Jump to content

polarity changer


ALcamp

Recommended Posts

I have seen auto ones but years ago. I thought under IEE regs polarity changers are technically illegal.

IEE regs state clearly how electrical points should be wired if it is then possible to reverse that wiring I don't see how it can be legal. For the same reason you will not find any commercially made polarity reversed adaptors.

 

If you are worried about reverse polarity why not just change your sockets to double pole switched or unswitched ones.

 

Dave,

If you fitted a polarity change over & the customer had an injury do to the polarity being incorrect could you be held liable?

Years ago when I worked for W4 I refused to consider making them for this reason.

 

 

 

Link to comment
Share on other sites

Although GOOGLE-ing indicates (or appears to indicate!) that there are patents for automatic polarity reversing devices, there seems to be no evidence that they are commercially available nowadays. All I found were links to manual 'switches' like the one shown on the following website:

 

http://www.riverswayleisure.co.uk/acatalog/30600.html

 

As lennyhb says, there are work-around ploys, but installing a polarity reversing device will be the simplest and most fail-safe approach as it addresses the (perceived) problem at source.

 

Link to comment
Share on other sites

"Dave,

If you fitted a polarity change over & the customer had an injury do to the polarity being incorrect could you be held liable?"

 

I don't see any reason why I could be held responsible. The polarity changeover unit has an audible warning of reversed polarity as well as different coloured LEDS for correct or reversed polarity. I provide all users with clear instructions on how to use the unit both in written and verbal forms with a demonstration. The unit also warns of no earth situations which are potentially more dangerous.

 

If a user ignores all this and manages to injure themselves because of a reversed polarity situation (which in itself is extremely unlikely) then the problem is entirely theirs.

 

As for whether or not reversed polarity is dangerous, well why do we insist on wiring electrical plugs correctly if it wasn't important? :D

 

D.

Link to comment
Share on other sites

I would never wish to own a manual power changer, its so easy to carry an additional reverse polarity device. All that is needed is a short stub of a connection say about 1 foot from the source to your normal long connection.

 

The continental connection pins are a different shape anyway, if that's what you had in mind.

Link to comment
Share on other sites

davenewell@home - 2010-02-13 2:19 PM

 

"Dave,

If you fitted a polarity change over & the customer had an injury do to the polarity being incorrect could you be held liable?"

 

I don't see any reason why I could be held responsible. The polarity changeover unit has an audible warning of reversed polarity as well as different coloured LEDS for correct or reversed polarity. I provide all users with clear instructions on how to use the unit both in written and verbal forms with a demonstration. The unit also warns of no earth situations which are potentially more dangerous.

 

If a user ignores all this and manages to injure themselves because of a reversed polarity situation (which in itself is extremely unlikely) then the problem is entirely theirs.

 

As for whether or not reversed polarity is dangerous, well why do we insist on wiring electrical plugs correctly if it wasn't important? :D

 

D.

 

Dave,

 

I am just concerned with this modern attitude of sue anyone over anything, that if there was a problem I don't think your liability insurance would pay up as the wiring would contravene the IEE Regs.

 

It is only with UK wiring that polarity is important other countries use double pole MCB' & switches.

 

 

Link to comment
Share on other sites

I don't believe this unit does contravene the regs as its purpose is to correct wrong polarity and warn both by audible and visual means of reversed polarity and/or no earth situations. If I was concerned about being sued over things like this then I'd never fit anything, how about cruise control for example. Some mindless eejit sets the CC and heads into the back for a coffee and his van is written off so he sues me because I fitted the CC for him? I know the Winnebago story is an urban myth but I think you get my point.

 

D.

Link to comment
Share on other sites

lennyhb - 2010-02-13 3:52 PM

 

 

Dave,

 

I am just concerned with this modern attitude of sue anyone over anything, that if there was a problem I don't think your liability insurance would pay up as the wiring would contravene the IEE Regs.

