Marina power supplies

[pheran]

Many thanks to everyone who responded to my anti-freeze question. Now for my next one, which on reflection, sounds a bit naive, but I suppose they are all easy if you know the answer!

Many marina power supplies, especially those abroad, are limited to around 5 amps which is often not enough for our needs. If I make up a Y-shaped adapter to connect my shore power supply cable to two separate sockets simultaneously, will the current draw be automatically be shared between the two, giving me 10 amps and avoiding tripping out the curcuit breakers.

Thanks in advance

<hr width=100% size=1><font color=blue>A hangover is just the Wrath of Grapes</font color=blue>

 

[Robin]

This does work I believe if done correctly, which is difficult to do whilst keeping everything properly waterproof. However this can be thought of as socket hogging in a busy visitors marina and is a sure way of sparking off a stinkie v raggie incident!

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[Robin]

PS

I am not sure how this could be done without some risk, with only one arm of the Y plugged in, the other (plug) will be 220v live and therefore very dangerous. Expert electrical advice is required!

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[vyv_cox]

What are you running that needs more than 5 Amps? Our biggest consumer is the immersion heater in the calorifier which, from memory, is rated at 850 Watts. I have run this on a supply that was nominally 2 Amps and we didn't blow any breakers.

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[ParaHandy]

now you're being silly .... how do you know that the polarity (live to live & neutral to neutral) of both connections are identical?

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[Abigail]

Couple of points- some marinas don't allow you to have two sockets (Brighton won't for instance) - even if you only want one temporarily to plug in a lead for using power tools on the pontoon. Secondly I just read an horrific account of a fire in a US marina caused by bad AC shoreline connections.

Maybe easier to get good solar and/or wind to cut down on the need for (paid for) shore power

<hr width=100% size=1>Sarah&Pip

 

[pheran]

Thanks for your responses

ParaHandy - because I would plug in my polarity tester first. Every boat should
have one, particularly when visiting parts of France. I also carry a
simple polarity reverser.

Robin - regarding your PS. Oooppps, hadn't thought of the dangling plug
angle. Just shows the value of asking questions.

vyv-cox - a small electric oven rated at 2100 watts ie around 9 amps @230V

I take the point about socket availability and clearly there would need to be spares. Far from wishing to be anti-social in this respect, my aim was to avoid neighbouring boats having to sit there listening to my generator running. But...the safety issues do weigh heavy with me. Grateful for any other thoughts.

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[Robin]

Polarity Tester

Hear hear about using these, cost about £10 +/- from Homebase and the like for the basic one, fancy jobbers that can correct the error are about £30 I believe but not sure who from, saw one on another boat. Actualy the French have improved their electrics a little since they moved to the blue plug/socket system same as ours, I cannot remember seeing a polarity error on the new ones.

The normal French supply runs our immersion 1200w + battery charger at the same time without a problem. It sometimes runs the fan heater at 2000w OK, sometimes it will eventually trip but 1000w on the fan heater is no problem.



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[Forty_Two]

Re: Polarity Tester

I have found Live-Neutral polarity reversed Euro blue sockets in St Malo (2000) and four weeks ago in Nice (varied across sockets on the same box).

Using two sockets paralled to one shore-line would be disasterous if the sockets used were on different phases - as does happen to spread the loads evenly. Voltage across phases can be 440v!

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[davel]

Don't do it !
If the sockets you choose happen to be on different phases you'll end up with a voltage of over 400 volts across your appliances.


<hr width=100% size=1>Dave L.

 

[Paulka]

Basically, yes.
But the fuses, or CB will blow immediately, possibly up to the distribution transformer.

Thus, don't do it!

Paul

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[Evadne]

Good grief

I can't believe that the average marina installer is going to run two separate phases down the same pontoon. The average urban street runs off the same phase from the substation. Mind you, it would be interesting to see what happened if they did...

