Reverse polarity

[bazwold]

I hope someone here can throw some light on my problem. I have an 05 Autotrail Scout which, when not in use, lives in a friend's barn where I have access to a power point for trickle charging batteries. Recently I decided to use the main hook-up lead to check everthing was working OK and, to my horror, noticed that the red 'reverse polarity' warning light was glowing brightly. At the time, the leisure batteries were both very low in power as I had forgotten to disconnect them from the system and someone told me that they could have effected the system. I have since charged the batteries fully and they are holding onto charge well - but I still have a reverse polarity light showing on the PSU unit. The strange thing is that everthing seems to be working as normal from the electric plate on the cooker to the roof-mounted air-con unit. Anybody got any ideas because I can't get any sense out of either Autotrail or Sargeant.

Many thanks in anticipation.

Bazwold

[alan k]

as I understand it just about everything will work normally, but there is a potential safety problem if one of the appliances has an internal fault.

 

See other threads where this has been discussed at length by using the search facility

 

happy camping

 

alan

[trooper]

I would check the sockets, it may be reverse polarity,normaly everything still works the same. I had a customer had lived in house over 10 years, had new kitchen built etc I went round on heating breakdown and found whole house wirered reverse at meter, only problem he had was new electronic w/machine kept failing .

 

cheers

[Clive]

You have a modern motorhome and it is equipped with an earth leakage current detecting main circuit breaker. (RCD) These breakers do this by accurately comparing the current flowing in the NEUTRAL wire with that flowing in the LIVE wire. If these currents are not almost identical (because some has flowed elswehere - like via earth back to the transformer) then the trip will operate disconnecting both LIVE and NEUTRAL connections.

 

If you have an appliance with an earth leakage fault and the Mains hookup is connected correctly then the earth leakage trip will operate when you switch on that appliances ON/OFF switch.

 

If the mains hookup is connected with reverse polarity and you have an appliance with an earth leakage fault then the trip will operate as soon as you connect your hookup irrespective of the appliances ON/OFF switch (unless its double pole switching).

 

If you have an OVERLOAD situation then the circuit breaker supplying the circuit which has the overload will open irrespective of supply polarity. If this overload is because of an earth fault then the earth leakage trip will operate anyway.

 

So, I would not worry about reverse polarity unduly as faults will get picked up one way or another. Quite possibly sooner if the polarity is reversed!.

 

 

As you know the latest Autotrails, Autocruise, Kontiki, Bessacar and Timberland motorhomes include an indicator lamp to warn of reversed mains polarity.

 

Hope that helps

 

 

[Brambles]

Baswold,

I think a point has been missed above. The fault light might not be because the polarity is wrong, but the earth in the supply socket is faulty.

It may have a fault that could be potentally dangerous if the earth supply in your van is connected to the chassis or any appliance you plug in or is connected has an earthed casing. For example the earth could be floating, and if another appliance on the same earth circuit develops a fault you could have mains on the earth connection. Your friend needs to check out his socket for a good earth as well as reverse polarity.

Jon

[Clive]

Yes Brambles you are right, the earth may be faulty in the barn. If the Sargent system needs the earth to check for reverse polarity and put on the little light then most certainly. However it will also come on in Norway irrespective of the polarity in some areas as the earth connection at the substation can be mid way between live and neutral supplies.

 

But the underlying point in my previous post was that for a real earth fault the main earth leakage circuit breaker will pick up the current unbalance between live and neutral irrespective of polarity. Even in Norway!

 

[Derek Uzzell]

A personal tale about reverse polarity and woolly thinking...

 

A few weeks ago we turn up on a French campsite for a one night stay. I select a pitch that looks stable and capable of supporting a motorhome and plug my mains-tester into one of the 4 electrical outlets on the nearest service-post. Personally, I don't care about reverse polarity, but I do like to ensure there's actually 230V power present at a service-post before parking the motorhome and, if the supply seems really 'funny', I'll look for another service-post. 3 lights happily glowing on the tester revealed that all seemed well and I parked and hooked up the 'van.

