AC Fridge In Campervan -.Power Consumption Test

[wildebus]

change of subject a little ....
I was working on configuring the Multiplus to work with Lithium and used the Fridge as a way to fool it into seeing a lower Battery Temp for testing purposes (sensor put into icebox in fridge). This exposed something quite intriging on the Inventor Fridge ...

This is what I usually record with the a Temp Sensor in the Fridge section of the Inventor Fridge. Typical pattern is the temp fluctuates very little (it is excellent in that respect in fact)
View attachment 2802

But today I put the battery sensor in the Icebox as I said (note that this is an identical sensor, but connected to the MP, not the Venus GX)
This is what the Icebox is doing when the Fridge is doing its normal power duty cycle
View attachment 2801
The Freezer seems to go down to -15C rapidly as soon as the compressor comes on, but as soon as it goes off, the temp goes up again nearly as fast. It actually looks like the Fridge Compressor duty cycle is linked to the freezer temp, kicking on when it is at OC, and off when down to about 15C?
Now the Info for the Fridge does say that the Icebox is not designed to be a freezer, but I would have expected much less of a range variation!
(PS. For info, in the chart above, the fridge is running on mains, not inverter)

Right now I can't do it, but next week I will put a sensor in Fridge AND in Icebox and map the pattern. Also today is a pretty hot day and that could have affected how it works somewhat.

Only got one sensor reading available currently, so I thought I would just swap it over this afternoon from Icebox to Fridge to double-check it (the sensor) is still ok, as the cycling was so unexpected (to me, anyway).
Took the sensor out the Icebox, left it out for a short while to show ambient and then put it in the fridge....

So back to what is expected with a slight raise when fridge is off. The Icebox is definately only useful for icecubes and icepops. Stuff that doesn't matter if it starts to defrost and then refreezes.

 

[PeteS]

Just an observation but I'm guessing the icebox is empty? I think the characteristics would change with some frozen products in the icebox

 

[wildebus]

Just an observation but I'm guessing the icebox is empty? I think the characteristics would change with some frozen products in the icebox

totally empty right now. I think you are right it will have an impact, but it is just a surprise there is so much variation. I had noticed that sometimes I would take out an ice-pop or lolly or whatever and sometimes it seemed soft - now I know why!

 

[trevskoda]

AS mine is a smart inverter all above no use,but keeping an eye on fridge with a small temp clock all is well,we bit up on very warm days and inverter works harder,2 -3c always mind you.

 

[buyone]

Yes but it's not 240 W all the time and if 400 Watt's of Solar Panels are sat there doing nothing and there's enough sun to get 240 W, think of the gas I'm saving and the diesel I'm saving not having to drive to the garage to refill the bottle.

I used the fridge as a load as I was trying the code to monitor AC consumption into the van, I just thought I'd add to this thread. Also as it totals consumed I can set the limit so I never have to pay for electricity over and above that included at some sites.

240W is only 1/3 bhp, which is just a light touch on the throttle. You are not making a real saving.

 

[SquirrellCook]

Internal combustion engine burning petroleum to make electricity is supposed to be 20% efficient, I expect it’s more like 10% So 90% is heating the planet! In fact the remaining percentage will end up as heat.
I was going to use an old lister to burn waste oil to make electricity, after running the numbers I found I had a central heating boiler that made a little amount of electricity. More so if I captured the exhaust heat.

 

[xsilvergs]

I run our 3-way Thetford fridge freezer on a Victron 12/500 inverter. I tried running the inverter in Eco mode which reduces power consumption in the off periods but the sample rate in this period needs to be quite short or the fridge initially ignites on gas and then goes to inverter. Also, if i look at the fridges control panel it switches between gas and 240v which isn't probably good for it.

With 450 watts of solar panel it still manages to charge the Lithiums which are only allowed to discharge to 75% before the inverter is switched off.

And this is the ON/OFF cycle

 

[wildebus]

I run our 3-way Thetford fridge freezer on a Victron 12/500 inverter. I tried running the inverter in Eco mode which reduces power consumption in the off periods but the sample rate in this period needs to be quite short or the fridge initially ignites on gas and then goes to inverter. Also, if i look at the fridges control panel it switches between gas and 240v which isn't probably good for it.

