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Hot Water Diversion

PV inverter support assistant and DVCC


I have been succesfully using the PV inverter support assistant of a Multiplus 2 to control an external heater (excess solar energy dump in off grid system) via frequency shifting. My system had lead acid batteries.

Now I changed to Pylontech batteries. Charge control is now done via DVCC.

This caused the PV inverter assistant to stop working. I can configure the assistant, and as long as I don’t plug in the VE.bus cable of the inverter in the Cerbo unit, it works: ac output frequency is increased by Multiplus, as expected.

However, as soon as I plug in the cable, and thus establish communication with the inverter, the DVCC seems to overrule the inverter and PV inverter assistant stops frequency shifting.

Is there a way to make this work?



alexander-aerts asked
alexander-aerts commented ·

1 Answer

Excess solar diverting

I’ve just fitted a Cerbo GX to my boat. My set up is 780w solar panels, 100/50 Victron MPPT, multiplus inverter which hardly gets used as the boat is mainly a 12v set up and a smart BMV 712..

I’ve fitted a 300w 12v element to my hot water tank which works well, it’s wired in by a manual switch that I have to switch on and off.

is there a way of getting any excess solar load to heat the water when the batteries are at 100%.

Possibably to be able to trigger it remotely via the cerbo when we are going to the boat to arrive to a tank of hot water.


Simon Coram asked
Rob Duthie answered ·

4 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
taylortops edited ·

10 Answers

Ac Thor in off grid system using dvcc, will this work ?

Hello I have a great working off grid system sytem based on a easysolar 48v/3000 two pylontech us3000c batteries and 5Kwp solar. There is no solar on ac out. Only a dc charger (part of the easysolar)

The system is set to use dvcc. My question is : iff I use the frequency shifting function on ac out to regulate a ac thor on ac out ,will that work ? The ac thor will regulate a water boiler.

Especially considering the use of dvcc, I have read on this comunity sometimes problems ocure when using an ac thor in off grid instalations. These problems could then (partly) be solved by further ajustments of float voltage etc. In vdcc that (ajusting voltages) is not possible because the battery determines the voltage and current it gets. So do you think it will work ? Has anybody got this working ?

arie asked
klim8skeptic commented ·

0 Answers

Dumpload – Hot Water – Legionella, Efficiency ?

I am still in the planning phase of an off-grid system (MP II + AC-coupled Fronius or Fimer + LiFePO4 battery), reading for months now all relevant infos.

Using a hot water boiler as a dump load in case of excess PV inverter power sounds attractive, otherwise that power would just be lost (because the MP II would throttle down the solar PV inverter when the batteries are full).

But it does raise a few issues :

a) Legionella

Most water boilers (at least in France) take a long time to heat up, depending on volume of the boiler and capacity of the heating element (anywhere from 1,5 up to more than 5 hours).

During summer this may not be an issue : provided the solar system is correctly dimensioned there will be plenty of excess PV inverter power over the day and the water heats up to the temperature configured on the water boiler (typically a mechanical thermostat in simple boilers), say 55+ C.

However during winter this is rather unlikely and water may be heated up to e.g. only 35 C. That´s a perfect temperature for legionnella bacteria colonies to grow (growth range : 25 – 45 C). You won´t be taking a shower at 35 C, so you will need some means to increase the temperature (e.g. gas heater). Unfortunately, while showering the water temperature gets increased to e.g. 55C in the gas heater for only a very short time, not long enough for legionella bacteria to die, which takes 5-6 hours @ 55C and still more than 30 minutes @ 60C).

You would have to heat up the water to 70 C for the legionella bacteria to die instantly. But that takes a lot of extra gas ….. and so you would loose the energy saved by means of the dump load, possibly even more.

Legionella is not wide spread in western Europe, but if not recognised and treated early on potentially very dangerous.

All this makes me wonder if a boiler dump load is a sensible solution. Any comments ?

b) Efficiency : AC Thor, SoC

Heating water electrically is not very efficient, but who cares about efficiency if that electricity would otherwise be lost ….

