B
Bloater
Guest
Re: Shorepower
Ah, beat me to it.
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Ah, beat me to it.
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Marina power supplies
- Thread starter pheran
- Start date
Mezzanine
New member
Re: Polarity Tester
Reversed polarity within AC CIRCUITS makes no difference
as the polarity alternates 50 times a second anyway. (In Europe)
(USA different again)
Phase testers are useful for checking that the correct voltage is present and that you only have one phase present.
I would find it very surprising to find 2 phases present at a small local distribution point on a marina pontoon, that’s not to say the next distribution point further along the same pontoon is on the same phase.
Electrical equipment and supplies are dangerous and only qualified personnel should really be dealing with problems associated with electricity or its distribution equipment.
You cant see it or smell it but by god you can feel it. DC is just as dangerous as AC if not even more so.
Be careful
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Reversed polarity within AC CIRCUITS makes no difference
as the polarity alternates 50 times a second anyway. (In Europe)
(USA different again)
Phase testers are useful for checking that the correct voltage is present and that you only have one phase present.
I would find it very surprising to find 2 phases present at a small local distribution point on a marina pontoon, that’s not to say the next distribution point further along the same pontoon is on the same phase.
Electrical equipment and supplies are dangerous and only qualified personnel should really be dealing with problems associated with electricity or its distribution equipment.
You cant see it or smell it but by god you can feel it. DC is just as dangerous as AC if not even more so.
Be careful
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Mezzanine
New member
Re: Shorepower
mmmm well if you two are going to gang up on me..
You are both correct in what you say. But how many AC circuits in reality are purely resistive from a mathematical point of view?????
I don’t think at this time of the day we really want to travel this road do we????
Unfortunately it is with reluctance that I have run out of time
as I am being called for dinner.
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mmmm well if you two are going to gang up on me..
You are both correct in what you say. But how many AC circuits in reality are purely resistive from a mathematical point of view?????
I don’t think at this time of the day we really want to travel this road do we????
Unfortunately it is with reluctance that I have run out of time
as I am being called for dinner.
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pheran
New member
Without wishing to appear ungrateful........................................I'm out of here!!!
All I want to do is to oven-cook my shop-bought take-away pizza. Could I use a DIY gas blowlamp instead?/forums/images/icons/laugh.gif
<hr width=100% size=1><font color=blue>A hangover is just the Wrath of Grapes</font color=blue>
All I want to do is to oven-cook my shop-bought take-away pizza. Could I use a DIY gas blowlamp instead?/forums/images/icons/laugh.gif
<hr width=100% size=1><font color=blue>A hangover is just the Wrath of Grapes</font color=blue>
Moose
New member
No forget the blowlamp. Take a 4.5kg Calor gas bottle and chop the top off it with an axe or similar tool, take a match while holding the Pizza above the jet of gas and light the jet; hold pizza in this position for about 1second(turn over if possible to cook evenly on both sides).... Pizza Cooked!! And you will have done everyone else in the marina a favour by cooking there dinner for them/forums/images/icons/smile.gif
A little story about Marina Electricity, my Freind with a massive great Squadron left his berth (attempted to) while still "plugged in", 50 tons of boat and 1200hp managed to rip the entire power point out of the pontoon and into the water!! There was a HUGE MASSIVE great bang and a cloud of smoke rose about 50 feet into the air!! He somehow managed to trip the entire supply to the WHOLE MARINA/forums/images/icons/smile.gif and plunged it into darkness (it was evening) while the problem was sorted out by an electrician.
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El Alce
A little story about Marina Electricity, my Freind with a massive great Squadron left his berth (attempted to) while still "plugged in", 50 tons of boat and 1200hp managed to rip the entire power point out of the pontoon and into the water!! There was a HUGE MASSIVE great bang and a cloud of smoke rose about 50 feet into the air!! He somehow managed to trip the entire supply to the WHOLE MARINA/forums/images/icons/smile.gif and plunged it into darkness (it was evening) while the problem was sorted out by an electrician.
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El Alce
Alex_Blackwood
Well-known member
To answer the original question. Don't even think about it! In simple theoretical terms yes you could draw 10 amps from two 5 amp supplies in parallel IF they are from the same phase. If one supply has phase and nuetral reversed you would have a short circuit between phase and nuetral at the Y connector. If the supplies were from different phases you would get a short between phases or if one was reversed a short between both phases and nuetral. In none of the above scenarios would the marina thank you and you would be as popular as the proverbial fart in a spacesuit with the other berth holders.
