12v fridges

[Boater Sam]

a) The batteries are not fully charged.

b) The cables are too thin.

[Alan de Enfield]

a) The batteries are not fully charged.

b) The cables are far too thin.

[Kathymel]

 

Quote

They only use a single thermostat (in the fridge) and boats can go below the minimum operating temperature, especially if left unattended in winter. This means that the fridge never turns on so the freezer defrosts. This applies to most 240 volt fridges too, especially fridge freezers in garages and outbuilding.

 

...........Dave

 

 

I had a conversation about this on a white goods forum (yes, I know how to live) because my house kitchen was regularly dropping below the temperature that kept the fridge functional and the freezer was defrosting. 

 

It took a while while to get out of them that it was the temp inside the fridge that was causing the problem, at which point I realised that allowing the bulb to stay on when the fridge door was closed would raise the temp sufficient to keep everything happy. 

 

I was given dire warnings from many patient, knowledgeable men as to the dangers to myself and my fridge if I should follow this through. They included condensation, food poisoning, rust, rotting and eternal damnation in the fires a white goods hell. 

 

I tested several differently rated bulbs to find one that would do the job without killing me or the fridge and, 15 years later, both my fridge and I have survived with no ill effects (apart from a small patch of rust on my left knee).

7 minutes ago, Alan de Enfield said:

a) The batteries are not fully charged.

b) The cables are far too thin.

Thanks guys.

 

What would I see with better wiring?

 

Is it possible to work out how much extra power I am using as a result of too thin wiring? 

 

 

Not sure how those two replies merged ... ?

[Alan de Enfield]

3 minutes ago, Kathymel said:

Thanks guys.

 

What would I see with better wiring?

 

Is it possible to work out how much extra power I am using as a result of too thin wiring? 

 

a) You would not get the volt drop with the fridge running (you should be looking at a maximum of 0.2v drop)

b) You will get a fridge that works correctly and runs for far less time (normally around 15 minutes per hour)

Get some 16 / 18 / 20mm squared cable and you'll see the difference.

[Tony Brooks]

If you are ge4tting that much voltdrop when the motor is running the voltdrop you get as the motor starts will be much higher and is likely to trip the fridge under voltage protection.

 

With thicker wires you will see far less voltdrop and less likelihood the  fridge will trip on under voltage as it starts.

 

You may be using less power because the fridge trips out and defrosts but that question in my view is not worth concerning yourself with. If it were any other motor on the boat apart from the fridge you may  ell be at risk of burning it out.

[Kathymel]

22 minutes ago, Alan de Enfield said:

a) You would not get the volt drop with the fridge running (you should be looking at a maximum of 0.2v drop)

b) You will get a fridge that works correctly and runs for far less time (normally around 15 minutes per hour)

Get some 16 / 18 / 20mm squared cable and you'll see the difference.

Thanks. Is there any reason I couldn’t just double up the existing cable rather than entirely replacing it with the expensive thick stuff?

 

18 minutes ago, Tony Brooks said:

.

You may be using less power because the fridge trips out and defrosts but that question in my view is not worth concerning yourself with. If it were any other motor on the boat apart from the fridge you may  ell be at risk of burning it out.

Partly an academic question, but  I’m curious to know by how much the power consumption would reduce as the cableling isn’t cheap and, if it would take several years to recoup the cost, it might not be worth it. 

 

My current set up runs the fridge as it is without it turning off and defrosting. 

[mrsmelly]

Cor blimey, why oh why?? As a long term full time liveaboard so obviously leccy savvy as we know we have to often produce it whilst not on hook up, I went all mains years ago. Present boat everything is mains. Modern mains stuff uses much the same as 12 volt. In fact my latest mains fridge uses less than the 12 volt did. They are better made and dont come on and off so often. I run 24/7 365 an undercounter fridge and undercounter freezer, neither are ever switched off. Just been way off hook up for 3 nights and my battery bank of 4 by 110 amp hours managed with ease with just one charging up per day and doesnt drop below 12.3 volt. If we fully charge to 8pm and watch telly during evening and with fridge and freezer on the batts are at 12.5/6 next morning. Everything costs literaly HUNDREDS of pounds less per item Fridges, freezers, tvs etc etc etc. A top notch inverter can be got with the difference alone on the cost of one set of white goods. On top of this having mains 24/7 365 makes everything easier and so many more places to buy stuff with ease. Bin the daft 12 volt fridge. No huge cabling to buy either on long runs.

