shorepower amp question

Mr Googler

Mr Googler

Well-Known Member
Joined
11 Apr 2008
Messages
5,922
Visit site
Probably a stupid question but here goes.

I have 16 amp shore power supply and connections however, my air con unit spikes above 16 amp when the compressor first starts tripping the power.

If i get a Y connector and plug into the other available shore power socket, have i got 32 amp?

I understand the risks of running 32 amp through 16 amp cable/ connectors but once running, it draws 10amp according to my volt meter onboard.

I cant understand why the shore power would have been underspecced from new but i guess as i have a generator, they assumed that would be used for air con.

Am i being foolish!!
 
FARSCO said:
Probably a stupid question but here goes.

I have 16 amp shore power supply and connections however, my air con unit spikes above 16 amp when the compressor first starts tripping the power.

If i get a Y connector and plug into the other available shore power socket, have i got 32 amp?

I understand the risks of running 32 amp through 16 amp cable/ connectors but once running, it draws 10amp according to my volt meter onboard.

I cant understand why the shore power would have been underspecced from new but i guess as i have a generator, they assumed that would be used for air con.

Am i being foolish!!
Click to expand...

Why not change / uprate the mcb in your on board consumer unit
 
FARSCO said:
Probably a stupid question but here goes.

I have 16 amp shore power supply and connections however, my air con unit spikes above 16 amp when the compressor first starts tripping the power.

If i get a Y connector and plug into the other available shore power socket, have i got 32 amp?

I understand the risks of running 32 amp through 16 amp cable/ connectors but once running, it draws 10amp according to my volt meter onboard.

I cant understand why the shore power would have been underspecced from new but i guess as i have a generator, they assumed that would be used for air con.

Am i being foolish!!
Click to expand...

OK, by far the most important thing is your Y connector. Picture it very clearly in your head (which is where it must stay, it must never see the light of day, ever!) Right, got the picture? you have 2 plugs (one for each 16A outlet) and 1 socket. You plug one plug in to a live socket. Now, here is the thing, in your other hand you have a nice little 240V cattle prod with barely hidden live pin.
Now, OK, you want to go ahead. You carefully switch off the supply before connecting everything, good. You will get a minor spike that wont heat anything and then runs just fine, no worries at all.
Sailorman seems to imply that its the on-board trip that goes, in this case the Y connector wont do anything, if its the dockside trip then your system will work. A better solution would be to explore a soft start for the air-con.
 
Dougal Tolan said:
OK, by far the most important thing is your Y connector. Picture it very clearly in your head (which is where it must stay, it must never see the light of day, ever!) Right, got the picture? you have 2 plugs (one for each 16A outlet) and 1 socket. You plug one plug in to a live socket. Now, here is the thing, in your other hand you have a nice little 240V cattle prod with barely hidden live pin.
Now, OK, you want to go ahead. You carefully switch off the supply before connecting everything, good. You will get a minor spike that wont heat anything and then runs just fine, no worries at all.
Sailorman seems to imply that its the on-board trip that goes, in this case the Y connector wont do anything, if its the dockside trip then your system will work. A better solution would be to explore a soft start for the air-con.
Click to expand...

mcb not rcd

circuit overload not earth leakage
 
I think the shorepower tower has an mcb on each outlet and an rcd coverong both. I have been told it will trip if anything more than 16amp is pulled.

Will look up LBOK now.

Thanks for the replies
 
Can you prove that the two 16A outlets on your shorepower outlet are on the same phase?

Imho Dougal has the right answer for your problem - get a soft-starter for your aircon.
 
As you can see from the link above, I had the same problem recently and received very good advice form the usual suspects, the best solution is to insist that your marina fit a 32a to your location and move if they say no...
I know that there are a lot of WWJFMD, questions on this forum, but he's usually right!

:)
 
Thanks for all the replies. I will read the thread and look at a soft start. Moving is not an option as there are only 2 marinas here, all government run with the same sparkies doing the work and setting our amp allowances............slowly ��
 
Do be aware of your neighbours though - if there is one socket per boat and you take two then there's a neighbour without a socket. I know this through long arguments with the boat beside me as he said he needed two sockets so I had to do without any as I'd arrived down to my boat later. Not the end of the world but a bit of a hassle getting him into the right headspace to realise what he was doing - as it happened he only became less grumpy after I'd rescued his wife's tiny lapdog which had missed the pontoon and swam the wrong way towards his bow.
 
The issue might be the Curve rating of your MCB, either aboard or on the supply post.

Commonly these are rated A, B C or D. For high torque motors these need to be at least C if not D curve, but often marinas install B curve. The curve is the speed of operation, the lower the letter the more sensitive the MCB is.

If you note the make and model of the breaker as the maker will likely offer a higher curve version. Buy one and ask their sparks to fit it for you, if you are not competent to do this yourself.

I do not like to dictate what folk on here should or should not do, but this one is more important - so as mentioned already ...

DO NOT CONNECT TO TWO SEPARATE SUPPLY POSTS UNLESS YOU KNOW HOW TO TELL THEY ARE ON THE SAME PHASE.

Even then this practice has significant hidden dangers.

If you do not know how to do this here is not the place to learn, and even if it were OK where you routinely berth sooner or later someone will plug the cross over lead device in at another location without checking the phases and the flash and bang as the second part is plugged in will be immense, and will still be in your hand as it explodes. The phase to phase voltage is full 400 volts even on a 240v post.

If you do not think just 16amps can do this think of the spark and power an arc welder can produce at just 13amps 240v - you will have 16amps at 400volts, fully short circuited.

Also the second and not yet plugged in male pinned plug will be live as soon as the first is connected - a lethally dangerous situation all round.
 
Thanks as ever Trevor. I have put the idea to bed and will look at a soft start. I didnt realise these can be retrofitted. For now i will just use it on the gennie. Needs a few hours on it anyway.
 
The fact you're asking suggests you're not 100% on the electrical side of things. As said, you must be absolutely sure the two sockets on the dock are the same phase, otherwise you will risk death (even more than on the same phase). In fairness, if the two sockets are side by side they're probably on same phase, but you need to be sure.

Then if someone comes along and thinks "cheeky git, taking two sockets" and disconnects one, the dangling disconnected one will have exposed live pins and could kill someone, especially a child. = manslaughter, seriously.

Hence the name LBOK

Perfectly ok to use LBOK if you are sure what you're doing and if you supervise and know that no walker-by will mess with it. Otherwise not. Best solution is to fit a soft start or get the marina to install a slower mcb as SH6K says (but my hunch is they might not want to mess with their text book installation). Also a combi inverter would provide the required current for the motor's start up, though is perhaps a £1500 job.

Good luck
 
Thanks John. I am certainly not 100% on the leccy side and will leave well alone.

My chiller is pretty old but functioning well so a soft start should do the trick. I will employ someone in the know to install too!!
 
A small Inverter will also provide a soft start function, and could let you squeeze a bit more capacity out by allowing it to run up to 60 hz, after all that's what they run when on US supplies.

An example for a 12,000 BTU/hr (1 HP) unit is found here ...

http://www.ebay.co.uk/itm/VFD007E43...599918?hash=item4b0c9468ae:g:krwAAOSwo4pYMGwG

But plenty more on Ebay. Check the FLA rating of the motor is at least 10% less than the inverter capability.
 
Thanks Trevor, I know my unit is 8500 btu. The dometic smart start is £400 so thats quite a saving.

I feel a long pm coming on how it's wired in! Not that I would do it myself but no one on the island is experienced in marine water chillers.
 
You must log in or register to reply here.

Share this page

Top