With 450 watts of solar panel it still manages to charge the Lithiums which are only allowed to discharge to 75% before the inverter is switched off.
View attachment 3767
And this is the ON/OFF cycle
View attachment 3768

You raise an interesting question...
you said "I tried running the inverter in Eco mode which reduces power consumption in the off periods but the sample rate in this period needs to be quite short or the fridge initially ignites on gas and then goes to inverter"
Is this when the SOC is above 75% AND the fridge is on one of the off-cycles so the power demand from the fridge is not sufficient to get the inverter out of eco mode? and in eco mode the fridge does not "wait" long enough for the inverter to turn before it decides AC is not available and tries to switch to gas?

The Phoenix inverters have (I think from memory) the ability to switch between Eco, Off and On modes via a three-way remote physical switch. Would it help if you incorporated this switch function into the SOC level control - so above 75% the inverters is in plain "On" mode and then below that it is in "Eco" mode?
I only started my fridge operating a couple of days ago after the winter 'layover' and I am wondering if my Fridge will do the same? (I am sure it will as mine is also a 3-way Thetford with AES and the inverter has AES (different AES - similar to ECO) enabled)

(Oh, I am wanting to have my Inverter available down to any SOC, so rather than disable it at a set SOC level, I just disable the AC output going to the Fridge and Water Heater)

 

[wildebus]

Added an extra switch to my control circuitry design ....

I have AES enabled in the Victron Easyplus, but I also have an assistant loaded that will disable AES and just have the Inverter active if the accessory input (actually the Temp Sensor on the Easyplus repurposed) goes high. (the idea being sometimes I want to be able to use the Inverter for low power AC devices that wouldn't make the inverter turn on by themselves).
This AES disable is controlled currently by using the 2nd Relay in Cerbo.

The Extra Switch is the bottom-right one on the diagram above - the "Override AES" switch. When in the top position, the AES works as normal but can be still disabled by Relay 2; If it is in the bottom "Orange" position, then AES is disabled whenever the SSR is activated e.g. When SOC is above the specifed level, or if the "Active on SOC" Control is either overrided generally or the delay timer is activated.
The idea being that if the Fridge and/or Heater are being use, the Inverter will stay on and avoid them being 'confused' potentially by momentary outages (when AES activates), but I still have the option of running AES normally.
(Had to add a relay in as well as the switch as the control input works by closing the connection between two terminals and not applying a voltage. This will result in a bit of overhead from the relay when the Multiplus AES mode is disabled, but none when it is not)

I might move the Relay 2 connection to just a simple +12V connection - so the upper position means AES alway disabled, lower position AES follows the SSR as above, and the middle (off) position leaves AES running as standard. (having to go into the Remote Panel to disable AES can be a bit of a pain sometimes).

 

[xsilvergs]

You raise an interesting question...
you said "I tried running the inverter in Eco mode which reduces power consumption in the off periods but the sample rate in this period needs to be quite short or the fridge initially ignites on gas and then goes to inverter"
Is this when the SOC is above 75% AND the fridge is on one of the off-cycles so the power demand from the fridge is not sufficient to get the inverter out of eco mode? and in eco mode the fridge does not "wait" long enough for the inverter to turn before it decides AC is not available and tries to switch to gas?

The Phoenix inverters have (I think from memory) the ability to switch between Eco, Off and On modes via a three-way remote physical switch. Would it help if you incorporated this switch function into the SOC level control - so above 75% the inverters is in plain "On" mode and then below that it is in "Eco" mode?
I only started my fridge operating a couple of days ago after the winter 'layover' and I am wondering if my Fridge will do the same? (I am sure it will as mine is also a 3-way Thetford with AES and the inverter has AES (different AES - similar to ECO) enabled)

(Oh, I am wanting to have my Inverter available down to any SOC, so rather than disable it at a set SOC level, I just disable the AC output going to the Fridge and Water Heater)

For info to others, the Off/Eco/On can be controlled from the Remote Console:

as my Phoenix is connected to my RPi/GX via VE.Direct-USB. I run the Venus/Cerbo GX Large Image version of the GX software on an RPi 4, this includes Node-Red.