[MtB]

20 minutes ago, Kathymel said:

Thanks. Is there any reason I couldn’t just double up the existing cable rather than entirely replacing it with the expensive thick stuff?

 

No reason not to at all. This would be fine. 

 

21 minutes ago, Kathymel said:

Partly an academic question, but  I’m curious to know by how much the power consumption would reduce as the cableling isn’t cheap and, if it would take several years to recoup the cost, it might not be worth it. 

 

I think this is un poisson rouge. Any change in power consumption would be trivial and if solar is the source, the payback period would be infinite!

 

There are plenty of technical reasons the cables ought to be fat enough, but economy isn't one of them. In my poorly informed opinion.

 

 

[Kathymel]

9 minutes ago, mrsmelly said:

Cor blimey, why oh why?? As a long term full time liveaboard so obviously leccy savvy as we know we have to often produce it whilst not on hook up, I went all mains years ago. Present boat everything is mains. Modern mains stuff uses much the same as 12 volt. In fact my latest mains fridge uses less than the 12 volt did. They are better made and dont come on and off so often. I run 24/7 365 an undercounter fridge and undercounter freezer, neither are ever switched off. Just been way off hook up for 3 nights and my battery bank of 4 by 110 amp hours managed with ease with just one charging up per day and doesnt drop below 12.3 volt. If we fully charge to 8pm and watch telly during evening and with fridge and freezer on the batts are at 12.5/6 next morning. Everything costs literaly HUNDREDS of pounds less per item Fridges, freezers, tvs etc etc etc. A top notch inverter can be got with the difference alone on the cost of one set of white goods. On top of this having mains 24/7 365 makes everything easier and so many more places to buy stuff with ease. Bin the daft 12 volt fridge. No huge cabling to buy either on long runs.

Thanks Mrsmelly,

 

I do have a fairly good inverter so that is an option I’m thinking about. Sounds a lot easier too. 

 

I’m also considering the freezer/fridge conversion below. The guy reckons he uses between about 150 and 180 watts a day to power it.

 

Having a top-opener makes a lot of sense. Every time I open my fridge atm, all the cold air falls out. And that’s with trying to keep all the spaces filled. 

 

http://www.aselfsufficientlife.com/chest-freezer-to-fridge-conversion-the-most-energy-efficient-fridge-ever.html

 

7 minutes ago, Mike the Boilerman said:

 

No reason not to at all. This would be fine. 

 

 

I think this is un poisson rouge. Any change in power consumption would be trivial and if solar is the source, the payback period would be infinite!

 

There are plenty of technical reasons the cables ought to be fat enough, but economy isn't one of them. In my poorly informed opinion.

 

 

Thanks for this, Mike. 

[MtB]

12 minutes ago, Kathymel said:

Thanks for this, Mike. 

 

Yerwelcome

 

 

12 minutes ago, Kathymel said:

The guy reckons he uses between about 150 and 180 watts a day to power it.

 

This however makes no sense at all. A Watt is a unit of power (rate of consumption of energy). AmpHours or WattHours tell you how much energy the thing uses in a given time period (e.g. a day). 

[MtB]

The chest freezer idea seems a fundamentally good idea but I'm no fan of running an inverter all the time. It just feels WRONG and clumsy. 

 

We know mrsmelly likes the idea but this is the man who threw out a set of fantastically expensive, superb traction batteries from his boat and replaced them with el cheapo leisures. Nuff said, eh? 

[WotEver]

1 hour ago, Mike the Boilerman said:

This however makes no sense at all. A Watt is a unit of power (rate of consumption of energy). AmpHours or WattHours tell you how much energy the thing uses in a given time period (e.g. a day). 

I just read the article. He quite pointlessly admits that he’s used the incorrect units and corrects them to 150Wh to 180Wh per day. So if we believe him, that would be less than 20Ah at 12V. It compares well to the usual finger in the air daily consumption of 24Ah often used as an example for a standard 12V fridge. 

 

But it’s not a huge reduction. 

[MtB]

3 minutes ago, WotEver said:

I just read the article. He quite pointlessly admits that he’s used the incorrect units and corrects them to 150Wh to 180Wh per day. So if we believe him, that would be less than 20Ah at 12V. It compares well to the usual finger in the air daily consumption of 24Ah often used as an example for a standard 12V fridge. 

