12v or 240 A+ Fridge

[Clifford]

On our boat, we are going to try to get fridge Ah use down drastically - with a radical approach I've seen discussed on the tinterweb (but not, I think, here).

 

The idea is, in warmer months only, to run a small chest freezer at fridge temperatures, just to keep the essentials (meat and milk) fresh in warm weather.

 

This is apparently low on leccy for two reasons. First because warm air doesn't whoosh in to replace all the expensive cold air everytime you open the door. Second, because a freezer has much more effective insulation than a fridge. Running a freezer 20-25 degrees C warmer than its design temperature will maybe halve the energy consumption (because you more than halve the inside/outside temperature differential).

 

I've read of two approaches to raising the running temperature. Some people say that all freezers have a coarse temperature adjuster at the working end if you look close enough, and with a bit of trial and error it's easy to set it to the temperature you want. Other people leave the controls alone but switch the power on and off via get a cheap (less than 20 quid?) digital temperature controller (with remote sensor) off ebay.

 

This approach seems to be quite a hot(ahem) topic in the homebrew community. They are making "kegerators"!

 

As soon as I've bought a chest freezer, I'll report on progress...

[i love my narrowboat]

We are remodelling our kitchen and have bought a shoreline 12v fridge/ freezer, we were very lucky to bid and win it on eBay,it was bought for use in a beach hut but never used, it cost us £300. We were going to get another 240 one but just happened to be in the right place at the right time.

[Neil2]

On our boat, we are going to try to get fridge Ah use down drastically - with a radical approach I've seen discussed on the tinterweb (but not, I think, here).

 

The idea is, in warmer months only, to run a small chest freezer at fridge temperatures, just to keep the essentials (meat and milk) fresh in warm weather.

 

This is apparently low on leccy for two reasons. First because warm air doesn't whoosh in to replace all the expensive cold air everytime you open the door. Second, because a freezer has much more effective insulation than a fridge. Running a freezer 20-25 degrees C warmer than its design temperature will maybe halve the energy consumption (because you more than halve the inside/outside temperature differential).

 

I've read of two approaches to raising the running temperature. Some people say that all freezers have a coarse temperature adjuster at the working end if you look close enough, and with a bit of trial and error it's easy to set it to the temperature you want. Other people leave the controls alone but switch the power on and off via get a cheap (less than 20 quid?) digital temperature controller (with remote sensor) off ebay.

 

This approach seems to be quite a hot(ahem) topic in the homebrew community. They are making "kegerators"!

 

As soon as I've bought a chest freezer, I'll report on progress...

I've heard of this approach, and it seems to make sense The key to it I think is having a decent quality temperature controller. Where to put a chest freezer in an existing NB could be an issue.

[WhiteSuit]

Sorry if I am hijacking this thread but here goes anyway. I run a 240v fridge through an inverter 24/7 but also have the option of using a travel power whilst cruising.

Question is, is it more efficient to use travelpower when underway to run the fridge and the inverter when moored?

To my simple brain I should get more charge into my batteries if using the travel power.

 

I also want to put some holes in the floor behind the fridge so increasing the heat exchange efficiency so the fridge has to run less.

[Ex- Member]

Powering your fridge through inverter drains battery. So if travel power is running you could swap to it. However your travel power might also charge your batteries via a mains charger, so it that case it wouldn't make much difference.

 

We have 2 x 100mm floor fans directly below the back of the fridge, they are set over 2 holes. We also have the same in the bedroom area under the bed for cooling in the summer.

 

 

We found that switching the fridge off at night can save some energy as the inverter can go off too. We've had 4 bleak days and our solar was struggling. We set the fridge on coldest through the day, then switch off evenings, inverter too. Simply switch back on in morning, set to coldest and let the solar do the rest. The fridge probably wouldn't use much power anyway under that regime, but then the inverter is off as well. We find doing this seems to save a fair bit of energy.