@wildebus I could switch between the different modes but Eco upsets the Fridge and the induction hob we use if they are plugged in. I have shortened the sample time for Eco mode so the fridge doesn't try to ignite the gas but I don't know how the fridge (or anything else for that matter) likes to have 230V applied and removed repeatedly. The 'Off' period of the fridge is about 12 minutes and the 'On' period about 35 minutes on the inverter, so possibly not being able to get into Eco for 12 minutes is probably a small price to pay.

In the image for my inverter control (post #407) I have 3 switches, ON turns the inverter on and it would stay on until a low voltage cutout. AUTO allows the inverter to run down the the 75% SoC. OFF turns it off. These changes of mode would be visible in the image above.

The two buttons with the up and down arrows allow the SoC switch point to be set to any level so the 75% is not fixed.

If your Cerbo ran the 'Large Image' I guess Node-Red could control the EasyPlus instead of your Override AES Switch. I can't tell from the Inverter node in Node-Red as Node-Red has to see an EasyPlus in the system before it displays the functions available.

How long can your batteries (not sure of their total capacity) run the Truma?

 

[wildebus]

I wouldn't think the fridge would care that much about having 240V come and go - it would be more a matter of maybe trying to switch to gas repeatedly which could potentially not be liked?
My point in the previous post was to remove the need to MANUALLY switch modes if you don't want to have ECO active when using the Fridge. I can also turn off the Multiplus AES via the Remote Console, but you have to remember to do it. Automation is a much more reliable way.

Ref Phoenix ECO vs Multiplus AES .... you can control ECO directly via a switch or console, but to program AES on a Multiplus you have to run the VE Config software program, and you cannot switch AES on or off without it unless you add the assistant I mentioned and add external switch control. This is the way Multiplus's work and I very much doubt Node-Red would be able to change that?

It maybe the way you describe it above, but using a "AES Override Switch" as in my diagram would actually work better then having it controlled by a straight SOC level. In the setup I showed, when in the Override setting, the AES would be disabled until the batteries went down to the "Fridge cutoff" SOC (say 75%) and then it would be enabled again immediately and stay enabled until the Batteries rose again to the "Fridge Enable" SOC (say 90%) - which gives some power saving without having to remember to enable manually again (I much prefer automation as you can tell )


ECO (or AES in 'Search Mode') can have an annoying feature with some plugged in devices. The built-in Induction Hob in my camper would beep every few seconds as it detected power. It was simple enough to sort that by wiring through a switched spur. other devices such as an Amazon Echo will start up and of course lose power virtually immediately afterwards. ECO/AES are very useful powersaving features but certainly have their drawbacks - so being able to control if they are on is very handy (especially if how you control the mode is programmable as well).
Another option I have with the Multiplus if the Fridge does not like ECO is to change the AES setup from 'Search Mode' to 'Modified Sine Wave'.
In Search Mode it is just like ECO, but in MSW, there is always a voltage out, but it is reduced to save power. This *may* make a difference but I don't know. What I have seen with MSW mode is things like lights will still more but be dimmer (for example, with the 240V Compressor Fridge, in ECO or AES Search Mode the fridge light flashes on every couple of seconds but in AES MSW, the light stays on but is dimmer. Other devices that have a wide operating range of 100~240V will also work without the inverter actually "coming on". Haven't tended to use AES MSW though as the power saving is better in AES Search Mode.

Capture of the modes below:

Can't recall how long I could run for. I have only recently installed the Solar Array and that is the key to using the Water Heater or Fridge on 240V off-grid.
The fridge uses approx 220W for around 75% of the time once down to temp, and the Truma Water Heater uses 800W for around 20 minutes or so (depending on starting water temp) - so how long is a function of how much solar harvesting as well as Battery Capacity (I am happy to draw around 250Ah out of my 300Ah bank if I need to - that is only just over 80% DoD)

 

[xsilvergs]

@wildebus I've looked at the 12/1600 EasyPlus manual but can't make out if there is VE.Direct or VE.Bus or some other communication available between it and a GX device available?

 

[wildebus]

@wildebus I've looked at the 12/1600 EasyPlus manual but can't make out if there is VE.Direct or VE.Bus or some other communication available between it and a GX device available?

