Clever Switching for water heating.

[SquirrellCook]

Simple configuration. Plugged into the Mains hookup and you can flick a switch for the 240v element in the calorifier.
As above but a Multiplus is inline with the switch on the output side. So you could heat the water from batteries.
Battery saving/extra harvesting. Use a BMV relay to operate a relay across the switch so that it can be set to close the circuit above 98% and open at 95%.

Worries.
Whilst on EHU and fully charged the relay would close across the switch whether it was off or on.
If in storage it could still keep heating water unless you disabled the BMV closing the relay.

Does it need to be more complicated or have I missed something?

 

[wildebus]

Got a few options you can utilize...
Firstly I would say you need to get an SSR - Solid State Relay - that lets you control the AC Circuit via a DC level signal (e.g. BMV Relay). Example of a SSR - https://amzn.to/3wmf3ba (These are the ones I use). Depending on the wattage, you may or may not need the heatsink. I'd suggest fitting one - never hurts to keep it cooler
On the AC Side, connect Live from MP to one AC terminal, Live to Calorifier to other AC terminal. Connection DC -ve to ground (could use AC Ground line if you wanted) and DC +ve goes to BMV NO and BMC COM to +12V.
Setup the BMV Relay so it goes on below 95% and off at 98% and toggle the "Invert Relay" switch in the BMV settings.
(side note - the BMV Relay is designed to enable 'something' when the SOC DROPS. you want to enable something when the SOC INCREASES, so you have to inverse the logic)

You could add a "storage switch" - physical switch in line between BMV and SSR to disconnect relay signal and ensure heater not on.

One issue - the Heater will only go on when the battery is above 98%. If you have a low battery and then have EHU and want to use the mains to heat the water, you need to wait until the battery is charged to >98%.
Options -
1) Go into the BMV settings via VE Connect and switch the relay off (which will enable the SSR). Can be a pain to have to do it that way
2) instead of a on/off "storage switch", fit an on/off/off "Master Switch" - this can let you chose "Heater On", "Heater Off" & "Heater controlled by BMV" with the one switch - but you have to remember to set it back to Controlled by BMV
3) fit an timer to the signal between BMV and SSR, and use this in conjunction with a "Master Switch" - but this time the "Heater On" function becomes a "Timer Override" function. You can set the timer for say 30 minutes for example, and flick the switch to "Timer". It will then operate for 30 minutes and then the timer resets and you are automatically back to controlled by the BMV - this is probably the 'safest' option and still simple.

In my setup I use a SSR, along with the Cerbo Relay (exactly same functionality as the BMV one), a countdown timer and a 3-way switch to operate just like option 3 above for Inverter control
My setup is slightly different however as when I am on EHU, the Boiler bypasses the Inverter so is potentially always on - I control that with a physical 240V Spur Switch which will override anything the Cebro and Multiplus wants to do. That is my "storage switch" I guess.

 

[wildebus]

If it is of interest, I did a write-up here - https://wildebus.com/how-to-automate-power-to-fridge-water-heater/

Mark, if you want a chat on this, just let me know

 

[SquirrellCook]

Yes David, that's along the lines I was thinking. I'm going to use the Cerbo also, so that makes it easier.
I do like the idea of the forced battery run, I might include that.

So operating from the EHU with a user on/off switch. Not forgetting the calorifier has a thermostat.

Operating on batteries based on SOC. Again once hot nothing may happed due to the thermostat.

Forced battery operation using a timer. As above.

In EHU mode the multiplus's relay connects through the multiplus. I guess a relay could be placed here using the Cerbo to open in the event of no EHU power. Otherwise in uses battery power.

In other modes it would operate with a second relay in parallel to the first.

Ideally the user on/off switch as mentioned first would inhibit all other actions.

 

[wildebus]

Are you planning on having an EHU only supply as well, bypassing the Multiplus? It is good to have an EHU-only supply for use with a Room Heater which you would never want on Inverter, and if you had EHU only, you could use a Auto-switching Relay alongside the SOC-controlled control.

Getting the right balance of controllability and ease of use can be fun.
I went out a few days ago in my Motorhome and wanted to use the Fridge on 12V DC driving and 240V AC when stopped (Gaslow tank being empty). But the fridge couldn't connect to the AC . I forgot that I had gone into the Cerbo Console and turned the relay on manually a few days before to make sure the fridge didn't go on as didn't need it
So did the Manual Start as per below:

Remembered that at lunchtime and turned off the relay (so the Fridge AND Water Heater came on).
As mentioned, the whole Victron thinking is you can only turn a device on when the SOC goes low, not when it goes high, so by manually turning on the relay (to turn on the 'generator'), it turns off the SSR (due to the way it is wired).


When I got home, emptied the fridge of the days food and turned it off on the control panel. But ... I forgot I turned the Water Heater on the Spur Switch and the effect of that can be seen below.

Every two hours the heater came on for 10 minutes as the thermostat kicked in, each time taking around 10Ah out the battery.

This would have carried on until the Low SOC check kicked in (I noticed it around 7AM when I saw the Lithium SOC was so low and realised from the pattern in the chart what it must be), but if you bypassed the SOC check with a switch, it would run until the battery voltage was too low to start the Inverter.

It is the first time been out and using stuff since set it up so just familiarity and recollection really. I did some explanation of how the switches work which I need to print off and keep in the van as a reminder
FWIW, I added another feature into the mix to let me control the behaviour of the Energy Saving (AES) mode of the Multiplus as sometimes I want to use it for low-power things which would not be enough to wake it up by itself (for example, right now I have a 18V Ryobi Battery Charger plugged in and that would not be enough).