 

Also it rests the batteries and by morning they're generally reading back to half full or 12.2v sometimes a bit lower sometimes a bit higher.

Edited April 6, 2014 by Julynian

[Kwacker]

Sorry if I am hijacking this thread but here goes anyway. I run a 240v fridge through an inverter 24/7 but also have the option of using a travel power whilst cruising.

Question is, is it more efficient to use travelpower when underway to run the fridge and the inverter when moored?

To my simple brain I should get more charge into my batteries if using the travel power.

 

I also want to put some holes in the floor behind the fridge so increasing the heat exchange efficiency so the fridge has to run less.

Don't forget, if you are pulling a volume of cold air from the bilge to cool the fridge condenser, you will need a large enough outlet vent above the back of the fridge to let that (now heated) air out.

[Phil Ambrose]

Seriously as an ex chef (now retired) it is not a good idea to have food constantly cooling then warming. The amount of power saved at night will be minimal plus you use extra power to bring the warm fridge back down to temperature again. I rather think some people get rather hung up on the power thing and let it take control of their lives. You have a PV array and an engine, just use them as you need to so you can lead a normal life. 14 years living aboard experience.

Phil

[Ex- Member]

Seriously as an ex chef (now retired) it is not a good idea to have food constantly cooling then warming. The amount of power saved at night will be minimal plus you use extra power to bring the warm fridge back down to temperature again. I rather think some people get rather hung up on the power thing and let it take control of their lives. You have a PV array and an engine, just use them as you need to so you can lead a normal life. 14 years living aboard experience.

Phil

 

You don't open the fridge at night, so it pretty well holds it's temperature, especially as I suggested to run on coldest prior to doing so. Our fridge is still plenty cold enough in the morning. Many people survive without a fridge at all and just use cool places for perishables, a fridge is not a necessity. It's simply something you can do on occasions when energy gets low and it's too late to run an engine. Great for occasionally resting the batteries too.

 

Oh and you don't necessarily use extra power to re cool the fridge, solar will replenish, and you've also saved inverter losses as well.

 

I don't consider turning of an electrical appliance abnormal living

Edited April 6, 2014 by Julynian

[Phil Ambrose]

I stand by what I said, it is never a good idea to allow food to warm then cool etc etc, still its your life.

Phil

[Robbo]

 

You don't open the fridge at night, so it pretty well holds it's temperature, especially as I suggested to run on coldest prior to doing so. Our fridge is still plenty cold enough in the morning. Many people survive without a fridge at all and just use cool places for perishables, a fridge is not a necessity. It's simply something you can do on occasions when energy gets low and it's too late to run an engine. Great for occasionally resting the batteries too.

 

Oh and you don't necessarily use extra power to re cool the fridge, solar will replenish, and you've also saved inverter losses as well.

 

I don't consider turning of an electrical appliance abnormal living

 

If the fridge pretty well holds it's temperature at night then whats the point in turning it off as it won't use much power keeping it cool. Anyhow, the main losing point of a fridge losing it's cool (bar opening the door) is insulation, the more you can add the more efficient the fridge will be.

[Ex- Member]

 

If the fridge pretty well holds it's temperature at night then whats the point in turning it off as it won't use much power keeping it cool. Anyhow, the main losing point of a fridge losing it's cool (bar opening the door) is insulation, the more you can add the more efficient the fridge will be.

 

Inverter off too, resting batteries.

Edited April 7, 2014 by Julynian

[Robbo]

 

Inverter off too, resting batteries.

 

I was only thinking 12v !

[Kwacker]

I've heard of this approach, and it seems to make sense The key to it I think is having a decent quality temperature controller. Where to put a chest freezer in an existing NB could be an issue.

It's going to get awfully wet inside a chest freezer run at fridge temperatures. Frost will form on the sides whilst the unit cools, then thaw when it stops (the majority of the time). This will then just run into the bottom, which doesn't matter if all it contains is a beer barrel, but if food is involved, I'm not so sure.

