Cooling Fridge with air from bilge.

[Guest]

I know this has been discussed before, but can't find quite what I am looking for with search.

 

It has come to my attention during the recent heat wave that the back of our fridge gets very hot. The fridge is enclosed in the usual two sided enclosure with a back and worktop. My plan is to route an aperture in the wooden floor, remove some ballast, and fit a grill over the aperture with a small fan in and blow some cool air up behind the fridge. I am also considering a small fan at the top to help remove hot air. Any suggestions/better ideas etc?

Many thanks.

[Wrinkley]

It should work, mine didn;t. I fitted a cheep computer fan to a hole cut in the floor. It ran fine but I disconnected the fan last winter when we were on a mains hook up because of the noise. Did not reconnect when we left and I have not noticed any difference on the fridge performance or the battery use. We can still sit for the same three day with out charging the bank. But no noise!

[Keeping Up]

Adding a computer fan, drawing air from the bilge and blowing it over the back of the fridge, definitely made a difference when the fridge was working hard. The Shoreline fridge has a couple of fan connections to ensure that it only runs when the compressor is running, and I also fitted an old central-heating room-thermostat to the wall behind the fridge, set to operate at 25 degrees so the fan doesn't come on unless it's needed. I also fitted a switch so I could turn it off at night if I wanted to.

 

It was noisy when I bolted it straight to the floor. Inserting some rubber strips between the fan and the floor got rid of 90% of the noise.

[ditchcrawler]

It should work, mine didn;t. I fitted a cheep computer fan to a hole cut in the floor. It ran fine but I disconnected the fan last winter when we were on a mains hook up because of the noise. Did not reconnect when we left and I have not noticed any difference on the fridge performance or the battery use. We can still sit for the same three day with out charging the bank. But no noise!

Maybe you fridge was installed with the correct amount of ventilation around it, lots aren't

[Phil Ambrose]

Wrinkly seems to have answered a nagging doubt that I've had about cooling fridges, afterall when I lived ashore our fridge and our freezer were built in and worked fine with no extra cooling fans and I can see no difference to the setup in our house and our boat.

 

Phil

[onionbargee]

It's the black grille on the back, the condenser, that is supposed to radiate heat, getting a good air stream blowing over it is good for effecientcy, If this condenser is water cooled you can get a much bigger saving in power drain.

 

You see a lot of fridges where the back is boxed in with no ventilation.

[Ex- Member]

Our fans cool the rear of the fridge too, we already have an A+ efficient fridge, but we also benefit from cool from the bilge anyway especially when cooking as some of the cool air goes to the back of the fridge and some is split off to blow into the galley from under the kitchen units.

 

We also have comp fans fitted under the bed that cool the bedroom area in the summer.

 

It's best to mount fans on elastic type rubber bands they are almost silent when running then.

 

 

In this instance I used hair bands which are a good size and really strong. Their set on Allen bolts and the fans hover above about a 1/4 inch over the holes drilled the same size as the fan. You can just hear them if you make an effort to, if that makes sense.

 

Fans are 0.35 amp

 

I even rigged up a small fan for use around the boat.

 

 

It's very light and portable so you can have it close to you, I'm using it now, plenty of air flow if only a few feet away.

 

 

It's what happens when you buy a job lot of 10 computer fans from e-bay for a fiver inc postage LOL

[smileypete]

I know this has been discussed before, but can't find quite what I am looking for with search.

 

It has come to my attention during the recent heat wave that the back of our fridge gets very hot. The fridge is enclosed in the usual two sided enclosure with a back and worktop. My plan is to route an aperture in the wooden floor, remove some ballast, and fit a grill over the aperture with a small fan in and blow some cool air up behind the fridge. I am also considering a small fan at the top to help remove hot air. Any suggestions/better ideas etc?

Many thanks.

 

With my verry ineffcient mains fridge I found a few 120mm fans directly on the black condenser grille thingy helped:

 

 

They only run when the compressor runs, and run at 9V instead of 12V, so not too loud and even help disguise the compressor hum.