There is, as a matter of interest, no way you could get 440volts from phase and nuetral supplies. You would always have a short circuit!
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There is, as a matter of interest, no way you could get 440volts from phase and nuetral supplies. You would always have a short circuit!
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IanBBA
New member
THIS IS EXTREMELY DANGEROUS!
If you unplug one plug (by accident or otherwise) the pins will be live.
Ian.
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If you unplug one plug (by accident or otherwise) the pins will be live.
Ian.
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andyball
New member
At my marina, they offer 16 amp or 32 amp supplies in the list....there are no larger "special"sockets that I've seen, so wonder how they would provide it : I'll ask next time I'm there.
But talking generally...
No way there should ever be two different phases on adjacent outlets.....hence the prominent labels on ships,large buildings etc where there's a danger of equipment on one phase being used in an area on a different phase.
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But talking generally...
No way there should ever be two different phases on adjacent outlets.....hence the prominent labels on ships,large buildings etc where there's a danger of equipment on one phase being used in an area on a different phase.
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Robin
Well-known member
Re: Polarity Tester
Useful info, I hadn't found any on the regular pontoons so assumed they had an electrician who knew how to do it, obviously not.
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Useful info, I hadn't found any on the regular pontoons so assumed they had an electrician who knew how to do it, obviously not.
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VicS
Well-known member
Re: Metering power used
I think you are wrong there in saying the power used is measured by current drawn. The meter, in your house for example, is surely a watt-hour meter. When I was at school I'm sure Physics text books explained how they worked. (We also all learnt Latin)
<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>
I think you are wrong there in saying the power used is measured by current drawn. The meter, in your house for example, is surely a watt-hour meter. When I was at school I'm sure Physics text books explained how they worked. (We also all learnt Latin)
<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>
MartinGPerry
New member
Re: Metering power used
We have a built in polarity meter on our Westerly shore power panel. Two weeks ago in Cherbourg 'some' sockets on P pontoon were showing reversed polarity.
An electrician friend on board told me this is not a problem in France, if so why do I have lights on the panel to show me when the polarity is wrong?
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We have a built in polarity meter on our Westerly shore power panel. Two weeks ago in Cherbourg 'some' sockets on P pontoon were showing reversed polarity.
An electrician friend on board told me this is not a problem in France, if so why do I have lights on the panel to show me when the polarity is wrong?
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vyv_cox
Well-known member
Re: Metering power used
I'm no electrician but this is how I see it. The word 'polarity' is incorrect. Polarity changes 50 times per second. What it shows is which of the wires is the live one. If 'polarity' is incorrect it means that the switch on your sockets is not effective in isolating the power before the appliance, as the neutral will in fact be the live one. In the vast majority of cases, where you have double-insulated appliances, there is no difference unless you go sticking metal objects in the neutral socket. Only where you use appliances that are more complex/older/need earths do you need have any concern.
Personally, I don't use anything on board that is not double insulated and earth free, so I have no concerns.
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I'm no electrician but this is how I see it. The word 'polarity' is incorrect. Polarity changes 50 times per second. What it shows is which of the wires is the live one. If 'polarity' is incorrect it means that the switch on your sockets is not effective in isolating the power before the appliance, as the neutral will in fact be the live one. In the vast majority of cases, where you have double-insulated appliances, there is no difference unless you go sticking metal objects in the neutral socket. Only where you use appliances that are more complex/older/need earths do you need have any concern.
Personally, I don't use anything on board that is not double insulated and earth free, so I have no concerns.
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Col
New member
Re: Metering power used
My Sterling charger has warnings all over it about L&N reversals causing instant damage.
<hr width=100% size=1><A target="_blank" HREF=http://www.arweb.co.uk/argallery/colspics> Cols Picture Album</A>
My Sterling charger has warnings all over it about L&N reversals causing instant damage.
<hr width=100% size=1><A target="_blank" HREF=http://www.arweb.co.uk/argallery/colspics> Cols Picture Album</A>
tome
New member
Re: Metering power used
Vyv
You're correct that the polarity changes 50 times per second except that at the power station the neutral is physically connected to earth. By the time the neutral arrives at the pontoon there will be maybe 6 or 10 V between it and ground, hence both live and neutral need to be insulated. However, you will not get a shock from touching the neutral whereas you most certainly will from the live. A polarity indicator is useful to show up such problems.
If you have a mains battery charger chances are it isn't double insulated.
I wouldn't count on marina supplies following logical (safe) phase isolation and would not ever connect to two outlets for the very good reasons given by others: potential reverse polarities, possibly connecting 2 phases together, and the fact that the second plug in the Y becomes live.