 

It is only with UK wiring that polarity is important other countries use double pole MCB' & switches.

 

 

I can understand the concern, but I assume that Dave would follow the manufactures instructions for installation, Red wire to the L , earth to earth, Etc, So how could he be liable ?

 

Rgds

Link to comment
Share on other sites

No one is doubting Dave's capabilities it's the idiot end user despite all the warnings could switch to the incorrect polarity. Most of the time it would not cause any problems.

 

From a personal point of view polarity is not a concern to me as my van has unswitched sockets & I think anything I am likely to plug in is double insulated.

 

 

 

 

Link to comment
Share on other sites

lennyhb - 2010-02-13 9:19 PM

 

...it's the idiot end user despite all the warnings could switch to the incorrect polarity...

 

If I were an "idiot end user" and had any inkling of my technical-knowledge shortcomings, I'm sure I'd prefer to get a professional like Dave to install a polarity-swapping switch in my motorhome, rather than attempt the daunting task of creating a change-over power-cable adapter myself. On the other hand, perhaps such a hypothetical dope might think reverse polarity was an unusual Eastern European marital practice. ;-)

Link to comment
Share on other sites

The starting point, before worrying too much about reversed polarity, is to understand how the van is actually wired.  Ours, rather like Lenny's, is polarity neutral.  That is to say it is wired to mainland German standards, for sale in Germany.  It has double pole MCBs, and an RCD main switch.  All sockets are unswitched.  It is designed to allow the power to "flow" in either direction through its system, while providing equal protection of circuits and people whatever may be served up.  I understand that some UK manufactured vans now adopt this principle, and for these, a reversed polarity supply should not be a safety issue.

If the more normal UK practise of installing SP MCBs (only in the "live" circuits), with SP switched socket outlets, has been adopted, then the reversed polarity "live" supply will by-pass the SP MCBs in the main panel, and the socket outlet switch, to give an unprotected live feed where the neutral should be.  This means that the live circuits are devoid of overload protection right up to any connected appliance.  That does contravene what IEE says, but is a supply and not a wiring fault, which IEE does not, to my knowledge address.  If it did, I suspect, following their logic, they would call for the supply fault to be remedied. 

I am told that most modern appliances sold on the UK market now have DP on-off switches so that, even with internal faults, they will be "safe" when plugged in and that a risk will not arise until actually switched "on".  Most, so far as I know virtually all, are also double insulated, so the safety risk in normal use should be pretty much eliminated. 

The main residual risk, given an RCD main switch, would be fire from overload of an unprotected "live" circuit where the MCB (now on the "neutral" feed) did not trip in response.  I guess this would be possible if a low amperage circuit had become bridged onto a higher amperage circuit inside the main panel, so that the "live" feed was up the lighter cable, but was returning via a heavier duty MCB intended to protect a heavier cable.  In the absence of a RCD main switch, a similar fault could arise if the circuit bridged to earth, but most site feeders also now have RCD on them, so the supply should disconnect at source rather than at the van.  The terminals inside most mains panels are well shrouded, and it is very difficult to see how a loose wire, possibly loosened by vibration while travelling, might actually contact properly clamped wires on other circuits.  The other possibility is a wiring error on assembly.  Both are possible, but relatively unlikely, and would need to occur in conjunction with some other fault to cause a real problem.  So, a very low risk, but with potentially nasty consequences.

The upshot is that it seems to me only worth worrying (slightly! :-)) over reversed polarity if the installation in the van is based on UK standard SP MCBs in the main panel.  Of greater concern, is that there should be an RCD main switch.  Under these circumstances there is a small benefit to safety from correcting polarity, so that things are working as designed.

On the other hand, if the wiring is of "continental" type, with DP MCBs, and an RCD main switch, it is really of no consequence how polarity is arranged and not worth trying to correct it.  At any rate, that is my take on the subject!

Link to comment
Share on other sites

Archived

This topic is now archived and is closed to further replies.

×
×
  • Create New...