Reverse Polarity?

[RupertW]

Dont think so, I read that yours is not a lead between shore power and socket inlet to boat?

No it is a lead that I plug the shore power lead into at one end then plug the other into the boat socket inlet. I could plug it into marina outlet I suppose but suspect it's too useful and nickable.

 

[jimbaerselman]

Does an isolating transformer render mains polarity irrelevant?

 

[Lon nan Gruagach]

Does an isolating transformer render mains polarity irrelevant?

No, and yes.
No it dosent since the transformer primary will still be reversed may or may not be an issue and only under fault conditions.
Yes it does from the secondary onwards since you then have absolute control over your mains supply. Floating, centre tapped, earthed, earth neutral bond, what ever you like.
However isolating transformers are big, heavy and noisy.
A polarity sensor and a polarity fixer is by far the best way to go.
Simplest sensor is 2 neons, one green expected live to earth and one red expected neutral to earth (although plug in testers are so easy to buy then why roll your own?)
My preferred polarity fixer would be a 2 pole change over switch, being damned sure it is absolutely break before make.

 

[<152587>]

Does an isolating transformer render mains polarity irrelevant?

Absolutely, and the added bonus of separating the shore earth from the boat earth, very desirable on a metal boat.

SmartGauge website goes into depth on this subject, interesting reading. See technical info, page 2.

 

[jimbaerselman]

No, and yes.
.

I like that answer!
Your explanation was very clear. Thanks.

 

[Cariadco]

No, and yes.
No it dosent since the transformer primary will still be reversed may or may not be an issue and only under fault conditions.
Yes it does from the secondary onwards since you then have absolute control over your mains supply. Floating, centre tapped, earthed, earth neutral bond, what ever you like.
However isolating transformers are big, heavy and noisy.
A polarity sensor and a polarity fixer is by far the best way to go.
Simplest sensor is 2 neons, one green expected live to earth and one red expected neutral to earth (although plug in testers are so easy to buy then why roll your own?)
My preferred polarity fixer would be a 2 pole change over switch, being damned sure it is absolutely break before make.

Great answer.....Like it!!

 

[nigelmercier]

May I suggest to anyone considering making a neon based polarity checker that:

[1] It's pointless, they are a couple of quid, for example this one* or this one
[2] A struck neon has virtually zero resistance, therefore see [3]
[3] Suitable series resistors must be used. Calculating these for a polarity checker is not easy, therefore see [1]

* I have one of these in a blue 16A plug, handy for testing, and for finding the one power outlet that works on a Greek pontoon.

 

[sailinglegend420]

Just to throw another thought into this thread!

A glowing polarity light may not mean a "Reverse Polarity" problem unless it is glowing at full brightness?

With a voltage of 3-4 volts between the earth and neutral you will get a faint glow, 8-10v and it is bright. The voltage between Earth and Neutral should be 0v, with a Reverse Polarity it will be 240v. This problem of a dull light indicates poor wiring on the pontoon, which is very common.

 

[Lon nan Gruagach]

Just to throw another thought into this thread!

A glowing polarity light may not mean a "Reverse Polarity" problem unless it is glowing at full brightness?

With a voltage of 3-4 volts between the earth and neutral you will get a faint glow, 8-10v and it is bright. The voltage between Earth and Neutral should be 0v, with a Reverse Polarity it will be 240v. This problem of a dull light indicates poor wiring on the pontoon, which is very common.

Thats not exactly right.
In common domestic supplies the neutral and earth are bonded (probably at the sub-station). Downstream of that, due to volt drop in the neutral conductor it is always the case* that neutral is not exactly the same as earth (which really should be carrying no current at all)


* yeah yeah, if there is no load then there is no volt drop, but thats not the point.

 

[sailinglegend420]

Thats not exactly right.....
.....* yeah yeah, if there is no load then there is no volt drop, but thats not the point.

So what is the point of criticising my post which was correct. The volts between neutral and earth are so low - relative to the 240v of a reverse polarity situation - that the reverse polarity light is not on. If the wiring is not capable of carrying high currents then with increasing loads on a pontoon the Reverse Polarity light might come on. Move further down to the start of the pontoon and the light may not come on.

I always try and make helpfull comments which can't always cover ever minute detail of the problems. If you can't be helpfull and just want to make pedantic posts I suggest you go back to the Lounge.

 

[michael fesler]

I wonder if somebody could help me. On my switch panel there is an orange light, above which it says "Correct Polarity if lit". Does that mean i need to do something if it is lit, or does it mean the polarity is correct if it is lit. I am quite confused. I noticed the light on after I fitted a failsafe galvanic isolator inside the boat close to the incoming supply. Any advice much appreciated.

 

[Lon nan Gruagach]

I wonder if somebody could help me. On my switch panel there is an orange light, above which it says "Correct Polarity if lit". Does that mean i need to do something if it is lit, or does it mean the polarity is correct if it is lit. I am quite confused. I noticed the light on after I fitted a failsafe galvanic isolator inside the boat close to the incoming supply. Any advice much appreciated.

Ahh, the joys of the English language.
Dunno is the only answer. However you can find out, get one of the plug in testers and compare results.
http://www.maplin.co.uk/p/mains-socket-tester-wd53h