It might work better on a Frost Free undercounter freezer though, as this is designed to deal with the condensate.

[Phil Ambrose]

I'm ducking out of this, its all a bit silly, the amount of power used by a fridge overnight cannot be more than 6 or 7 a/h surely your batt bank can cope with that. Living on a boat doesn't mean you have to go camping.

Phil

[Paul C]

Powering your fridge through inverter drains battery. So if travel power is running you could swap to it. However your travel power might also charge your batteries via a mains charger, so it that case it wouldn't make much difference.

 

We have 2 x 100mm floor fans directly below the back of the fridge, they are set over 2 holes. We also have the same in the bedroom area under the bed for cooling in the summer.

 

 

We found that switching the fridge off at night can save some energy as the inverter can go off too. We've had 4 bleak days and our solar was struggling. We set the fridge on coldest through the day, then switch off evenings, inverter too. Simply switch back on in morning, set to coldest and let the solar do the rest. The fridge probably wouldn't use much power anyway under that regime, but then the inverter is off as well. We find doing this seems to save a fair bit of energy.

 

Also it rests the batteries and by morning they're generally reading back to half full or 12.2v sometimes a bit lower sometimes a bit higher.

 

 

 

Inverter off too, resting batteries.

 

I think you need to decide if the power drawn by a fridge and inverter is too much for overnight use, thereby needing it to be turned off (and of course, the temperature will go up a little, requiring a longer run in the morning and not saving as much power as you thought); or whether you can cope with the power drawn through the night (with no solar power at night, of course). We have a 12V fridge and leave it on overnight. We have solar power too. Yes, there is a power draw through the night but that's what the batteries are for, and they do the job with no issues.

[Ex- Member]

 

 

 

I think you need to decide if the power drawn by a fridge and inverter is too much for overnight use, thereby needing it to be turned off (and of course, the temperature will go up a little, requiring a longer run in the morning and not saving as much power as you thought); or whether you can cope with the power drawn through the night (with no solar power at night, of course). We have a 12V fridge and leave it on overnight. We have solar power too. Yes, there is a power draw through the night but that's what the batteries are for, and they do the job with no issues.

 

It's a way of conserving energy if batteries are low in bleak weather when using solar, read post 55

[Paul C]

Read post #55 - I quoted post #55, so obviously I've read and understood it! I've also read your other posts, for example in post #11 you say that the inverter runs 24/7 for 18 months, now you reveal that you do in fact switch it off overnight if you don't get enough solar. I think it would be helpful for everyone if you review your own posts and explain the inconsistencies in what you say, just for 100% clarity.

[Ex- Member]

Read post #55 - I quoted post #55, so obviously I've read and understood it! I've also read your other posts, for example in post #11 you say that the inverter runs 24/7 for 18 months, now you reveal that you do in fact switch it off overnight if you don't get enough solar. I think it would be helpful for everyone if you review your own posts and explain the inconsistencies in what you say, just for 100% clarity.

 

Yes in the last week LOL

Edited April 7, 2014 by Julynian

[Staarek]

Some old thread but I suppose the debate is always on…

I run some test last couple of weeks, I bought “13A Plug In Energy Saving Monitor” from Maplin to see exactly how much energy my 240V Fridge uses. This little device shows power draw, amount of electricity used for given period & maximum current draw. The fridge is Bosch KUL15A60GB Energy rating: A++ (140 kWh per year).

After 10 days the monitor showed 1.3kWh (≈11Ah/day). We also have to take into account the inverter standby draw etc. but at this stage we have our inverter on 24/7 anyway as our solar setup produces more power than we use.