Stay safe!
Tom
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Vyv
You're correct that the polarity changes 50 times per second except that at the power station the neutral is physically connected to earth. By the time the neutral arrives at the pontoon there will be maybe 6 or 10 V between it and ground, hence both live and neutral need to be insulated. However, you will not get a shock from touching the neutral whereas you most certainly will from the live. A polarity indicator is useful to show up such problems.
If you have a mains battery charger chances are it isn't double insulated.
I wouldn't count on marina supplies following logical (safe) phase isolation and would not ever connect to two outlets for the very good reasons given by others: potential reverse polarities, possibly connecting 2 phases together, and the fact that the second plug in the Y becomes live.
Stay safe!
Tom
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andyball
New member
Re: Metering power used
if you didn't have a residual current circuit breaker....you'd be relying on fuses for two things.
1: to blow if there was too much current drawn due to a fault/too much switched on.
2:to blow if a fault meant that a live wire was touching the metal case of some piece of gear aboard, thus making the case "live" (& rather dangerous).
The "neutral" wire on many metal cased items is connected to the chassis. If the "polarity" is reversed, it'll be the "live" wire instead & the metal case will also be live, but your fuse won't blow.
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if you didn't have a residual current circuit breaker....you'd be relying on fuses for two things.
1: to blow if there was too much current drawn due to a fault/too much switched on.
2:to blow if a fault meant that a live wire was touching the metal case of some piece of gear aboard, thus making the case "live" (& rather dangerous).
The "neutral" wire on many metal cased items is connected to the chassis. If the "polarity" is reversed, it'll be the "live" wire instead & the metal case will also be live, but your fuse won't blow.
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Alex_Blackwood
Well-known member
Re: Metering power used
I am not sure, as I have never used French shore supply. However it could be that French Marinas work between phases as opposed to the British phase and nuetral. This won't make any difference to the working of your kit on board. EXCEPT! If all your switches are single pole then even with the switch OFF you will have a LIVE present at the equipment so if you are poking about you will get a belt. The plus side is that if working 220 volts between phases then if you do strap yourself across one phase to earth you will only get 110 volt (ish) shock. The bad news is that anything over 50 volts ac RMS is considered LETHAL! But 110 is not quite as lethal as 220! The other thing is that if you have RCD's in your circuit they will only be about 80% effective if connected between phases as opposed to P & N.
As I said I am not sure but it may be the reason for your P&N meter showing reversal on some sockets. If you stick a multimeter between each pin and earth and get 110 volts then you are between phases. No doubt there is someone out there who knows for certain.
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I am not sure, as I have never used French shore supply. However it could be that French Marinas work between phases as opposed to the British phase and nuetral. This won't make any difference to the working of your kit on board. EXCEPT! If all your switches are single pole then even with the switch OFF you will have a LIVE present at the equipment so if you are poking about you will get a belt. The plus side is that if working 220 volts between phases then if you do strap yourself across one phase to earth you will only get 110 volt (ish) shock. The bad news is that anything over 50 volts ac RMS is considered LETHAL! But 110 is not quite as lethal as 220! The other thing is that if you have RCD's in your circuit they will only be about 80% effective if connected between phases as opposed to P & N.
As I said I am not sure but it may be the reason for your P&N meter showing reversal on some sockets. If you stick a multimeter between each pin and earth and get 110 volts then you are between phases. No doubt there is someone out there who knows for certain.
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Birdseye
Well-known member
Re: Metering power used
i was told (but cannot vouch for the correctness) that in France what we would call the neutral and the live wires are both live , but 120 volts either side of the earth, so to speak. thus an earth to one live wire shock would be 120v and less dodgy than the 240v back here (but dont try it at home, children) - but the 2 live wires give a 240v shock.
however, the split is not exact so you sometimes get 125 volt on one side and 115 on the other - and depending on which wire has which, then your rcd either trips out or not.
as i said, i cant vouch for its correctness. i did find it worthwhile to make a simple polarity reversal tool and it always worked.
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i was told (but cannot vouch for the correctness) that in France what we would call the neutral and the live wires are both live , but 120 volts either side of the earth, so to speak. thus an earth to one live wire shock would be 120v and less dodgy than the 240v back here (but dont try it at home, children) - but the 2 live wires give a 240v shock.
however, the split is not exact so you sometimes get 125 volt on one side and 115 on the other - and depending on which wire has which, then your rcd either trips out or not.
as i said, i cant vouch for its correctness. i did find it worthwhile to make a simple polarity reversal tool and it always worked.
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