Shore power testing is there a good device out there?

Hurricane

Hurricane

Well-Known Member
Joined
11 Nov 2005
Messages
9,854
Location
Sant Carles de la Ràpita
Visit site
It's amazing how bad electrical supplies are at marinas.

Having had problems in the past, I always now check a shore supply before plugging in.

Recently, we were given (had to rent) a connector at a marina that picked off one of the three pase supply using a prewired short length of flex that we were supposed to connect onto. I always keep spare connectors so connected up and got some very strange readings from my multimeter. After a lot of fiddling around, it turned out that the flex had been previously overloaded and some of the cables were fused together.

On a recent trip up the Spanish coast, we tested the shore supply before connecting - in three days, we used three different marinas with three different polarities of shore supply.

I use a cheap multimeter and check that I there is 230v between Line and Neutral - 230v between Line and Ground (Earth) - and very little voltage between Neutral and Ground. This technique also spots any pahse to phase problems - yep - been there - had one of those as well!!!

Testing is a bit of a pain. I usually check the supply at the (boat's) end of my own leads so it means holding the sprung flap open and shoving the multimeter's probes in - they often dont make very good connection.

So, I wondered if there was anything out there that tests the supply thoroughly. There are lots of plug in ring main testers but most of them dont say what they actually testing for. And those that do say, dont seem to test for earth polarity reversal.

Our boat does have a couple of neons connected to check the line and neutral voltage polarity but thats all.

I'm tempted to make a little box with three voltmeters but it does seem a bit overkill.

Does anyone have any good solutions?
 
The martindale testers are probably as good as you can get.

If you have 32A shorepower, just change the plug for a 32A type.

If you want to continue using the multimeter, make up a box with 3 4mm test sockets, live, neutral & earth (same type of sockets as the multimeter) connected to a short shorepower lead.

The neons fitted to most mains panels, should be before the main breaker, so you can check for reversed live & neutral before powering the boat up.
 
You could use a cheap voltmeter, such as this one :

http://cgi.ebay.co.uk/85L1-AC-0-500..._Measurement_Equipment_ET&hash=item33661307a0

One meter and a changeover switch, or three meters. Either way, include an on/off switch.

If you fit an LED across the live and neutral, the wrong polarity, it will light up if the L/N are reversed. Or you could fit two, one wired the correct way, the other the wrong way, when you plug in, if the correct LED is lit, press the switch to check the voltage.
 
John100156 said:
Try one of these from RS Components:-

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0253535

I have the 13A type in my Panole - look at the following to see indicators:-

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=7161073
Click to expand...

Thanks John
But it seems to me that these devices only check polarity - I've had two cases now where a supply has been offered with the L and N across two phases.
If I had a box with three meters (or a box with a meter and a switch), I think it would check everything. Certainly as good as the procedure that I use now.

PaulGouch
Thanks - I did a search for cheap voltmeters but didnt find any as cheap or suitable at those.
Not sure I like the changover switch idea. I know you said include a master on off switch but if the master switch was on, the changeover switch would need to have break before make contacts. I think 3 meters would be better and quicker to use and almost as cheap at those prices.

starfire
Actually, I know the input circuitry of the P67 quite well. Another recent completely unconnected incident meant that I had to get the circuit diagrams from Princess. Up until quite recently, I thought like you, that the first place the power went to was the RCDs and polarity neons at on the AC control panel by the main helm. In fact, the shore power goes to an AC panel in the lazerette first where a control circuit is taken off to feed the polarity neons and the generator/shore power selector switch. This switch then controls a series of contactors to select shore power or generator. Princess, as usual, were very helpful in providing the circuit information.

The separate incident I refer to was a shore power surge - lightening strike or substation problem - we cant be sure but some other boats were hit as well. In our case, thankfully, it blew the coils in the contactors first. I'm now in the process of fitting some surge protectors - thanks again to John for his help in finding a suitable surge protector - I might start a separate thread - there are some interesting things to watch out for with surge protectors.
 
Shorepower is one of the most variable things we have had to deal with.

We had one case, in Malta, where the shorepower was 240v, but center tapped earth, so 120 - 0 - 120, how & why it was provided that way, we never did find out, much fun that caused.

Last time I was in Marina Bay Gib, there was a reasonably large mobo, with an 1.5" dia shore power cable, connected to what would best be described as 'electric string', the connection between the two wrapped in a plastic bag, the rest of the cable running across the concrete for 30m +, then plugged into a 125A 3 phase outlet, shudder!.

