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Craig Allen avatar image
Craig Allen asked

Help / advice needed for 3 phase ship system starting with single phase install

I've looked for other answers, but not found something that answers the specifics of below


For background and context to the questions.

I have an old ship that takes 3 phase shore power and internal wiring / consumption across all 3 phases. The current shore power is 16amp at 400v (Sweden) giving peak usage of 11Kw across all three phases.

The system is all 240v on the consumption side baring an achor winch and old electric heating (not used) at 400v. There is a 6kw sh*ty 3 phase 6kw generator (will be replaced).

The DC side is 24v, with a 100 amp engine alternator for starter and house battery charging, plus an old Victron Skylla 24v mains charger. At the moment the house batteries are 200AH (5ish Kwh).

I cannot afford 3 multiplus' in one purchase, but I need to install at least one invertor to fix the issue that I have no power when the shore power is removed (existing inverter not working and modified sinewave, installed by last owner).

Off shore power I will need max 9kw (3kw per phase) across all phases for brief periods with average of about 2kw peak for induction hob and oven



So, the questions are...


Can I install a single multiplus to power all phases as a short term solution until I can purchase 3?


Can I install a multiplus to power just a single phase when not on shore power?


If I have 3000/24 on a single phase, can I use self consumption from the batteries even if I am plugged into shore power for the phase in question? I guess this is phase compensation, but with only one phase?


The 24v 3000VA multi is technically 2400w, if I set it to disconnect none-essential loads when not on shore power, I can keep the usage below 2400 peaks, but I'm kind of on the border of needing the 5000VA version. IS the 5000VA overkill rather than managing usage instead?


If I put in more batteries to spread the current draw over say 10 x 100AH 12v which would give 24v 500AH supply, with peak draw of 500amps at 1C and I would be peaking at approximately 400amps to deliver 9Kw, is this considered too much draw for 24v? The batteries will only be 1.5m cable run from the multis and the draw would be 130amps ish per multi. The average draw will be in the 30 - 50 amp range when in use


The ship systems are all 24v, but would it be best to consider 48v storage and then use 48v to 24v converters to power the ship systems and install a 24v to 48v battery charger to draw power from the engine alternator?


Sorry, for a long post, but I am trying to decide the best solution, so I can begin to install :)


Look forward to your replies


Craig






MultiPlus Quattro Inverter Charger
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5 Answers
thorenj avatar image
thorenj answered ·

Hi Craig,

I'll answer your questions briefly, hopefully, others will chime in to form a complete answer.

  • Can I install a single multiplus to power all phases as a short term solution until I can purchase 3?
    • In principle, no. It might work with your 240 V (single phase-neutral) appliances, but will definitely not work with anything 400 V (3-phase). Since this is a system designed to use all 3 phases, with a mix of single-phase and 3-phase, you'd have to thoroughly inspect and modify the wiring to make sure no 3-phase appliances are connected. This will most likely be too much work for a temporary solution, and if not done correctly, stuff will break.
  • Can I install a multiplus to power just a single phase when not on shore power?
    • This will be easier, but still risky. You'd need to be very sure that no 3-phase appliances are trying to turn on. It would be best to temporarily disconnect the unpowered phases completely.
  • Can I use self consumption from the batteries even if I am plugged into shore power?
    • If you get the multiplus working on one phase, it can use power assist to boost a weak shore connection.
  • Is the 5000VA overkill?
    • The best person to answer this is you, or an on-site consultant. It all depends on to what extent the non-essential loads can really be considered non-essential.
  • Is 400 A considered too much draw for 24v?
    • It depends on the battery type used, and how brief these maximum high-power scenarios are. You'll have to read the datasheet for your batteries. Check the discharge table in this pdf for an example. In general, it's better to use fewer, larger batteries, rather than a bunch of smaller ones. 1 C from a 200 Ah battery is the same load as 1 C from two 100 Ah batteries in parallell.
    • The cabling is no problem, just make sure to use large enough cables.
  • Would it be best to consider 48v storage and then use converters?
    • In most cases, no. This introduces more losses, more stuff to go wrong, increased risk of unbalanced batteries, and more complicated wiring. Since your normal load is less than 50 A at 24 V, keep it simple.
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Craig Allen avatar image Craig Allen commented ·

HI Thoren,


Thank you for answering, this makes sense and I appreciate you taking the time to reply


Craig

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thorenj avatar image
thorenj answered ·

No worries, glad to help. Where in Sweden are you located?

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Craig Allen avatar image Craig Allen commented ·

I'm based in Stockholm at the moment :)

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thorenj avatar image thorenj Craig Allen commented ·

Ah, great, then you are close to both the outstanding Victron distributor, Odelco, as well as a number of competent installers, should the need arise. I've had good experiences with BN Marin on Dalarö, as well as Teknoservice in Saltsjöbaden.

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Craig Allen avatar image Craig Allen thorenj commented ·

Cool, I'll check them out. I am trying to find out as much information as I can so I can have an educated conversation with a supplier / installer without being "oversold".

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max-b avatar image
max-b answered ·

About, the sizing of the Multiplus, the data sheet state a temporary max load which is significantly much than the permanent power output capacity. In my own experience, we lived 12 years in an autonomous house with a 2000/24/60 and I can testify than the inverter is able to cope with temporary power surge. We now replaced the Multi for a 3000/24 and are more confortable. My Prius plug-in charges on it (the battery is feed from an hydro turbine, this AC ->DC->AC setup ensuring clean and steady power).

