Combine 3 x single phase/220v = 3-phase power?

[prv]

I'm not sure about using 3 different shore sockets as I don't see how you would know whether they were all on the same phase or on separate phases.

The idea (for normal boats, which don’t discharge their washing-up water through a riot cannon) is that each input supplies a completely separate subset of on board equipment which is not interconnected. So it doesn’t matter if the inputs are on the same phase or different ones. Quite commonly one input runs air conditioning and another runs everything else. I don’t think it would be usual to supply sockets from more than one input, which meets the “touching distance” rule you mention if they do happen to be on different phases sometimes.

Pete

 

[DownWest]

There is another way round the water pump. One presumes it normally runs off a 3-phase genset of at sea, so why not isolate it from the rest of the onboard electrics and just run the genny when the pump is needed, which can't be for very long? The wiring would have to be altered so that when shorepower is connected to single phase, the genset must be isolated from all but the pump. Quite do-able.

 

[halcyon]

So, all of the equipment on your boat is 3 phase ? You have a 415v washing machine, kettle, toaster, light bulbs, TV, laptop charger etc etc ?

I think not, so does Brian (Halcyon). We think you have a three phase connection into the boat, which consists of three 240v phases. Once onboard this connection can be used to run 3 phase equipment (obviously) but it can (and almost certainly does) run normal 240v equipment. Normal practice here would be to take a 240v circuit from 1. 2 or 3 phases, as required. Typically something along the lines of all low current type devices from one phase (lights, sockets, maybe water heater), then the washing machine and dishwasher from the 2nd phase and perhaps air-con from the 3rd phase. With such and installation you could supply the 1st phase from a single 16a input, the 2nd phase from a single 16a input and the 3rd phase from yet another single 16a input. If only 1 input was available, you at least have lights and basic services.

Along side our house running up the field is 4 power lines, 240 VAC 3 phase, the house below draws power from one phase, we draw power from another and the house above uses the the third phase, we all share the common neutral. The 3 phase supply also supplies other houses in our corner of the village.

In the past, 1990 we supplied Sealine 450 with dual supply switch panels, they fitted two sockets and used two leads, back then marina sockets were 16 amp. What the OP has I think is 3 AC circuits, but instead of splitting the 3 phase mains supply, the marina feeds down the pontoon. You can then plug a single cable into the socket and supply 3 separate AC circuits in the boat, cleaner than than 3 cables to each boat and many sockets on pontoon.

If this is the case, as Paul says, you just need to wire three plugs into your normal 3 phase type socket, then plug into 3 single phase sockets with your 3 phase cable.

Only problem if you have a piece of equipment that is 220 volt AC 3 phase, in which case fit a single phase motor or alternate single phase pump.

Brian

 

[PaulRainbow]

This isn't hard to sort out.

The pump should be disregarded in port and only used at sea, powered by the genset. For "emergency" use when in post and unable to get to sea to empty the gry tank a 12v waste pump will shift more than enough grey water for a days use in just a few minutes.

The240v electrics should be split into two separate circuits, one for essential services such as lights and sockets, the other for less essential circuits such as the washing machine and dishwasher. Two 16a shore power inlets need to be fitted, in addition to the existing 3-phase inlet.

A set of remotely operated contactors should be fitted, with 12v dc coils, all should be normally open. A changeover switch also needs to be fitted, with 4 settings, genset, 3-phase shore power, single phase shore power and off. The changeover switch and contactors will be configured so that only the relevant circuits are closed, obviously.

This will allow the genset or a 3 phase shore power connection to run all 240v circuits and the 3 phase pump as they do now. It will also allow a single 16a inlet to power essential services and the 2nd 16a inlet to power the washing machine etc if a 2nd supply is available.

It's not rocket science.

If the grey water system was improved up it would be even simpler. I don't see the point of routinely storing up to 2000 litres of grey water.

 

[TernVI]

The pump is for grey water discharge. Just checked it again and it's actually 3kw, which suggests that a single phase 220v/16a could pull it, if I can only convert it to 3-phase power?

EDIT: I could add this phase converter on a single 220v/16a phase to run it? Simlug Frequency Converter, 220V 3KW Single-phase Inverter Output 3-Phase Frequency Converter: Amazon.co.uk: Business, Industry & Science



View attachment 102123

Not much call for 3kW of grey water discharge in the marina....

 

[JumbleDuck]

Not much call for 3kW of grey water discharge in the marina....

And yet someone fitted that pump. So either they were insane or they had good reasons which we (ie you) don't know.

A 2000 litre holding tank is pretty big. That suggests a pretty big boat, so the tank could easily be 2m below the discharge point. A 3 kW motor with a centrifugal pump will do about 1.5 kW of pumping, which is enough to move 75 kg/s up 2m. At that rate it would take 30s to empty the tank - longer, of course, if it has to pump through a hose as well.

That doesn't seem unreasonable if (a) grey water discharge at sea is banned and (b) discharge ashore is at a shared pump-out where the aim is to turn up. empty quickly and go.

