Best small inverter to power 240V fridge

[Mitchellmoxo]

Hello,

I have purchased an A++ rated 240v fridge from ikea. It is rated at 0.5A and has a yearly consumption of 96kwh. I require a small inverter to run it does anybody have any recommendations?

 

regards

mitch

[MtB]

Any 600w inverter will probably do the job.

5a transient start up current is likely.

[Jen-in-Wellies]

6 hours ago, Mike the Boilerman said:

Any 600w inverter will probably do the job.

5a transient start up current is likely.

Depends on the fridge. Depends on the inverter. My backup 600W modified sinewave one trips out if it tries to start the fridge. The problem is that starting the compressor motor draws a very high inrush current for a fraction of a second, before settling down to a low current draw. The 0.5A quoted by the OP's fridge manufacturer is an average and doesn't include this. To work my fridge off the 600W inverter, when the main 1600W one was on the blink involved switching the fridge on, the inverter tripping off, then immediately switching the inverter back on again so that the compressor motor was still spinning. The thermostat inside the fridge had to be turned to its lowest temperature (highest setting), so the compressor never went off. Not practical, or economic for long turn use.

I would say at least 1000W to be sure not to run in to this. Another thing to look at is the no load current draw of the inverter. Generally cheaper inverters draw more current when the fridge is not running and waste more generating AC when the fridge comprressor is running. If you are mostly using the inverter for the fridge this will be a significant extra drain on the batteries. Go for brands with good reputations like Victron, Mastervolt etc, rather than landfill stuff from Ebay. Less risk of component failure and fire if the boat is left with the inverter running unattended. Inverters have a hard life that is tough on their components.

Jen

Edited March 19, 2018 by Jen-in-Wellies

[PaulJ]

As Jen says. I have run a small fridge off a 500 watt inverter before but it trips it out sometimes on start up and I dont think the inverter would last for long doing so.

Have fitted these before with no problems (as far as Im aware) if you want to risk cheaper and the 1200 watt is on special at the moment-  https://www.sunshinesolar.co.uk/prodshow/1200W___12V_Pure_Sine_Wave_Sunshine_Power_Inverter/VP1200.html

[mrsmelly]

6 hours ago, Mitchellmoxo said:

Hello,

I have purchased an A++ rated 240v fridge from ikea. It is rated at 0.5A and has a yearly consumption of 96kwh. I require a small inverter to run it does anybody have any recommendations?

 

regards

mitch

In theory a 600 watt GOOD quality inverter will run it. However the initial start up draw from many fridges is enough to trip the unit so bigger is better. My last boat had mains fridge ( so does this one now ) and I ran it off a Mastervolt 1200 watt inverter. Mastervolt are simply streets ahead which is why they are expensive but I bought that one secondhand on Gumtree for £120 in perfect condition. 

[MoominPapa]

As you're going to be leaving the inverter on all the time, get one with "power save" mode where the inverter shuts itself down when there's no load, and checks to see if anything has been switched on every second or so. That reduces the 24/7 current draw by the inverter from about an amp to a fraction of that.

Second the comments about startup surge from fridges. Ours uses nearly  1 kW as it starts.

We use a Xantrex Statpower 1800W inverter which is rated 2600W surge. It's a great piece of kit, but old, and probably only available second hand these days.

 

MP.

 

[ditchcrawler]

2 hours ago, Jen-in-Wellies said:

Depends on the fridge. Depends on the inverter. My backup 600W modified sinewave one trips out if it tries to start the fridge. The problem is that starting the compressor motor draws a very high inrush current for a fraction of a second, before settling down to a low current draw. The 0.5A quoted by the OP's fridge manufacturer is an average and doesn't include this. To work my fridge off the 600W inverter, when the main 1600W one was on the blink involved switching the fridge on, the inverter tripping off, then immediately switching the inverter back on again so that the compressor motor was still spinning. The thermostat inside the fridge had to be turned to its lowest temperature (highest setting), so the compressor never went off. Not practical, or economic for long turn use.

I would say at least 1000W to be sure not to run in to this. Another thing to look at is the no load current draw of the inverter. Generally cheaper inverters draw more current when the fridge is not running and waste more generating AC when the fridge comprressor is running. If you are mostly using the inverter for the fridge this will be a significant extra drain on the batteries. Go for brands with good reputations like Victron, Mastervolt etc, rather than landfill stuff from Ebay. Less risk of component failure and fire if the boat is left with the inverter running unattended. Inverters have a hard life that is tough on their components.

