Mains Fridge - How to power it?

[The Boat Studio]

Hello,

 

I have spent a bit of time looking round the forum for advice relevant to 'Fridges' and 'Inverters' but thought it was just easier to post about our specific problem!

 

We bought our new boat last August and it came with a 79w mains fridge. The previous owners had it in a boat yard hooked up to mains.

We however continuous cruise most of the summer.

Over winter we just did without a fridge and didn't really miss it but as you can imagine these hot sunny days have been tricky with no refrigeration! 

 

I think we have decided as the fridge is fitted already in the kitchen it wouldn't make sense to take it out and replace with a 12V Fridge. Therefore what inverter is recommended? I have been looking at these two at Midland Chandlery:

 

https://www.midlandchandlers.co.uk/store/category/1342/product/vl-451.aspx

 

https://www.midlandchandlers.co.uk/store/product/vv-025.aspx

 

They are pretty expensive and I just wanted some advice before parting with the cash! I can see from previous threads its not necessarily a straightforward topic.

 

We have three 12v leisure batteries ( they are hooked up to a 50w panel that trickle charges them)

 

Also on our old boat we tended to have the fridge on only when cruising and turned it off over night and would be happy to do the same with this one so it would be a fridge some of the time and a cool box the rest.

 

Cheers in advance.

[mayalld]

13 minutes ago, The Boat Studio said:

Hello,

 

I have spent a bit of time looking round the forum for advice relevant to 'Fridges' and 'Inverters' but thought it was just easier to post about our specific problem!

 

We bought our new boat last August and it came with a 79w mains fridge. The previous owners had it in a boat yard hooked up to mains.

We however continuous cruise most of the summer.

Over winter we just did without a fridge and didn't really miss it but as you can imagine these hot sunny days have been tricky with no refrigeration! 

 

I think we have decided as the fridge is fitted already in the kitchen it wouldn't make sense to take it out and replace with a 12V Fridge. Therefore what inverter is recommended? I have been looking at these two at Midland Chandlery:

 

https://www.midlandchandlers.co.uk/store/category/1342/product/vl-451.aspx

 

https://www.midlandchandlers.co.uk/store/product/vv-025.aspx

 

They are pretty expensive and I just wanted some advice before parting with the cash! I can see from previous threads its not necessarily a straightforward topic.

 

We have three 12v leisure batteries ( they are hooked up to a 50w panel that trickle charges them)

 

Also on our old boat we tended to have the fridge on only when cruising and turned it off over night and would be happy to do the same with this one so it would be a fridge some of the time and a cool box the rest.

 

Cheers in advance.

Those are NOT expensive inverters!

 

Expensive inverters are 3kVA and come in at over £2,000

 

As these are considerably cheaper than many 12 volt fridges, they look like a snip.

 

The one thing to look at is what is the instantaneous startup power on the fridge. This will be MUCH more than the running power and you need to ensure that the inverter will cope with that short term surge.

[Alan de Enfield]

2 minutes ago, mayalld said:

I think we have decided as the fridge is fitted already in the kitchen it wouldn't make sense to take it out and replace with a 12V Fridge. Therefore what inverter is recommended? I have been looking at these two at Midland Chandlery:

 

https://www.midlandchandlers.co.uk/store/category/1342/product/vl-451.aspx

 

https://www.midlandchandlers.co.uk/store/product/vv-025.aspx

The second Inverter is apparently 800 watts (1500 watts peak) and has a cigarette lighter plug.

 

I am a little confused as to the suitability of this.

 

Cigarette lighter sockets / plugs are normally rated at 10 amps.

An 800w inverter (at full power) will be drawing approx. 80 amps from the batteries,

 

The resulting mess will take some sorting out.

 

Many years ago I plugged a "Electrolux 47 watt" fridge into a cigarette lighter socket after a few seconds there was a cloud of smoke and a smell of burning plastic - switched of the electric master switches and investigated, the cables leading to the cigarette lighter socket had melted all the way back into the wiring harness, It took some time to rebuild the harness.

 

Maybe it was incorrectly fused but it happened.

