isolating transformer

[jddevel]

Even more questions for the knowledgeable ones. Looking at Isolating Transformers without wading through a load of technical bumf most of which will go over my head if a IT is the way to go -funds allowing- rather than a galvanic isolator why is there such a wide range size wise available. Are they directly aimed at your likely usage when attached to a landline? Plus do they protect you from faults from other vessels. Finally if usage when attached to a landline is limited to maybe charging and the odd kettle is a IT necessary at all?

[Chewbacka]

It's all about risk management.   I am  very rarely on shore power, literally just an hour or two per year, so for me a GI is fine as in that limited time not much will corrode.  However if I was on shore power a lot - say most of the winter - then I would fit an IT.  In answer to your final sentence, it is not dependant upon the amount of power use, but the length of time plugged in to shore power even if using very little power.  

[jddevel]

So why do they seem to vary so in size/capacity/cost? Would a small inexpensive one do?

[jonathanA]

Yes if you want to run small low power stuff. The bigger capacity ones need more /thicker copper wire and therefore cost more. A bit of an over simplification but you get the idea.

If your use is limited or your not sure what power ( size) you need the why not buy a galvanic isolator. They both do the job there is no dispute about that.

 

 

[nicknorman]

Bear in mind that a fundamental difference between a GI and an IT is that with the former, no power passes through it (except briefly, under fault conditions) whereas with an IT, all the power you are using passes through it and thus it must be rated for the maximum current you could take, normally 16A for a standard inland shore supply.

If you want to fit a smaller IT, be sure it's protected by an appropriately rated breaker.

[tomsk]

1 hour ago, nicknorman said:

Bear in mind that a fundamental difference between a GI and an IT is that with the former, no power passes through it (except briefly, under fault conditions) whereas with an IT, all the power you are using passes through it and thus it must be rated for the maximum current you could take, normally 16A for a standard inland shore supply.

If you want to fit a smaller IT, be sure it's protected by an appropriately rated breaker.

Wise words.

[Neil Smith]

If you fit a gi make sure it has lights that show when there is a fault as some don't so you will not know until you dry dock for blacking, then to late.

Neil

[jddevel]

 Thank you all. From that information GI is all I need at  current anticipated usage.

[Tony Brooks]

38 minutes ago, Neil Smith said:

If you fit a gi make sure it has lights that show when there is a fault as some don't so you will not know until you dry dock for blacking, then to late.

Neil

This ^^^

8 hours ago, jonathanA said:

If your use is limited or your not sure what power ( size) you need the why not buy a galvanic isolator. They both do the job there is no dispute about that.

 

Kind of gives the lie to the statement. A GI can and will conduct under certain condition, often external to the boat, so needs very regular monitoring. An IT can not and will not conduct on the earth circuit because there is no earth connection.

Edited April 29, 2017 by Tony Brooks

[jddevel]

 

59 minutes ago, Tony Brooks said:

An IT can not and will not conduct on the earth circuit because there is no earth connection

There seems a very wide range of products and prices on offer. Cynically do they all do the job or do I just dig deep and buy an expensive one. As stated seems monitoring your GI and being aware is the more responsible way.

[Robbo]

1 hour ago, jddevel said:

 

There seems a very wide range of products and prices on offer. Cynically do they all do the job or do I just dig deep and buy an expensive one. As stated seems monitoring your GI and being aware is the more responsible way.

You need one that is big enough to power the items you have on all at the same time, usually a good one to go for is the 3.6kw ones here https://airlinktransformers.com/category/boating-transformers as that will be big enough for the 16amp connection most boats have and shore power points provide.  The BT3231, BT3252 look promising.  

 

From Victron the 3600watt one ; https://www.victronenergy.com/upload/documents/Datasheet-Isolation-Transformers-EN.pdf.  You don't need the auto 3600watt unless going to 120v country's.

if you know that your not going to use the full 16amp shore connection you can go for smaller 2000 watt ones (but most kettles are 3000watt)   If your on a 32amp shore connection then the 7000 watt ones is needed if you use it.

Edited April 29, 2017 by Robbo

[WotEver]

1 hour ago, Robbo said:

usually a good one to go for is the 3.6kw ones here https://airlinktransformers.com/category/boating-transformers 

The Airlink is the one that I always point to. Specifically this one: https://airlinktransformers.com/product/boating-transformer-bt3231

[rusty69]

Are  these IT silent, or do they produce a continual hum? 