 

But it’s not a huge reduction. 

 

Yes I found that too after posting.

 

Thing is with solar, saving energy is all a bit pointless. Once the sun is powering your fridge, improving the efficiency of it is completely invisible. The only effect is the end of solar working when winter arrives gets moved forwards a few days, and vice versa. In proper winter, solar is useless no matter how efficient your fridge is. 

 

 

[Dr Bob]

2 hours ago, mrsmelly said:

Cor blimey, why oh why?? As a long term full time liveaboard so obviously leccy savvy as we know we have to often produce it whilst not on hook up, I went all mains years ago. Present boat everything is mains. Modern mains stuff uses much the same as 12 volt. In fact my latest mains fridge uses less than the 12 volt did. They are better made and dont come on and off so often. I run 24/7 365 an undercounter fridge and undercounter freezer, neither are ever switched off. Just been way off hook up for 3 nights and my battery bank of 4 by 110 amp hours managed with ease with just one charging up per day and doesnt drop below 12.3 volt. If we fully charge to 8pm and watch telly during evening and with fridge and freezer on the batts are at 12.5/6 next morning. Everything costs literaly HUNDREDS of pounds less per item Fridges, freezers, tvs etc etc etc. A top notch inverter can be got with the difference alone on the cost of one set of white goods. On top of this having mains 24/7 365 makes everything easier and so many more places to buy stuff with ease. Bin the daft 12 volt fridge. No huge cabling to buy either on long runs.

You said that on page one.

I agreed with you on page 2.

Why would anyone CC'ing choose to spend a fortune on a new 12v fridge and a whole load of 20 mm wiring if they have a decent inverter and the 240v wiring in place. It's a no brainer. 

[MtB]

1 minute ago, Dr Bob said:

You said that on page one.

I agreed with you on page 2.

Why would anyone CC'ing choose to spend a fortune on a new 12v fridge and a whole load of 20 mm wiring if they have a decent inverter and the 240v wiring in place. It's a no brainer. 

 

Depends what type of CCer Shirley? Those who CC to get around the system, fine, I agree with you.

 

 But those whose objective is to move the minimum possible distance (i.e. half a mile, once every three weeks)? What about thems?

 

 

 

[Tony Brooks]

10 hours ago, Kathymel said:

Thanks. Is there any reason I couldn’t just double up the existing cable rather than entirely replacing it with the expensive thick stuff?

 

Partly an academic question, but  I’m curious to know by how much the power consumption would reduce as the cableling isn’t cheap and, if it would take several years to recoup the cost, it might not be worth it. 

 

My current set up runs the fridge as it is without it turning off and defrosting. 

tell me the voltage and current when the fridge is running now and for how long it runs per day and then again when you have thicker cabling and I will work it out. Each persons fridge location, boat location, boat colour (solar heating) and internal temperature is different so you ask an impossible question.

 

If the fridge does not cut out on start up and beep/flash a lamp at you then the wiring is probably adequate even if the fridge settings have been altered to allow for undersized wiring. I have no idea if they have or not.

 

Not best practice but by all means double the wiring as long as both the old and new wires go through the same fuse bu tas I said if its not cutting out on start up the wiring will probably do. It may be different when you come off shorepower through but try it and see.

[Alan de Enfield]

42 minutes ago, Tony Brooks said:

if its not cutting out on start up the wiring will probably do.

When I changed my fridge I found that it was 'starting up' fine and would run perfectly (non-stop).

 

When we were out cruising the freezer would freeze and the fridge part kept everything cool.

When I went to get the milk out of the fridge in the morning the fridge was 'awash' with water and the freezer compartment (and its contents) were all wet & soggy.

After this happened a time or two I replaced the wiring to a size in accordance with the installation manual and everything was 'sorted'.

 

Whilst cruising and the alternator pushing out 14+ volts the fridge was getting a 'good enough' voltage (despite the volt-drop), but with the engine off and the batteries at 12.8v (ish) the fridge was only getting 'in the low' 11 volts.

 

 

Edited May 11, 2019 by Alan de Enfield

[MtB]

12 minutes ago, Alan de Enfield said:

Whilst cruising and the alternator pushing out 14+ volts the fridge was getting a 'good enough' voltage (despite the volt-drop), but with the engine off and the batteries at 12.8v (ish) the fridge was only getting 'in the low' 11 volts.

