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Hot Water Diversion

multiplus compact 12V 2000VA - how to isolate water heater while inverting


I am installing a multiplus compact 2000VA, 12V, 120V on a sailboat.

In previous installation using a 3000VA model, there was an AC-out2 output that was not powered while inverting. Since I want the water heater to be powered only by the AC-in, not by the inverter, it was easy to just connect it to AC-out2.

There is no AC-out2 on the compact 2000VA.

How would you recommend I integrate the water heater in the system? the idea is not having to use a source selector switch (ie shore/inverter rotary switch) .

Is there a way to program the aux relay so it's on only when inverting (AC-in off)?

this way, I can use it to control an external relay, with the water heater on a normally close contact. when it's inverting, the contact opens and disconnects the water heater.

Any help appreciated.


david-bossu asked
klim8skeptic answered ·

6 Answers

MultiPlus-II auf Netz, Akku und myPV Verteilung


ich will eine PV-Anlage mit maximalen Eigenverbrauch aufbauen. Möglichst KEINE Einspeisung ins Netz. Momentan sind folgende Komponenten geplant:

  1. MultiPlus-II
  2. BlueSolar <- PV-Panels
  3. 48V-Akku
  4. ColorControl GX
  5. Smartmeter EM24
  6. myPV-Thor-Heizstab

Nun zu meiner Frage, kann ich die Stromverteilung in dieser Konstellation so einstellen, dass

  • Prio1 - der Gesamtstrom (aller drei Phasen) vom PV-Strom bedient wird. Eine Bilanzierung soll ja im Stromzähler stattfinden, so dass ich auf nur einer Phase einspeisen kann.
  • Prio2 - der ggf. verbleibende Strom zur Ladung des Akkus verwendet wird
  • Prio3 - der ggf. restliche Strom mit dem myPV im Pufferspeicher verheizt wird

Ist so eine Priorisierung möglich oder findet das Laden der Akkus und bedienen des Netzes immer gleichermaßen statt.

VG Mazon

mazon asked
yvl answered ·

2 Answers

Can I use excess power to heat water off grid?

I'm turning a truck into a campervan/housetruck, and since I have the roof space I would like to use excess solar to run a small hot water system. I have 12x200W (40V@5A) panels, and I'm thinking 24V to match the truck. The loads will total less than 3000VA because I'm willing to use one cooking appliance at a time (I have been doing this already as a test). I'd rather ask dumb questions of online forums than people trying to make a living selling solar setups, so here I am :)

I think I want something like this: either MPPT 150/100 (3s4p, 120V strings) or MPPT 250/100 (6s2p, 240V strings) feeding a Multiplus 24/3000/70 with a Color Control GX and BMV-702 battery monitor. In Australia a Sentry 24V/150AH is $4000 ($1.05/Wh, charge at 60A) while the Victron 24/200 is $6695 ($1.35/wh, charge at 100A) and I'm not keen on spending the extra $3000 if I don't have to. I don't need the extra storage, just the extra charge current acceptance.

Hot water can be either 240V AC or 24V DC, element changes are easy. And the thermostat will cut power when the tank is hot enough.

The question is how I get the power diversion to work. I'm told it can be done but I have been wandering round the Victron website feeling lost. Please advise.

Second question: if I want to limit charge current to 60A, can I use a MultiPlus 24/3000/70 rather than needing a 24/5000/100 and program it to limit the charge current?

thanks for any help

moz asked
jomugu commented ·

8 Answers

Inverter loses charge every night. SOC reads 100%, but the inverter only turns on when the sun comes out.


Our inverter doesn't seem to hold a charge anymore. We've only had this system for a couple of months. Everything was working perfectly. Out of nowhere we began to lose power in our RV in the middle of every night despite the SOC being very high and us using little electrical appliances during the night. The app shows the inverter is set to "off", despite trying to turn it on. Once the sun begins to rise, the app shows the inverter is still "off" while it is charging back up, and is usually at a super low voltage around 4-8V. After a few hours, it's up to around 13V, but then doesn't get much higher than that.