Jen

This is such a good reply, so many people think that small inverters will use less power and its far from the case. Read the spec on a 1500watt Mastervolt true sine, I think you will be hard pushed to find a more power friendly one.

 

[OldGoat]

31 minutes ago, ditchcrawler said:

This is such a good reply, so many people think that small inverters will use less power and its far from the case. Read the spec on a 1500watt Mastervolt true sine, I think you will be hard pushed to find a more power friendly one.

 

I did a lot of 'research' last year when trying to find a small inverter for a fridge freezer to replace an aged Batts-Lec unit.

Tried several inverters, low cost one from Bimble, PSW  and PSW combi and MSW from Sterling. All of them ran a 2 compressor large domestic FF with no problems. None of them worked well enough in power saving mode; they could detect the demand, but dropped out before the motor could start.

I was very impressed with the Bimbble  Epever high frequency 1Kw unit; it has an huge overload capability (tested) and started both the large and smaller FF units without any problem. It also ran a 2Kw fan heater without protesting for a few seconds before quietly dropping out. It was useless in power saving mode, however the standby current draw is said to be 450 mA - that's less than others whose published specs tend to be 850 mA  to one amp.   

[nbfiresprite]

2 hours ago, MoominPapa said:

We use a Xantrex Statpower 1800W inverter which is rated 2600W surge. It's a great piece of kit, but old, and probably only available second hand these days.

MP.

 

Still being made by Xantrex, as is it's smaller brother the PROsine 1000i  1000W (1500W Surge)

http://www.xantrex.com/power-products/power-inverters/prosine-international.aspx

UK Dealer

Adverc B.M. Ltd.
245 Trysull Road
Wolverhampton, England
WV3 7LG
Ph. 01902 380494

http://www.adverc.co.uk/products/2012

[MoominPapa]

16 minutes ago, nbfiresprite said:

Still being made by Xantrex, as is it's smaller brother the PROsine 1000i  1000W (1500W Surge)

So it is! I highly recommended these.

On the subject of power save standby current, I measure is at about 150mA, with very short pulses to about 1A every second when it does the load test.

 

MP.

 

Edited March 19, 2018 by MoominPapa

[MtB]

5 hours ago, Jen-in-Wellies said:

Depends on the fridge. Depends on the inverter.

 

I was basing my suggestion on the fridge spec quoted by the OP. 0.5a did seem a bit low though!

 

5 hours ago, Jen-in-Wellies said:

The problem is that starting the compressor motor draws a very high inrush current for a fraction of a second,

 

Which is why I suggested an inverter capable of ten times the current.

 

5 hours ago, Jen-in-Wellies said:

The 0.5A quoted by the OP's fridge manufacturer is an average

 

You could be right there. An average of 0.5a over say an hour of use. probably more like 1a when actually running, and a 10a transient start-up current. Very misleading of the manu. 

[Alan de Enfield]

1 hour ago, Mike the Boilerman said:

 

You could be right there. An average of 0.5a over say an hour of use. probably more like 1a when actually running, and a 10a transient start-up current. Very misleading of the manu. 

Not really, manufacturers are unlikely to test start up currents and write the owners 'manual' for the half-a-dozen boaters who might buy their fridge and want to run off an inverted battery supply.

The start up current, and even the 'running' current are pretty insignificant when you have, effectively, an unlimited supply. What is important to the 99.999% of buyers is 'how much electricity does it use ie cost to run"

According to the charity "wastewatch" in the UK some 2.4 million fridges are thrown away each year, assuming that (as a minimum) these are replaced the manufacturers are hardly likely to be 'bovvered' by a few boaters accusing them of being 'misleading'.

[smileypete]

I'd say 1500W up, to be on the safe side, especially with a cheapo inverter.

For a ballpark figure unplug the fridge for a while so the compressor goes cold, then measure the resistance between the L and N terminals on the plug with the thermostat turned to 'max'.

If the fridge is just for the odd tub of marge, butter, bacon milk and stuff it might not be worth buying a £££££ inverter.

 

Edited March 19, 2018 by smileypete

[MtB]

17 hours ago, smileypete said:

For a ballpark figure unplug the fridge for a while so the compressor goes cold, then measure the resistance between the L and N terminals on the plug with the thermostat turned to 'max'.

 

That's a good idea.

Ohm's Law should work fine to calculate the DC start-up current for the first half cycle or so of AC, before inductance sticks its oar in. And this IS the transient current the inverter needs to be capable of delivering. 