 

 

I think I have a similar problem on one of my boats. 

 

Brand new fridge, runs 24/7 and takes about a day of cruising to get properly cold. Never gets properly cold if I stay moored up when I visit. (Is on a beautiful country mooring.) 

 

Judging by the abysmal standard of the rest of the wiring in the boat, I'll be amazed if the fridge wires are big enough. Time I pulled it out and measured the terminal voltage. 

 

 

[MtB]

12 hours ago, Kathymel said:

I finally got round to dragging the fridge out and measuring the voltage. 

 

With the battery at 12.8v, the voltage at the back of the fridge is 12.6 with the fridge off and 11.7 when it’s drawing. 

 

What does that tell those that know about these things?

 

Well the first thing this bit tells us your multimeter probably isn't working correctly. One would expect the voltage to be the same with the fridge off, even if there was a bad connection. 

 

<Awaits incoming>

 

[mrsmelly]

9 hours ago, Dr Bob said:

You said that on page one.

I agreed with you on page 2.

Why would anyone CC'ing choose to spend a fortune on a new 12v fridge and a whole load of 20 mm wiring if they have a decent inverter and the 240v wiring in place. It's a no brainer. 

Mike would cos hes a dinosaur innitt . The thing is I find that most peeps who dont agree with mains stuff have never even owned an all mains boat, indeed some are not even liveaboards. When inverters first came in ( I was a liveaboard then ) they were hopelesly inadequate for full time use, in fact there were no pure sine jobbies either. In the past 25ish years or so the standard, quality and ability of inverters has risen very considerably. During that time with the ever increasing pressure on companies to reduce electrical consumption of all white goods and combined that means that today a quality, correctly installed mains system is a no brainer. Not only for the price which is hugely less on buying fridges, tellys and a whole host of other stuff but simply cos lots of stuff thats available today can be instantly used as and when needed. I am oft quoted as being a dinosaur by members and yes I am when it come to fones and stuff but I have long since gone fully mains. My choice is based on long term living aboard with a mix of boats over the years with, 12volt only, some mains and some stuff 12 volt and recently with mainly mains with just lights, pumps etc 12 volt. 

[MtB]

16 minutes ago, mrsmelly said:

The thing is I find that most peeps who dont agree with mains stuff have never even owned an all mains boat,

 

 

The thing I find is non-technical peeps (ex-coppers for example) simply have no concept of just how dangerous it can be to mix 240Vac and water, when there is a perfectly safe alternative, 12Vdc.

 

 

 

 

 

[mrsmelly]

1 minute ago, Mike the Boilerman said:

 

 

The thing I find is non-technical peeps (ex-coppers for example) simply have no concept of just how dangerous it can be to mix 240Vac and water, when there is a perfectly safe alternative, 12Vdc.

 

 

 

 

 

Tosh!!  Many things can be dangerous, firearms for one. The idea is not to look down the barrel. Mains is as safe as the very safe gas we all use. Instalation and maintenence being what its all about. 

[MtB]

Just now, mrsmelly said:

Tosh!!  Many things can be dangerous, firearms for one. The idea is not to look down the barrel. Mains is as safe as the very safe gas we all use. Instalation and maintenence being what its all about. 

 

Q.E.D.

 

 

[WotEver]

3 hours ago, Mike the Boilerman said:

Well the first thing this bit tells us your multimeter probably isn't working correctly. One would expect the voltage to be the same with the fridge off, even if there was a bad connection. 

It’s quite possible that as currently wired the fridge feed is shared with other circuits. It may well come from the main dis board instead of directly from the batteries. Certainly that’s what those voltages suggest to me. 

[Johny London]

On 27/02/2019 at 18:32, Jennifer McM said:

I don't know that answer at the moment, tomorrow we'll turn off switches, leaving just the inverter on to get a reading. Thanks  

I'd be very interested to know this.

It seems to me that if you can really have an inverter as Mr Smelly has that is only self consuming 300ma, that would be the way to go. 

I have a 3kw Victron combi and was very surprised to find that is seems to self consume over 3a - and has almost certainly been the cause of all my battery woes over the years as I was estimating it at 0.5a!