GI

[jonathanA]

1 hour ago, Tony Brooks said:

 

Totally agree, but I wonder how many boaters actually test their GIs, let alone know how to do it.

in the case of safe shore with the status leds its as simple as connecting a 9V battery across the GI and seeing if the led lights (. They even supply a PP3 battery connector so you can do the test along with instructions on how to do it.

 

I think the bigger issue is people not appreciating the risk of the fault currents damaging the GI and testing it after a significant Overload/Over current event usually accompanied by a big blue flash and a bang !  (as opposed to an Earth leakage trip)

 

I wonder how many people with IT's actually have them correctly located  off the boat  - not many I suspect.  (yes I know the risk of a problem is limited to the cable to the IT but it is just as valid as the risk of Diode damage to GI) 

 

At the end of the day its a pays your money take your choice situation and people need to make an informed decision based on their circumstances/needs. 

[GUMPY]

1 hour ago, IanD said:

And if they do fail, they're likely to fail short-circuit which means they don't work as a GI any more...

I would have thought open circuit was more likely after a huge inrush current.

 

6 minutes ago, jonathanA said:

wonder how many people with IT's actually have them correctly located  off the boat  - not many I suspect.  (yes I know the risk of a problem is limited to the cable to the IT but it is just as valid as the risk of Diode damage to GI) 

Mine was by the supply until I changed mooring. Then it went into an HPDE case at the back of the boat 18" from the inlet and was fed with double insulated cable inside a plastic conduit. Still means there could have been a problem where the HO7 cable crossed the rear deck but it reduced the chances of a problem by a large percentage.

[PeterF]

7 minutes ago, GUMPY said:

I would have thought open circuit was more likely after a huge inrush current.

I agree, I always thought the problem was going open circuit and your hull is then no longer connected to the shore earth cable which is a safety issue should you then have a live to hull incident.

 

If they failed closed circuit then you would have no galvanic protection but still be connected to earth so not a safety issue.

[cuthound]

39 minutes ago, jonathanA said:

in the case of safe shore with the status leds its as simple as connecting a 9V battery across the GI and seeing if the led lights (. They even supply a PP3 battery connector so you can do the test along with instructions on how to do it.

 

I think the bigger issue is people not appreciating the risk of the fault currents damaging the GI and testing it after a significant Overload/Over current event usually accompanied by a big blue flash and a bang !  (as opposed to an Earth leakage trip)

 

I wonder how many people with IT's actually have them correctly located  off the boat  - not many I suspect.  (yes I know the risk of a problem is limited to the cable to the IT but it is just as valid as the risk of Diode damage to GI) 

 

At the end of the day its a pays your money take your choice situation and people need to make an informed decision based on their circumstances/needs. 

 

Not much more difficult to check any GI.

 

1. Disconnect shore lead 

 

2. Use a short length of cable to temporarily short across the incoming and out going earth connection. This discharges any filtration capacitors that maybe fitted and can affect the multimeter readings. Remove temporary cable.

 

3. Set multimeter to "diode test" function.

 

4. Connect multimeter across GI input and output terminals. Meter should show mV and rise to a bit less than a volt.

 

5. Discharge filtration capacitors as in 2.

 

6.Reverse multimeter leads and repeat 4.

 

If the readings for 4 and or 6 are  not a bit less than a volt (typically 0.7 - 0.9 volts depending on GI), then the GI is faulty and needs replacing.

 

I check mine annually and also every time there has been an electrical fault which resulted in a tripped circuit breaker.

Edited August 30, 2023 by cuthound
Missing letter

[magnetman]

45 minutes ago, jonathanA said:

 

 

I wonder how many people with IT's actually have them correctly located  off the boat  - not many I suspect.  (yes I know the risk of a problem is limited to the cable to the IT but it is just as valid as the risk of Diode damage to GI) 

 

At the end of the day its a pays your money take your choice situation and people need to make an informed decision based on their circumstances/needs. 

 

I assumed the IT would need to be remote from the boat by definition. It seems obvious although I know some mooring providers will not allow items on the pontoons. 

 

Mine has always been remote from the boat and is on the pontoon. 

 

It seems to me that having it on the boat would risk defeating the purpose of having it in the first place. 