The My-PV ´AC Thor´ is a technically clever solution, but rather expensive (because you also pay for a lot more functions which you will never use in a ´dump load only´ scenario, a fancy LCD which you will never look at again once the system is correctly up and running, data logging, etc). IMHO technically it may be the best, but no pay back in a reasonable time frame.

Switching on the boiler via the relay built into the MultiPlus II based on SoC is a standard feature at no extra cost, except for boiler, piping, cabling and RCD. But it will eat some battery capacity and if for example you switch on at 99% SoC and off at 95% SoC it will likely take a very long time for the boiler to warm up (switching on-off-on-off- ….), with the potential risk of the (literally) tiny problem mentioned under a) …..

All this makes me wonder if it is not far better to save the money otherwise spent on a dump load solution and put it in the budget for larger battery capacity.

Any thoughts / comments ?

rvicev asked
rvicev commented ·

1 Answer

Activate dumpload before 100% soc

I have a situation where my batteries reach about 80% soc by 8am on sunny days and the bateies lower thier charge current to say 20A although I may have a potential 100A available, i have a dumpload relay that turns on an immersion heater when the soc reaches 100% and off again when it goes down to 98%, this works well but I know on sunny days I could turn the dumpload on much earlier (at say 75-80% soc) so I was thinking of having the relay triggered by a light intensity sensor connected to an arduino.

Sorry if that was a bit long winded but I'd be interested In hearing people's thoughts or design idea's

Set up is

SmartSolar 150/100

Multiplus 48/3000/35/50


2x pylontech us2000b

8kwp solar

lief ryan asked
lief ryan commented ·

2 Answers

Will running an ac water heater on a viltron inverter lead to premature failure of the inverter?

We have a sailboat equipped with a multi plus compact 12/2000/80 inverter charger, 4 200 AH Victron Lifepo4 batteries, a Victron Smart BMS and 650 watts of solar panels. Currently our inverter feeds only our onboard AC outlets but we are using very little of our solar power that is available during the day since we have few energy consumers installed on our boat (dc watermaker, dc refrigeration, no freezer, low draw autopilot etc). We asked our Marine electrician if we could connect our AC water heater to the inverter for occasional use during the day while solar power is high. There are similar questions mostly about automating the process, I don't want the process to be automated, I just want to be able to switch on the water heater at the panel with the inverter operating and an excess of solar power available. After an hour or two and before the batteries are significantly depleted, I would switch off the water heater.

Our marine electrician is concerned that the inverter will be strained with a load like the 1500 watt water heater and it will lead to premature failure of the inverter. Is the Victron 12/2000/80 adequate for running a 1500 watt water heater by manually switching it on and off when there is excess solar available and will it lead to premature failure of the inverter?


audreytaylor asked
wkirby answered ·

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
matt1309 answered ·

2 Answers

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
taylortops commented ·

1 Answer

Hot water power diversion idea

I've seen a few questions of the forum about how to use excess power to heat water. Here's my plan (img) for a fully off-grid installation. I'm using a microcontrolIer to nuance the logic (and happy to share that code). I could use the relay out of a Cerbo for simplicity but I'm using the GX in the EasySolarII so no relay available. BMV relay also a nice option.

I'm using a cheap (arduino-based) microcontroller to read for sufficient SoC and PV Power (and possibly Charge State and Battery Power) to then drive a logic pin tricking the temperature differential controller into thinking it has heat in a liquid solar collector. The TDC drives a beefy MOSFET into conduction if heating is in demand. Note, there's no additional AC load impacting the inverter twins, this is purely "opportunistic" 50VDC load.

You could bypass the TDC and have the microcontroller read temps and drive the transistor, but I'm using the TDC to also shunt heat out of a wood stove during winter and it needs to manage both sources. The design presented here helps in the summer months, when there's excess solar and less wood heat. The logic is described in the image.

The Tank140 logs the state changes for me so that I can view the activity remotely. I plan to add a second BMV to track the diverted power. The TDC also has a remote dashboard that tells the whole story. I tend to idle the water at 30degC then ramp it to 55degC some hours before needed.


taylortops asked
taylortops edited ·

0 Answers

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

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

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

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