Fridges (again)

[Trilby Tim]

Would it be possible/practical to remove the heat sink from the back of the fridge and attach it to the side of the boat, or even better to the base plate? Could potentially make the fridge far more efficient......

[Nickhlx]

If we add insulation to reduce the rate of heat loss to our houses, why don't we add ( more) insulation to our fridges / freezers to reduce the rate of heat ( gain) into them ? Actually I have done to our large domestic upright freezer, by adding 2" thick polystyrene insulation to the sides and top, and it seems to come on much less....

 

So presumably it would work for a fridge and reduce the electrical demand, thus saving fuel, wear and tear on the fridge and engine / generator and therefore money ! I would imagine even a further 1" would be noticeable....

 

Nick

[withoutapaddle]

If we add insulation to reduce the rate of heat loss to our houses, why don't we add ( more) insulation to our fridges / freezers to reduce the rate of heat ( gain) into them ? Actually I have done to our large domestic upright freezer, by adding 2" thick polystyrene insulation to the sides and top, and it seems to come on much less....

 

So presumably it would work for a fridge and reduce the electrical demand, thus saving fuel, wear and tear on the fridge and

 

I remember a thread somewhere where it was suggested using a domestic freezer with a modified thermostat instead of a fridge as they have not only more powerful compressors which would run less frequently (though would draw more current presumably so the benefit would need to be measured carefully) but they also had superior insulation built in. It was mentioned that if you ran a top loading freezer there would be the potential additional benefit that the chilled air wouldn't fall out in a great lump all over your slippers when y' opened the door

Edited July 11, 2009 by withoutapaddle

[Justme]

by adding 2" thick polystyrene insulation to the sides and top, and it seems to come on much less....

 

I would imagine even a further 1" would be noticeable....

 

Nick

 

 

I think I am right that with insulation that to double the savings you have to add double the thickness.

 

So to make the same savings again that the 2" made you would need to add another 4", the extra 1" will not be noticeable.

[Nickhlx]

I think I am right that with insulation that to double the savings you have to add double the thickness.

 

So to make the same savings again that the 2" made you would need to add another 4", the extra 1" will not be noticeable.

 

 

Seems logical, although no figures to hand to attempt to verify... Presumably this assumes the same type of insulation used. I think that manufacturers use some sort of injection applied expanding foam that sets - I have no idea how good that is compared to other materials that are insulators, but obviously they have to use something that is quick easy and pretty efficient at the task when in production. It may be that even humble polystyrene or thinsulate or something is better than this injected foam, so even a small thickness may be quite beneficial....

 

Without more knowledge it is difficult ( impossible) to predict results - does anyone know e.g. from the refrigeration / heating / insulation industry ?

 

Thanks,

 

Nick

 

edited to say: Just spent some time browsing the subject and it seems polyurethane foam is pretty good at insulating and it's also quite important to prevent radiated heat getting to the item to be kept cold, as well as convected and conducted heat, so a "space blanket" is worthwhile to incorporate as well - or maybe a layer of aluminium foil..

Edited July 11, 2009 by Nickhlx

[ditchcrawler]

If we add insulation to reduce the rate of heat loss to our houses, why don't we add ( more) insulation to our fridges / freezers to reduce the rate of heat ( gain) into them ? Actually I have done to our large domestic upright freezer, by adding 2" thick polystyrene insulation to the sides and top, and it seems to come on much less....

 

So presumably it would work for a fridge and reduce the electrical demand, thus saving fuel, wear and tear on the fridge and engine / generator and therefore money ! I would imagine even a further 1" would be noticeable....

 

Nick

That is what I did a couple of years ago. 1"on each side, Flexible insulation as used behind radiators between the condenser and the back of the fridge

 

I think I am right that with insulation that to double the savings you have to add double the thickness.

 

So to make the same savings again that the 2" made you would need to add another 4", the extra 1" will not be noticeable.

Well here are my results, not a scientific test,

 

I have been running another set of tests on our 240 volt fridge.

The fridge runs via a Mastervolt Mass Sine 24/1500 and all current

readings are take from a Sterling Battery Management unit.

 

The inverter + Fridge + fans =3.5 amps

The Inverter + Fridge = 3.4 amps

The Inverter = 0.4 amps

 

I have connected a RS hour meter across the refrigerator compressor to

record compressor run hours.

