Refrigerator Water Cooled to Fresh Water Tank

[capn_billl]

One concernt I would have. Using a 55 gal tank as a heat sink for a 650BTU chiller is no problem. Drinking the water after it has circulated through a non-potable water heat exchanger is not something I would do. Nickel is toxic, so is the lead used in soldering heat exchanger coils. After circulating sea water through these coils they will be full of garbage. Water sitting in these coils when the unit is turned off will grow bacteria and algea that will be injected into your drinking water the next time you turn it on. Finding a place to dump heat in a tropical area is a problem, the easiest solution is to use the ocean. Using a heat exchanger built for potable water is the best solution. Putting the return on the top of the tank through a spray nozzle will aerate the water and dump additional heat if the tank is not full.

[goboatingnow]

unless frioboat approve the unit for potable water cooling I wouldnt use it. Your onboard water is too precious to go fouling it in any way.

Dave

[JimJohnston]

Kitym,
the unit is a frogomatic W50 model, and scanning the literature I see that it is a Danfoss compressor, but I can't find particulars. The water pump is a shur-flo. After I posted my last message I turned off all the lights and found that the freezer/pump combination were drawing just under 4 amps. I'm pleased with this performance.

[kiltym]

Originally Posted by JimJohnston

Kitym,
the unit is a frogomatic W50 model, and scanning the literature I see that it is a Danfoss compressor, but I can't find particulars. The water pump is a shur-flo. After I posted my last message I turned off all the lights and found that the freezer/pump combination were drawing just under 4 amps. I'm pleased with this performance.

Wow, that seems pretty low. I also have the W50, and the Flojet pump.

The W50 is rated at:
2000 rpm: 4A
2500 rpm: 4.7A
3000 rpm: 5.7A
3500 rpm: 6.8A

So, even if you had your fridge dialed all the way down to 2000 rpm (there is an adjustment at the compressor you can take a look at, at the bottom of the control board, and Frigoboat recommends dialing up as high as reasonable for water cooled systems, not down), you would be drawing more than 4A. The pump, assuming there is not a lot of lift involved, is probably running at .5-.75A, so at a minimum, I would expect to see 4.5A, yet you are seeing < 4A.

I would be pleased with that performance also . But I have to say something doesn't add up quite right. Are you sure nothing is adding to the battery bank (solar/wind for example) when you took the reading?

[GordMay]

Originally Posted by capn_billl

... Drinking the water after it has circulated through a non-potable water heat exchanger is not something I would do. Nickel is toxic, so is the lead used in soldering heat exchanger coils..

Originally Posted by goboatingnow

unless frioboat approve the unit for potable water cooling I wouldnt use it. Your onboard water is too precious to go fouling it in any way.
Dave

INDEED!

[JimJohnston]

Kitym

I too wondered about the possibility of other sources beforehand so waited until dark on a windless night. I turned off almost all instruments except for gps anchor alarm and all lights ( except for masthead led). There might have been a cabin light on, again led. I got the 4.0 A reading while the freezer was running as indicated by the thermostat - I suppose it is possible that the unit was not actually engaged, but I did note that it had been 'calling' for power for some time but I did not actually put my hand on the compressor to ensure that it really was running. Since nothing else was 'on' at the time, I presumed the power draw to be the freezer. Maybe a bright moon tricked the solar panels.

[kiltym]

Originally Posted by JimJohnston

Kitym

I too wondered about the possibility of other sources beforehand so waited until dark on a windless night. I turned off almost all instruments except for gps anchor alarm and all lights ( except for masthead led). There might have been a cabin light on, again led. I got the 4.0 A reading while the freezer was running as indicated by the thermostat - I suppose it is possible that the unit was not actually engaged, but I did note that it had been 'calling' for power for some time but I did not actually put my hand on the compressor to ensure that it really was running. Since nothing else was 'on' at the time, I presumed the power draw to be the freezer. Maybe a bright moon tricked the solar panels.

Easiest thing to do is throw a portable volt meter/amp meter inline with the fridge + lead and see what that says. Obviously you dont need to do this for me , but I would be curious if I were you as to what was going on, because something seems a bit strange to me. Or, just ignore it and be happy your water cooled fridge is drawing < 4A .