 

 

[IanD]

1 hour ago, magnetman said:

 

I assumed the IT would need to be remote from the boat by definition. It seems obvious although I know some mooring providers will not allow items on the pontoons. 

 

Mine has always been remote from the boat and is on the pontoon. 

 

It seems to me that having it on the boat would risk defeating the purpose of having it in the first place.

 

 

I think you're confused about what the primary purpose of an isolating transformer (or galvanic isolator) on a steel-hulled boat is, which is to prevent any galvanic corrosion due to either having a non-zero potential on the incoming ground or any stray currents through the water from something nearby with earth leakage.

 

All that matters here is that the primary winding/earth (connected to shoreline) is isolated from the secondary winding/earth (connected to boat), it doesn't matter where the transformer is physically positioned.

 

If you're worried about shorts on the incoming cable (e.g. incoming earth to boat hull) then shorts on the live/neutral ought to be a much bigger concern... 😉

[magnetman]

I'm not that worried about danger to life. The boat being corroded or catching fire is far more serious than dying.

 

It just seems to me that the idea of isolating the earth should involve removing the thing from the boat. 

 

I do know how both of the devices work and why they are installed. 

 

 

[IanD]

20 minutes ago, magnetman said:

I'm not that worried about danger to life. The boat being corroded or catching fire is far more serious than dying.

 

It just seems to me that the idea of isolating the earth should involve removing the thing from the boat. 

 

I do know how both of the devices work and why they are installed. 

 

Why? The case of the IT isn't connected to the incoming (shoreline) GND, so what's the point of having it off the boat?

 

https://www.victronenergy.com/upload/documents/Datasheet-Isolation-Transformers-EN.pdf

[GUMPY]

11 minutes ago, IanD said:

Why? The case of the IT isn't connected to the incoming (shoreline) GND, so what's the point of having it off the boat?

 

https://www.victronenergy.com/upload/documents/Datasheet-Isolation-Transformers-EN.pdf

That's not a good example!

Victron have it wrong. The case and the internal screen should be connected to the incoming earth.

If the internal screen is connected to the boat side earth as Victron does it then in  the case of the primary winding shorting to screen/earth, very rare I know,  the boat could become live. MCB and RCD are there as a backstop things should be designed so that in the event of failure they fail safe and not in a dangerous way.

 

 

[IanD]

2 minutes ago, GUMPY said:

That's not a good example!

Victron have it wrong. The case and the internal screen should be connected to the incoming earth.

If the internal screen is connected to the boat side earth as Victron does it then in  the case of the primary winding shorting to screen/earth, very rare I know,  the boat could become live. MCB and RCD are there as a backstop things should be designed so that in the event of failure they fail safe and not in a dangerous way.

 

 

Regardless of whether you think Victron are right or not -- and you have to consider all possible fault mechanisms not just one -- the fact remains that there's no reason why the IT should be on shore, and several good ones why it should be on the boat... 😉

 

P.S. If you connect the case/screen to the incoming (shoreline) earth and the case has an electrical connection to the hull via mounting bolts, you've just connected the hull to the shoreline GND which defeats the entire point of an IT... 😞

Edited August 30, 2023 by IanD

[GUMPY]

Yes I know.  Yawn, that's why the one on Loddon is  in an HDPE box.

There is no good electrical reason to have the IT on the boat. I will listen if you can come up with one because neither Gibbo or I could find one.

If you care to go back through the forum Gibbo and I listed the electrical reasons it should be on the bank. Just accept for once you might not be correct on this one.

 

[jonathanA]

2 minutes ago, IanD said:

Regardless of whether you think Victron are right or not -- and you have to consider all possible fault mechanisms not just one -- the fact remains that there's no reason why the IT should be on shore, and several good ones why it should be on the boat... 😉

there are no technical reasons for having the It on the boat.  There are good technical reasons for having it on shore and thats where it should be ideally, but practically it may be easier to have it on the boat. .  As Gumpy says if you follow the victron advice (which in the IT situation, is usually accepted as being wrong) then the case will be earthed and if on the boat defeats the purpose of the IT.  If the incoming cable is damaged you could get a stray earth to hull again defeating the purpose of the IT.  Quite rightly as pointed out by someone earlier a cable fault that doesn't trip the shore bollard is unlikely and can be mitigated by careful physical installation.  