 

About 10 days later we return to the same campsite and, because the weather has turned nasty and it's blowing and raining hard (remember that March week-end?) I decide to park in a different place well away from the trees. I plug in the mains-tester and just a single (leftmost) light comes on. "That's ****** odd", I think and try another outlet. Still just the left-hand light on the tester, so I try another service-post. No difference - all the outlets produce just the leftmost illuminated light on the tester.

 

At this point two things need saying - 1) We rarely use campsites and, when we do, don't often use hook-ups and 2) I've only relatively recently needed to use reading-glasses, but I can't now read small print without them.

 

So I continue to try power-outlets, while pondering over what can have gone haywire with this campsite's power-supply since our previous visit and generally cursing my luck. Eventually I admit defeat and get back into the motorhome, moan pathetically to my wife, find my reading-glasses and examine what the small printed instructions on the mains-tester say about a single left-hand light illuminating. And, to my embarrassment, what they say is "L and N Reversed". By sheer chance, when I tested the outlet on our first visit, I must have found the only one on the campsite where the polarity matched the UK standard: all the other 230V outlets evidently had reversed polarity. I've now committed to memory what the various combinations of lights on my mains-tester mean!

[bazwold]

Thanks for all your comments - they were very much appreciated.

 

I have just collected the Scout from its barn home and am pleased to report that, having plugged into my house electrics, I now have an unlit reverse polarity warning lamp! As someone here remarked - the problem may be in the barn electric system. I shall be talking to the owner later to suggest he gets an electrian to run some checks!

Cheers,

Bazwold

[trooper]

Hi Bazwold,

Glad you are sorted

[djchapple]

This topic, which recurs very regularly, always creates a lot of different views in the range -

 

1. I'm not at all interested in safety and I will use the supply no matter how dangerous is AND I've been doing this for the last 150 years

 

to

 

2. The expert who will quote verbatim the full details in the 500 page Electrical engineering regs explaining the dangers involved.

 

Surely, as there is some danger involved with reverse polarity the easiest way out is to make a short adapter lead, that goes between the van and the ehu lead, which has either the plug or socket (not both) wired with the neutral and live reversed.

 

This way the problem can be solved in 10 seconds by inserting this adapter.

 

The main danger is when an overload current is drawn and the fuse in the plug blows. This will cut off the supply AT THAT POINT. Now as the fuse is now in the neutral lead and not the live lead the device will remain live and thus potentially very dangerous as most people will think that it is dead.

 

If there is a short to earth within the device the main control unit will trip and make the device safe.

 

Is it worth taking even the slightest risk with 230V electricity? Of course not - use an adapter lead.

[Wills Wagon]

Not quite the same as your problem but could be linked. Our 2 year old AutoTrail Cheyenne had a "burning bakellite" type smell in September but everything worked. We were sure the smell was from PSU, spoke to Sargeants as we were quite near to there depot and they asked us to take the van in and they would test PSU. Tested for 2 hours but no problem. They also said that there was nothing in the PSU to make such a smell. Two weeks later electrics went off twice and when it came back on reverse polarity light came on. Only 230 volt circuits affected, 12 volt system all OK. Pushing the PSU box caused the light to go out and all sockets tested OK. As our 2nd year service was due Brownhills gave it the once over and concluded that one of the mains input wires had come out of its connector. When we pushed the PSU box it pushed the wire into the connector and all was OK. Seemed a logical explanation and everything worked until 25 November when we lost all 230 volt power again and RCD light came on before all the mains circuits went dead. Spoke to Brownhills and they thought the PSU was faulty. Took it in 2 days later and they put a new PSU on and everything has worked fine since. I got the impression that there have been a few PSU problems because they keep spares in stock. Since then I have looked in a few 04 and 05 Autotrails and yes they have 2007 PSU's so there has been aproblem. Sorry to be long winded but you have all the info now. Perhaps your wires are loose like ours or the PSU is on its way out.