Wiring in 2000w inverter

[lw395]

The impression I got when I watched the first video is that the mega was initially connected between the line and neutral on the supply side of the RCD. This will NOT cause the RCD to trip as there is no residual current flowing through the RCD. The same when the line/neutral was shorted to the "earth" (centre) tap.

It was only later in the video that the output of the RCD/MCB was shorted to earth (centre tap) or line/neutral.

If I am wrong please tell me.

There was a lot of video of totally expected behaviour to sit through, to find the bit where the Testbox connected between load side of RCD, N or L, to 'E' didn't trip the RCD.

I would suggest that the E terminal of the invertor is not a low impedance to anything resembling zero volts, so connecting the test box to it did not draw anything like 30mA from either N or L.

The fact that connecting 'E' to the incoming DC minus created an error condition on the inverter further shows that 'E' is not a centre tap.

I would speculate that the 'E' pin is some kind of protection which shuts down the inverter if it senses either L or N is shorted to it.
I.e. it's a different protection scheme to find the first fault as I alluded to in Post 56.

I'm no expert on inverters, I am not familiar with wiring regs etc in this field, this is fundamental circuit electronics, which is what I do.

 

[rogerthebodger]

The "earth" line /neutral voltage measures seem to indicate a centre tap like a centre tap transformer where the centre tap is connected to earth/ground so the now line 1 and line 2 give a balanced output

I don't think RCD's were intended to use on balanced systems where balanced systems would normally have 2 pole switching at the appliance.

The normal UK system is a single supply and a grounded neutral which allows for single pole switching and the earth line or ground spike connection allows for a return path via the earth wire connected to the metal case of the appliance or through the ground spike possibly through a person if there is on or faulty earth wire connection.

If I had a centre tap inverter where the centre tap is connected to the socket earth pin I would not use that earth but connect the earth wire (yellow/green) to the neutral pin to make it the same as a normal domestic supply setup with RCD and MCB which is what I have

 

[lw395]

The "earth" line /neutral voltage measures seem to indicate a centre tap like a centre tap transformer where the centre tap is connected to earth/ground so the now line 1 and line 2 give a balanced output .....

No they don't!

 

[lw395]

....
I don't think RCD's were intended to use on balanced systems where balanced systems would normally have 2 pole switching at the appliance.

The normal UK system is a single supply and a grounded neutral which allows for single pole switching and the earth line or ground spike connection allows for a return path via the earth wire connected to the metal case of the appliance or through the ground spike possibly through a person if there is on or faulty earth wire connection.

If I had a centre tap inverter where the centre tap is connected to the socket earth pin I would not use that earth but connect the earth wire (yellow/green) to the neutral pin to make it the same as a normal domestic supply setup with RCD and MCB which is what I have

The inverter in the video is not a simple centre-tapped inverter.
Leaving the 'E' connection at the inverter flaoting and earthing the N as you suggest is probably a valid way forwards and has the benefit of being familiar and well understood.
It's possible that in some circumstances, the strange and not-well-understood-by-us 'E' pin system of this inverter might have advantages. For instance if it was better to raise an alarm rather than shut down the system in a single fault situation. I can't see why that would be the case on a boat though, unless the inverter was powering something essential to the safety of the boat, rather than the fridge or microwave.

 

[PaulRainbow]

The inverter in the video is not a simple centre-tapped inverter.

I agree with you and so do Durite, who made the thing. They refer to it as "centre tied", whatever that might mean, most likely a bunch of caps and resistors making it look vaguely like a centre tapped device, especially if you try testing for centre cap with a digital meter, very unreliable way of doing it. As you also said earlier (and others did in the original thread) the meter readings absolutely do not show this to be centre tapped, although the video title say that it is. Even now, in post #36 of this thread, Matthew is still referring to the Durite inverter as being centre tapped.

Durite said that this doesn't need a RCD, it's internal safety devices would shut the output down faster than an RCD, should a fault occur.

You hit the nail on the head in post #58 "Either the tester is broken, the RCD is broken, or the tester is being used wrongly."

The whole exercise was doomed because of the assumption that the inverter was centre tapped, followed by a flawed test to confirm that it was, and finally, ignoring the actual readings (because it was assumed to be centre tapped).

The reason the RCD didn't trip was because the wrong tests were carried out, based on the above. I suspect that if it was connected and a fault had occurred it would have tripped. It did trip when tested across load L and line N, because this is a totally different test, it's the same test you get if you press the RDC test button.

 

[PaulRainbow]

I will just say it one more time, there is a big difference between having a portable inverter onboard and an installed one.