 

From a practical and security point of view many people do have their It on board and nothing necessarily wrong with that so long as they have considered the issues and made appropriate mitigations. 

 

xposted with Gumpys far more pithy response. 

[IanD]

48 minutes ago, GUMPY said:

Yes I know.  Yawn, that's why the one on Loddon is  in an HDPE box.

There is no good electrical reason to have the IT on the boat. I will listen if you can come up with one because neither Gibbo or I could find one.

If you care to go back through the forum Gibbo and I listed the electrical reasons it should be on the bank. Just accept for once you might not be correct on this one.

 

 

If you have it on the boat then it goes where the boat goes, so if you plug in somewhere away from home you're still protected and the scallies can't nick your IT off the bank... 😉

 

(if it's on shore then obviously the case should be connected to the shoreline GND, for the same reason as it should be connected to the boat GND if it's on the boat -- like in the Victron schematic)

 

It's true that a on-shore IT with case/shield GND will stop the boat potentially becoming live in the event of a winding-shield short, though as you say this is very unlikely. If you're only ever going to moor and plug in the boat in your home mooring and there is a place an IT can be secured/thiefproofed landside then that's a good idea. But it does mean if you ever go anywhere else to plug in you leave the IT behind -- and the Victron boat application is clearly aimed at boats (with an onboard IT) that go places, not ones that don't ... 😉

 

There's a balance to be made between ideal technical reasons (IT on shore preferred) and practical ones (IT on boat preferred). Neither solution is perfect, as usual both have pros and cons... 🙂

 

None of which matter to most canal boaters, who go for the much cheaper GI solution... 😉

Edited August 30, 2023 by IanD

[GUMPY]

What was your good electrical reason why the IT should be on the boat I must have missed it.

You are assuming that I said that a metal cased transformer should be bolted down in the boat, I didn't.

As for earthing the screen and case to the supply that's good electrical practice and is another reason an IT shouldn't be in the boat.

 

If you actually look at the Victron the shore earth is terminated inside and is not connected to anything.

The screen and case are connected to the boat.

1; If there is a short between the incoming live and the case the boat goes live.

2; If there is a breakdown to the internal screen the boat goes live

3; If the incoming cable gets chafed and live shorts to the hull  the boat goes live.

None of these can happen if the IT is on the bank.

Not all IT are in metal cases the Airlink one was developed after input from Gibbo and myself to try and mitigate the problems of having it on the boat, strangely its in a plastic case. However any input cable should be double insulated and enclosed in plastic conduit to mitigate the chances of point 3 above happening.

 

Kindly point out where I am wrong

 

I'm still waiting for a good electrical reason to have the IT on the boat!

 

 

 

Edited August 30, 2023 by GUMPY

[IanD]

42 minutes ago, GUMPY said:

What was your good electrical reason why the IT should be on the boat I must have missed it.

You are assuming that I said that a metal cased transformer should be bolted down in the boat, I didn't.

As for earthing the screen and case to the supply that's good electrical practice and is another reason an IT shouldn't be in the boat.

 

If you actually look at the Victron the shore earth is terminated inside and is not connected to anything.

The screen and case are connected to the boat.

1; If there is a short between the incoming live and the case the boat goes live.

2; If there is a breakdown to the internal screen the boat goes live

3; If the incoming cable gets chafed and live shorts to the hull  the boat goes live.

None of these can happen if the IT is on the bank.

Not all IT are in metal cases the Airlink one was developed after input from Gibbo and myself to try and mitigate the problems of having it on the boat, strangely its in a plastic case. However any input cable should be double insulated and enclosed in plastic conduit to mitigate the chances of point 3 above happening.

 

Kindly point out where I am wrong

 

I'm still waiting for a good electrical reason to have the IT on the boat!

 

I'm not saying you're wrong, as you'd realise if you read what I just posted... 😉

 

The reason for having the IT on the boat is to have it on the boat where it's secure and goes where the boat does, as I said this is a practical reason not an electrical one.

 

In this case if it has a metal case like the Victron ones, this should be connected to the boat GND.