BTW, I know I'm getting on a bit (43), but am I alone in finding that phrases like "plugging the boat into the the mains" or "feeding the GPS into the laptop/PDA for primary navigation" are so far outside my experience of sailing as to be incredible? I know it takes all sorts, and it would be boring if we were all the same, and of course apologies to StinkieOwners who find this sort of behaviour normal but I have trouble keeping the nav. lights working from one season to the next, let alone a data bus or Serious Current interface like a mains plug. If it doesn't corrode internally, it falls off.
Maybe its like marriage, and what I need is a boat of less than half my age to keep up with the times instead of the older, more reliable model I currently consort with, but I hope not. (Fortunately SWMBO doesn't browse this forum).


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[Bloater]

Shorepower

Marinas do frequently run 3 phases down the pontoons. You should never try to connect two of them together just in case. The marina would certainly have a rule against this practice anyway.

Electricity takes the path of least resistance, therefore if you do connect two MCBs up in parallel you will get more current out than a single MCB, however it will be somewhere between double and nothing extra at all. If you are pulling more than the rating for a single MCB, then the supply could trip at any time.

Also just to confuse things, the nearer you are to the power source, the less the voltage drop and the less current that you will draw for the same power output - therefore less likely to trip the MCB.

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[pheran]

Well......................................it was only an idea ...............and probably a pretty daft one at that!! Thanks to everyone for coming to my protection.

<hr width=100% size=1><font color=blue>A hangover is just the Wrath of Grapes</font color=blue>

 

[Evadne]

Re: Shorepower

I stand corrected. Thanks.


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[Mezzanine]

Re: Shorepower

Yes i am confused, Forgive me if i am wrong or have picked up the wrong end of the stick.

But as far as I remember Less voltage = more current, More voltage = less current

Shown

P=VxI
V=P/I
I=P/V

EG a 1kw heater at 240volts ac = amps?

I= 1000/240

I= 4.1 amps

Reduce the voltage

I= 1000/220

I= 4.5 amps

Increase the voltage

I= 1000/260

I= 3.8 amps

This is a rather simple formula and dosnt take into concideration many other anomilies which can affect AC circuits dependent on the type or equipment providing the load,

But I think I might be correct.......

If the original poster wants more power it should be only a matter of requestingfrom the marina that the breaker be upgraded for your supply say 10 amp MCB. the plugs used are rated at 16 amps and provided that his cable is of sufficiant size (minimum 2.5mm2 ( 4mm2 would be better))then there should be no problem.

I hope this is of some use



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[Col]

Re: Polarity Tester

Cherbourg holding pontoon ( the one you have to dinghy to / from ) was revesed 2 weeks back when I was there.

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[charles_reed]

If you're talking about the French 5 amp plug (fortunately only found in older installations) you'll find the trip will take up to 7.5 amps.

What I usually do is to run 2 lines into the boat and have one for the "heavy" user (the fan heater) and the other for computer/electric kettle/charger.

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[Evadne]

Re: Shorepower

Don't forget that the resistance of a device usually stays constant, so if you reduce the voltage applied to it you reduce the power. 1kW means maximum power or the power drawn at the rated voltage (P = current x voltage = v-squared / resistance).
e.g. a 1kW 240V device has a resistance of 57.6 ohms, apply 110 volts to it and you draw 1.9 Amps instead of 4.2 Amps which is 209 Watts.
Calcs for AC supplies are transposable as long as you use RMS values.

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[Bloater]

Re: Shorepower

This is going to open a can of worms...

Yes Mezzanine, you are sort of right, but it all depends...

All those equations you correctly show do not take into account that for a resistive load the resistance is fixed and hence when the voltage drops, then so does the current, and the power absorbed is therefore not constant.

Therefore for resistive loads, when the voltage drops, the current drops in proportion, however as P=I x I x R, then the power absorbed will be reduced by a squared factor.

Think about it, if we apply 110v to a 220v appliance, eg a kettle, then it will take 4 times as long to boil.

The annoying thing is that we pay for electricity which is priced in KWh, but is metered from the current drawn, not the actual power used. Any marina that has a big voltage drop is costing us money.

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