It's a VE.Bus system. the EasyPlus is basically a Multiplus with an AC Consumer Unit

 

[xsilvergs]

It maybe the way you describe it above, but using a "AES Override Switch" as in my diagram would actually work better then having it controlled by a straight SOC level. In the setup I showed, when in the Override setting, the AES would be disabled until the batteries went down to the "Fridge cutoff" SOC (say 75%) and then it would be enabled again immediately and stay enabled until the Batteries rose again to the "Fridge Enable" SOC (say 90%) - which gives some power saving without having to remember to enable manually again (I much prefer automation as you can tell )

Yes I could swap to Eco once below 75%, I'd just have to add a relay to isolate the fridge from the 230 as you have. The Rpi GPIO pins are available and these could switch the relay.

It's a VE.Bus system. the EasyPlus is basically a Multiplus with an AC Consumer Unit

That requires the MK3-USB lead I guess.

I think the EasyPlus is on the cards, not today though, need to recover from buying the Lithiums

 

[wildebus]

Yes I could swap to Eco once below 75%, I'd just have to add a relay to isolate the fridge from the 230 as you have. The Rpi GPIO pins are available and these could switch the relay.



That requires the MK3-USB lead I guess.

I think the EasyPlus is on the cards, not today though, need to recover from buying the Lithiums

Yup, that would have hurt the wallet!

And yup, for an RPi Setup, the MK3-USB Dongle is required (around £50 ish?). It has other uses such as programming or firmware updating.
For a non-Venus OS system, Victron do the Smart Dongle which is a neat device but not really relevant to your setup though.

 

[wildebus]

I did my 3-way test yesterday (posted a new thread as more appropriate - see https://motorhomebuilder.com/thread...-in-a-motorhome-power-consumption-test.67235/)
I had the Multiplus in AES mode and I found the fridge didn't seem to care. Put the Fridge into its AES setting and it switched to AC even with the Inverter in Low Power

Came on and off as expected until approx 20 to midnight when the battery SoC hit 65% and the relay cut the AC to the fridge circuit

I don't know if the fridge has any kind of timer for AC outage?
When in AES and 12V is detected it will not switch to gas for 15 minutes once 12V is removed (on assumption may have stopped to refuel so no gas ignition wanted). It is possible switching from AC might have a timeout of some duration as well?
I am still thinking even though it does not seem to be affected it could be better not to have intermittant 240V anyway so might add that switch I put in the circuit diagram anyway?

 

[xsilvergs]

Today has been a day with little sun so the batteries had to rise from there night time low of 67.1% up to 76% before the inverter would run to power the fridge and then deplete the batteries down to 75%. At 75% the inverter goes off and and we have to wait for them to charge to 76% again. The ON period is short but it saves using the LPG.

 

[wildebus]

You have a much shorter AC ON time than I do I see. Is the Fridge switching to Gas for a period in-between each AC On time?

 

[xsilvergs]

You have a much shorter AC ON time than I do I see. Is the Fridge switching to Gas for a period in-between each AC On time?

Well yesterday was a good 'worst conditions' day, with the 450W of solar putting about 1.5A into the battery and I would guess there was another 1A going to supplying the two RPi's and the router.

So at a guess the 1% of battery capacity (76% down to 75%) powered the parasites and the fridge for about (very rough) 12 minutes, then the inverter goes off and the fridge reverts to gas. How much I saved in gas yesterday is probably pennies.

The solar controllers went OFF at about 20:30 yesterday and at that point the SoC was about 72%, this morning the solar controllers came on at 07:00 and the SoC was down to 60% after an evening with the TV and lights on plus the parasites.

As I don't data log from the fridge all times are a guess.

 

[wildebus]

Well it is a saving

One of the unknowns is the impact on the unit of keep changing energy sources? Each time you ignite the gas on a burner, I understand something 'burns away'? miniscule effect maybe but it all adds up over time, so could igniting the gas on an hourly basis eat into the operational life of a gas appliance to any significant degree?
I really don't know but I am slightly wary about having the fridge not seeing a 'proper' AC supply when switched to it (i.e. when inverter is in ECO/AES mode) even though there are no apparent issues. I am a lot more wary about having the fridge restarted on Gas on such a frequent basis.
Personally, and on no basis other then my own feelings, I wouldn't set up the Stop/Start parameters so tightly