 

I would not use an inverter that plugged into  lighter socket (except maybe something like a 60 watt one for phone charging or similar)

[Jen-in-Wellies]

600W in my experience isn't enough to start a fridge compressor. The inrush current when they first start is many times the current when running. The 800W might cope, but to be sure I'd want at least 1000W. The other thing to look at is efficiency. The amount of your battery capacity they use in inverting. As you'd expect, high efficiency costs more. A 50W solar panel won't keep pace with a fridge. My 240W of panels can just about keep up in sunny summer weather with the fridge, but that is it. A 12V fridge will have similar problems. Many use more power than a 240V one and inverter.

 

Jen

 

10 minutes ago, Alan de Enfield said:

The second Inverter is apparently 800 watts (1500 watts peak) and has a cigarette lighter plug.

 

I am a little confused as to the suitability of this.

 

Cigarette lighter sockets / plugs are normally rated at 10 amps.

An 800w inverter (at full power) will be drawing approx. 80 amps from the batteries,

 

The resulting mess will take some sorting out.

 

Many years ago I plugged a "Electrolux 47 watt" fridge into a cigarette lighter socket after a few seconds there was a cloud of smoke and a smell of burning plastic - switched of the electric master switches and investigated, the cables leading to the cigarette lighter socket had melted all the way back into the wiring harness, It took some time to rebuild the harness.

 

Maybe it was incorrectly fused but it happened.

 

I would not use an inverter that plugged into  lighter socket (except maybe something like a 60 watt one for phone charging or similar)

The photo on the Midland Swindlers site is wrong. It is a 180W inverter, not the 800W. Hence the fag lighter. Around 15A, which is still a lot for a fag lighter socket to cope with.

[Chewbacka]

As Jen says above, mains fridges take a lot to start them.  My guess is that mine takes the best part of 2000W for a fraction of a second, so a 1000w continuous, 2000w peak may be ok, can't say for certain as I don't know if your fridge is better or worse than mine.

 

Another thing to consider with inverters is how much power they use themselves (some will use 25W doing nothing) and some also have a power saving mode where the inverter uses less than a couple of watts when there is no demand for power.  Given that a decent fridge with plenty of ventilation will be 'off' for half the time and off for longer in cooler weather then your inverter losses could be greater than the fridge use.

[Detling]

The 800 watt victron should be fine, because it is a low frequency inverter it has more oomph (whatever that is) than a high frequency sterling. But 50 watts solar no chance, 500 will power the inverter and fridge happily in this weather and just about cope on a cloudy day. Turning the fridge off doesn't save much power as the fridge just runs longer to get cool again, if off for long periods then what is the point of the fridge? Remember it takes several hours to get the ice cubes frozen for the g & t.

[Boater Sam]

I'll repeat my idea. Wire the fridge stat to switch the inverter on. Then  the inverter only runs when the fridge need it, no standing loss.

[mrsmelly]

2 hours ago, Detling said:

The 800 watt victron should be fine, because it is a low frequency inverter it has more oomph (whatever that is) than a high frequency sterling. But 50 watts solar no chance, 500 will power the inverter and fridge happily in this weather and just about cope on a cloudy day. Turning the fridge off doesn't save much power as the fridge just runs longer to get cool again, if off for long periods then what is the point of the fridge? Remember it takes several hours to get the ice cubes frozen for the g & t.

Total agree Why the hell switch the damn thing off at night. The door is not opened at night and keeps food etc at a safe temperature. Switch on in the morning and it has to work its arse off to cool again, completely bonkers and yo yo ing food temperature is dangerous.

[Alan de Enfield]

Just now, mrsmelly said:

completely bonkers and yo yo ing food temperature is dangerous.

There speaks a man who has 'done' his Food Safety / Hygiene Certificate.

[mrsmelly]

9 minutes ago, Alan de Enfield said:

There speaks a man who has 'done' his Food Safety / Hygiene Certificate.

