Inverter Search Mode + Modern Fridge

[Bundas]

I know this question came up before but I can't seem to find any info about a solution:

 

So I got a Victron multiplus 3000/24 and a A++ modern fridge. It all works fine but in the dark winter months every Ah counts so wanted to save some power activating AES (Victrons power saving mode) in search mode but it just can't seem to be able to turn it back on when the fridge goes off - I suppose inverter fridges draw such low powers for startup that it just not enough to wake up inverter and vica versa - so catch 22 really. 

 

I see people talking about doing stuff with their compressors or putting a load on the invertern when the fridge wants to turn on or even a timer on the fridge but all of these seems to be quite theoretical and can't find any info from people who actually made this work - somehow. 

 

Any info is most welcome

[Boater Sam]

4 hours ago, Bundas said:

I 

 

So I got a Victron multiplus 3000/24 and a A++ modern fridge. It all works fine but in the dark winter months every Ah counts so wanted to save some power activating AES (Victrons power saving mode) in search mode but it just can't seem to be able to turn it back on when the fridge goes off - I suppose inverter fridges draw such low powers for startup that it just not enough to wake up inverter and vica versa - so catch 22 really. 

 

 

 

Any info is most welcome

Do you mean when the fridge thermostat calls for cooling? The problem is most unlikely to be lack of required current, all fridges take more current starting than running.  What is your fridge, never heard of an "inverter" fridge. !2v fridges with Danfoss compressor use a sequential switched  power supply, not strictly an inverter but converter.

Edited December 26, 2019 by Boater Sam
added more

[nbfiresprite]

3 hours ago, Boater Sam said:

Do you mean when the fridge thermostat calls for cooling? The problem is most unlikely to be lack of required current, all fridges take more current starting than running.  What is your fridge, never heard of an "inverter" fridge. !2v fridges with Danfoss compressor use a sequential switched  power supply, not strictly an inverter but converter.

He using an inverter to power a 240v fridge.

[Alan de Enfield]

A fridge rarely runs overnight unless you are opening the door every hour to get more beer, it sound more like you are trying to reduce the amps-used (quiescent current) by the Inverter itself.

 

Why not just switch the inverter off overnight ?

That will halve your quiescent current usage.

[nbfiresprite]

It does seem to be a common problem from looking at the Victron Energy community site

 

Phoenix-inverter-eco-mode-issue-with-refrigerator

 

Using-an-refrigerator-in-eco-mode-phoenix-inverter

 

Anyway your fridge will be rated to keep cool without power for x number of hours with the door kept shut. Commonly between 12 and 15 hours. So just turnoff at night.

[Detling]

I have never succeeded with AES mode and a fridge. I think it basically checks for a load every 10 seconds but whilst it would find hairdryer, it never found the fridge or plug in chargers(expected behaviour) sometimes opening the door on the old fridge would kick it in (halogen bulb).

 

[MoominPapa]

We use a Xantex inverter wilth the equivalent facility and a Bosch fridge and it works fine. The fridge has a bi-metallic thermostat which switches the compressor motor. I can imagine that modern fridges may well have electronic temperature controls and that would be a problem: The electronics will need power to start the motor but without the motor running there's no power.

 

Incidentally, we discovered a useful feature of our fridge by accident. The fridge has a freezer compartment, but you can't leave the boat in winter and leave stuff in the freezer because when the amibient temperature is low, the fridge doesn't run and the freezer defrosts, It turns out that there is a switch which turns the internal light on low power even when the door is closed. That puts enough heat into the fridge to make the compressor run sometimes and the freezer stays cold even when the ambient temperature is below 8 degrees. It's a bit of a power hungry solution because is keeps the inverter alive all the time, but it is useful. On shore power it would be very useful.

 

MP.

 

[Boater Sam]

Got it now, electronics won't waken the inverter so there is no power to run motor.Same problem with electronic controls on washing machines, not enough current draw to wake the inverter. Old fashioned 'stats don't have this problem.

[Jen-in-Wellies]

2 hours ago, Alan de Enfield said:

A fridge rarely runs overnight unless you are opening the door every hour to get more beer,

There is the answer to this and many other problems! Of course, it brings problems of its own, liver sclerosis, having to go to the shops for more beer etc.