I was planning to switch the fridge off for the winter (Nov-Feb) as the Solar Harvest is considerably lower and I don’t think I can afford using ≈30Ah/day just to have the inverter on. As I mentioned the little monitor also shows maximum current draw by the appliance (which was just under 900 watts on the fridge start-up) which helped in seizing dedicated (smaller) inverter just for powering the fridge. I bought 600W TBS pure sine wave unit, (Psurge 1000W). This unit has around 5W (0.4A) no load consumption and Automatic Standby Function which reduces no load draw to 0.4W (0.03A) I tested the inverter on both settings with and without ABS on (I wasn’t sure if Automatic Standby would work with the fridge) but it works perfectly. I will keep you updated as I want to test the setup for a longer period but it seems it won’t be switching the fridge off for the winter

[Top cat]

 

We have 2 x 100mm floor fans directly below the back of the fridge, they are set over 2 holes. We also have the same in the bedroom area under the bed for cooling in the summer.

 

 

 

 

Thats an interesting way of installing the fans, am I right in thinking you are suspending them in midcair from bungy chords? I presume it cuts down on noise.Could you please share details on how you did it.

 

Thanks

 

 

TC

[Ex- Member]

Some old thread but I suppose the debate is always on…

I run some test last couple of weeks, I bought “13A Plug In Energy Saving Monitor” from Maplin to see exactly how much energy my 240V Fridge uses. This little device shows power draw, amount of electricity used for given period & maximum current draw. The fridge is Bosch KUL15A60GB Energy rating: A++ (140 kWh per year).

After 10 days the monitor showed 1.3kWh (≈11Ah/day). We also have to take into account the inverter standby draw etc. but at this stage we have our inverter on 24/7 anyway as our solar setup produces more power than we use.

I was planning to switch the fridge off for the winter (Nov-Feb) as the Solar Harvest is considerably lower and I don’t think I can afford using ≈30Ah/day just to have the inverter on. As I mentioned the little monitor also shows maximum current draw by the appliance (which was just under 900 watts on the fridge start-up) which helped in seizing dedicated (smaller) inverter just for powering the fridge. I bought 600W TBS pure sine wave unit, (Psurge 1000W). This unit has around 5W (0.4A) no load consumption and Automatic Standby Function which reduces no load draw to 0.4W (0.03A) I tested the inverter on both settings with and without ABS on (I wasn’t sure if Automatic Standby would work with the fridge) but it works perfectly. I will keep you updated as I want to test the setup for a longer period but it seems it won’t be switching the fridge off for the winter

 

Hi Staarek

 

Our Bosch fridge is now 7 years old I think, when purchased it was described as A+ 117KWH per year, in fact they're still on sale today. It's interesting that yours is 140KWH but A++ I wonder weather the rating system has been changed, or possibly because your fridge has a freezer compartment it's so rated as a different product.

 

http://www.rgbdirect.co.uk/Products/Appliances/Fridges/BOSCH/KTR18P20GB

 

We would easily manage with our solar through winter with fridge off, but the coming winter, I'm going to try and additional 200w of flexi solar over the winter to see if it can cope better. We used to run the engine for 1.5 hours a day in the morning for bulk charging on most days and some generator running early evenings for an hour or so. I'm trying to reduce the generator running early evenings as engine running also provides hot water.

 

Switching the fridge off though Is a good option IMO if the inverter can go off too, but last winter was so mild that it would have been difficult to keep food cool even in our back cabin so we left it all running. We really should cut down on lap top use as well LOL

 

Keep updating though interesting stuff.

[Paul C]

Some old thread but I suppose the debate is always on…

I run some test last couple of weeks, I bought “13A Plug In Energy Saving Monitor” from Maplin to see exactly how much energy my 240V Fridge uses. This little device shows power draw, amount of electricity used for given period & maximum current draw. The fridge is Bosch KUL15A60GB Energy rating: A++ (140 kWh per year).

After 10 days the monitor showed 1.3kWh (≈11Ah/day). We also have to take into account the inverter standby draw etc. but at this stage we have our inverter on 24/7 anyway as our solar setup produces more power than we use.