Yes............boring I know but its scary what people do. As a for instance theeeeeeeeeeeeeeeee most dangerous food is cooked rice that people then keep in the fridge and re heat. If its not stored correctly its evil stuff often in the fridge................overnight...................☹️

[Alan de Enfield]

5 minutes ago, mrsmelly said:

Yes............boring I know but its scary what people do. As a for instance theeeeeeeeeeeeeeeee most dangerous food is cooked rice that people then keep in the fridge and re heat. If its not stored correctly its evil stuff often in the fridge................overnight...................☹️

Completely agree, monitoring fridge & freezer temps 4x per day - Boooooooring.

 

Daughter-In-Law (Phillipino) who has been living with us for over a year, re-heats (several times) left over rice, for days after original cooking, (its not refrigerated, just stands in the rice-cooker) she cooks chicken and pork from frozen, but apparently its the norm for them.

 

All total No-No's - we often say we don't know how she isn't ill - if we were doing that when we had the restaurant we'd have been closed down.

Edited July 17, 2018 by Alan de Enfield

[Boater Sam]

We eat in the Philippines all winter, never ill and we eat out all the time. Sometimes in places where nobody but locals eat, its the best food.

[mrsmelly]

19 minutes ago, Alan de Enfield said:

Completely agree, monitoring fridge & freezer temps 4x per day - Boooooooring.

 

Daughter-In-Law (Phillipino) who has been living with us for over a year, re-heats (several times) left over rice, for days after original cooking, (its not refrigerated, just stands in the rice-cooker) she cooks chicken and pork from frozen, but apparently its the norm for them.

 

All total No-No's - we often say we don't know how she isn't ill - if we were doing that when we had the restaurant we'd have been closed down.

But Alan theres nowt to it is there ? anyone can run a pub, Restaurant or café...........its realy realy easy!! money for old rope innitt!!

[stegra]

31 minutes ago, Boater Sam said:

I'll repeat my idea. Wire the fridge stat to switch the inverter on. Then  the inverter only runs when the fridge need it, no standing loss.

I've done this. Did it on my motorhome about 8 years ago and still going strong. Best to use the most basic of fridges. For reasons I don't understand, most thermostats are linked to the interior light. I used the predecessor of this fridge which doesn't have a light. I used a £50 pure sine 500w (1200w peak) inverter with soft start. Originally I used a relay to switch the inverter but later changed it to link in to the inverter's switch. 

[Boater Sam]

At last someone who understands the best way to power a mains fridge, thank you stegra.

[stegra]

Also has the advantage that the inverter can be right next to the batteries so no concerns about voltage drop. 

[Alan de Enfield]

32 minutes ago, mrsmelly said:

But Alan theres nowt to it is there ? anyone can run a pub, Restaurant or café...........its realy realy easy!! money for old rope innitt!!

Yup, its easy - 18 hours per day, 7 days a week, No holidays for 8 years

Edited July 17, 2018 by Alan de Enfield

[WotEver]

7 hours ago, Alan de Enfield said:

The second Inverter is apparently 800 watts (1500 watts peak) and has a cigarette lighter plug.

Look closer - they’ve used the wrong picture. The image is of a 180W inverter. 

[Alan de Enfield]

1 minute ago, WotEver said:

Look closer - they’ve used the wrong picture. The image is of a 180W inverter. 

Yes - Jen pointed that out in post #4

 

800 watt text

180 watt pictures

[WotEver]

Just now, Alan de Enfield said:

Yes - Jen pointed that out in post #4

 

800 watt text

180 watt pictures

Yup, posted before getting to the end of the thread. My bad. 

[smileypete]

There's cheaper pure sine inverters too:

 

https://www.amazon.co.uk/1000W-power-inverter-battery-electricity/dp/B00AEVHTNG

 

Also there's some really cheapo ones out there but most (all?) of these are best avoided.

 

For a ballpark estimate, a typical inverter should have a continuous rating which is 10x the wattage of the fridge.

 

Mastervolt and victron etc are good but somewhat over rated as they're not 100% reliable for everybody.

Edited July 17, 2018 by smileypete

[The Boat Studio]

3 hours ago, Boater Sam said:

I'll repeat my idea. Wire the fridge stat to switch the inverter on. Then  the inverter only runs when the fridge need it, no standing loss.