240v 16A/32A correct polarity & an earth. Most places.

240v 16A/32A, reversed live & neutral, its causes problems with UK spec installations where only the Live is switched, most continental fuseboards & kit switches both live & neutral, so not a problem.

240v but supplied from a 3 phase connector, i.e Red 5 pin 3 phase + N + E, with an adapter to a single phase socket. Ok if it wired correctly, as you have found, you may get connected across 2 phases if it is not.

240v with no earth.

Continental sockets, thankfully rare, unless you are in the Greek islands & have impromptu shorepower from the local restaurant.


There is a lot to said for having an on board isolation transformer, but it is a big, expensive lump & will not protect against having 415v up it, but you have control of what happens on the boat side of things.

There are some protection relays which will trip the contactors or breakers if an over voltage is applied, again not cheap, but relative to the cost of the boat, very little.

I am surprised that more high end manufacturers do not give more thought to the electrical installation on board, instead of assuming all shorepower the boat will be connected to being 100% correct, rather than as we have found, there are all sorts of permutations.
 
Mike,

Not completely sure what you want?

Do you want to plug in your lead to a shore power supply, with the box end of the lead first connected to a box of tricks that analyses the shore based electrical supply before you then connect your lead to the boat?

If so, precisely what would you like your box of tricks to tell you? Clearly we do not want to be considering osciliscopes as an electrical meter normally suffices, so let me have a list of precisely what you want your box of tricks to tell you, then we can get to work.....:

1)
2)
3) etc

166lna0_th.jpg
 
John100156 said:
Mike,

Not completely sure what you want?

Do you want to plug in your lead to a shore power supply, with the box end of the lead first connected to a box of tricks that analyses the shore based electrical supply before you then connect your lead to the boat?

If so, precisely what would you like your box of tricks to tell you? Clearly we do not want to be considering osciliscopes as an electrical meter normally suffices, so let me have a list of precisely what you want your box of tricks to tell you, then we can get to work.....:

1)
2)
3) etc

166lna0_th.jpg
Click to expand...

Its just for testing, John
To do what I do with a multimeter but easier to use.

I suppose I'd like to check thet the voltage is just 230/240v and I dont think that the Martindale style ring testers do that. There's nothing that actually says what the little neon indicators are checking.
For example if I plugged one of these Martindale ring testers into a supply where the (so called) line and neutral were across two phases (380/415 volts) I wonder what it would say.

I think that the expensive instrument you found at RS is just too complex.

I just think that just three voltmeters would tell me all I need to know.
The one across the Line and Neutral should read 230/240v
The one across Line and Ground should read 230/240v
and the one across Neutral and Ground should read a small voltage


Does anyone else check these things?
 
Last edited:
The simple test plug does not tell you voltage, but the sequence of lights tell you if the following faults are present at a glance:-

Live-Neutral Reverse
Live-Earth Reverse
No earth
Neutral Fault
All OK

You could use the above and and a simple volt meter with 3 position switch, when the polarities are established as OK, you switch the voltmeter between L-N / L-E and N-E but make sure the switch has 6 poles and contacts break before make to give you what you want.

If your worried about 3 phase voltages, you could use a 500v meter to do the voltage test first but make sure your switch is 400/415v rated!

Would that do what you want?

RS link in my last post just for fun......

JC
 
I would suggest something like a Kewtech 107 socket tester as well, this will also prove the earth connection is reasonable and allows a quick rcd test.


Searching suggests none of these quick socket testers are proof against 415V.


For quick tests on electrical installations, I use one of these :- http://www.dilog.co.uk/_vct_DL6790.htm. It may be more suitable than a multimeter, certainly more useful on a boat.
 
Yes, I tend to use a Fluke multimeter or probe tester, both on boat, also with the socket tester which is useful. I have a lead made up with a standard socket on the end with the socket tester plugged-in for a quick check. But normally I just plug in then sort the problem out with my meter. I must say though it was a pain when we stopped in Almerimar when we had a problem, not what you want when you are tired and hungry!

Looking at one meter with multi-position switch as I suggested above, you could still read 240/240/0 with correct wiring and also with a N-E reversal! As below:

Correctly wired switch positions would test:
Sw position 1 (L-N) would read 240
Sw position 2 (L-E) would read 240
Sw position 3 (N-E) would read 0

N-E Reversed switch positions would test:
Sw position 1 (L- wrong E) would read 240
Sw position 2 (L- wrong N) would read 240
Sw position 3 (E-N) would read 0

Oh well back to the drawing board.....