We have 3 lithium batteries connected that are fully charged. We see the inverter dies at night, and the app shows the low battery warning, yet the SOC is still very high (usually above 80%).

We believe the SOC trickles down to 80% because our lights are hardwired into the batteries.


We haven't had a problem for months up until now. We think it may have had to do with a recent software update. Also, we bought a space heater and used it in our outlets for a couple of days. We made sure our batteries didn't go below 70% while using it, just wanted to heat up the RV in the mornings. Sometimes, when using the heater, the power would cut out and then turn back on.


We've tried resetting everything to default, checking for updates, restarting the system - nothing works. Any help would be greatly appreciated.

liahskoolie asked
Alexandra edited ·

3 Answers

The PV inverter assistant not working well

Daniel Boekel@victronstaff

5 Kw Multi plus inverter, Blue solar 250 / 100 charge control. My PV AC Thor. 5.2 Kw PV. 48v LiFePo battery pack 216 Ah.

The PV support assistant is not working well. In the morning the solar input charges the batteries up to absorbtion level. The Multi then increases the frequency, and the MY PV AC Thor sends power to the immersion element.

As soon as the batteries reach float level, the Multi reduces the frequency to 50 Hz, and the AC Thor stops delivering power to the immersion. For the rest of the day the frequency remains at 50 Hz even when there is plenty of surplus PV power.

Please advise how to improve this. The AC Thor is an expensive device, and it is frustrating that we cannot get help sorting out why it is not performing as it should in conjunction with the Multi plus.

Robert Bazalgette asked
shaneyake commented ·

2 Answers

components needed to charge batteries and then go to hot water heater

Good day all.

I am new to this technology and am getting conflicting answers in the "retail world".

I would like to set up a solar system (2x350 Watts) to charge 4x100aH LiFePo4 Batteries and when those are topped up to switch over to start a hot water heater (Bosch or Rheem) to heat the water. Of course at a set temperature I would want to switch off the heater and not have it switch on again until it dropped several degrees so it is not cycling on and off too often.

What components do I need (and what specs) to make this work efficiently. I am thinking I would like to use the Cerbo GX to monitor all of these (and more) devices.

I would appreciate the solution details and any things I should be concerned about that could go wrong.

Many thanks,

davidervin asked
shaneyake edited ·

1 Answer

Hot water diversion assistant setup Mulitplus2 with overload shut off

I have some answers about hot water diversion based on SOC readings and load control with programmable relay, genset assistants with a 3kw Mulitplus2.

Answer i have found for grid tied and off grid system: Under testing 12/04/2021.

Re Diversion control of surplus PV power. EG Hot water cylinder heating, with a small Multiplus2 3kw 48v inverter with overload control, turn off hot water cylinder when other loads come on. Main house loads are top priority, hot water cylinder is second priority

This is what is have done and tested to date and it's works like this.

Start genset assistant first with inverted relay function open relay, and set loads to suit inverter type, times, watts etc.

Then add programmable relay with off function with low SOC %

Then add another programmable relay on function with high SOC % Note: not required works without the SOC high function, this might cure the overload if you exceed the high% set point?

Note1: If you have the high SOC below 100% any thing above that % will stop the over load function from working and keeps the relay on all the time, in which case you will get a overload warning alarm or shut down etc. So to stop this remove this last assistant.

Note2: If it says lower% but that logic is reversed, anything above activates the relay

Note3: With just the Genset start and the first relay assisant installed the system works perfectly, in that it diverts the excess PV power to water heater load and shuts off when the loads are to great.

Example system test:

generator start and stop (size:197)

*) Use primary programmable relay to start generator.

*) Open relay to start generator.

*) Start generator when load higher than 1200 Watt for 2 seconds

and stop generator when load lower than 1100 Watt for 2 seconds.

