Isolation Transformer - faulty?

[sailorbenji]

hi all,

Our shore-power isolation transformer is original to the boat (built 2003). It's been perfectly reliable until recently.

Around 3 weeks ago, we visited the boat (in the water) and left 2 120W tube heaters and a humidity controlled de-humidifier running on board....all was fine (they were running for 2 days or so before we left).

A recent check on the boat, found no shore-power present. Further inspection found the breaker in the isolation transformer had tripped. Attempting to re-set the breaker just resulted in it tripping again.

To try and rule out any faulty AC equipment on board, we unplugged everything, and turned off the main AC distribution RCD.

Still the breaker inside the transformer trips immediately.

I think this means either :

a) fault on the wiring from transformer to main AC distribution panel

OR

b) faulty isolation transformer.

I find the former hard to imagine, considering no changes to wiring or anything and the fact she's tied up snug in a marina.

Leaving, in my mind at least, the most likely thing to be a fault within the isolation transformer itself.....would anybody agree, or differ in opinion to that?

 

[sailorbenji]

I'm not sure with the update if anyone saw this? Any advice at all gratefully received!

 

[Alex_Blackwood]

hi all,

Our shore-power isolation transformer is original to the boat (built 2003). It's been perfectly reliable until recently.

Around 3 weeks ago, we visited the boat (in the water) and left 2 120W tube heaters and a humidity controlled de-humidifier running on board....all was fine (they were running for 2 days or so before we left).

A recent check on the boat, found no shore-power present. Further inspection found the breaker in the isolation transformer had tripped. Attempting to re-set the breaker just resulted in it tripping again.

To try and rule out any faulty AC equipment on board, we unplugged everything, and turned off the main AC distribution RCD.

Still the breaker inside the transformer trips immediately.

I think this means either :

a) fault on the wiring from transformer to main AC distribution panel

OR

b) faulty isolation transformer.

I find the former hard to imagine, considering no changes to wiring or anything and the fact she's tied up snug in a marina.

Leaving, in my mind at least, the most likely thing to be a fault within the isolation transformer itself.....would anybody agree, or differ in opinion to that?

Again, these things are difficult to give a definitive answer without seeing the system. However, as you have said that you have isolated your AC dist. by opening the RCD I would suspect that there is a fault on the transformer. I am assuming that the shore side breaker remains closed . Can you disconnect your shore supply from the shore bollard , make sure everything is Dead and then disconnect the output at the transformer. Or Disconnect the input to the AC dist. panel. Reconnect the shore supply and see if your Tx breaker still trips. That will prove it is the Tx. at fault. Make sure you know what you are doing, otherwise get professional advice. Is there any smell of burning lacquer/insulation from the Tx?

 

[William_H]

If indeed the transformer has cooked with the heater load then a close inspection inside will reveal a very dark brown smell. A sure sign of insulation failure in the transformer. ie dead. ol'will

 

[Iliade]

Or, albeit unlikely, the trip itself is faulty. Have you tried it with the shore power off?

 

[Old Harry]

https://forums.ybw.com/index.php?th...ior-lights-before-please.531896/#post-6998474

 

[Old Harry]

https://forums.ybw.com/index.php?th...ior-lights-before-please.531896/#post-6998474

 

[Graham_Wright]

Is it a simple overload breaker or does it detect earth leakage?

 

[matthewriches]

If still struggling, get it out the boat and off to someone who works with electric motors or small transformers for them to test. You could, before doing so, take it away from the boat and try in a completely different environment to see what happens just to rule out if the boat could be at fault.

What about wiring as a temp supply, bypassing the transformer? Then see what transpires.

 

[Gumpy]

Can you tell us the make and model of transformer?
Some (Airlink) use a varistor as a soft start and these have a habit of self destructing.
How electrically competant are you? I have written a detailed set of instructions for testing transformers but it does require some knowledge of how to use a meter to follow.

J

 

[sailorbenji]

Can you tell us the make and model of transformer?
Some (Airlink) use a varistor as a soft start and these have a habit of self destructing.
How electrically competant are you? I have written a detailed set of instructions for testing transformers but it does require some knowledge of how to use a meter to follow.

J

Hi I'm competent with electrics, though not formally trained, the guide would be super helpful, I'm just heading up to the boat now with meter to try and diagnose the fault.

 

[Gumpy]

Hi I'm competent with electrics, though not formally trained, the guide would be super helpful, I'm just heading up to the boat now with meter to try and diagnose the fault.

Only just seen this will send you a pm

 

[Gumpy]

sent

 

[sailorbenji]

For anyone in the future searching this, in our case it turned out that the person keeping an eye on our boat had noticed the shore-power feed had stopped at the panel.

Tracing back the fault to the isolation transformer, unfortunately I presume they'd thought there were 2 breakers.

Flicking both switches, they found only one kept tripping instantly.

The first switch was actually the 115V/230V selector...and it had been moved to 115V position in the UK, so of course the breaker was tripping.

No way I even thought about that as a potential diagnosis from afar, but lesson learned.

 

[Alex_Blackwood]

The first switch was actually the 115V/230V selector...and it had been moved to 115V position in the UK, so of course the breaker was tripping.

No way I even thought about that as a potential diagnosis from afar, but lesson learned.

Neither did any one else! As I keep saying online diagnosis of faults without seeing the system is fraught with danger especially on mains power.