The SOC control and AES add-on is shown below, along with using the 230V Auto Relay and how the setup interfaces with the Cerbo (and how I'm using the NC rather than the NO to accomodate the way we want to use the SOC in the opposite way Victron assume people do)

 

[mb2tv]

All this sophistication scare me! I will need a system that once set does not need any attention or tweaking, as I will not be the only user, and I do not want to scare the 'other' user away.

 

[SquirrellCook]

All this sophistication scare me! I will need a system that once set does not need any attention or tweaking, as I will not be the only user, and I do not want to scare the 'other' user away.

Shockingly, that's what it's all about. (excuse the pun) Murky is setup on switches and one relay I think. It's remembering how to do what.
I've convinced (maybe) Anita that this will be a simple automated version. And more efficient.

 

[wildebus]

All this sophistication scare me! I will need a system that once set does not need any attention or tweaking, as I will not be the only user, and I do not want to scare the 'other' user away.

The initial setting up has complexity, but once in place you can just leave it with the defaults (OH Mode) , or use the override if you want (Geek Mode).

Some of these things are fairly common elsewhere - for example in the house my hot water and CH timer includes a feature where it is on, off or on the programme - and if you want more heat when the system is off, you press a button and it goes on again until the next cycle. I've seen others where you have a 1 hour boost.
So not really much different from household systems. I like the idea that you can use a Motorhome/Campervan without having to learn lots of new things where possible, but need to have the background system in place to do that

 

[st3v3]

Which multiplus do you have? My AC2 output is programmed to do this without any extra gubbins. It's the generator start assistant you use, PM me if you have an AC2 output and want the details. Cheers.

Edit: here's the details, was easier to find than I thought

Feature Request: Use AC2 Output As a Diversion Load - Victron Community

community.victronenergy.com

 

[wildebus]

Which multiplus do you have? My AC2 output is programmed to do this without any extra gubbins. It's the generator start assistant you use, PM me if you have an AC2 output and want the details. Cheers.

Edit: here's the details, was easier to find than I thought

Feature Request: Use AC2 Output As a Diversion Load - Victron Community

community.victronenergy.com

he doesn't have the AC2 out

But thanks for the post - I forgot about this feature.
Remind me on a detail please .. Can you activate this on an external signal coming in - i.e. the relay control from a BMV? I am looking at a setup which won't include a Venus setup and the SOC value within the Multiplus is not accurate enough to rely on.

 

[st3v3]

he doesn't have the AC2 out

That answers that then lol.

 

[wildebus]

That answers that then lol.

I think the AC2 out is only present on the 3000 or bigger?
Having said that, I do have a dedicated EHU Only Out on my EasyPlus 1600, but that is a pure hardware device wired up alongside the MCBs.

 

[SquirrellCook]

I think the switching the supply to the immersion element will be easy by just using a solid state AC relay. If it sees mains on the EHU the relay will connect it and vice versa.
If I use a BMV-712 on the habitation battery I can use it's relay along with - https://amzn.to/3wmf3ba do do the surplus harvesting.
It's a shame that another switch will be required to run the wildebus timer. This I would happily have it as "one shot" So if you knew you wanted hot water you just operate the switch and it runs for the set time. To use it again the switch would need to be switched of and then on again.
The eberspacher water heater is on a one hour timer.

 

[SquirrellCook]

Relays ordered, lets hope I can shoehorn them into the consumer unit as I'm running out of space!

 

[wildebus]

My first version was suitable for the BMV or Cerbo, but I reworked my electrics to the Fridge and Water Boiler yesterday and eliminated the need to use the EHU-Only supply and a 230V relay - just using the SSR now and added an extra condition into the programmable Relay in the Cerbo GX. This would be for the Cerbo (or Venus or equivalent device) though and not the BMV.

BTW, you can set the relay in the BMV so if it activates it had a run time of at least X minutes - that might be of some use?

 

[SquirrellCook]

Well I've made a start on the clever water heating from surplus solar. A relay is now mounted in the consumer unit along with a wire connecting it.

 

[wildebus]

Looking Good
PS. Little tip ... If you are grounding your AC installation to the chassis (the usual way forward) you can connect SSR Terminal 4 (-ve DC) to the CU Earth busbar. Saves you running a -ve in from outside. and just need the one wire from the Cerbo

I'm at the Kelso meet this weekend and finally got Kens setup working (he is using the excess to run the 3-way fridge on solar via Inverter). Victron supplied a duff BMV-712 (relay worked internally but they didn't connect it to the terminals at the back of the unit!) so needed a new '712.

 

[SquirrellCook]

Enjoy your time away David. I hope you don't spend it all in other people electrics

 

[SquirrellCook]

To make it easier for those with a smaller inverter there is now a 12 volt 300 watt / 240 volt 750 watt element for your calorifier.
12 Volt/240 Volt Twin Immersion 2 1/4" BSP

Marine Immersion heaters

Surecal TITANIUM immersions are superior to all other marine immersion heaters and have been specifically designed and engineered over 30 years to provide an outstanding and long lasting product. Available in various sizes from 500watt – 3000watt. An immersion spanner is available for sale if...

www.surejust.co.uk

 

[SquirrellCook]

I have life in the box, but my HDMI connection doesn't want to work. Another cable ordered as you never know. I had toyed with the idea of mounting a touchscreen display in the door, but that would limit my options on teasing Wildebus The relay in the consumer unit is showing signs of life too. Some reinforcement on the box plus a door, and soon it should find it's way into Betty. Still unsure as to what MIFI to go for.