The problem is the E-N reversal, but in a T-N-C-S they are connected together in any case.....
 
OK here's a possible solution:

Inside the box you have a standard RCD wired for correct polarity. You insert a test button across L-N with a resister and neon in series that exceeds the RCD trip current. When you press the test button, the neon lights. When you get 240/240/0 you press the test button, if the RCD trips you have an N-E reversal if it doesn't all is well!

That should do it....!
 
John100156 said:
Yes, I tend to use a Fluke multimeter or probe tester, both on boat, also with the socket tester which is useful. I have a lead made up with a standard socket on the end with the socket tester plugged-in for a quick check. But normally I just plug in then sort the problem out with my meter. I must say though it was a pain when we stopped in Almerimar when we had a problem, not what you want when you are tired and hungry!

Looking at one meter with multi-position switch as I suggested above, you could still read 240/240/0 with correct wiring and also with a N-E reversal! As below:

Correctly wired switch positions would test:
Sw position 1 (L-N) would read 240
Sw position 2 (L-E) would read 240
Sw position 3 (N-E) would read 0

N-E Reversed switch positions would test:
Sw position 1 (L- wrong E) would read 240
Sw position 2 (L- wrong N) would read 240
Sw position 3 (E-N) would read 0

Oh well back to the drawing board.....

The problem is the E-N reversal, but in a T-N-C-S they are connected together in any case.....
Click to expand...

In the UK, TNCS would not be allowed for shorepower supplies, BS7671 specifically prohibits this.

I still fancy the idea of a socket tester that includes a crude rcd test, this introduces a known (30mA) fault between live & earth, if N & E are correct the rcd will trip, if incorrect (N & E reversed), or the rcd is faulty, the rcd will not trip.

The fun starts when there are several rcds cascaded, i.e. one in the marina supply, one in the pontoon supply & one in the shorepower pedestal. While the ones upstream should be time delayed (and 100mA), I know from experience this is not always the case.

Uproar from other boats on the pontoon when it's you that has tripped the rcd(s) is usually a clue.
 
John100156 said:
OK here's a possible solution:

Inside the box you have a standard RCD wired for correct polarity. You insert a test button across L-N with a resister and neon in series that exceeds the RCD trip current. When you press the test button, the neon lights. When you get 240/240/0 you press the test button, if the RCD trips you have an N-E reversal if it doesn't all is well!

That should do it....!
Click to expand...

Yes that should do it, but skip the neon, for nominal 230v supplies and 30mA trip current you would need a resistor of 7.6k ohm, say 7.5k for standard resistor values.

edit: a normal 240v neon with its internal series resistor, in parallel with the 7.5k ohm resistor would do what you describe.


Sometimes, in testing 'interesting' electrical installations, a 'real world' earth is useful, often as simple as a screwdriver stuck in the garden.
 
Last edited:
Neon just to confirm test button is working and current is flowing (and because I have one in my toolbox!) I may knock this up for Mike if he wants me to, just for fun! If we assume say 220v and a 30ma trip current I would opt for say 7.3k or less. 220/7300=30.1mA and if say 240/7300=32.8mA. Have to watch the power dissipated though, P=I^2R so say 6.6W at 220v and 7.9W at 240v. May make one up for me too! Off to RS and Maplin.
 
John, I think you've missed my point.

Twice, I've been given a supply that is actually across the phases.
The first, in Tunisia was actually a supply wired across the phases, the second was in Valencia last summer - this one is closer to us - a 63a three phase plug with a short lenght of flex was supplied to us to connect to the 63 amp three phase shore socket. The short bit of flex looked OK but in fact it had been previously overloaded and somehow it was causing our single phase to show 380v. And, of course, strange things were happening on the neutral. Note we didn't wire it up incorrectly - it was definately a bad bit of flex.

I, almost, dont worrk about polarity, as I say the boat has an on board set of polarity neons. Its the test for more than 230/240 volts that I'm really concerned about.

And what I'm really having trouble with is the lack of information from the manufacturers
See here is an example http://www.pat-services.co.uk/socket-professional-tester-658.htm
The sales splinge says "Detects good plus 13 wiring fault conditions" - so why oh why dont they say what the fault conditions are?

Actually, I have found one of these which might make the test using my multimeter a bit easier. Then all I have to do is make up a 3 pin UK style socket on the end of a blue plug.
http://www.pat-services.co.uk/kewtech-kewcheck-socket-adapter-872.htm
 
Last edited:
You must log in or register to reply here.

Share this page

Top