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floydraser

Fridges - 12v Or Mains?

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Firstly, apologies if I'm in the wrong area and further apologies for bringing up an old chestnut. My excuses start with the fact that I have searched around the boaty forums and I get the impression the information available is relatively old in relation to modern movements in prices and technology.

The Denham Owl currently has a mains 66lt Logik fridge which came with the boat. Not a problem while we're on shore power until next year when we want to cruise further than the length of the cable. If anyone suggests a longer cable I'll chuck 'em in! :default_2gunsfiring_v1:

I want to fit a fridge of a more practical size as part of a major electrical revamp - new consumer unit, 12v fuse boards, control panel etc. and I know it'll hurt me in the wallet. However, the difference costwise between a 12v fridge and a mains + inverter fridge doesn't appear to be great so I'm torn between the two. In particular, I wonder if an inverter would run other mains appliances at the same time? I would be interested in other's experiences.

Thanks in anticipation, I'll be over on Sunday to fit a new poo pipe.

Floyd.

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If you can run to a genuine danfoss compressor 12v fridge then I would definitely say this is the way to go. I have had 3 Waeco and one Inlander and all have performed faultlessly.

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Trouble with running mains stuff off an inverter is the drain on your batteries. Power in always equals power out, less losses. So 2 Amps at 240 volts equals 40 amps at 12 volts. Something to bear in mind. Also, some fridges advertised as mains/12 volt have a built in inverter, so they still need lots of Amps on 12 volts. Go for a good quality 12 volt fridge is my advice.

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Hi Floyd I have a waeco dual fridge it works on mains when plugged into shore power, then when 240v drops out it switches to 12v automatically then when 240v comes back on switches back to 240v i find this prevents forgetting to switch manually when casting off, if you run a 240v from a inverta you will use more battery power for no gain. John

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6 hours ago, annv said:

Hi Floyd I have a waeco dual fridge it works on mains when plugged into shore power, then when 240v drops out it switches to 12v automatically then when 240v comes back on switches back to 240v i find this prevents forgetting to switch manually when casting off, if you run a 240v from a inverta you will use more battery power for no gain. John

Ours is a Dometic which I understand is basically a Waeco.  It certainly hit the wallet but is a brilliant fridge. We can hardly hear it. In fact it’s so quiet I used to check it was still working!  We did have to get a rectifier to automatically switch between 12 and 240v at an extra cost of £90 as it doesn’t come in the box.  It goes from room temp to 3 degrees in about ten minutes if you start it up on boost then turn it down to number 3 and temp is perfect.  We have run the fridge for 24 hours on 12v without any noticeable effect on our domestic batteries and didn’t need to run the engine. 

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Marthams have the isotherm fridges that run direct off the domestic battery bank, and are plugged in when you pick the boat up and stay on all the time, I have had a few times when I havent cruised for a day (generally at the may meets and wooden boat show weekends) and the fridge has just carried on, no problems no alarms, mind you on a Martham boat there isnt much else (other than the lights) that uses the domestics, I do love their plain and simple approach, basically I think they have sized the domestic power bank to run the fridge for several days without cruising.

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Look at the power consumption of what you are interested in.

A fridge using 4 amps per hour on 12v will flatten a fully charged 110 leisure battery in about a day and it will take the engine 2 hours to charge that one battery alone.

The Waeco, Shoreline, Domestic ranges are low consumption in normal use but on a hot sunny day that will increase.

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Hi, we have a waeco  it runs with no problems.

If you have a battery charger there is no need for a rectifier when hooked up, the charger will take care of that!

Thus saving £90 to spend towards a better fridge or one of those enticing drinks fridges.

paul

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If you pay for the extra power saver gadget (about £150) for the 12/24v danfoss compressors they run much more efficiently by varying compressor speed and running higher when the volts are higher (ie charging) so the food itself acts as an accumulator without actually freezing, I think mine is 65L and cost nearly £700 with the extras but it means I can stay off grid for longer, I also have the box that switches over to shore power when available automatically.

I don't think you will get anywhere near the efficiency from a domestic/inverter setup.

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I would say that the best approach is to never run anything on a boat from an inverter if you don't have to.

There aren't many things you need to in reality as you can get 'mains' TV's which actually have a 12V transformer (I have one - You just need to make up a lead, or buy one) and there's plenty of USB and laptop chargers etc for cigarette lighter sockets.

I'd fit a 12V fridge and then maybe have a separate 'switchover box' (a rectifier) if you have shore power.

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19 minutes ago, oldgregg said:

I'd fit a 12V fridge and then maybe have a separate 'switchover box' (a rectifier) if you have shore power.