[David Mack]

42 minutes ago, MoominPapa said:

 

Incidentally, we discovered a useful feature of our fridge by accident. The fridge has a freezer compartment, but you can't leave the boat in winter and leave stuff in the freezer because when the amibient temperature is low, the fridge doesn't run and the freezer defrosts,

 

This is because there is only one thermostat, in the fridge section. So if the fridge is down to the set temperature, the unit doesn't run, and the freezer slowly defrosts. Not a problem in a warmer environment, but the same can happen if you keep a fridge freezer in an unheated garage.

[OldGoat]

Methinks the problem is more fundamental than discussed above. I did some land based tests some while ago with an ancient Bosch twin compressor tall fridge freezer and a domestic 4 star mid height FF for the boat.

I borrowed a high frequency inverter from Solwise and had both a PSW and quasi SW combo units from Sterling ( I don't care what you say....) None of them would start either unit in power saving mode. Either the fridge motor(s) would 'hunt' and not start / run properly or not start at all.

Switch off the eco mode and everything was perfic'.

 

Rather than faff around with potentially snake oil solutions - just get a inverter whose basic standby current draw is as small as you can get and / or have a decent amout of battery capacity to sustain all your power needs.

[GUMPY]

On my victron inverter there are two search modes one PSW one MSW it says that PSW one might be to slow to sense the load and the MSW one should be used in this case.

Edited December 26, 2019 by Loddon

[OldGoat]

40 minutes ago, Loddon said:

On my victron inverter there are two search modes one PSW one MSW it says that PSW one might be to slow to sense the load and the MSW one should be used in this case.

That's very interesting - I wish I'd known that when doing my tests.

[Alan de Enfield]

20 minutes ago, OldGoat said:

That's very interesting - I wish I'd known that when doing my tests.

But what about 'things' that require PSW (and won't run on MSW) ?

[OldGoat]

49 minutes ago, Alan de Enfield said:

But what about 'things' that require PSW (and won't run on MSW) ?

You've given me an excuse to come back with my further queries on the above.

Firstly (as most folks usually do) - I only scanned the previous post and assumed that there were two SEARCH modes - thus - mebe the user could continue in MSW or PSW modes for the power cycle. Assumptions can be dangerous... But why should Victron have a MSW option is a PSW unit - doesn't compute for my less-than-expert knowledge

 

Another definition has always bothered me. What exactly (in detail) is MSW. In the very early days, it was pretty much that, a rectangular wave form. That has changed over the years to a series of reducing 'height' rectangular boxes. Some of these boxes  merge together  and look like a very dirty sine wave - but would an A/C fridge motor know the difference for its own operation?

I ask because I have one of Sterling's MSW 2.4Kw chucked out by Charles and nobody wanted it, thus I got it for peanuts. I digress, In it there's a massive torroid transformer with loadsa' iron core - surely you don't need that for battery charging or MSW output??

AFAIK there are no standards for the 'modified' tag description, thus could it bet that some 'modified' units have better quality waveform than others, and that maybe why some folks on here write that all their equiment runs perfectly well on a MSW power supply??

As a separet query what is a high frequency inverter? (cheaper / lighter / don't get hot). I was impressed with Bimble's unit. However, Bimble (used to) put the caveat of 'don't run the unit near it's rated capacity' Poor cooling (it's a small case)? Not reliable? > I think it fear of having returns? It worked well for me, ran the fridge and - for a short time an 1Kw fan heater.

 

Hmm.

 

Any suggestions folks??

 

TIA.

Mike N

[cuthound]

4 minutes ago, OldGoat said:

You've given me an excuse to come back with my further queries on the above.

Firstly (as most folks usually do) - I only scanned the previous post and assumed that there were two SEARCH modes - thus - mebe the user could continue in MSW or PSW modes for the power cycle. Assumptions can be dangerous... But why should Victron have a MSW option is a PSW unit - doesn't compute for my less-than-expert knowledge

 

Another definition has always bothered me. What exactly (in detail) is MSW. In the very early days, it was pretty much that, a rectangular wave form. That has changed over the years to a series of reducing 'height' rectangular boxes. Some of these boxes  merge together  and look like a very dirty sine wave - but would an A/C fridge motor know the difference for its own operation?

