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Post by Bora on Oct 2, 2020 7:53:05 GMT
Over the summer in Croatia I was having real trouble keeping the fridge cool with temperatures in the cabin around 30 during the day (probably more when the sun was shining through the companionway directly onto the stove area where the compressor is.)
My freezer has a heat exchanger plate on the hull which I could feel was warm when I was swimming but the fridge compressor is just air cooled it seems.
The fridge compressor must have been running most of the time as I was getting some pretty high loads on the 12v throughout the day.
I haven't actually looked too closely but I assume that there is a fan in there already as I can hear something running some of the time. Has anyone fitted an additional 12v fan to help with air circulation in the compressor space?
I had a reefer engineer have a look when I was in Dubrovnik marina and the pressures in both the fridge and the freezer were correct.
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Post by jy51 on Oct 2, 2020 9:50:12 GMT
Very confusing because I was led to believe that it was one or the other, the water cooled fridge on my previous boat had a copper coil fitted in the sink drain through hull fitting and did not have a fan, the whole idea of a water cooled fridge is to stop heat being dispersed throughout the boat by a fan.
If you have need the addition of a fan, it seems the system is not working properly or maybe you are mistaken, and the plate is in fact an earth plate? Just saying!
Regardless of the engineers investigation it defiantly sounds like the fridge is working overtime to keep cool, maybe a leak around a seal, insufficient insulation or a gas pressure issue. Alternatively maybe the compressor pump is just not working properly.
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Post by Bora on Oct 2, 2020 9:56:46 GMT
I thought perhaps the gas was low on the fridge so I got the reefer tech to check both of them and he confirmed both were at the right pressure, i think the freezer took a very small amount.
When I asked about the cooling system he confirmed that the fridge was air cooled and the freezer gas/compessor was cooled by the hull plate.
I'll have to have a good look around next time i'm on the boat.
She's a 2013 469 if anyones wondering.
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Post by jy51 on Oct 2, 2020 10:00:30 GMT
I thought perhaps the gas was low on the fridge so I got the reefer tech to check both of them and he confirmed both were at the right pressure, i think the freezer took a very small amount. When I asked about the cooling system he confirmed that the fridge was air cooled and the freezer gas/compessor was cooled by the hull plate. I'll have to have a good look around next time i'm on the boat. She's a 2013 469 if anyones wondering. I would start with the battery power at the fridge and if you are getting sufficient power then look for poor insulation or leaks around the doors.
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Post by Zanshin on Oct 2, 2020 10:37:58 GMT
I have a similar setup, my freezer is keel-cooled and the fridge is fan-cooled.
I got a computer fan and hooked it up to the fridge controller so that when the compressor is running it also runs (in addition to the normal fan attached to the fridge. This second fan is set to blow air out of the compressor compartment back to the hull and seems to have worked somewhat in reducing my compressor runtime.
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Post by Bora on Oct 2, 2020 11:17:20 GMT
I'll certainly look at installing a similar fan to aid the air movement in the space.
Once i've installed the 5x firefly's i'll recheck the voltage, i think they hold up a bit better than the Rolls and someone else had suggested that the battery voltage could be what's causing the fridge to not run as efficiently.
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Post by moonshadow on Oct 2, 2020 11:25:57 GMT
My setup is the same as yours. I have looked for access to add insulation but there is no easy way and I felt there was just too much in the way to disassemble everything I would need to. So adding insulation is not on my list for now. I considered spray foam but I know someday I will need to access something back there. I like the idea of adding a fan to the compressor area to help the refrigerator. I’m guessing that the freezer, keel cooled, would not see much change. How do you signal the fan to run? Is there a terminal on the control at starts the compressor available to run a fan? I see air flow ducting out of the compressor area and I wonder about using a duct fan to help?
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Post by Bora on Oct 2, 2020 11:29:05 GMT
Is your cooling plate actually in the keel? or just a generic reference? My freezer leads to a plate on the outside of the hull, stbd side. Can be accessed by lifting the bottom off the hanging locker in the stbd aft cabin.
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Post by rene460 on Oct 3, 2020 0:50:40 GMT
Hi Findhorn, confirming that you have a water cooled freezer and air cooled fridge, and having the systems checked by a professional is a good start to working out what is going on. It is reasonable now to assume that there are no faults that stop your system performing as intended.