*) The generator is not stopped by AC input.

programmable relay (size:30)

*) Use primary programmable relay.

*) Set relay off

*) when SOClower than 78%. See Note1

programmable relay (1) (size:30) See Note: 2

*) Use primary programmable relay.

*) Set relay on

*) when SOChigher than 100%.


Rob D


Rob Duthie asked
Rob Duthie edited ·

3 Answers

Blue smart 12v/30A 3 outputs - I only need 2 outputs

Can the unused output be safely left floating?

michael-furminger asked
Stefanie answered ·

1 Answer

Multiplus generator assistant to switch ACOut2 to run a electric hot water system

I have a multiplus 24/3000. 400AH @24V lithium battery bank. I want to heat hot water when on shore power and also when battery is close to full. Heating element 1500W. (it is in a heat exchanger that is heated by bus hot water too). I am looking at powering hot water off multiplus the AC2 circuit. Looking to use the generator assistant to control the AC2 outlet

*)Use ACOut2 relay to start generator

*)’open relay to start generator' - this inverts the logic

(start generator = open relay to turn off ACOut2)

*)’start generator when load higher than 5000 W for 5 seconds’ -and

Open ACOut2 when load higher than 2400W for 10 seconds

Turn off hot water when load higher than 2400W for 10 seconds

'stop generator when load is lower than 1800 W' -

Close ACOut2 when load is lower than 1800W

Turn on the hot water when load is lower than 1800W for 10 seconds

*)’Start generator when DC input voltage is lower than 26.5 volt' -

Open ACOut2 when DC input voltage is lower 26.4

Turn off hot water when voltage is lower than 26.4 will have to experiment with this to get about the SOC I want especially with voltage sag.

*)stop generator when DC input voltage is higher than 26.61 volt' -

Close ACOut2 when the DC voltage is above 26.61

Heat hot water when the voltage is above 26.61

*)When the generator is started must stay on for a least 10 seconds

When ACOut2 is Open and the hot water system is off must stay off for 5 minutes longer.

*)The generator is not stopped by AC input

I am not sure about this command, I assume it applies to the assistant as a whole, that is not effected by inverted logic with the start/stop, but will allow the assistant to run or remain in its current state even if AC input is active. That is I have shore power.

Francis Hemeter asked
Francis Hemeter answered ·

4 Answers

Using Smart Solar MPPT relay switch to divert source solar to PWM 12v DC dump load

I am looking to upgrade the solar controller on my boat and would like to add a 12v immersion heater to use any excess solar to produce hot water once the batteries are charged. I've read other posts and the challenge with using relays controlled by the MPPT controller to switch the load on and off on the battery side is sizing the 12v heater load so that it doesn't exceed the solar's excess charging capacity and micro-cycle the batteries.

Hot water is the last remaining item that we currently can't generate without shore power or running the engine. We plan to cruise and even if it takes 2-3 days to heat our 8 gallon water tank it would still be worth the effort.

I was wondering if it's feasible to instead of placing the relay on the battery side of the MPPT controller, to put it on the solar array side to divert some but not all of the solar array to a separate PWM load controller attached to the immersion heater.

So when the batteries need charging the programmable relay is off and all of the solar panels are feeding to the Smart Solar controller. Once the Smart Solar controller reaches float stage, it turns the programmable switch on which activates a DPDT relay that switches the main 400 watt collection of panels over to the PWM load controller directly attached to the immersion heater (no battery) while 100 watts of solar remain attached to the MPPT controller to maintain the float voltage.

If the load on the MPPT controller increases and it can't maintain float, the switch would turn off and add the 400 watts back to the MPPT controller. I'm thinking that the Smart Solar controller would 'see' the drop in available wattage as if a cloud moved over a portion of the array and adjust based on the remaining wattage.

Would this work as an alternative to looking at another brand of MPPT controller that has an integrated auxiliary output? I'd really like to build my system out using Victron.

