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Old 25-10-2011, 07:25   #1
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Reverse Polarity - Help

On the boats electical panel the "reverse polarity" light is on both when (a) we are plugged into shorepower or (b) when we turn the invertor on.

If the reverse polarity light was only on when plugged into shore power then that might mean the problem was in the shore based power supply which would seem more easily resolved.

There has always been a faint light on the reverse polarity light which I believed was caused by the close proximity to the shore power light.

Looking at it now both lights are on but the reverse polarity light is not as bright as the shore power light or any of the other lights.

What could cause the reverse polarity light to now be on when running on the boats internal invertor. Is there a test or something I could do?

Is it possible that we could have been affected since plugging into shorepower and now have permanent damage?

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Old 25-10-2011, 07:53   #2
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Re: Reverse Polarity - Help

I will take a stab at this. It means that the neutral and hot are reversed. The lamp measures the voltage between the NEUTRAL and GROUND. It should be 0-Volts. Neutral and ground should be tied together some place.

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Old 25-10-2011, 08:03   #3
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Re: Reverse Polarity - Help

I have discovered that a poor ground will also make the reverse polarity light glow dimly. In your case, with both shore power and inverter causing the same situation, the problem is likely in the on-board wiring. You should check all the ground connections, especilally those at the inverter, since both your shore power and inverter grounds are there.
There should be no lasting problems once you have corrected the actual fault.
Good luck and let us know what you find!
Do not go where the path may lead.........
go instead where there is no path........
and leave a trail.
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Old 25-10-2011, 08:27   #4
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Re: Reverse Polarity - Help

I agree with checking all the ground connections. All the connections for that matter. An electrical system doesn't reverse it's polarity all by itself.
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Old 25-10-2011, 08:53   #5

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Re: Reverse Polarity - Help

Silvana, if you chase around a bit you'll find threads on this. Invertors and generators often do not have a true neutral separate from the ground, or have been hooked up incorrectly. Check the wiring versus the recommendations in the manuals and you'll probably find the culprit is a neutral+ground crossed, skipped, or combined someplace. Not so much a "real danger" as a "necessary compromise".
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Old 25-10-2011, 09:01   #6
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Re: Reverse Polarity - Help

We could try to help you, but wiring in OZ is upside down and backwards:

Wiring colours

The standard wiring colours in the UK are (as of 2006) the same as elsewhere in Europe, Australia, and New Zealand and follow international standard IEC 60446. This colour scheme had already been introduced for appliance flexes in the UK in the early 1970s, however the original colour scheme recommended by the IEE for fixed wiring was permitted until 2006. As a result, the international standard blue/brown scheme is as of 2006 found in most appliance flexes. In fixed wiring, the blue/brown scheme is only found in very new (post-2004) installations, and the old IEE black/red scheme is likely to be encountered in existing installations for many more decades.
Pre-1977 IEE Pre-2004 IEE Current IEC
Protective earth (PE) Green Green/yellow bi-colour Green/yellow bi-colour
Neutral (N) Black Black Blue
Single phase: Line (L)
Three phase: L1 Red Red Brown
Three phase: L2 Yellow Yellow Black
Three phase: L3 Blue Blue Grey
The standard colours in fixed wiring were harmonized in 2004 with the regulations in other European countries and the international IEC 60446 standard. For a transitional period (April 2004 – March 2006) either set of colours were allowed (but not both), provided that any changes in the colour scheme are clearly labelled. From April 2006, only the new colours should be used for any new wiring.
[edit]Other colour schemes

Cables of USA origin will have White as Neutral and Black as live. This can occur on IEC mains leads and dual 220V/110V imported equipment.
On telecommunications nominal 48V DC supplies, the live is usually -42V (flat batteries) to almost -57V(float charge), the positive power wire is thus red (the wiring providing the earth/ground connection at the power source is conventionally-coloured as often will be earth connections not intended to carry power, i.e. on older installations being green); the same principles were also applied to equipment operating at lower voltages which used non-floating power supplies. It is now unusual to encounter such wiring in a domestic installation due to the absence of power supplies for modern systems involving a separate float-charged battery and the general non-provision of backup power; such wiring in domestic premises in any case was only required for the short distances between the rectifier or power unit, battery (if any) and the device receiving the main power feed.
[edit]Potential for confusion
The colour change has been controversial and was delayed for three decades, because the colour blue which was previously used as a phase colour is now the colour for neutral, and the colour black which was previously used for neutral now indicates a phase. While confusion in identification of these conductors could be dangerous, the combinations of colours used usually resolves ambiguities. The installation of cables with the 'new' colours in an installation where the 'old' colours exist, could leave the way open for confusion; it is important in such situations that consideration is given to correct identification of the cables – with the use of marker tags if necessary. It has also been suggested that the new phase colours are difficult to distinguish in low-light conditions, but the same can be claimed for most colour combinations, including the old British phase colours.
[edit]Direct current systems
Direct current mains are now only of historical interest in the UK but they also gave rise to possible confusion because the colours used were red for positive and black for negative. With a three-wire distribution system (similar to an AC split-phase electric power system) it was possible for either positive or negative to be live, creating an additional opportunity for confusion.

Really, a lot depends on where and when your boat was wired--the reverse polarity indicator light should be wired between the neutral and ground (Protective Earth) wires on the boat. If it is glowing weakly, that probably means the protective earth is floating and not properly connected.
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Old 27-10-2011, 06:53   #7
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Re: Reverse Polarity - Help

Thanks everyone for your help and guidance - still working on it now

In Italy - coming to the end of our 6 month trip sailing around Europe. Shipping boat back to Australia - looking forward to 2 summers in one year

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