 

[prv]

The pump should be disregarded in port and only used at sea, powered by the genset. For "emergency" use when in post and unable to get to sea to empty the gry tank a 12v waste pump will shift more than enough grey water for a days use in just a few minutes.

Surely the genset could be flashed up briefly just to run the big pump and empty the tank, meaning no need for additional plumbing. Given the size of the tank it’s presumably an infrequent event, and with the size of pump not an excessively lengthy one. Assuming that you even wanted to empty the whole two thousand litres, that is, which agreed might be antisocial in a marina depending how dirty the water is.

Pete

 

[prv]

A 200 litre holding tank is pretty big.

How would you categorise the OP’s two thousand litre one, then? ?

Seems massive for a ”typical” 65-footer, so I’m intrigued to see what kind of vessel we’re talking about here. Ex fishing boat, perhaps, or something built in a similar style?

Pete

 

[rolf.nielsen]

Thanks for all your reflections. Yup, 2000l is big, no I never actually fill it, yes it's a converted fishing boat indeed, yes the tank is a couple of meters below the discharge point and there's a meaningful amount of pipes to go through, yes the stream does come out quite strong, yes it's probably overkill but that's how the boat came equipped.

My conclusion thanks to all your great insights and tips is clear: as a back-up to when 3-phase shore power is not available, I'll install 3 x single-phase shore power connections to power directly each of the ship's onboard phases/groups, with switches and galvanic isolators where needed. I'll run the pump off the generator or, if it is not too challenging to install, run the pump off a 1->3 phase converter a la the model a previous poster shared that gradually ramps up the hz to avoid tripping the fuse when the pump comes on. This is a fairly simple intervention and gives me the added advantage that I can choose which of the boat's 3 groups I want to run if I can only get 1 or 2 x single phase power suppliers when the marina's plugs are in high demand.

 

[JumbleDuck]

How would you categorise the OP’s two thousand litre one, then? ?

Seems massive for a ”typical” 65-footer, so I’m intrigued to see what kind of vessel we’re talking about here. Ex fishing boat, perhaps, or something built in a similar style?

Pete

Sorry, I meant 2000 litres.

 

[PaulRainbow]

Surely the genset could be flashed up briefly just to run the big pump and empty the tank, meaning no need for additional plumbing. Given the size of the tank it’s presumably an infrequent event, and with the size of pump not an excessively lengthy one. Assuming that you even wanted to empty the whole two thousand litres, that is, which agreed might be antisocial in a marina depending how dirty the water is.

Pete

The option of running the genset would still be there, but i'd be looking to achieve 2 things, 1) Not pump 2000 litres of dirty water into a marina in one go, 2) not have to run a 3 phase diesel genset just to get rid of my washing up water.

For instance, it would be a minor job to tee a small grey tank from the existing one, fit a water sensor in it and connect it to a normal DC waste pump. The pump would only run for short periods, as required. The 2000 litre grey tank would only need to be used if in a marina that prohibited the discharge of grey water and then emptied at sea by running the genset and the 3 phase pump.

 

[superheat6k]

A very concerning thread with what is simply dangerous nonsense being talked about by many contributors so far.

I wish I had seen it earlier on in the discussion, but ...

1 Be in no doubt 3 phase 400 VAC is seriously dangerous if not understood and properly used.

2 No you cannot safely expect to connect to three separate single phase supplies and know with any certainty whether ...

a. All three are from the same phase

b. Two from one and one from another phase

c. All three are on synchronous separate phases of the same supply.

d. One or another phase could be from an entirely separate supply HV transformer (although this is less likely).

The three phases running on four cables along a field are not 240v 3 phase. They are 400V three phase from a star connected secondary at the HV transformer, where the fourth cable is the neutral which connects to the starpoint. As such each phase to any other phase is 400VAC. Any phase to neutral is 240VAC.

If you do not understand why one phase to neutral is 240v and not 200v you are, I am afraid, not qualified to make comments on this thread of any value.

Neither should anyone attempt to apply 240 vac single phase to a 3 phase 240vac Delta connected 3 phase motor, and comments made in this regard show a dire lack of knowledge of 3 phase motors and how they are made because 240vac 3 phase does exist elsewhere in this World, but is not used in the UK.

So happy to answer any questions I can on use and application of 3 phase supplies and how a single phase supply is derived from it. BTW this is a significant part of my day job.

Stay safe people please.

 

[JumbleDuck]

A very concerning thread with what is simply dangerous nonsense being talked about by many contributors so far.

Almost all the points about which you are concerned have been carefully covered in the thread.

 

[rogerthebodger]

If I was in that situation I would do one of the following.

Replace the 3 phase motor with a single phase.

You could also connect a seperate single phase motor to the fan end of the three phase and have either operating (no clutch necessary)

You could also drive the pump from the main engine (may need relocating the pump but using vee belt drives from the main engine would also allow the pump drive to be disconnected by slackening the tension on the vee belts. This could be done by removing the motor fan and connection the drive vee belt pully to the end of the motor shaft

I have a single phase water circulating pump for my keek cooled air conditioning system.

A vee belt drive could also drive a 3 phase alternator using a similar vee belt drive and the speed adjusted to give an alternator output at 50hz.