From my past experience with boats, I'd say that many are way to power hungry. We can now be much more efficient in power with no loss in confort. Having a 3 phases system for only one appliance (the anchor winch) may be questionable. It all depend of the effective power you need on the winch and rather than rebuilding a 3 phase system, wouldn't a single phase winch be a much cost effective option ?

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Craig Allen avatar image Craig Allen commented ·

I have been considering changing the winch to single phase and investigating options, but it has been a low priority, but you make a good point for sure. I purchased the ship with everything already installed, but needing attention and upgrades. I am definitely open to changing to single phase, just trying to figure out if there is a downside to this option.

With regard to converting everything to single phase, one challenge I may have is that single phase shore power is usually max of 10amps at 240v. This is might be limiting for peak usage that I have at the moment, is there a way to take 3 phase 16amp and get it to still be 11Kw on single phase on the ship?

Thank you for your help :)

Craig

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thorenj avatar image thorenj Craig Allen commented ·

If you're not planning on using the old 3-phase heating, and if you're open to changing your winch, a single-phase system might work long term. It all comes down to what your off-grid power use will be, and whether a Multiplus 3000 (or larger) can handle these loads.

You can't (with reasonable cost) combine 11 kW 3-phase into the same power on one phase. You can, however, try to segment your loads, so that you can still use a 16 A 3-phase shore connection. This will then be treated as three single-phase connections of 16 A each, which gives you some 3.7 kW to use on each phase. You will then have to spread out your one-phase loads on the three phases so that no single phase is loaded with more than 16 A. One of these three phases will be connected to your Multiplus, and all your off-grid 230 V single-phase loads.

(1/2)


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thorenj avatar image thorenj thorenj commented ·

(2/2)

If you use the Multiplus 3000, you'll be limited to about 10 A continuous on the off-grid phase, with about 25 A surge. With the 5000, you can use design the loads för 16 A continuous, so more in line with the other phases. Both the 3000 and the 5000 will be able to use Power Assist to boost the shore connection on this phase if you temporarily need more than 16A. Power Assist can also be used if you want to use a single phase 10 A shore connection in a guest harbour.

With a single-phase shore connection. you can't use the appliances on the "non-off-grid" phases, but at least you'll be able to charge your batteries and power your most essential 240 V loads.

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Craig Allen avatar image Craig Allen thorenj commented ·

Thank you again for a great reply. Let me summarise so I understand.

Remove any 3 phase devices (winch, heating...). Choose essential loads and place them on an "off-grid" 240v phase and other loads that are non-essential onto the other two phases. Install MP/Quattro onto the "off-grid" phase to power key systems and set up a single phase connection for guest harbours to charge batteries etc, but not power all three phases, when off-grid.

Hopefully, that makes sense and I understood correctly?

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thorenj avatar image thorenj Craig Allen commented ·

Yes, exactly!

Just a small note regarding the shore connection; the corrrect solution is to install a separate inlet for one-phase use, combined with a transfer switch to select one- or three-phase shore power. A simpler solution is to build an adapter cable that lets you connect the shore power single phase to the off-grid phase.

You should also consider installing a way to limit shore power amperage, either a Multi Control, or a CCGX.

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JohnC avatar image
JohnC answered ·

I very much like the single phase scenario. Just the saving on a replacement single phase genny might go a fair ways to compensate the cost of a new winch motor.

3 phase shore, you already have a Skylla for one, and will have a Multi for another. Both can charge batts concurrently.

Your 'separate phase' circuits can simply become separate circuits once you leave shore. Sizing your Multi for future 3~ service goes out the window, just pick out a single (or a bigger Quattro) to do the lot.

Just thoughts, tis your ship Cap'n. :)

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boekel avatar image boekel ♦ commented ·

I agree, also the standby-consumption goes down, and imbalance on phases can be problematic on 3 phase systems.

If you only have a winch on 3 phases, you can probably use a VFD (Variable Frequency Drive) for that.

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max-b avatar image max-b boekel ♦ commented ·

Imbalance on phase are problematic on stand alone setup. Depending of the shore equipment it may not be dramatic to have only two phases loaded as suggested by Jonh. The big Multi in power-assist to feed that (hungry) boat. The Skylla to compensate on the battery DC. Most probably it will not last too long at peek power so that may be a smart setting if correctly wired.

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Craig Allen avatar image Craig Allen max-b commented ·

@Max_B She is definitely hungry :) Old trawler that has been converted to live on... I'm trying to make things more efficient :) put her on a diet! Have diesel heating now, so that shaved off immense electrical load... For example, there's an 2kw 240v water pump for the water maker and an 800w 240v water pump for shower, taps etc, 1kw electric water heater, induction hob and oven at 2kw each. This is part of the challenge, install inverters for the current load, or install for lower load and work on making things more efficient. The main issue at the moment, is no shore power, no 240v without running an old generator that was designed for power tools and fries electronics. Making a poor decision now could end up costing a lot more in the longer term. I really appreciate all your answers and advice, it is really useful to bounce ideas around and things i'd not thought of

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Craig Allen avatar image Craig Allen commented ·

@JohnC Thank you, definitely makes sense. It's a case of planning out the right changes from the start and making steps in the right direction so as not to waste money. :) One bigger unit makes sense and cost effective vs three smaller units.

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boekel avatar image
boekel answered ·

When configuring a 3 phase system to 1 phase, please take care that wiring is up to spec: a 3 phase cable with 1 neutral, can only carry 'return current' through the single neutral cable (where as in a 'fully loaded' 3 phase setup it doesn't carry any current)

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Craig Allen avatar image Craig Allen commented ·

Good point, thank you. I was planning to get an electrician to look at it to give me advice. I'm planning to do the DC part of the install, but get a pro to look at the AC and review my DC install as well.

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