System details:

4x 100w solar panels (12v parallel) on DPDT relay

2x 50w solar panels (12v parallel) directly attached to Smart Solar

Smart Solar controller with programmable switch

PWM load controller (TBD)

50A DPDT relay with outputs to Smart Solar and PWM controller

300w 12v immersion water heater

4x Trojan T-125 6v FLA house batteries (series + parallel, 12v, 480AH)

gregtorok asked
daniel1957 edited ·

1 Answer

how to divert excess PV energy when Solar Controller is in float mode

I have a 48v stand alone energy system comprising 2200 AH gel batteries charged by 2 PV arrays of 5kw each.

The Victron management system comprises a 10kw Quattro, 2 x 250/100 MPPT controllers, BMV712 and Venus.

On average the batteries go 100% SOC each morning at about 10:00 and by 12:00 (midday) they are on float with PV largely not utilised.

I wish to utilise the excess energy into water heating whenever the MPPT controllers have the batteries on float.

It seems to me that the system SOC is not a good, effective nor efficient way of tripping this point.

Water heating by 230v AC is a far better method of energy collection than solar hot water collectors however the Victron management system appears to not cate for this most basic requirement!

Years ago when I operated a 10kw wind turbine, I built a voltage regulator in the DC turbine output that would divert raw DC output (prior to the battery charging regulator) from the alternator into a water heater. I had it set up so I could adjust it from 58 - 62 v. It worked brilliantly and helped to keep an even load on the turbine thus saving it feathering the blades in strong winds.

Surely the Victron MPPT controllers should have something similar with suitable hysteresis parameters triggered by the float condition?

daniel1957 asked
daniel1957 edited ·

3 Answers

Heating Water

I haven't bought any solar kit yet. I want to charge 420Ah of batteries on a boat and I have a Mastervolt Combi, Inverter, Charger 12v/1500/65. Space limits me to 2X150W to 200W panels mounted on the side rails. I want the opportunity to wire them in series or parallel, I also want to load divert to an 800W 220Vac water heater. How do I do it what kit do I need?

Andy Todd asked
oceanwolfe answered ·

1 Answer

Choose victron Hybrid system with 5x LG X NeON®2 365 W

I am new in victron solar system.

I got:

5x LG X NeON®2 365 W on my roof, (i had to install panels during new roof instalation)

300L 3000W unused water boiler connected to my water network (i use gas)

48V 10AH unused bike battery with BMS (

i am ongrid but want to be able to have power during cutoff during day with solar panels for water boiler, or little lights during night (3W *4).

My questions:

With victron system, can i realize that:

-use real time solar production with regulation to send it to water boiler below 3000W depending on production, and never use battery

-is a Bike battery like i have can be used in a victron system, but only for powering victron system and little lights in case off cutoff

-What configuration do you advise? Multigrid or other? i will add other panels in few years.

In case victron system cannot regulate power consumption to production, what system do you advise?

Thank you for your assistance

julio asked

0 Answers

Can I use 150/35 controler to directly power 48 volt heating elements?

I plan to use the 150/35 to power 48 volt heating elements in a water tank. My question is: can I power the controller with a 48 volt d.c. power supply (powered, obviously, from a separate, existing system) instead of a battery bank? Thank you.

openplanet asked

0 Answers

How a GX do to estimate de unused MPPT power ?

There is many threads about unused MPPT power and how to optimized load like water heater using this information but my question is specifically on a GX function.
The GX has yet an option to goback to grid all unused MPPT power. My GX interface is in french but the option is Something like "Feed-in excess solarcharger power".
When this option is set i see a variation of the AcPowerSetPoint parameters when MPPT is in absobtion or float mode.
I prefer to use the any unused MPPT power to activate specific load (like water heater but not only) rather than do grid injection.
My questions are quite simple :
- How the GX calculate de correct AcPowerSetPoint regardless the unusedpower ?
- Is there any MQTT topic(s) to catch this information ?

amrane asked
Phil Gavin commented ·

7 Answers


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