 

Plus there's one blowing up from the bilge:

 

 

As others say if the fridge is an efficient model with plenty of natural ventilation and a condenser that hardly gets warm, adding fan cooling probably won't make a lot of difference.

 

On the 12V Danfoss based fridges there's a dedicated fan output on the ECU, for mains fridges one of those desktop PC intelliplugs might do for switching a low voltage power mains supply for the fans whenever the fridge is running:

 

http://www.amazon.co.uk/gp/product/B000MPJSL0/ref=olp_product_details?ie=UTF8&me=&seller=

http://www.amazon.co.uk/gp/offer-listing/B000MPJSL0/ref=dp_olp_all_mbc?ie=UTF8&condition=all

http://www.eevblog.com/forum/reviews/intelliplug-desktop-teardown/

 

cheers, Pete.

~smpt~

Edited August 25, 2013 by smileypete

[MtB]

 

It has come to my attention during the recent heat wave that the back of our fridge gets very hot.

 

I'm not sure why this matters, it's how they are designed to work.

 

Does your fridge still work in the hot weather?

 

 

MtB

[Ex- Member]

It's not just the effect fans can have on the condensing mechanics of a fridge. Heat build up at the back, sides and top of a fridge is trying to warm the unit up whilst the insulation is trying to keep the cold inside. If your fridge is in a cooler environment it will use less energy to remain cool. The other benefit not to the fridge though is maintaining good air flow through the bilges. Bilge temperature will remain pretty constant as canal water does.

 

Just to add When I posted about 45 minutes ago I switched the galley fridge fans on, temp was reading 23.4c now 20.9c Temp gauge is 5 f/t away from the fans in the galley. It can take a couple of hours to cool such a large area though and only works if all doors & hatches are closed, much like air con.

[by'eck]

I had a Frigoboat fridge that had the condenser cooling fan venting into the side of the adjacent back cabin wardrobe. It got so hot you probably cook an egg in there at times despite the wardrobe door being vented. Nevertheless the fridge ran faultlessly for 16 years, 7 of which in the Caribbean.

[Guest]

 

I'm not sure why this matters, it's how they are designed to work.

 

Does your fridge still work in the hot weather?

 

 

MtB

Yes, and yes, but I am looking at increased efficiency to save battery power.

[bizzard]

If all those floor fans aren't rotating in the correct direction the fridge'll be heating and drying out the bilges nicely instead.

[Biggles]

I did it a few weeks ago.

 

Blog Linky

 

Very pleased with the result.

Edited August 26, 2013 by Biggles

[onionbargee]

If i had time i would fettle with a Danfoss unit and heatsink the condenser right onto the bottomplate, see how good that works. Unless you want to put a keel cooler in under the water line, but drilling holes in boats is not a great idea to my way of thinking.

 

The best fridges now are using vacuum panel insulation by the way.

[George94]

If all those floor fans aren't rotating in the correct direction the fridge'll be heating and drying out the bilges nicely instead.

 

Sounds like a very good idea.

[MtB]

Yes, and yes, but I am looking at increased efficiency to save battery power.

 

The reduction in power consumption is going to be marginal at best.

 

If you are running out of battery power an extra battery or improving your charging system slightly will be far more effective than fecking about with adding fans.

 

Just my opinion

 

 

MtB

[rjasmith]

 

The reduction in power consumption is going to be marginal at best.

 

If you are running out of battery power an extra battery or improving your charging system slightly will be far more effective than fecking about with adding fans.

 

Just my opinion

 

 

MtB

 

Mike,

 

Don't know whether you've ever had a look at the book "Energy Unlimited" by Reinout Vader (MD of Victron - not a relative of the more famous Darth from Star Wars as far as I know)?

 

The book is available online here and if you go to page 35 (section 6.3) he gives a detailed analysis of the real problem of running a fridge on a boat from batteries.