The refrigerator is a LEC Elan and sits under a work top with 25mm air

gat each side and 50mm between the top of the refrigerator and the

underside of the work top. The air space behind the refrigerator is

well over the recommended space as the hull side slopes from the floor to

the gunwale.

There are ventilation holes drilled in the floor behind and below the

fridge. Also there are 4 computer fans mounted in the floor connected in

series parallel that when running blow cool air from under the floor up

the condenser. All readings were taken with the fridge in normal use.

 

The fridge thermostat was set at 3 and had been running for a couple of

days to allow things to stabilise before readings were taken at 1700 hrs

each day. The thermometer inside the fridge was reading at the top of

the acceptable range.

 

At the end of the first day with the fans off and the fridge running as

normal the hour meter recorded 7.6 hrs in 24 hrs.

On the second day the fans were switch on and the reading at the end of

24 hrs was 7 hrs.

The next day the fans were switched off and the hours run were 7.1

This indicates to me that the fridge was adequately ventilated as

installed. That night I insulated the fridge on both sides and the top

with sheets of 25mm close cell insulation foam covered on both sides

with aluminium foil as used in the building trade. At this point things

got interesting which I can't explain. The running hours were slightly

less but the internal temperature of the fridge fell. Over the next 2

days I adjusted the thermostat setting to bring the internal temperature

back to its original level. This resulted on it now being set at 1.5 as

opposed to the original 3. I don't know why this happened as in my book

the thermostat should keep the inside of the fridge at a constant

temperature. I suspect it is a timer and not a stat.

 

Once this had settled down I started recording readings again which run

between 6.3 and 5.7 hours per day

11/8/06 1700hrs 1170.2

12/8/06 1700 hrs 1177.8 7.6

Fan on

13/8/06 1700hrs 1184.7 6.9

Fan off

14/8/06 1700hrs 1191.8 7.1

Insulation added and fans on

15/8/06 1700hrs 1198.5 6.7

reduced stat setting

16/8/06 1700hrs 1205.0 6.5

17/8/06 1700 hrs 1211.3 6.7

18/8/06 1700hrs 1217.0 5.7

19/8/06 1700hrs 1223.6 6.6

20/8/06 1700hrs 1230.0 6.4

21/8/06 1700hrs 1235.5 5.5

22/8/06 1700hrs 1241.2 5.7

--

[bramley]

intresting topic, which i know has been covered lots of times.

 

I am in the throws of looking for a fridge for my GRP norman 23. Only problem i have is my Honda outboard has a 6amp altenator...hehe (some peoples hell lol)

 

She has 2x110 batterys and a normal car battery as a starter, it seams the best thing i can buy is the 12v cool box fridges with a danfoss compressor i think. i am thinking about getting a solar panal just to help things along even if only 10/20watts

 

nice thread

 

Ross

[ditchcrawler]

intresting topic, which i know has been covered lots of times.

 

I am in the throws of looking for a fridge for my GRP norman 23. Only problem i have is my Honda outboard has a 6amp altenator...hehe (some peoples hell lol)

 

She has 2x110 batterys and a normal car battery as a starter, it seams the best thing i can buy is the 12v cool box fridges with a danfoss compressor i think. i am thinking about getting a solar panal just to help things along even if only 10/20watts

 

nice thread

 

Ross

There are some Wilderness owners who run 12 volt fridges on Solar Panels

[Cosmic]

One idea I had was to keep a supply of balloons, and use them to fill any empty spaces in the fridge. No idea how much this will save, but it won't cost much to give it a try.

[WotEver]

... came across this from BSS in sept 2008. Has there been any gas fridge produced since this was published which would be suitable for boat use.

 

Hi,

 

To the best of my knowledge this still holds true (braces himself for incoming).

 

We pulled out our old Electrolux last year and replaced it with a 12V Waeco at HUGE expense - hey, it's 'marine'

 

Don't forget to put nice fat cables in to feed the fridge if you go 12V.

 

Regards,

Tony

[tomandsophie]

The thing about the BSS does still hold true, but it is only 'advisory' so it is still fine to put in a gas fridge. Our boat is only 4 years old and I put in a non-room-sealed gas fridge and it was fine in our recent BSS test.