I ask because I have one of Sterling's MSW 2.4Kw chucked out by Charles and nobody wanted it, thus I got it for peanuts. I digress, In it there's a massive torroid transformer with loadsa' iron core - surely you don't need that for battery charging or MSW output??

AFAIK there are no standards for the 'modified' tag description, thus could it bet that some 'modified' units have better quality waveform than others, and that maybe why some folks on here write that all their equiment runs perfectly well on a MSW power supply??

As a separet query what is a high frequency inverter? (cheaper / lighter / don't get hot). I was impressed with Bimble's unit. However, Bimble (used to) put the caveat of 'don't run the unit near it's rated capacity' Poor cooling (it's a small case)? Not reliable? > I think it fear of having returns? It worked well for me, ran the fridge and - for a short time an 1Kw fan heater.

 

Hmm.

 

Any suggestions folks??

 

TIA.

Mike N

 

Diagram showing different inverter output waveforms attached.

 

A high frequency inverter uses a switch mode power supply (which operates a a high frequency, typically 20kHz) rather than a transformer and thyristors operating at 50Hz to chop the DC, and has the advantages you state.

[OldGoat]

2 minutes ago, cuthound said:

 

Diagram showing different inverter output waveforms attached.

 

A high frequency inverter uses a switch mode power supply (which operates a a high frequency, typically 20kHz) rather than a transformer and thyristors operating at 50Hz to chop the DC, and has the advantages you state.

Aha - yes, I missed that one. I've seen even finer variations of the third entry above - almost indistinguishable from a PSW

[GUMPY]

As I understand it its only the sense part that is MSW as soon as the inverter turns fully on its PSW.

[Bundas]

I understand I got a few options to save power with the inverter such as:

1. Turn off inverter for overnight
2. Put a thermostat in the fridge and use a contactor to turn on inverter when temprature is above whatever setting it is to cool down again
3. Combine the two above

Reason I have opened this thread was that I was hoping that if you fork out so much money for an inverter in 2019 and buy a very common household fridge, Victron have overcome this problem as offgrid setups seem to be more and more common. Was hoping as it came up so often there might be a solution to this issue already..

 

Done a fair bit of look around the internet but can't see any real solutions. The issue is that the fridge having a very effcient danfoss 240v compressor it draws very little power (2W) before the compressor kicks in and by the time that would start up inverter goes back to sleep. Maybe on other inverter brands (such as Outback) you could adjust the inverter search period (when its on..) but as I see on Victron you cant. 

 

Attached a screenshot how the options are on Victron AES (power save mode), the MSW seem to be only on when its in powersaving but this is only saving a few Watts however the actual search mode is a significant (about 70%) saving on power. 

 

This won't be an issue during the summer but momentarily parked up in Durham and being cloudy the 1200W panels producing about a 100Wh a day which is nothing so keep the engine running a few hours a day to keep us charged..

 

[cuthound]

23 minutes ago, Bundas said:

 

 

Pedant Mode On - The "modified sine wave" in the image below isn't a sine wave of any description, it is a series of positive half cycles (there are no half cycles below the zero line).

 

Quote

 

 

Edited December 26, 2019 by cuthound
Clarification

[Bundas]

I think Victrons description of that modified sine wave is that its pulling the sinewaves narrower or something. Whichever way it is my fridge also doesn't like that so not an option anyway..

[GUMPY]

Try adjusting the start wattage down to 20w

And the stop up to 15w

this will give a wider band to work with.

Or leave it and just open the door every 6hrs so the inverter switches on

 

 

Edited December 26, 2019 by Loddon

[Bundas]

yeah I tried them all but unfortunately this is the lowest setting allowed. I would need eirher a 3sec on period (say 3waves when its searching) or a 2w difference to turn it back on but the lowest allowed is 12W..

[Alan de Enfield]

16 minutes ago, cuthound said:

 

Pedant Mode On - The "modified sine wave" in the image below isn't a sine wave of any description, it is a series of positive half cycles (there are no half cycles below the zero line).

 

 

What if the 'zero' line was there but not shown ?

 

Just a rough hand -drawn line.

 

 

[cuthound]

14 minutes ago, Alan de Enfield said:

What if the 'zero' line was there but not shown ?

 

Just a rough hand -drawn line.

 

 

 

Yes that would work.