Food always in fridge

[rusland]

I'd like to be able to leave food in the fridge and fridge working, while yacht is in the marina, without danger of running down the batteries if shore power fails. Can this be done?

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[fireball]

It depends how your wired ...

If you are using the shore power through a transformer to give you 12v you should be able to put in a 2 way switch for the fridge to select either shore power or battery ... if the shore power fails, your fridge goes off, when it comes back on again so does the fridge (with the now smelly cheese inside!)

If your using the shore power to top up your battery then I think it would be more difficult, but then I'd find a suitable transformer and wire as per the above option!

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[rich]

The compresser Fridge I fitted this year is supposed to run for 10 days, and still leave power to start the engine, maybe one day i will see what happens, fingers crossed.

<hr width=100% size=1>http://www.jersey-harbours.com

 

[ccscott49]

Can this be done? No. If the shorepower goes off and stays off your fridge will flatten your batteries, eventually. But in the winter, would take a long time. If the power goes off for a day or so, then comes back on, no problems, your battery should manage to keep up with that. How big (ah) is your domestic battery? That is the governing factor.

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[john_morris_uk]

Some modern fridge controllers are supposed to monitor the battery charge state and turn themselves off when the batteries are nearing discharged state or very low charge - certainly with enough charge left in the batteries to save them from destroying themselves. The Waeco intelligent controller does this I believe - I only know because we were thinking of updating out compressor unit etc ready for the big blue sailing thing.

They also can have a holding plate fitted so that when the engine is on or other charging means are available, the holding plate freezes down as rapidly as possible. The next phase is an economy mode when the fridge detects no charging is taking place. Finally the fridge turns itself off when the batteries are running low.

They are not particularly cheap, but I hear very good reports of the system.

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[ccscott49]

Sounds a good system, mine do have the low battery thing, but not the other stuff. If I ever get a newish boat, I would equip her with this type of gear, for sure.


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[Talbot]

Holding plates are useful if the only way you can run your fridge is to turn on shore power or the engine for a short time, and then rapidly freeze the plate into a block of ice. The alternative is to have an evaporator which is designed for more continuous cycles from the battery. Thus for some people the holding plate suits them, but for others the evaporator is the better answer. However, you also need to understand that in order to make a holding plate work, you need to have a bigger compressor (or run one faster, or have a smaller fridge or freezer) as the evaporator is designed to keep the fridge/freezer at the correct temp, whilst the holding plate is designed to freeze things down quickly. So you have to decide how you want to be able to use your system. Long term liveaboard that is cruising, the evaporator would probably be better provided there is sufficient solar/wind power available. Weekend use where you want to chill some tinnies down quickly, the holding plate is the better option (but is more expensive for the same size).

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[john_morris_uk]

I take you point, but its a bit of 6 and two 3's as far as I can see.

Notwithstanding that the most important consideration is adequate insulation, the holding plate vs evaporator argument doesn't seem cut and dried. The holding plate takes advantage of 'spare power available' - and thus allegedly saves the batteries from the continuous drain that our current (pardon the pun) compressor requires.

The evaporator might maintain a more uniform temperature - but with a higher average power requirment.

I suppose the real test is whether one's wind/solar panels are providing enough to run the thing without lengthy periods of main engine or generator (or shore power).

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[Wiggo]

depends on the fridge, but our main one is bisexual anyway (AC/DC). It will run on 240V AC if it's available, then switches to 12V DC as and when shorpower fails. You can leave the fridge turned way down, and as you won't be there to keep opening and closing it, and the ambient temp is low, it should not draw much at all.

From memory, the Danfoss compressors draw an average of 1 amp in 'normal' usage (4 amps when running, but a 4:1 duty cycle). I'd expect the duty cycle in winter for an unattended fridge to go out to 10:1 or better, so it may use 10Ah per day or less. An 85Ah domestic could therefore be expected to survive about 3 days or more with no shorepower, longer if you have a wind genny or solar panels.

<hr width=100% size=1>Si hoc legere scis, nimium eruditionis habes.

 

[richardandtracy]

What sort of food?

There is a fair bit of food usually put in fridges that's OK out for moderate times. I've survived quite happily on margarine that wasn't refrigerated for about 5 weeks during summer (went a bit oily, but didn't do me any noticable harm). Carrots, onions, mushrooms, indeed most veg don't need to be refrigerated (especially if bought from a non-refrigerated farm shop).

As for meat. Would you really want to store meat in a fridge for a week anyway?

That puts us in the realm of milk & dairy products as the only things needing refrigeration, and UHT milk these days is good enough to be indistinguishable from the equivalent pastureised milk (go on, next time you're in a supermarket buy 1 carton & try it - if you hate it you'll only have wasted 32 to 45p). So no need to refrigerate the milk.
Can you cope without yogurt or cheese? If you can, there's probably no need to keep the fridge running anyway.

Regards

Richard.


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[Talbot]

{quote]The evaporator might maintain a more uniform temperature - but with a higher average power requirment. [/quote]
Think you may actually have this the wrongway round. If you look at the size holding plate, and compressor required to maintain a specific sized fridege/freezer, the evaporator would be quite a lot smaller. The difference in power requirements is then a function of duty cycle for the system, which would be totally dependent on insulation, ambient temperature and frequency of access to the cold items/adding warmer ones. I have no data on this but gut feeling is that for the long term cruiser, the evaporator is somewhat more power efficient provided as I aid before, you can make enough power without running the engine. If you have to run the engine anyway, then the holding plate starts to make more sense. Therefore I dont think there can be any hard and fast rules about it, you just have to decide which way you want to operate, and then set up your boat accordingly. - for me, I hate having the engine on!