Had I upgraded my battery charger before upgrading the fridge I'd have left this bit out but I only had a 2x 5A output charger at the time, now have 30A 3 outlet charger so could easily do without the switchover box.

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Simple answer is to buy a fridge that uses either source. I picked up an el cheapo Chinese jobby from a car boot sale in the spring, brand new for twelve quid and it's been blessed brilliant, keeps the white wine, milk for the tea and my maggots at a perfect temperature! 

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Hi A Fridge that uses 4 amps does not use that amount all the time so would not run your battery down in a day unless you left the door open, and as for charging what is your alternator output does it have a smart regulator, my setup will recharge a 110ah battery 15 min theoretically. any fridge with a danfoss compressor is most likely to be the most efficient at the present time until a new design becomes available on the markit. John

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our gas fridge died at the wooden boat show 3 years ago, nipped to brian wards, got a waeco 65 ltr 12v fridge works extremely well, 3 domestic batteries which have a solar panel to run the fridge when moored , we cango for days without using engine so are self sufficient

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I was going to hold off untill the new year but as you are talking fridges I have one in storage. It was working fine when I brought the boat and doesn`t look very old at all, I just wanted a bigger one. From memory it is a compressor 12/24v Waeco, think it is 52L but could be bigger, I can check serial number/ model plate tomorrow. 

Was hoping for around 50% of cost of new as it really is clean and I will guarantee it or money back for a forum member. PM a number if you want to take a look and I`m around Brundall this weekend.

Also have a tidy smev oven with burners above.

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Well a big thanks for all the replies here!

I'm sure I ticked the "notify me of replies" box but checking my email during the day made me think no-one loved me any more.:default_sad:

The votes seem to be stacking up for 12 volt but the jury can stay out for a bit as plans proceed. I think I should share a bit more information about what the set up is currently so I'll put it on hold until Monday. I'm going over to the Owl on Sunday and I'll do a short video of the batteries, chargers and stuff, and check the model numbers; there is an inverter already on board but the manual I have covers 10 models from 150w to 1500w. It works but trips out when the fridge starts so it's probably well under the required power output.

Thanks again, I'll report back here on Monday.

OBB - pm sent

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10 hours ago, annv said:

my setup will recharge a 110ah battery 15 min theoretically

seriously? How many amps are you charging at, and how do you stop the battery exploding. Even from a 50% discharge my rough calculator suggests in excess of 200A? 

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Yes i have two connected to a Sterling  smart regulator tottel 265 amps as i said theoretically, these are connected to four 110 amp batteries. John

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But you can't charge any flooded battery at anything  like that level of current, theoretically or otherwise, without damaging it. Even enhanced batteries like EFB and AGM should not be charged at currents higher than 30% of their capacity and even then only for a short period.

My workshop charger rates upto 60a and can be automatic or manual (it calls it forced). At 60a it would destroy the plates in a 110a battery in minutes. On auto with as much current available as the battery can handle then the fastest it can recharge a fully discharged deep cycle battery is around 4 hours,

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As promised here's some further info. I know I said Monday but it's still nearly Monday isn't it? Sorry I'm late.

Further info to that in the video: Previous owners of the Owl have been pushing her towards liveaboard use, hence the mains fridge and domestic cooker. I want to bring it back towards floating caravan/practical cruiser kind of use. It's perfectly usable as it is and none of this urgent, I'm just trying to plan ahead.

The video shows the present fridge in it's place and the space measures 52cm wide, 66cm high and 55cm deep. I also found the engine drives two fairly new looking alternators although I didn't check the output of them.

The vetus charger: https://www.vetus.com/en/electricity-on-board/battery-chargers/battery-charger-12v-9899.html

What does the team think?

 

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Pretty much the same battery charger as my Waeco. Two outputs that can be paralleled to the domestic bank, and a 2 Amp trickle charge output for the starter battery. Capable and trouble-free bit of kit.

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What is the minimum size inverter needed to run just a standard undercounter fridge ?

I have a 300w inverter and a domestic 240v fridge, i have never run it on it but might need to after it is at temperature.

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300W at 240V is 1.25 Watts. You need to know what your fridge draws when starting and running. It might be man enough to run it after, but the initial starting current could trip out an inverter at it's limit. It sounds a bit too low-powered to me.

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12 hours ago, Regulo said:

300W at 240V is 1.25 Watts

Maybe Amps even...........:default_beerchug:

(Just as you thought I'de gone quiet..........):default_rofl: 

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Late night brain fade, Bill! Well spotted.

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