Marina Power

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ip485

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Most (and I appreciate not all) marina power points supply 15 amps. My on board systems are able to operate on a 30 amp supply. Of course with a 15 amp supply care is needed what can be switched on at the same time and the water heater and air heaters quickly trip the supply.

Unfortuantely I only have a single deck plug. Is there any way of combining two 15 amp shore points to the single 30 amp deck plug to enable a full 30 amps to be drawn?
 
You would just need to run two parallel feeds from two shore supply's to your distribution panel,
 
ip485 said:
Most (and I appreciate not all) marina power points supply 15 amps. My on board systems are able to operate on a 30 amp supply. Of course with a 15 amp supply care is needed what can be switched on at the same time and the water heater and air heaters quickly trip the supply.

Unfortuantely I only have a single deck plug. Is there any way of combining two 15 amp shore points to the single 30 amp deck plug to enable a full 30 amps to be drawn?
Click to expand...

Is the deck plug and therefore the cabling on the "boat" side of it 15A or 30A? If it's a 30A plug you could rig up 2 x 15A cables in parallel. If it's a 15A plug the answer is no, not without a bit of re-wiring down below.

Richard
 
Not safely IMHO. Two adjacent posts could be on different phases of the source 3 phase 400 volt supply. Certainly if you do not understand what I have just written then definitely definitely not. If you do it is still potentially dangerous.

If you plug into two posts on different phases with a jury twin plug lead, as the second plug enters it will likely explode in your hand, plus the pins on on leg of the lead will be live. The second connection will be creating a full phase to phase short circuit, and at 400 volts.

If you were able tell safely if two posts were on the same phase then there is still a risk to others if someone else unplugs one post, as the exposed pins would be live.

Better to find a 32amp outlet.
 
superheat6k said:
Not safely IMHO. Two adjacent posts could be on different phases of the source 3 phase 400 volt supply. Certainly if you do not understand what I have just written then definitely definitely not. If you do it is still potentially dangerous.

If you plug into two posts on different phases with a jury twin plug lead, as the second plug enters it will likely explode in your hand, plus the pins on on leg of the lead will be live. The second connection will be creating a full phase to phase short circuit, and at 400 volts.

If you were able tell safely if two posts were on the same phase then there is still a risk to others if someone else unplugs one post, as the exposed pins would be live.

Better to find a 32amp outlet.
Click to expand...

Would two 16A sockets on the same distribution post be on different phases as the boats in my marina with two 16 cables always seem to plug into two adjacent sockets? I appreciate that these are presumably not simply parallel cables but do run to separate circuits onboard.

I have assumed that the OP is referring to a situation where a 32A marina socket is not available but I might be misreading the post.

Richard
 
Yes from the boat plug onwards it is all 32 amps and I have plugged into 32 amp shore supplies on a few occasions (not that they are that common). At the boat side the input runs directly to a 32 Amp Charleston IsoTransformer. Most marinas have post supplies with two or more 16 amp plugs and sometimes more than one plug is available (hence the question). If not there is often a free plug a post away.

Superheak6K I take your very good points and presumably there is no easy and safe way?

I assume an alternative would be to install an additional port on the boat but this wouldnt negate the issues without wiring both supplies to seperate circuits which would be a substantial work up and hardly justified?

Richard - yes, correct.

Edited to add I have seen the boat fitted with two shore inputs and the 120/240 V panel is divided into two parts, so there are definitely two circuits on board. I guess the two circuits may route to one shore plug in my case and an option is to split the supply to two shore plugs. I will need to look at the circuit diagram.
 
Last edited:
RichardS said:
Would two 16A sockets on the same distribution post be on different phases as the boats in my marina with two 16 cables always seem to plug into two adjacent sockets? I appreciate that these are presumably not simply parallel cables but do run to separate circuits onboard.

I have assumed that the OP is referring to a situation where a 32A marina socket is not available but I might be misreading the post.

Richard
Click to expand...
I would be surprised if two separate sockets on the same post would be on different phases, but I am not a marina sparky.

The concern with having two leads re live pins would still stand. If the leads are on completely separate circuits, then they would be fine, but plenty of room for Darwin Award contention, as it might be possible for the inlet receptacles to be switched together, especially if an owner has decided to connect them for other reasons.

I am wiring a large chiller control panel presently, with several control power transformers. I have been very careful to making sure all these are fed from the same two phases, even though the power is going to separate devices, and then further converted to low voltage AC and DC control systems.
 
superheat6k said:
I would be surprised if two separate sockets on the same post would be on different phases, but I am not a marina sparky.

The concern with having two leads re live pins would still stand.
Click to expand...

Interesting. Is there any kind of diode-type device which could be inserted into the two leads which would stop the live pin danger? This could be quite low-cost if such gizmos are available.

The two cables could then be securely fastened together so that the plugs could not be separated more than a couple of feet which would remove the danger of each plug being pushed into a different post .... assuming that the 1 post / 1 phase theory is correct. Is there a simple way for the OP to test that for the two sockets he selects each time?