 

Do you disagree?

 

If it's on shore then it should be connected to mains GND, as you say. But not many moorings have a place next to the boat where you can securely put an IT to make this practical -- and if it's secured there, what do you do when you go elsewhere to plug in?

 

TBH this is arguing about angels dancing on the head of a pin; either case is better than the GI which the vast majority of boaters use because it's much cheaper...;-)

Edited August 30, 2023 by IanD

[GUMPY]

15 minutes ago, IanD said:

In this case if it has a metal case like the Victron ones, this should be connected to the boat GND.

 

Do you disagree?

Yes 

It should be enclosed in a non conductive case.

Connecting it to the boat earth raises the possibility of a dangerous situation occurring as I said in 1 and 2 above   

Putting it bluntly anyone who designs an IT to go on the boat with a metal case is a (word removed)

Hence the Airlink one 

15 minutes ago, IanD said:

If it's on shore then it should be connected to mains GND, as you say. But not many moorings have a place next to the boat where you can securely put an IT to make this practical -- and if it secured there, what do you do when you go elsewhere to plug in?

In 30 years i think that i only plugged in maybe once or twice when away from the mooring  and then only for one night. 

I would take the minimal galvanic action that would happen over that period as an acceptable risk.

Edited August 30, 2023 by GUMPY

[magnetman]

31 minutes ago, IanD said:

I'm not saying you're wrong, as you'd realise if you read what I just posted... 😉

 

The reason for having the IT on the boat is to have it on the boat where it's secure and goes where the boat does, as I said this is a practical reason not an electrical one.

 

In this case if it has a metal case like the Victron ones, this should be connected to the boat GND.

 

Do you disagree?

 

If it's on shore then it should be connected to mains GND, as you say. But not many moorings have a place next to the boat where you can securely put an IT to make this practical -- and if it's secured there, what do you do when you go elsewhere to plug in?

 

TBH this is arguing about angels dancing on the head of a pin; either case is better than the GI which the vast majority of boaters use because it's much cheaper...;-)

My airlink IT is hardwired into the shore line so if the boat is moved from the mooring the transformer gets placed on the boat and if the boat is plugged in elsewhere the transformer gets placed on the shore/pontoon as part of the setup. 

 

I wouldn't think it that wise to have it with an outlet as it discourages you from unplugging your electric thus making it easy for anyone else to use it when you are away. 

 

In my case it is a CRT mooring bollard which has a switch on it which cuts the power if you remove the 32a plug from the bollard. 

 

I suppose some of the ITs may be heavy but the airlink is not particularly. 

 

The theft risk is there but I'm not convinced it is a high risk. 

 

Edited August 30, 2023 by magnetman
Edit to remove accidental mild sex references

[blackrose]

12 hours ago, Tracy D'arth said:

GIs are a ridiculous price when you consider what is inside, a few bucks worth of sand.  I never trust one with a monitor as I don't see how they can monitor the earth leakage with causing some of the same; albeit very small.

 

Don't they monitor conductivity through the diodes?

 

Lots of things are a ridiculous price when you consider what they are but that's the free market economy for you. One could even could make one's own GI if the expense really is that much of an issue and one's time is worth less 

[IanD]

15 hours ago, magnetman said:

My airlink IT is hardwired into the shore line so if the boat is moved from the mooring the transformer gets placed on the boat and if the boat is plugged in elsewhere the transformer gets placed on the shore/pontoon as part of the setup. 

 

I wouldn't think it that wise to have it with an outlet as it discourages you from unplugging your electric thus making it easy for anyone else to use it when you are away. 

 

In my case it is a CRT mooring bollard which has a switch on it which cuts the power if you remove the 32a plug from the bollard. 

 

I suppose some of the ITs may be heavy but the airlink is not particularly. 

 

The theft risk is there but I'm not convinced it is a high risk. 

 

So here's the Airlink equivalent of my IT.

 

https://airlinktransformers.com/product/bt7230-bt7230

 

Like the Victron it's in a metal box rated at IP23 so it can't go outside. It also weighs 45kg, which is 50% more than the Victron equivalent.

 

Not everyone has the same use case as you -- or I -- do... 😉

[magnetman]

Thats interesting. 

