220v to 110 Reverse polarity ?

[Don2]

Connecting my 220v shore power using a standard 110v step down “tool” transformer I get a reverse polarity warning light. This generally indicates that there is voltage between ground and neutral. Checking the transformer I found that there is 65v between ground and neutral and this is common in step down transformers used in building sites. ( I checked 2)


My question: Is there a special transformer used for this purpose or should I not worry about the reverse polarity light?

 

[Wiggo]

Not sure I understand the question - is your boat wired for 110V i.e. a US import so you need to step down the UK 240V pontoon supply?

 

[Don2]

Yes. It is USA boat so I need to step down to 110v.

 

[Wiggo]

OK, so I'm guessing there's no earth pins on the US mains sockets. In that case, it shouldn't make any difference.

 

[jfm]

I think it's fine. IIRC much of Europe and the USA has a "live" neutral wire. In other words there is 65v between both live and earth, and between neutral and earth, to make the 110v.

I think the UK elec system is a bit unique in that there is nil volts between neutral and earth. The full 240v AC is between the live wire and earth, so it alternates between -240v and 240v.

So in other words, no problem on your boat

I have a UK boat in France and get the same "rev polarity" light becuase the Frecnh "nautral" does have a voltage difference with Earth. Another symptom is that the RCD trips if a neutral leaks to earth, not merely a live leaking to earth. But despite all that, it works just fine so I think you should have no problem

 

[Take5]

Hi,

UK "site type" transformers are what is called "Center Tapped"", this results in the 65 volts running thru earth.

You can get a UK Auto transformer which will alleviate this problem. However, Auto transformers have a big earth leakage and you will find if you have a sensitive RCD in your electrics this will keep tripping it.

The proper and most expensive option is the Isolating Transformer. But these cost close on a grand.

 

[zt260]

Look on www.airlinktransformers.com they do all the transformers for stepping up and down 220v to 110v when i brought a boat over from the states i got a transformer from them and fitted it on the boat,just then used shore power as normal.

ash

 

[Don2]

Thanks for all the help. I am on the right track now. I called airlinktransformers and they are very helpful.

 

[VicS]

[ QUOTE ]
UK "site type" transformers are what is called "Center Tapped"", this results in the 65 volts running thru earth

[/ QUOTE ] Almost right.

As you say such transformers are centre tapped and the centre tap is earthed. Earth is earth there are are no volts "running through" it but what you do have is both conductors live compared with earth to the tune of 55 volts.
You have no neutral, just two lives but at a voltage relative to earth that is not dangerous in most conditions.

 

[ccscott49]

I guess you have nothing onboard that is Herz sensitive? As UK is 230 x 50hz and US is 110 x 60hz.