Hi thanks for commenting so you mean wire the fridge thermostat to switch the inverter on? 

2 hours ago, stegra said:

I've done this. Did it on my motorhome about 8 years ago and still going strong. Best to use the most basic of fridges. For reasons I don't understand, most thermostats are linked to the interior light. I used the predecessor of this fridge which doesn't have a light. I used a £50 pure sine 500w (1200w peak) inverter with soft start. Originally I used a relay to switch the inverter but later changed it to link in to the inverter's switch. 

This all sounds good but I am not sure I understand fully! Can you explain a bit more how it would work? So you would use the inverter for the initial surge yes? and then only when the thermostat registers it needs more power to cool down does it turn the inverter on again?

28 minutes ago, smileypete said:

There's cheaper pure sine inverters too:

 

https://www.amazon.co.uk/1000W-power-inverter-battery-electricity/dp/B00AEVHTNG

 

Also there's some really cheapo ones out there but most (all?) of these are best avoided.

 

For a ballpark estimate, a typical inverter should have a continuous rating which is 10x the wattage of the fridge.

 

Mastervolt and victron etc are good but somewhat over rated as they're not 100% reliable for everybody.

Thanks that is handy also good to know that we should be looking for an 800 watt continuous rating.

[The Boat Studio]

8 hours ago, Jen-in-Wellies said:

600W in my experience isn't enough to start a fridge compressor. The inrush current when they first start is many times the current when running. The 800W might cope, but to be sure I'd want at least 1000W. The other thing to look at is efficiency. The amount of your battery capacity they use in inverting. As you'd expect, high efficiency costs more. A 50W solar panel won't keep pace with a fridge. My 240W of panels can just about keep up in sunny summer weather with the fridge, but that is it. A 12V fridge will have similar problems. Many use more power than a 240V one and inverter.

 

Jen

 

The photo on the Midland Swindlers site is wrong. It is a 180W inverter, not the 800W. Hence the fag lighter. Around 15A, which is still a lot for a fag lighter socket to cope with.

Yeah - I wasn't by any means suggesting my 50w solar panel could power the fridge! Just thought I would mention our set up. When you say 'high efficiency costs more' can you give me an example of the more efficient inverters on the market. Are Victron and Sterling any good?

6 hours ago, Chewbacka said:

As Jen says above, mains fridges take a lot to start them.  My guess is that mine takes the best part of 2000W for a fraction of a second, so a 1000w continuous, 2000w peak may be ok, can't say for certain as I don't know if your fridge is better or worse than mine.

 

Another thing to consider with inverters is how much power they use themselves (some will use 25W doing nothing) and some also have a power saving mode where the inverter uses less than a couple of watts when there is no demand for power.  Given that a decent fridge with plenty of ventilation will be 'off' for half the time and off for longer in cooler weather then your inverter losses could be greater than the fridge use.

Good thing to bear in mind - thank you.

[The Boat Studio]

3 hours ago, mrsmelly said:

Total agree Why the hell switch the damn thing off at night. The door is not opened at night and keeps food etc at a safe temperature. Switch on in the morning and it has to work its arse off to cool again, completely bonkers and yo yo ing food temperature is dangerous.

Yes - I know its not ideal. I only mentioned it as we did it on our old boat. We don't live on our boat and def don't mind going without ice cubes for the times we are on it.. Ideally we just want something to keep the milk from congealing and the cheese turning rank! Other wise we don't eat meat and most stuff we cook fresh and eat there and then. 

 

 

Edited July 17, 2018 by The Boat Studio

[Boater Sam]

Use a fridge with a thermostat that is simple old mechanical, no electronics.

Remove the wires from the stat and connect them together so the fridge runs all the time.

Take 2 wires from the stat to the inverter next to the fridge and connect them across the on/off switch in the inverter. Turn the inverter switch off or disconnect it.

Plug the fridge into the inverter.

Now when the fridge needs power, it will start the inverter up until it is cold enough, then it goes off, inverter uses no power unless the fridge wants it.