Wiring Multiplus and heavy loads

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5teve asked Feb 13, '19

Wiring Multiplus and heavy loads

Hi

I'm new here and new to Victron Products - I have just picked up a used Multiplus 12/3000/120 and am just doing some planning before installing into my boat. I'll have heaps of questions but i'll post them one by one.

The boat already has a 240v system and this will be integrated into it, however I have some questions.

The boat has a couple of heavy draw items the main one being the water heater (works on engine but also 1800w element) which I obviously do not want to be connected to the Multiplus.

My question as this is an older multiplus, and doesnt have AC out 2, is how do people generally wire for this type of system, i'm thinking the shore power / genset feed gets split into the inverter and also into a separate feed. This way the hot water operates on genset / shore and the remainder of the mains sockets can operate off the inverter (heaviest of loads will be the kettle which may get used a couple of times per day) but i'm figuring this will need another MCB / RCD protecting the split non inverter side..

As an aside I have 800ah of batteries split into 2 banks of 4x 100ah each bank on either side of the boat, combined by a selector switch and cables all the same length to the centre of the boat. then a single 12vdc cable out to house loads - this will include the inverter but wiring will be upgraded to 95mm2 as the main feed and 70mm2 from each bank to the selector

If anyone has any wiring diagrams to share that would also be awesome..

Steve

Phoenix Inverter

2 |3000

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Answer 1 · 2019-02-13T19:35:39Z

ben answered · Feb 13, 2019 at 07:35 PM

A common approach is a primary distribution panel serviced by the shore supply, with a single circuit dedicated to the inverter-charger. The inverter-charger output then feeds a subpanel where all the inverter-supported loads are placed.

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Answer 2 · 2019-02-14T03:34:06Z

JohnC answered · Feb 14, 2019 at 03:34 AM

Hi Steve. Like Ben sez, it should be fairly simple.

But seems you have 8x batts in parallel. Presuming Pb's, you're going to have to keep a close eye out for imbalance, especially as they age. That may manifest itself in raised temps in the odd batt under heavy charge. Just a touch-test may suffice, but it's something to be aware of.

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Answer 3 · 2019-02-14T04:09:51Z

5teve answered · Feb 14, 2019 at 04:09 AM

Thanks Both

Not a straighforward integration into the existing but shouldnt be too hard by the looks of it.. I'll likely need a new mains board anyway as the existing is 20plus years old. The water heater is already on its own circuit so shouldnt be hard to break out.

Re the batteries, yes I puzzled over this for a long time last year. essentially I have 2 parallel banks (i have no real option for anything else due to the way the storage area in the rear of the hull is laid out.) - 4 batteries each, each bank is linked with 70mm2 as short as possible (probably 200mm) positive and negative feeds are from the end 2 batteries to keep things as balanced as possible. Each cable to the combiner switch will be 70mm2 (currently 35mm2 which was fine for house loads) and is within 10mm length wise of each other - likewise with the negatives. and they are no more than 1.8m long.

From the combiner switch there is a single cable to the loads (will be 95mm2 once inverter is in) Charger currently is connected to the switch on the single output side of the switch and is 60a - when the Multiplus is in I dont think I will be running much more than 80amp charge (10%) unless I need to stuff charge in from the genset. All house negatives feed from a shunt (currently a cheap wireless one that works very well, but is only 300a so am likely to need to upgrade to 500-600a, but will look at what victron has to offer to intergrate.

the advantage I see for using the switch is that should anything happen to a battery, I can isolate a bank and still carry on with my weekend or whatever - just being mindful of power. Far better and less risky than 1 bank of 8 in paralell

I run a pair of single direction VSR's for charging from the alternators, once cranks are up to voltage the VSRs open allowing both alternators to fight it out for charging the house bank - and it appears to work ok.

The original wiring (pre multiplus and only 600ah) is as attached below - just a quick knock up using tinycad.

leeder-layout-as-built.png (36.8 KiB)

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JohnC ♦ commented · Feb 14, 2019 at 04:57 AM

Yeh, you seem to have it pretty well sorted. Re the batts, If one fails, the others could discharge into it. It will get hot, and if you ever see that, just lift a terminal from the offender and carry on with what's left.

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5teve JohnC ♦ commented · Feb 14, 2019 at 06:56 AM

Yep a bit of thought went into it - I'm not convinced its right but its better that it could have been. Certainly not best practice! I do need to add a buzzer for a low voltage alarm which should show a problem - It can be driven by the wireless shunt until I get something better.

Steve

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