[mikereed100]

Kiltym,

Frigoboat offers a keel cooler without the sintered bronze case for $150 less than the bronze model. I believe this is simply a copper loop held by plastic supports. You might check with the distributer, but I don't think there are any solder joints that would come in contact with your water supply.

Mike

[OzePete]

The Ozefridge C450 system has a very unique air / water cooled condenser. The condenser is a large cross finned type with tree passes. Two are used for condensing the refrigerant gas and the third is for water to pass through, cooling the condenser fins which in turn cools the refrigerant. This means that there is no direct contact of the water with the refrigerant galleries and therefore no possibility of gas leaking into the water and then as a consequence, water leaking into and destroying the refrigeration system. Another benefit is that it operates as an air cooled, water assisted condenser and can operate as an air/ water cooled or air cooled alone if the water was unavailable or failed. A small 3 watt pump circulates the water either raw or from the boat's tank. At ambient temperatures above 26C the small 1/4 amp consumption of the water pump is more than compensated for by lower compressor consumption rate and shorter run times. This is most noticeable at higher ambients.

[first.contact]

I have an OzeFridge installed in my yacht and live in the tropics. When I installed it, I plumbed it into my fresh water tanks. It's been running 24/7 on auto for just under a year now with no issues. In fact it's great. The only hint it's running is the occassional "gurgle" that comes from the breather pipe for the fresh water tank that's behind the saloon furniture. Otherwise, for us, it's been set and forget refrigeration. We have jsut intalled a rutnad 914i wind generator to supplement our solar generation whilst offshore. Cameron.

[sailorchic34]

Just a note that copper /nickle heat exchangers are used in larger domestic water heaters all the time. Nickle linings have also been used for hot water storage tanks... It's not a problem. Most solders used now a days will not contain lead. I would expect the solder to be silver bearing for refrigeration units due to higher pressures. Lead solders generally are not rated to 150+ psig required in refrigerant systems

The only danger I see is if there is a leak in the coil then you'll get refrigerant and refrigerant oil in the water tank, which would be a problem. Of course you have a similar problem with most hot water coils in the typical marine water heaters. Its just a single coil and does not meet building codes, though boats are not buildings. On the plus side the domestic water pressure is higher then engine cooling pressure, so a leak would go into the engine water.

From a strictly will it work with a fresh water tank, then yes it will. Is it safe. Mostly until there is a refrigerant leak into the water

[hellosailor]

Sounds like a good idea, but yet one more reason to have at least two water tanks onboard. And of course if you USE the water in that cooling tank...the reefer's going to overheat then, isn't it? Making the water in that tank not something you'd really want to use in the first place?

Catch-22?

The "newish" keel plate coolers seem like a better idea every time I think about them.

[senormechanico]

Originally Posted by GordMay

INDEED!

Oh, come on! It's a hunk of Bronze.

[CeesH]

A DIY Water Cooled Condenser made for a RV, the water cooled condenser is putted in serie with the standard air-cooled condenser.