 

My Airlink IT is in a composite box not metal and its outdoor rated I think its IP67. Happy outdoors at all times. 

 

I'm guessing yours is rather larger given your power needs. 

 

 

 

 

[GUMPY]

12 minutes ago, IanD said:

So here's the Airlink equivalent of my IT.

 

https://airlinktransformers.com/product/bt7230-bt7230

 

Like the Victron it's in a metal box rated at IP23 so it can't go outside. It also weighs 45kg, which is 50% more than the Victron equivalent.

 

Not everyone has the same use case as you -- or I -- do... 😉

Good luck trying to find 32amp sockets to plug that in to or have you had your mooring specially wired with 32amp 😂

Normal people only have 16 amp supplies and use something like this

https://airlinktransformers.com/product/boating-transformer-bt3240

 

If you contact Airlink there is a good chance they can do it in an IP rated plastic case that is what I asked them for in 2006 that led to them producing it commercially.

One thing to note about Airlink IT (most IT are the same) is that the no load output voltage is 10volts above the incoming voltage, this gets a bit awkward when the input voltage is above 247v as it means  Combis and chargers won't always switch on due to the high voltage. If I was having another one built I would get a dual tapped primary (230, 250) to get round this problem.

[magnetman]

Ironically my mooring has a 32 amp supply but I use virtually no electrical power. 

 

 

 

 

[IanD]

1 hour ago, GUMPY said:

Good luck trying to find 32amp sockets to plug that in to or have you had your mooring specially wired with 32amp 😂

Normal people only have 16 amp supplies and use something like this

https://airlinktransformers.com/product/boating-transformer-bt3240

 

If you contact Airlink there is a good chance they can do it in an IP rated plastic case that is what I asked them for in 2006 that led to them producing it commercially.

One thing to note about Airlink IT (most IT are the same) is that the no load output voltage is 10volts above the incoming voltage, this gets a bit awkward when the input voltage is above 247v as it means  Combis and chargers won't always switch on due to the high voltage. If I was having another one built I would get a dual tapped primary (230, 250) to get round this problem.

 

It's forward planning (series hybrid, remember); most sockets are 16A today, there are a few places with 32A sockets but this may increase in the future if CART ever put charging points for electric boats in (yeah, right...) -- the inverter can charge the batteries at 7kW so for the sake of a few hundred quid it makes sense to have the IT capable of this too.

 

There's a 32A socket on the boat and I have two cables, one with 32A on both ends and one with a 16A on the shore end (which can be plugged together to make an extra-long 16A one). I know about the IT step-up, that's OK with the Victron system (wasn't with Mastervolt according to Ricky...). The IT (and all the rest of the electrics) are already in the boat... 😉

Edited August 31, 2023 by IanD

[Alan de Enfield]

24 minutes ago, IanD said:

There's a 32A socket on the boat and I have two cables, one with 32A on both ends and one with a 16A on the shore end

 

 

And, because we keep coming across 32a bollards that no one uses we have a 32a Plug (to plug in the bollard) and a 16a socket (to fit the standard lead) adapter. 

 

Yes I know its wrong, the forum keeps telling me every time I mention it.

[GUMPY]

1 hour ago, IanD said:

I know about the IT step-up, that's OK with the Victron system

Sits back sniggering. 😂

Having run Victron kit with an Airlink IT I can say that unless you set the acceptable voltage range to some excessive figure like 265v it will shut down on a regular basis if the shore voltage is above 247v. Luckily my old mooring sat at about 235v so not a problem, the last mooring varied between 235v and 250v depending on the time of day in the end I switched off the input to the Combi used the inverter gand just relied on the Solar to keep the batteries up.

I was never comfortable feeding equipment designed for 230v at 260v.

If you are not drawing full load on the IT there is a way round it but I will leave you to work out what it is😉

1 hour ago, Alan de Enfield said:

 

 

And, because we keep coming across 32a bollards that no one uses we have a 32a Plug (to plug in the bollard) and a 16a socket (to fit the standard lead) adapter. 

 

Yes I know its wrong, the forum keeps telling me every time I mention it.

Of course you have an in line  16amp MCB in the cable 🤔