 

Obviously the book is intended as a sales pitch for Victron products but they don't make fridges so perhaps we can go along with his ideas a bit on this particular subject.

 

His book is more aimed at sea going yachts which probably have even more difficulties with electrical power than canal boats.

 

He does conclude that it's a good idea to do things to improve the efficiency of a fridge (or indeed any heat pump system in use on a boat) and he mentions cooling the condenser or improving the insulation around the cold box or even both.

 

I certainly plan to fix up some sort of condenser cooling arrangement and have left a small area of the hull side free of insulation in the position where the fridge is going so I can get some sort of contact panel against it to transfer heat away from the fridge.

 

I haven't bought a fridge yet so the detailed design of all this is yet to be done!

 

Richard

[BEngo]

Do be careful that your contact panel area is all well underwater. The black bits of a narrowboat don't half get hot when they are in the sun and will hinder the condenser rather then help in that case.

 

N

[rjasmith]

Do be careful that your contact panel area is all well underwater. The black bits of a narrowboat don't half get hot when they are in the sun and will hinder the condenser rather then help in that case.

 

N

 

Yes certainly a good point and I've chosen an area low down from just above the baseplate to a foot up and about 2 foot wide.

 

All of it should be well below the waterline.

 

Richard

[Guest]

Thanks for input, which has given me some ideas.

A fridge is just like an air-con unit on a building, one part takes hot air out of the building (or the fridge) and the other bit loses that heat outside of the building (or inside the boat.) On air con units they put a big fan on the outer unit to help cool it, and I can't see why this wouldn't have a similar effect on a fridge in an enclosed unit. Of course the fan will consume some of the energy that is being saved.

 

Another analogy would be a car radiator, which normally has a fan to cool it.

I did it a few weeks ago.

 

Blog Linky

 

Very pleased with the result.

Aound 30 deg C drop is mighty impressive. That must surely save some energy

[Captain Zim]

I don't know if this is the right way to put a link in...

 

http://www.wbryant.com/StellaBoat/Projects/galley/fridge/

 

Anyway, it shows home made vacuum panels as mentioned above

[MtB]

Thanks for input, which has given me some ideas.

A fridge is just like an air-con unit on a building, one part takes hot air out of the building (or the fridge) and the other bit loses that heat outside of the building (or inside the boat.) On air con units they put a big fan on the outer unit to help cool it, and I can't see why this wouldn't have a similar effect on a fridge in an enclosed unit. Of course the fan will consume some of the energy that is being saved.

 

Another analogy would be a car radiator, which normally has a fan to cool it.

Aound 30 deg C drop is mighty impressive. That must surely save some energy

 

I'm sure it does. More than the fan uses?

 

How would you know until after you've paid the money, done the work and installed it, and run endless tests?

 

I have better things to do with my time. OTOH if you like playing with these things then that's fine, just don't kid yourself it is gonna save you £500 a year in reduced diesel costs

 

MtB

[ditchcrawler]

 

The reduction in power consumption is going to be marginal at best.

 

If you are running out of battery power an extra battery or improving your charging system slightly will be far more effective than fecking about with adding fans.

 

Just my opinion

 

 

MtB

I think a lot depends on whether you fridge as sufficient ventilation in the first place. I have seen several that don't. When I improved the insulation on my fridge it was to the detriment of rear ventilation, so I fitted fans to compensate for this.

[Guest]

 

I'm sure it does. More than the fan uses?

 

How would you know until after you've paid the money, done the work and installed it, and run endless tests?

 

I have better things to do with my time. OTOH if you like playing with these things then that's fine, just don't kid yourself it is gonna save you £500 a year in reduced diesel costs

 

MtB

Thing is Mike a couple of computer fans cost buttons, and it won't take ages to cut a hole in the floor. As for kidding myself, I won't. I was just interested in other people's findings who had done such modifications. Thanks for your thoughts, which I have taken on board.