[Robbo]

1 minute ago, rusty69 said:

Are  these IT silent, or do they produce a continual hum? 

They do hum when heavily used, bit like a inverter.

Edited April 29, 2017 by Robbo

[rusty69]

Just now, Robbo said:

They do hum when heavily used, bit like a inverter.

Thanks. Not too intrusive then? 

[Robbo]

Just now, rusty69 said:

Thanks. Not too intrusive then? 

You wouldn't put it next to your bed or in the same room as where you do your living.

[rusty69]

Just now, Robbo said:

You wouldn't put it next to your bed or in the same room as where you do your living.

Damn! I sleep above the engine with the batteries! 

[Robbo]

1 minute ago, rusty69 said:

Damn! I sleep above the engine with the batteries! 

Don't you have a missus?  Does she know you sleep with the batteries? :-)

3 minutes ago, rusty69 said:

Damn! I sleep above the engine with the batteries! 

Note I have the Victron which may hum more than the Airlink, and only when really been heavly used, anyone with a Airlink can confirm it's huminess.

[rusty69]

7 minutes ago, Robbo said:

Don't you have a missus?  Does she know you sleep with the batteries? :-)

Note I have the Victron which may hum more than the Airlink, and only when really been heavly used, anyone with a Airlink can confirm it's huminess.

Of course how else would we keep them warm. 

[BruceinSanity]

We have the Airlink, very pleased with it. We use it externally, hiding it away when cruising (it's in the same type of case as a 230 -> 110 site transformer, so waterproof). I put three carpet tiles under it to prevent hum transmitting through the deckplates, otherwise it's pretty well silent.

As I've said before, the other big advantage of an IT is that any faults stay in the boat, good when sharing a power bollard and it starts tripping. You can put your hand on your heart and say "not me, guv!"

[jddevel]

Now I`m understanding a bit more about the ITs. and if my understanding is correct as they sort of guarantee no galvanic corrosion I`m a mind to buy one of those and forget the application of Zinga. The Zinga was going to be applied as an additional protection against galvanic corrosion. If my interpretation of the facts is correct it`s price wise a no brainer. Better to have the boat out every couple of years to inspect and black anyway even if it`s just to see what`s going on. Have I interpreted correctly please?

[Robbo]

I would zinga it IMHO.

[Tony Brooks]

10 minutes ago, jddevel said:

Now I`m understanding a bit more about the ITs. and if my understanding is correct as they sort of guarantee no galvanic corrosion I`m a mind to buy one of those and forget the application of Zinga. The Zinga was going to be applied as an additional protection against galvanic corrosion. If my interpretation of the facts is correct it`s price wise a no brainer. Better to have the boat out every couple of years to inspect and black anyway even if it`s just to see what`s going on. Have I interpreted correctly please?

As far as the IT goes then probably but as for galvanic corrosion I rather think probably not.

Galvanic corrosion takes place when two differing metals are immersed in an electrolyte (canal water). The steel of the hull is not of a uniform alloy so there are differing metals all over it, plus the welds, prop, shaft etc. This is different to the active corrosion an IT should stop. Anodes are fitted to try to combat galvanic corrosion but their sphere of influence is very much less than many believe. I have seen 6ft quoted so the centre of most hulls is not protected. The Zinga shoudl go some way address that but I am less sure it is value for money if you are going to have the boat out every couple of years.

[jddevel]

Thank you Tony. As I said it appears to make sense to have the boat out every couple of years anyway even if it`s to see "what`s going on". Still toying with the idea of additional anodes along the waterline attached with magnets. I realize lock sides may "remove these but suitably located fenders should help except in the ultra narrow ones.

[WotEver]

21 minutes ago, jddevel said:

Now I`m understanding a bit more about the ITs. and if my understanding is correct as they sort of guarantee no galvanic corrosion...

No, they guarantee no 'Stray Current' Corrosion. Galvanic Corrosion, as Tony B explains above, is entirely different. 

I wish that Stray Current Corrosion wasn't referred to everywhere as Galvanic Corrosion because it isn't. A Galvanic Isolator has nothing to do with galvanic Corrosion.