In general, a "portable" inverter is a "stand alone" appliance and should not be connected to the boats AC system. This could be used in a number of different applications, boats, motorhomes, caravans, tents, emergency power in any number of situations, etc, etc. It's exact use will be dependant upon the particular application to which it is being used in and the type of inverter.

An inverter that is connected to the AC systems is an "installed" inverter and is governed by the same rules as any other AC source (shore power and genset). As far as i am concerned, the only inverters that should be used in an installation are those that can be connected Neutral to Earth, that applies equally to an installed generator. All installed sources should have N-E bonded at source (shore power at the marina, genset at the genset and inverter at the inverter). All sources should be connected to a changeover device that only allows one source to be used at a time and it should be break before make.

If, as was suggested earlier in this thread, the OPs inverter were to be connected to the boats earth circuit you would have a situation (when the inverter and shore power were both on at the same time) where shore power earth, shore power neutral, inverter earth, inverter neutral and possibly -12v, were all bonded together. This is clearly not acceptable. You would have also made it a much greater risk of getting a shock if a single fault developed. If the toaster became live all you need to do is touch anything on the boat that was part of the earth circuit and you will get a severe shock, there's no RCD protection. Had it been left free of an earth connection it remains a separate, fully isolated appliance, whilst you are holding the live toaster you can merrily go around touching anything you like, provided you don't dismantle something plugged into the 2nd socket and get hold of the neutral, in which case you will get a shock.

If the inverter is kept isolated you can connect a long live wire to the inverter live, stick it in your mouth and jump overboard, you will get wet. Had you have connected the inverter to earth, you will get wet and dead. Please don't try this at home !

 

[matthewriches]

Sorry just finished working :disgust:

To the original question of earthing/grounding... A floating system (which this particular inverter would be) is only safe when being used with 1 single piece of equipment at a time (read plugged in at a time) and only if that piece of equipment is double insulated as denoted on the equipment plate). And by virtue of the manual stating it should be grounded, then it should be grounded; professionally, that is what would be done, period.

In the case of using multiple pieces of equipment at once, there is a possibility of touching (either directly or indirectly by way of a fault or misuse) both live and neutral. Result is 230V electrocution with only a plug top fuse to protect you which would be of no use for protection against life.

Other issue is for example: should you plug your 230V halogen flood light in with a fault whilst holding it and then touch the case with a fault on the AC side, again, you would be electrocuted.

You'd definitely not breakout the inverter sockets by extending them to wall sockets or extension strip leads as this could cause the same issue as 2 or more pieces of misused or damaged equipment.

So in the case of using it as a standalone isolated DC to AC power inverter, use only 1 piece of equipment at a time, as in only plug 1 piece of equipment into the inverter at any 1 time.

Although not relevant to the OP, I'll address the other stuff later but remember these were "open eyed" videos made on peoples suggestions of how to get the RCD to trip and whether it was or not actually centre tapped. It wasn't an instructional video or a how to.....

 

[PaulRainbow]

To the original question of earthing/grounding... A floating system (which this particular inverter would be) is only safe when being used with 1 single piece of equipment at a time (read plugged in at a time) and only if that piece of equipment is double insulated as denoted on the equipment plate).

That's incorrect. In the case of an AC source such that you describe, it is only one class one device and any number of class two devices (double insulated).

Although not relevant to the OP, I'll address the other stuff later but remember these were "open eyed" videos made on peoples suggestions of how to get the RCD to trip and whether it was or not actually centre tapped. It wasn't an instructional video or a how to.....

The video title says "centre tapped", you said in the video it was centre tapped, you tested the voltages between L-E and N-E and said it was centre tapped, even though the voltages didn't stack up to it being centre tapped. You still say in this thread it is centre tapped, it is not centre tapped.

 

[lw395]

Sorry just finished working :disgust:

To the original question of earthing/grounding... A floating system (which this particular inverter would be) is only safe when being used with 1 single piece of equipment at a time (read plugged in at a time) and only if that piece of equipment is double insulated as denoted on the equipment plate). And by virtue of the manual stating it should be grounded, then it should be grounded; professionally, that is what would be done, period.......

But when you grounded it to GND which happened to be DC -ve, it stopped working?

I'm aware there is a 'disconnect' between regualtions and circuit theory here. Once upon a time I worked in a lab full of scary electrical stuff, the first thing we did was disconnect earth wires. I do not advocate that for 'ordinary people' though.

 

[matthewriches]

What forum did you get your info from?

You have a damaged lead on a double insulated food blender in the galley and you're standing on it, you reach for the microwave which has a fault on the casing..... electrocution.

This is why the blue transformers used on the Underground for 230V equipment are only equipped with 1 socket so every transformer can only have 1 tool plugged in at a time.