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[john_morris_uk]

I think I probably agree with you - but an audit of power requirements on our boat indicates that even though the only 'power hungry item' is the fridge. (We have no invertor, TV, etc etc) it will be difficult not to run either an engine or a generator for an hour or more once a day whilst at sea or at anchor.

Whats the alternative? Solar panels of any reasonable power size are very expensive. I hate the engine on unless we have to - but I also hate the whizz of the wind generators that I have sailed with.

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[Talbot]

My most power hungry item at the moment is the eberspacher, but would not ne without it! very small alternator (and no way to go larger) means I needed an alternate power source, so I have a 180w solar panel mounted on my davits.If you hate the sound of a wind generator, then a towed system might be more appropriate (and provides more power than a wind system anyway) However, the new higher power larger bladed generators such as the duogen are a lot quieter.

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[macd]

I have two rules on my boat:
1. Don't fall overboard
2. Don't put cheese in the fridge. Horrible stuff if cold and unripe. Or maybe I just have delinquent taste-buds.

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[charles_reed]

Lateral thinking might

help.

Could I suggest that you only leave one battery bank turned on when you leave the boat?

For UK sailing it's doubtful if a fridge is really necessary (except for beer), however when the ambient temperature is up to 40C (as up the Guadiana) a refrigerator is a necessity or the butter runs to the lowest point it can find in very short order.

PS If you only have one battery bank it's about time you fitted another.

PSS The Grundfoss on my unit pulls 5.8 amps at startup and on supercool and 4.4amps in normal eco mode. How often it runs is directly proportional to 3 factors, the efficiency of the insulation, the ambient temperature and the fullness of the cooled box.

With 100 mm of closed cell PU and with a full 48 litre box, at 28C the unit cycles for c20 mins every 300 mins and takes about 6 days to flatten the domestic bank.

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[charles_reed]

Lateral thinking might

help.

Could I suggest that you only leave one battery bank turned on when you leave the boat?

For UK sailing it's doubtful if a fridge is really necessary (except for beer), however when the ambient temperature is up to 40C (as up the Guadiana) a refrigerator is a necessity or the butter runs to the lowest point it can find in very short order.

PS If you only have one battery bank it's about time you fitted another.

PSS The Grundfoss on my unit pulls 5.8 amps at startup and on supercool and 4.4amps in normal eco mode. How often it runs is directly proportional to 3 factors, the efficiency of the insulation, the ambient temperature and the fullness of the cooled box.
With 100 mm of closed cell PU and with a full 48 litre box, at 28C the unit cycles for c20 mins every 300 mins and takes about 6 days to flatten the domestic bank.

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[charles_reed]

Lateral thinking might

help.

Could I suggest that you only leave one battery bank turned on when you leave the boat?

For UK sailing it's doubtful if a fridge is really necessary (except for beer), however when the ambient temperature is up to 40C (as up the Guadiana) a refrigerator is a necessity or the butter runs to the lowest point it can find in very short order.

PS If you only have one battery bank it's about time you fitted another.

PSS The Grundfoss on my unit pulls 5.8 amps at startup and on supercool and 4.4amps in normal eco mode. How often it runs is directly proportional to 3 factors, the efficiency of the insulation, the ambient temperature and the fullness of the cooled box.
With 100 mm of closed cell PU and with a full 48 litre box, at 28C the unit cycles for c20 mins every 300 mins and takes about 6 days to flatten the domestic bank.

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[halcyon]

Fit a powerlockout relay inline with the fridge, if battery falls to a preset value the fridge is isolated. The down side is you lose whats in the fridge.
Depending on how complicated you want to get, a reserve power relay would split the battery bank, to maintain a reserve, and leave the remainder to power the fridge. If your not back before the battery goes flat you still lose what's in the fridge, but still have battery power left in the part of the bank.
The other factor is what boat you have, a number of Westerly's, Sealines have a lock facility fitted as standard.
At the end of the day there are a lot of options, it depends what you want to achieve.


Brian

Brian

<hr width=100% size=1><A target="_blank" HREF=http://link>www.kddpowercentre.com</A>

 

[charles_reed]

Relay fitted as standard

on the ASU compressor unit

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[alan]

Answer is : yes.

There are a number of ways of doing this, as already mentioned. I have fitted a Frigoboat Digital Economy Controller to my boat (cost £46).

Obviously depends on the type of fridge/compressor that you have. This unit senses the battery volts and switches the compressor to a continuous running economy mode when the voltage falls below "X", this maintains the fridge at 10C (I think! I am writing from memory). If the battery volts fall below "Y" the unit swithches off the compressor. In the summer whilst cruising I use this unit with a 56W solar panel, plus engine charging usually twice a day (whilst anchoring/retrieving anchor) and I have never had a problem with flat batteries.

I found the biggest improvement to my fridges efficiency was to put two pieces of polystyrene on the top of the food, as the lid of the fridge on my boat is seriously whimpy and under-insulated (one day I make a serious effort for a more permanent intallation!! However, I made two pieces of poly as it is easier to insert/remove than one big piece). Maybe closed cell foam (as you can get from builders merchants - not boat builders 'cause the cost will triple!!) would perform better but in real terms I doubt the difference would be noticeable.

Frigoboat Economy controllers can be obtained in the UK from :
<A target="_blank" HREF=http://www.penguinfrigo.co.uk>http://www.penguinfrigo.co.uk</A>

Alan.
Nettuno, Italy.

<hr width=100% size=1>Alan Cloke<P ID="edit"><FONT SIZE=-1>Edited by alan on 04/12/2004 11:02 (server time).</FONT></P>