Perfect Polarity

[WatsonJohnG]

Just back from reading the mag and was very interested in the article "Perfect Polarity"

Nothing is new under the sun and I had until it died last year used a reverse polarity switch made by Crusader I think.Not quite as sophisticated but basically the same

This worked well for over 10 years on different vans and usually ensured that having got the facility to change over then the polarity would be right in the first place.

When I fitted mine I fitted it as near as possible to the inlet rather than as in the article near to the consumer unit.

In the last van I was able to fit it in a locker next to the inlet with the warning light visible by the mains plug.

Thus it was possible to change polarity without going into the van and there was no need to open up the consumer unit to install it.

 

[Lutz]

I would have thought that it shouldn't require rocket science to develop a device that could be plugged between the mains cable and the incoming power socket just ahead of the fusebox and which automatically detected polarity of a mains connection and then automatically reversed the polarity, if necessary. I'm not an electronics expert myself so I wouldn't know how to go about it but perhaps someone who is might have a bash at the idea. Who, knows, perhaps there's money to be made in offering such an item as an accessory on the market.

 

[Dave Football]

Lutz, I reckon you're right and that it wouldn't be difficult to make an automatic polarity changeover unit, but one of the best things about the one from Boat Owners Catalogue is the simplicity of it. As soon as it gets more complex, it gets more expensive. And if my experience is anything to go by, more likely to go wonky when it's needed...

 

[WatsonJohnG]

Even with such a device its still a good idea to use a polarity tester (Martindale) as this shows any faults in the connections to the plug and socket on the hook up lead.

They get quite a hard life on the ground etc .

I have found earth leads etc pulled out and always have the tester plugged in when leaving home so that a safety check of the cable and installation is easily made on arrival at site

After the way my change over switch melted the screw up connectors I think that I will stick with the reverse polarity lead in future.

 

[Lutz]

Actually, I was thinking of plugging it in between the hook-up lead and the caravan, John.

 

[WatsonJohnG]

Seems like we agree on something Lutz

Regards

 

[Jenks1]

Sorry if I'm a bit late following up here, but I'm a slow reader ;-) I've not handled the unit "in the flesh", but from the photos in PC, the changeover function appears to be performed by a simple rocker switch with no relay. Is it likely that a double pole rocker switch can handle 16 amps for any length of time? That's a lot of heat... Anyone got one for comment?

 

[rob_jax]

Hi,

16 amps will only generate heat if there is resistance in the line - no resistance, no heat.

A correctly rated mains double pole switch or relay should easily handle this level of current.

If the device has some auto-switching electronics, then those my get warm - but the switch should stay cool.

Robert

 

[DeliDave]

i use a wind out reel from screwfix with two sockets one wired for each polarity then a short lead into van you must unwind the lead but its tidy to store and cost about

 

[WatsonJohnG]

My change over unit had no electronics but just a red neon to indicate reverse polarity.

It worked fine for 10+ years but on changing the van at the beginning of this year I was surprised to find that the plastic on the screw up terminals had melted although the unit was still working and we had had no problems with the van electrics or any indication of a "fault"on the Martindale.