That's incorrect. In the case of an AC source such that you describe, it is only one class one device and any number of class two devices (double insulated).

 

[superheat6k]

I will just say it one more time, there is a big difference between having a portable inverter onboard and an installed one. ...

But the OP's opening statement was that he was installing his inverter, as opposed to having a portable inverter aboard, perhaps secured in some way.

Clearly such an inverter with an earth floating somewhere between the Live and Neutral should not have its normal earth tied to the neutral, which a proper installation would require, meaning this inverter may not be suitable for use as an installed device, unless the floating earth can be dispensed with, thus allowing the ships earth to be connected to neutral upstream of the device isolator switch device.

In this regard it is different to a portable device, perhaps secured to stop it moving around, but still portable, and not otherwise 'Installed'.

 

[matthewriches]

Yes, on my Durite inverter investigation which is somewhat weird. Together on the relevant post we never came to a conclusion and I actually tried on a little cheepie from the garage and when connecting earth pin to DC negative, it made a funny noise and a haze appeared. I'll find the video.

The multimeter I was using can measure "real" voltage. All my test equipment is calibrated every 6 months for use offshore and in industrial environments with certification available for the customer to retain.

Paul - in this thread http://www.ybw.com/forums/showthread.php?500331-quot-Occasional-quot-240v/page10 post number 94, you claimed the Durite one I tested was centre tapped but Durite referred to them as centre tied. Durite suggested it'd shut down quicker than an RCD. That wasn't signified by a fault or warning light?

So what is it?? Claim the videos are comedy but I seem to remember you commenting and thanking me for "taking the time to put the tests together".


Anyway, that age old management phrase... . there are not problems, only solutions.

But when you grounded it to GND which happened to be DC -ve, it stopped working?

I'm aware there is a 'disconnect' between regualtions and circuit theory here. Once upon a time I worked in a lab full of scary electrical stuff, the first thing we did was disconnect earth wires. I do not advocate that for 'ordinary people' though.

 

[PaulRainbow]

But the OP's opening statement was that he was installing his inverter, as opposed to having a portable inverter aboard, perhaps secured in some way.

You're absolutely right, in post #1 he did say "installing", which is no doubt why Vic said what he did in post #4, which would have been perfectly correct in a "proper" installation.

I've used the word "portable" more to denote that it isn't "installed" in the sense of bolted in place an hard wired to the boats AC circuits, rather than meaning it can be moved around the boat.

Clearly such an inverter with an earth floating somewhere between the Live and Neutral should not have its normal earth tied to the neutral, which a proper installation would require, meaning this inverter may not be suitable for use as an installed device, unless the floating earth can be dispensed with, thus allowing the ships earth to be connected to neutral upstream of the device isolator switch device.

Sterling inverters, for instance, can be set to centre tap or N-E bonded, i'd consider the centre tapped version unsuitable for a fixed installation too. IMO (and most, maybe all, regulations agree, fixed AC sources must be N-E bonded at source). The N-E bond should be made at each AC source, each source is then switched by the changeover switch.

In this regard it is different to a portable device, perhaps secured to stop it moving around, but still portable, and not otherwise 'Installed'.

I think we're on the same page here. Installed is connected to the boats AC systems, portable is stand alone, even if it's actually bolted down.

 

[davethedog]

The inverter I have fitted is bolted down and has its own dedicated sockets and is not connected in any way to the main 240v AC system (shore power or generator) and is not connected to the earth either.

So all should be good.

Dtd

 

[ltcom]

Sorry just finished working :disgust:

To the original question of earthing/grounding... A floating system (which this particular inverter would be) is only safe when being used with 1 single piece of equipment at a time (read plugged in at a time) and only if that piece of equipment is double insulated as denoted on the equipment plate). And by virtue of the manual stating it should be grounded, then it should be grounded; professionally, that is what would be done, period.

In the case of using multiple pieces of equipment at once, there is a possibility of touching (either directly or indirectly by way of a fault or misuse) both live and neutral. Result is 230V electrocution with only a plug top fuse to protect you which would be of no use for protection against life.

Other issue is for example: should you plug your 230V halogen flood light in with a fault whilst holding it and then touch the case with a fault on the AC side, again, you would be electrocuted.

You'd definitely not breakout the inverter sockets by extending them to wall sockets or extension strip leads as this could cause the same issue as 2 or more pieces of misused or damaged equipment.

So in the case of using it as a standalone isolated DC to AC power inverter, use only 1 piece of equipment at a time, as in only plug 1 piece of equipment into the inverter at any 1 time.

Although not relevant to the OP, I'll address the other stuff later but remember these were "open eyed" videos made on peoples suggestions of how to get the RCD to trip and whether it was or not actually centre tapped. It wasn't an instructional video or a how to.....