I would not try to make up 3 phase from 3 seperate single phases as its all to easy to not have the correct phased and phase rotation

 

[pawl]

The idea (for normal boats, which don’t discharge their washing-up water through a riot cannon) is that each input supplies a completely separate subset of on board equipment which is not interconnected. So it doesn’t matter if the inputs are on the same phase or different ones. Quite commonly one input runs air conditioning and another runs everything else. I don’t think it would be usual to supply sockets from more than one input, which meets the “touching distance” rule you mention if they do happen to be on different phases sometimes.

Pete

Well, I would have thought that it's bad enough having to have 240v on a boat without the potential of upping this to over 400v. People make all sorts of strange wiring changes to their boats. Any unknown and potentially dangerous change or fault could be present which may not show up when all shore power is from the same phase but which could be dangerous if two different phases were present. I don't see how you can be sure that in taking supplies from more than one outlet what phases they are on.

 

[JumbleDuck]

Well, I would have thought that it's bad enough having to have 240v on a boat without the potential of upping this to over 400v. People make all sorts of strange wiring changes to their boats. Any unknown and potentially dangerous change or fault could be present which may not show up when all shore power is from the same phase but which could be dangerous if two different phases were present. I don't see how you can be sure that in taking supplies from more than one outlet what phases they are on.

The OP already uses a three-phase supply when one is available.

 

[PaulRainbow]

Well, I would have thought that it's bad enough having to have 240v on a boat without the potential of upping this to over 400v. People make all sorts of strange wiring changes to their boats. Any unknown and potentially dangerous change or fault could be present which may not show up when all shore power is from the same phase but which could be dangerous if two different phases were present. I don't see how you can be sure that in taking supplies from more than one outlet what phases they are on.

The boat already has a 3 phase input and a 3 phase generator. The incoming 3 phase (whether from shore power or the genset) is then seperated into it's three 240v phases, each phase is obviously isolated from the other. What i have proposed is to bring up to three 240v inputs onboard and connect them to the existing 240v circuits. With appropriate switching and circuit protection, nothing has changed in terms of safety.

It does not matter if the three incoming supplies are on the same phase or not, the wiring is already installed to reflect that with the current genset and incoming shore power connection that all three 240 circuits absolutely will be on different phases.

Installations such as this are commonplace in industrial settings, where the incoming three phase will supply some of the shop floor and different 240v phases will supply 240v equipment on the shop floor and the offices etc. It's nothing new, back in the 70's my uncle had a new workshop built, the power to the workshop was 3 phase to power the four post ramp. Two 240v phases were taken around the workshop for all of the 240v equipment and the third one went to the house that stood beside the workshop.

There is nothing wrong with this type of installation, it's just your poor understanding that makes you think there might be.

 

[Graham_Wright]

Pedant comment.
Since we joined the EU or sometime later, single phase was standardised at 220-230 volts.

It's of particular interest to me as one of my machines expects 240 and won't fire up on a Sunday lunchtime!

 

[JumbleDuck]

Pedant comment.
Since we joined the EU or sometime later, single phase was standardised at 220-230 volts.

Yes, but it was a fiddle. Although EU standard is nominally 230V, there is a sufficiently large tolerance band (+/- 5%, from memory) to allow the UK to continue on 240V and furriners to continue on 220V, as before. Last time I measured mains voltage here, a couple of weeks ago, my meter said 239.5V

 

[pawl]

The boat already has a 3 phase input and a 3 phase generator. The incoming 3 phase (whether from shore power or the genset) is then seperated into it's three 240v phases, each phase is obviously isolated from the other. What i have proposed is to bring up to three 240v inputs onboard and connect them to the existing 240v circuits. With appropriate switching and circuit protection, nothing has changed in terms of safety.

It does not matter if the three incoming supplies are on the same phase or not, the wiring is already installed to reflect that with the current genset and incoming shore power connection that all three 240 circuits absolutely will be on different phases.

Installations such as this are commonplace in industrial settings, where the incoming three phase will supply some of the shop floor and different 240v phases will supply 240v equipment on the shop floor and the offices etc. It's nothing new, back in the 70's my uncle had a new workshop built, the power to the workshop was 3 phase to power the four post ramp. Two 240v phases were taken around the workshop for all of the 240v equipment and the third one went to the house that stood beside the workshop.

There is nothing wrong with this type of installation, it's just your poor understanding that makes you think there might be.

prv made a general point about using more than one shore supply, I was simply responding that I personally would not be happy to do this for the reasons stated. Obviously I know nothing about the OP's electrical arrangements, however, he did ask " Is it possible to take 3 separate single phase/220v cables from the shore and combine these into the ship's needed 3-phase power?" He seems to only need 3 ph for the water pump, this he is going to have to treat separately, given that, he then only needs the domestic single phase. He could easily run this from a single 32amp supply by connecting the three circuits together. Even a 16amp supply could provide about 3.5kw which is enough for most purposes if you're careful not to switch on too many heavy loads at one time. Having 3 phase in industrial premises, where the wiring has to be regularly checked and certified, is one thing. Having it in the amateur marine environment is another.