I was planning to switch the fridge off for the winter (Nov-Feb) as the Solar Harvest is considerably lower and I don’t think I can afford using ≈30Ah/day just to have the inverter on. As I mentioned the little monitor also shows maximum current draw by the appliance (which was just under 900 watts on the fridge start-up) which helped in seizing dedicated (smaller) inverter just for powering the fridge. I bought 600W TBS pure sine wave unit, (Psurge 1000W). This unit has around 5W (0.4A) no load consumption and Automatic Standby Function which reduces no load draw to 0.4W (0.03A) I tested the inverter on both settings with and without ABS on (I wasn’t sure if Automatic Standby would work with the fridge) but it works perfectly. I will keep you updated as I want to test the setup for a longer period but it seems it won’t be switching the fridge off for the winter

 

1) You need to factor in inverter standby/inverter inefficiency/inverter draw etc too, this makes a big difference.

2) In the winter, the fridge may be working even harder than spring/autumn, because the interior of the boat is being heated.

[b0atman]

Surely fans are also sucking in air from area around base losing efficiency ?

Have you a inlet vent elsewhere for air flow through underfloor space ?

[Staarek]

 

Hi Staarek

 

Our Bosch fridge is now 7 years old I think, when purchased it was described as A+ 117KWH per year, in fact they're still on sale today. It's interesting that yours is 140KWH but A++ I wonder weather the rating system has been changed, or possibly because your fridge has a freezer compartment it's so rated as a different product.

 

http://www.rgbdirect.co.uk/Products/Appliances/Fridges/BOSCH/KTR18P20GB

 

We would easily manage with our solar through winter with fridge off, but the coming winter, I'm going to try and additional 200w of flexi solar over the winter to see if it can cope better. We used to run the engine for 1.5 hours a day in the morning for bulk charging on most days and some generator running early evenings for an hour or so. I'm trying to reduce the generator running early evenings as engine running also provides hot water.

 

Switching the fridge off though Is a good option IMO if the inverter can go off too, but last winter was so mild that it would have been difficult to keep food cool even in our back cabin so we left it all running. We really should cut down on lap top use as well LOL

 

Keep updating though interesting stuff.

 

Hi Julynian,

 

I'm thinking about additional panels for the winter too, we'll see how much cheaper will tey get next couple of months... And yes the unit is Fridge/freezer that's probably why it uses little bit more.

 

http://www.bosch-home.co.uk/our-products/fridges-and-freezers/fridges/KUL15A60GB.html

 

 

1) You need to factor in inverter standby/inverter inefficiency/inverter draw etc too, this makes a big difference.

2) In the winter, the fridge may be working even harder than spring/autumn, because the interior of the boat is being heated.

 

Thanks Paul. I think the inverter is 92% efficient so I hope the losses won't be massive. Good point about the interior temperature in the winter.

[Ex- Member]

Thats an interesting way of installing the fans, am I right in thinking you are suspending them in midcair from bungy chords? I presume it cuts down on noise.Could you please share details on how you did it.

 

Thanks

 

 

TC

 

Hi TC I seem to have missed this.

 

Anyway the cords are actually elastic hair bands, they're just the right size for the job. The bands loop through the corners of the fan shrouds, the fans are 100mm

 

The bands then reach out to 4 button head M4 S/S machine screws per fan about 40mm long threaded into the floor via a 3.5mm hole, a single locking nut is applied before screwing into the floor, the nut is screwed up close to the button head leaving enough gap for the hair band to fit snugly into. This avoids the band slipping and allows for any up and down refinement in adjustment should the fan not be level and not hitting the floor.

 

The result is a fan as silent as it is when running being held between finger & thumb. The 2 in the photo are under the main double bed and inaudible.

Surely fans are also sucking in air from area around base losing efficiency ?

Have you a inlet vent elsewhere for air flow through underfloor space ?

 

Are you referring to my fans?

 

If so, I'm not sure what you mean by losing efficiency with regard to what?

All our bilges are ventilated as all bilges should be, the main source of ventilation is via the 2 vents either side of the cratch doors. There are other areas air can enter as well.

Edited May 12, 2014 by Julynian