Richard
 
RichardS said:
Interesting. Is there any kind of diode-type device which could be inserted into the two leads which would stop the live pin danger? This could be quite low-cost if such gizmos are available.

The two cables could then be securely fastened together so that the plugs could not be separated more than a couple of feet which would remove the danger of each plug being pushed into a different post .... assuming that the 1 post / 1 phase theory is correct. Is there a simple way for the OP to test that for the two sockets he selects each time?

Richard
Click to expand...

There are diode devices that will do the job, just that they have a side effect of also stopping the lekky when you want it.

What you really want is a plug with a switch buried between the pins.
 
RichardS said:
Interesting. Is there any kind of diode-type device which could be inserted into the two leads which would stop the live pin danger? This could be quite low-cost if such gizmos are available.

The two cables could then be securely fastened together so that the plugs could not be separated more than a couple of feet which would remove the danger of each plug being pushed into a different post .... assuming that the 1 post / 1 phase theory is correct. Is there a simple way for the OP to test that for the two sockets he selects each time?

Richard
Click to expand...
I can't think of a simple way of having two independent sources from the same phase. I suppose if you had a current sensing relay you could design it to cut the connection via a contactor on the boat, but it would need some thinking about. If everything went off the device would turn off, effectively isolating the supply on that or both legs.

A diode device won't work with an AC current.

I suppose you could also build in a phase to phase checking device to check for opposing phases.

But the more I think about this as I type the more complex the 'box' is becoming. Not sure I would want to wear the "Designer's" hat for this one.

In fact the only way I can see this done completely safely is with two isolating transformers, rectified to DC output which is combined as DC then inverted to provide the AC supply required. How complicated is that ?

You can't simply combine the transformer outputs because these will still be phase different if the incoming phases are different, plus the isolating transformer will back feed 240 v AC from the secondary circuit fed from the other supply's transformer.

It is simple enough to check two adjacent posts with an AC voltmeter, same phase 0 volts on the live pin, 400 volts is different phases, but this does not remove the danger of someone else plugging in, nor the possibility the sparks who wired the marina reversed Live & Neutral on one or more of the sockets.

So no perhaps not that simple to check !!!
 
A simple solution would be to run the usual 15amp supply to the boat's system and then a second cable to one of those camping kits with integrated RCD and use it (for example) just for the water heater and an air heater. Running those two devices on that supply would free up the main supply for all your sockets.
 
superheat6k said:
Not safely IMHO. Two adjacent posts could be on different phases of the source 3 phase 400 volt supply. Certainly if you do not understand what I have just written then definitely definitely not. If you do it is still potentially dangerous.

If you plug into two posts on different phases with a jury twin plug lead, as the second plug enters it will likely explode in your hand, plus the pins on on leg of the lead will be live. The second connection will be creating a full phase to phase short circuit, and at 400 volts.

If you were able tell safely if two posts were on the same phase then there is still a risk to others if someone else unplugs one post, as the exposed pins would be live.

Better to find a 32amp outlet.
Click to expand...

does bear thinking about! ��
 
I find it quite easy to keep my maximum demand below the 3kw limit, by if necessary switching something off.
 
Of course, but on larger boats it isnt always that easy - in my case the electric water heater (it is nice to have hot water) and a 3KW heater is just sufficient, as a 3KW heater when the outside temperature is in single digits doesnt do a great deal. I can and do juggle with the water heater but hey it is good to be cosy at times especially as I could run the Genset and not worry :-) I could get something smaller.
 
I often see big yachts and mobos hooked up to two 16amp sockets in a marina, using 2, 16 amp cables and plugs wired into a single 32amp socket.

I agree with the observations that this is potentially dangerous because if you plug-in one 16amp plug the pins on the other will be live. It's also possible that the two sockets will be be on different phases, but think that this is much less likely, if both sockets are on one utility post, it's more likely that different utility post will be wired to different phases, to even out the load per phase.
I can't think of an easy way to see if different sockets are on different phases, typical cheap testers will tell you if live and neutral are swapped or if you have a neutral earth fault, but I haven't seen simple system which will check the phases of 2 sockets.

I also view this as "antisocial behaviour", marinas are usually designed with one 16 amp socket per berth, when the marina is busy, if a berth uses two sockets, it will probably mean that someone else will be without power.
 
Re: CAUTION!

Pinnacle said:
Please be VERY careful.

Can I suggest you read all the way through this thread.... http://www.ybw.com/forums/showthread.php?469975-shorepower-amp-question&highlight=LBOK

A LBOK has the name for a good reason!
Click to expand...

Many of the issues are similar, of course ..... but in that thread the OP only has 16A circuitry on the boat-side of his 16A deck plug. The first thing we did on this thread was establish that the OP's boat and plug are 32A compliant.

Richard
 
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