[ditchcrawler]

48 minutes ago, Mike the Boilerman said:

 

That's a good idea.

Ohm's Law should work fine to calculate the DC start-up current for the first half cycle or so of AC, before inductance sticks its oar in. And this IS the transient current the inverter needs to be capable of delivering. 

Not being a refrigeration engineer I understand there is also another current higher than the running current but less than the transient which could flow for a bit longer known as the locked rotor current, that which will flow through the motor if it is stalled. I think this is what happens if you switch a fridge off while the compressor is running and switch it back on again and it can't start against the compressed gas.  Warning that could all be bull whatsit.

[MoominPapa]

20 minutes ago, ditchcrawler said:

Not being a refrigeration engineer I understand there is also another current higher than the running current but less than the transient which could flow for a bit longer known as the locked rotor current, that which will flow through the motor if it is stalled. I think this is what happens if you switch a fridge off while the compressor is running and switch it back on again and it can't start against the compressed gas.  Warning that could all be bull whatsit.

It's true for our (Bosch) fridge. Startup surge is ~100A at 12v, running current is 6-7A at 12v, but it you switch the fridge off whilst the compressor is running and then switch it on again, it takes about 25A at 12v. In that state the compressor can't be heard running. My understanding is that in this state, eventually the motor will get hot enough that the a thermal circuit breaker will trip and the system will reset after it's cooled. I've never tried to see is that's true.

 

MP.

 

[Matt&Jo]

Sorry for the dumb question here (new to canal boats) but are 12v fridges not more efficient and easier to use than then installing further electronics such as inverters? I know they are expensive but add the cost of the inverter is it more cost effective? Or should i keep quiet in the cheap seats 

[mrsmelly]

6 minutes ago, Matt&Jo said:

Sorry for the dumb question here (new to canal boats) but are 12v fridges not more efficient and easier to use than then installing further electronics such as inverters? I know they are expensive but add the cost of the inverter is it more cost effective? Or should i keep quiet in the cheap seats 

There are fors and againsts and those who prefer one or the other. I have had every system including gas. This boat had a 12 volt fridge and a 12 volt freezer fitted both in very good working order but again I have sold them and have a mains fridge. Plus points are that the choice of mains fridges, specs and sizes vastly outshine the 12 volt choice. A good mains undercounter fridge is £ 150 squids a crappy 12 volt thing is fourteen million pounds. In reality they use very similar amounts of leccy to run, this mains fridge build quality and weight due to better insulation means it actualy runs far less time than the 12 volt one did and much better space inside. If a boat is all 12 volt with no need for inverter for anything then 12 volt will do the job. We live aboard and are not cavemen so we have inverter on 24/7 365 so a mains fridge is by far better for us.

[MtB]

12 minutes ago, Matt&Jo said:

Sorry for the dumb question here (new to canal boats) but are 12v fridges not more efficient and easier to use than then installing further electronics such as inverters? I know they are expensive but add the cost of the inverter is it more cost effective? Or should i keep quiet in the cheap seats 

 

What do you mean by 'efficient'? 

 

[WotEver]

41 minutes ago, Matt&Jo said:

Sorry for the dumb question here (new to canal boats) but are 12v fridges not more efficient and easier to use than then installing further electronics such as inverters? I know they are expensive but add the cost of the inverter is it more cost effective? Or should i keep quiet in the cheap seats 

As the Smelly guy wrote, mains fridges are cheaper, wider choice, blah blah... but they do require a decent inverter. If you already have an inverter (especially if it’s on most of the time anyway) then mains makes much more sense. If you only have a 12V setup then the choice is much less clear cut. Our last boat only had a small inverter for occasional use (500W) so we fitted a 12V Waeco fridge. 

[ditchcrawler]

But if you don't already have the wiring for a 12 volt fridge then I can be a bit of mucking about adding it as it needs to be thicker than you may think.

[Matt&Jo]

Okay cheers gor the info all 

[WotEver]

37 minutes ago, ditchcrawler said:

But if you don't already have the wiring for a 12 volt fridge then I can be a bit of mucking about adding it as it needs to be thicker than you may think.

Indeed. 10mm is common and that’s pretty fat. 

[ditchcrawler]

3 minutes ago, WotEver said:

Indeed. 10mm is common and that’s pretty fat. 

Especially when you are trying to route it round a Narrowboat 

[Mitchellmoxo]

Thanks for the replies it looks like I will be using the 3kw inverter on board 24/7 rather than having a dedicated one just for the fridge!