a new generator? For the equivalent of 750 Euro  I can almost buy a nice Diesel generator.

[Ingo]

@phil.g00 The wiring diagram doesn't show the centre-tap connecting to earth, it shows it via the sealed Inverter unit inside the generator and I am not going to fiddle there. Last time I had a quick (read +2H disassemble/reassemble session) to trace wiring and it looked like a completely sealed unit.

@plonkster As I said before, all works well, no stray 110V anywhere except for the N-PE E/L safety issue I have. This generator cost me, way back when all this shenanigans started, around R18K. If I knew then what I know now I would have gone for a proper diesel one, the exact one you referenced. That said, I think they were going for R30K which was way more than the inconvenience cost of a few hours of downtime every few days or so.

[___]

There is a kind of earthing system known as TT (Terra-terra) where you don't have bonding. The RCD is still required and it still works: If you touch either side (neutral and live are at the same 115V potential) and enough current flows to ground, it still causes an imbalance and the RCD still detects it and trips. In such a system. I sorta-kinda feel like it might be okay to leave the bonding off. But then you need to earth the center point on the generator so that your two "hots" are tied to a 0V reference somewhere (in the middle in this case).

Probably best to ask an electrician to be sure, but right now I can't see why it would be a problem to temporarily convert the house to a US standard.

[Gabriel_2018]

49 minutes ago, plonkster said:

There is a kind of earthing system known as TT (Terra-terra) where you don't have bonding. The RCD is still required and it still works: If you touch either side (neutral and live are at the same 115V potential) and enough current flows to ground, it still causes an imbalance and the RCD still detects it and trips. In such a system. I sorta-kinda feel like it might be okay to leave the bonding off. But then you need to earth the center point on the generator so that your two "hots" are tied to a 0V reference somewhere (in the middle in this case).

Probably best to ask an electrician to be sure, but right now I can't see why it would be a problem to temporarily convert the house to a US standard.

Well, even he could have an IT scheme for generator and transformer, leaving tap on the "air"...

[Gabriel_2018]

Or may be, as @plonkster suggests, you can earth system on generator earth via trasfer switch when genarator runs, without transformer. The RBO would work well.

Edited January 5, 2019 by Javi Martínez

[Gabriel_2018]

1 hour ago, plonkster said:

 

I'm not sure. I suspect it's just because the primary target is the marine market. It has the whole NMEA2000 canbus thing built in.

I knew "blue wise man" would explain it!

[Ingo]

15 minutes ago, Javi Martínez said:

Or may be, as @plonkster suggests, you can earth system on generator earth via trasfer switch when genarator runs, without transformer. The RBO would work well.

That is a possible option, yes.

[phil.g00]

Well, this was a worthwhile issue to raise.

I had not considered it at all. I am still not convinced that Honda has introduced such an inflexible product, so I have emailed them for clarity.

Maybe they have, I'll report back.

[Ingo]

You all know what the next question is going to be... I'll ask in a separate thread.

[phil.g00]

This piqued my interest, and if I interpret SA regulations, any V-0-V generator is incompatible with a fixed installation. ( I think that includes with an  isolating transformer as well).

Maybe there is a jumper that can be removed between the two circled points?

 

[phil.g00]

Further reading: Sadly it seems that this point may not be accessible on a Honda.

[Ingo]

Correct. I was also looking for it when I took it apart some time ago.

[___]

Well what do you know... I am doing a bit of leisurely Sunday afternoon reading and I find it in SANS 10142-1.

[Ingo]

Back to my initial options. Is the isolation transformer enough to satisfy the requirement that the generator is not directly connected to a fixed installation?