Taken from http://www.zipworld.com.au/~frankp/condenser.pdf


DIY Water-Cooled Condenser for Danfoss BD35 Fridge Compressor

Apologies in advance for not taking step-by-step photos of my project. Should have done that but it was done over a year ago in hectic preparation for a 3 month trek.
I wanted to significantly improve the performance of the fridge in hot weather. It's all about efficiently removing heat from the refrigerant, and having read about a water cooled fridge condenser I thought I'd have a go at it as a DIY. I am told by the experts that water can remove about 100 times more heat from refrigerant than air at the same temperature. With that in mind I made a water cooled condenser that I had fitted in series in the refrigerant circuit – that is, the refrigerant come out of the compressor, through the water-cooled condenser, and then through the normal air-cooled condenser.
The water cooling increases the efficiency hugely. On the last trip prior to the project we were in the Kimberley with temps around 330-360, the duty cycle was 60%, fridge cabinet temps were too high, up around 100, even with the camper’s side wall (where the fridge is located) shaded.
After the project was completed the next trip was in hot northern Qld. Temps were up to 400, 40 warmer than on the previous trip. The compressor had a duty cycle of about 40%. As long as I kept the wall of the camper where the fridge is located shaded (I have a tarp for that) the fridge temp stayed pretty well in the blue zone - 00 - 40, maybe a tad above on occasions Additionally I was able to wind down the compressor speed which reduces the current draw when it is running. It was set to 3000rpm I think, drawing 4.5 amps from memory. Now, again from memory, it is about 2000 rpm, drawing 3.5 amps. That saving is partially offset by the water circulation pump which draws about 0.5 amp, but cuts in only when the compressor runs. It is switch selectable, so in cool weather you switch it out and save that 0.5 amp. The water is circulated from the large water tank.
We also use storage containers in the fridge to hold all the stuff. Two per shelf, these fit neatly side-by-side, are the full length of the shelves and the full height between the shelves and act as "buckets of cold" to hold much of the cold in when you open the door. You can also put more stuff in the fridge, which helps to increase efficiency, believe it or not. More thermal mass, I guess. Also, we don't use the tray under the ice-box, which I believe is there to control the "flow of cold" to stop stuff (vegies?) at the bottom of the cabinet freezing. Instead we use a slightly warmer setting on the thermostat (more power saving) and use a battery powered anti-stratification fan to keep the cabinet air
moving. Two D cells last at least a month. Total saving on amp-hours per day for the fridge in hot weather is around 50%. The person who did the refigerant work for me is the same guy who makes the eutectic Autofridges, but any competent refrigeration mechanic should be able to do the work. I got my technical info from Home I was advised that all you need for a Danfoss BD35 compressor is 1 metre of water jacket and 1 litre per minute of water flow. Ozefridge will also supply the small pump and food grade plastic tubing for about $50.00. Pipe and stuff comes from any plumbing supplier. Adaptors (nipples) for the half inch pipe to accommodate the plastic water line came from Pirtek.
Below is a photo of my prototype condenser. I decided to make a second one with the small pipe exiting the big one about 100mm further on so that both ends of the small pipe exit in the straight parts of the condenser. From memory, that makes the entry and exit holes for the small pipe about 1100mm apart. Give yourself a bit of extra pipe to work with. DO NOT use a hacksaw to cut the small pipe, and preferably not the big one either - copper dust in the small pipe will kill your fridge and/or compressor, and in the large
pipe will not taste good in your coffee (you will be circulating drinking water). Get a proper plumber's small pipe cutter - the type with a sharp wheel. I think I used 1.5m of 12mm annealed copper pipe and 1.5m of annealed 5mm. Maybe get 1.8 to be sure to be sure Make two holes in the large pipe 1100mm apart. Make them as oblique as possible. I drilled a 5mm hole straight in then used the shank of the drill to bend the wall of the 12mm tube to make the hole oblique to follow as much as possible the path of the 5mm pipe out of the larger one. In the sidewall of the 12mm pipe aim for as much copper-to-copper contact as possible with the 5mm pipe as it exits - a spoon-shaped depression under the 5mm and a slight dome over it is ideal. This gives maximum contact area for soft solder. (Silver or hard solder would be better if you can do it.) Straighten the pipes as much as possible, but don't work them too much - the more you flex copper the harder it gets and then you might have to re-anneal it. Thread the small pipe through the large one through the holes you have made. You might have to drive it a bit with a hammer. Cut off about 20mm of each end of the 5mm pipe to remove burred ends (from hammering) and also to remove any contamination that might have been picked up. Tape up the ends of the 5mm pipe to stop contamination. Now wind the whole lot around a 5 inch former. I found 5 inch was about the smallest inside diameter I could do without expensive special tools and without kinking the 12mm pipe, and even then you need to be careful. Arrange it so the two straight bits with the entry and exit points come out roughly parallel. Using solderable wire (I used tie wire from Bunnings) bind the small and large pipes tightly together near the entry and exit points for mechanical strength. If the coils don't lie snugly together, bind them too so that they do. Now generously solder the entry and exit points of the small pipe with the large, and also solder the wire binding.