As someone who may buy such an inverter one day and as a non electriacal knowledgeable person, are you saying that the inverter the OP has bought should only have one outlet? The picture shows 2 outlets but you say only ever use one at a time? I would be thinking of the unit simply being wired into the battery bank and the unit screwed to a bulkhead (what you guys are calling a "floating system" I think.
Thanks

 

[PaulRainbow]

Yes, on my Durite inverter investigation which is somewhat weird. Together on the relevant post we never came to a conclusion and I actually tried on a little cheepie from the garage and when connecting earth pin to DC negative, it made a funny noise and a haze appeared. I'll find the video.

I think this highlights the problems that can occur when trying to install centre tapped inverters. Hence my comments that only inverters that can be N-E bonded should be connected to the boats AC systems. It also highlights why i said the OP should not connect the earth terminal to the boats AC earthing circuit, his DC neg could also be connected there.

Paul - in this thread http://www.ybw.com/forums/showthread.php?500331-quot-Occasional-quot-240v/page10 post number 94, you claimed the Durite one I tested was centre tapped but Durite referred to them as centre tied. Durite suggested it'd shut down quicker than an RCD. That wasn't signified by a fault or warning light?

May have been a mix up of terminology in that post, but then i'm not really sure what "centre tied" actually means, if it doesn't mean centre tapped. Durite don't exactly publish much information here. They did say it would shut down faster than an RCD, which might suggest that particular inverter would make a good portable option (as in not part of the boats AC system, where it would be totally unsuitable, due to it's inability to have the N-E connection. No idea if there would be a warning light or not, they didn't say, i suppose if the power went off you'd know something was wrong

So what is it?? Claim the videos are comedy but I seem to remember you commenting and thanking me for "taking the time to put the tests together".

Absolutely, thanks for doing the videos, especially for posting them when things didn't go as expected. But it was you that said the thread was a comedy of errors I still extend my thanks for making them.

Anyway, that age old management phrase... . there are not problems, only solutions.

Indeed. Neither you nor i (or anyone else) can know the answer to every question when it comes to marine electrics, there are far too many pieces of equipment out there for either of us to have come across every possible combination. Sometimes we have to learn as we go and that's a part of what keeps the job interesting. Most jobs are routine, but some present a challenge and we may have to learn something new, we fit it, test it, and if all is well, we move on and have learned something.

The Durite inverter was something of a comedy, but as someone who doesn't fit Durite inverters as a rule, i certainly learned something, so thanks again :encouragement:

 

[matthewriches]

I'd not fit anything like what the OP has from a professional point of view, I'll only use or supply Victron or Mastervolt inverters. Sterling if I really really have to only because the customer wanted it but they'd have to supply it.

What the OP has fitted, does have its uses. I have something similar in my truck for Macbook charging and battery charger for power tools. Although it should be used with safety taken into consideration. Would I put one on my boat... no.

Mine has 1 socket although of course they are available with more but you pay your money and take your choice.

are you saying that the inverter the OP has bought should only have one outlet? The picture shows 2 outlets but you say only ever use one at a time? I would be thinking of the unit simply being wired into the battery bank and the unit screwed to a bulkhead (what you guys are calling a "floating system" I think.
Thanks

 

[ltcom]

I'd not fit anything like what the OP has from a professional point of view, I'll only use or supply Victron or Mastervolt inverters. Sterling if I really really have to only because the customer wanted it but they'd have to supply it.

What the OP has fitted, does have its uses. I have something similar in my truck for Macbook charging and battery charger for power tools. Although it should be used with safety taken into consideration. Would I put one on my boat... no.

Mine has 1 socket although of course they are available with more but you pay your money and take your choice.

Thanks

 

[matthewriches]

True in the case of chart plotters or a Windex or maybe a split charge relay but definitely not where mains voltage is present. Dicing with death learning on the job with that stuff

Sometimes we have to learn as we go and that's a part of what keeps the job interesting. Most jobs are routine, but some present a challenge and we may have to learn something new, we fit it, test it, and if all is well, we move on and have learned something.

Some sort of citation to justify this would be good, as it still leaves people at risk.

That's incorrect. In the case of an AC source such that you describe, it is only one class one device and any number of class two devices (double insulated).

 

[PaulRainbow]

True in the case of chart plotters or a Windex or maybe a split charge relay but definitely not where mains voltage is present. Dicing with death learning on the job with that stuff

Jesus, you don't give up, do you ? Not everyone knows everything there is to know about everything, considering you knew nothing about marine electrics just over a year ago you've done well to pick it all up :encouragement:

Some sort of citation to justify this would be good, as it still leaves people at risk.

Can't be bothered.