The photo above shows the mess in my compressor cupboard. Much of that is camper manufacturer’s doing, but I'm afraid I have followed suit. In splicing some other mods into their wiring I found that there is not enough spare length to re-route the original wiring and neatly terminate it in a junction block. It's electrically sound and safe, but a bloody mess.
The photo shows the condensor mounted on a bracket made from 1.5mm aluminium sheet. The bracket roughly an inverted, squared off U shape with the ends bent under to form tabs with holes to match the compressor mounting bolts. At this stage you will have to employ the services of a refrigeration mechanic who does small fridges because you have to recover the refigerant, cut into the gas circuit, install the condenser, evacuate the system and re-charge with refrigerant. Ideally the gas flow in the coil should be gravity assisted. So the coil you have just made should lie horizontally, with the outlet from the compressor connected to the uppermost end of the 5mm pipe, then the lower end of the 5mm pipe connected to the top of the original air-cooled condenser.
If it could be mounted on top of the compressor that would be ideal. However, space constraints in my camper made that impractical, so it had to be mounted
alongside, in a vertical configuration. I made the aluminium bracket to accommodate that.
The two condensers are in series, the water cooled one first in the gas circuit, followed by air cooled one. The compressor outlet should be plumbed to the top 5mm pipe. The bottom 5mm pipe (refrigerant outlet) should be plumbed to the top of the air cooled condenser. The water circulation should be contrary to the gas flow, so water should enter at the bottom 12mm pipe and exit at the top. I circulate water from the larger of my two water tanks.
I used a small gravity-primed centrifugal pump from Detail /Dimensions - the P3 micro pump kit. Ozefridge will supply a kit with food grade plastic tubing for around $50.00 plus P&P. (Food grade tubing because you may/will be circulating drinking water.) Being gravity-primed, the pump must be mounted at about the same level as the bottom of the tank it feeds from. I built a stone-proof enclosure and hung it off the side of my #2 tank at the bottom, using a drain valve already installed by the camper manufacturer. See the photo below. (I installed another drain plug on the other side to replace my now lost drain.) Encase the output tube and the very light duty twin core (figure eight ) electrical flex in split conduit, route it under the van and bring it up through the
compressor cupboard floor. Likewise the return line. I used the tank breather hose for a water return, and to prevent return water from being discharged to the road instead of into the tank, put a 12mm garden irrigation stop valve on the end of the breather. Just open the stop valve when you fill the tank and close it again afterwards. The tank can breathe quite adequately through the filler during use, albeit with a bit of audible gurgling. You MUST use a small gravity-primed pump. The one supplied by Ozefridge is almost silent (important for night time operation) and draws less than 0.5 amp. Self priming pumps are generally noisy, would keep you awake at night and all draw too much current so that you will lose the benefit of your work if you use them. The electronics of the Danfoss cannot drive the pump directly. You have to use a relay - I think I used a Jaycar SY4007 12 volt model in a plug-in base, the whole lot is mounted in the grey box in the forground of the messy picture. Only 65mA hold in current, that's the main thing, 10 amp contacts, way more than you need. Pinouts from the Danfoss are in your fridge manual. I wired the relay through a spare switch on the console so that I can switch the water cooling off in cool weather. AS mentioned in my previous post, the performace gain allowed me to reduce the compressor speed, which reduces current draw during the run cycle. The camper manufacturer has installed a small PCB on the Danfoss control unit, containing a small fixed resistor that sets the compressor speed to 3000RPM. I cut out the resistor, installed a small 10kohm preset potentiometer and set a value according to the table in the fridge book to reduce the compressor RPM to about 2000. What I should have done and didn't, was bring that pot out to the grey box to allow fiddling with compressor RPM without removing the SS grill on the sidewall. I am advised that although you get more cooling power at higher RPM it comes as a result of a law of diminishing returns - the compressor is actually more efficient at a lower speed - ie more heat removed from the fridge per watt of power consumed. Wierd. Refrigeration is a black art.
Some tech info for the Danfoss compressor is at the end of this document Well worth doing, IMO. Cheers

[HDYSTT]

how about if the op uses the same setup they have now but runs the input and output through a copper coil in the water tank? they would have to make a way to fill up the system but could use clean water in the loop so there would be no need for a filter and the pump should last near forever because there is no trash/salt running through it.