I suspect the next step is to take time to observe how much of the time each of the compressors run. Mine seems to run about half the time in summer. It is also worth putting a thermometer in the compartment to see what temperature is being achieved, though you will know if it is too cold due to a thermostat failure for example, as everything will freeze.
If the main problem is that sun coming through the hatch, folded towels on the bench top will reduce the heat input to the fridge. Or perhaps a section from one of those silverised car window shades, cut to sit neatly on top of the bench over the fridge, to reflect away the radiant heat from the sun.
In principle, water cooling gives a lower temperature sink for the heat rejected by the compressor, so should reduce the power consumption of the compressor by lowering the refrigerant condensing pressure. The main thing you can do there is keep that plate clean so that it is effectively cooled by the water.
The little fan on the air cooled fridge condenser is supposed to increase the heat transfer to the surrounding air, but if it only “circulates the air in the compartment” as you described, it is not doing much to remove the heat. The compartment needs to be ventilated with the coolest available air, though in a warm climate cool air is in short supply.
When I look at the compressor compartment on my boat, the fan blows air over the condenser coils, towards the vent in the door. But it is very difficult to detect any significant air flow out of the vent in the compartment door. And if there was any out flow, that air has to be replaced from somewhere. In my boat, it seems to come through gaps in the bulkheads where the cable ducts pass through. Air comes from under the saloon settee berth, or under the beds in the aft cabin, possibly both. And therein lies a problem. There is very little in the way of visible ways for fresh air to enter those compartments, and worse, the settee berth hides the hot water tank so is always a little warm, while the passage from under the aft bed contains the batteries and battery charger, so also heated, when we are on shore power any way.
I was interested in the comment made earlier about a little air duct into the compressor compartment. That could be intended to bring in cooler air from near the floor of the cabin, to replace that exhausted by the fan. I would suggest installing a little fan to assist air flow through that duct, into the compressor compartment, from where it will find its own exit and help carry away heat from the condenser. You can find terminals where the power connects to the compressor, a common 0 v and various others. One terminal is live when the compressor operates and can be used to power an extra small fan when the compressor is running.
You might ask what I have done in my boat considering that we also live in a relatively warm climate. I have obtained a fan to install, but my small boat does not have that duct, and I have been unable to work out a way of installing the fan that does not involve irreversible cutting of some of the wood panels, so I have been reluctant to start. There is not much spare space on a thirty foot boat. Almost as bad as making holes in the hull. The last couple of years have been dreadful for boating with weather and bushfires, so it has been on the back burner for a while. But I will get there. If you have that ventilation duct, it will be much easier to instal a fan that will improve the ventilation of the compressor compartment.
Rene460
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Post by rene460 on Oct 3, 2020 0:54:41 GMT
Hi Zanshin, I have been waiting with interest to see the results of your experiments with that extra fan. It’s good to hear that it seems to have produced some useful improvement. In the light of the problems being experienced by Findhorn, I wonder what the air flow through the compressor compartment is like in your installation and where you put the extra fan.
rene460
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Post by Bora on Oct 3, 2020 12:46:58 GMT
I have SensorPush sensors in the fridge, freezer and cabin so that I can monitor the temperature and humidity, they connect to a gateway that I have wired in with the wireless router so I can remotely check them as well. The graphs for the summer you can see that it never got cooler than 3.1 degrees and the average was 7.8 despite being on max setting the whole time. We were regularly defrosting the small freezer section as that was frosting up.
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Post by moonshadow on Oct 3, 2020 22:25:16 GMT
First, Keel Cooler I believe is the brand name of the hill mounted plate the the refridgerant runs through to cool. In my 469 the compressor area has both the air cooled fridge unit and the keel cooled freezer unit. I wonder why they didn’t use two keel cool units? And there is a duct at the back of the cabinet that brings air into the compartment. I don’t know where the other end is.
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Post by rene460 on Oct 4, 2020 12:14:51 GMT
Hi Findhorn, that is an impressive display, it’s interesting to think about what it is telling us.
The fridge temperature does not look totally right to me. As I understand it a fridge should be keeping things about 4 deg C, which that trace shows a a minimum only occasionally reached. I presume the really warmer readings are associated with putting a load of food into the fridge for cooling, but I would hope that something in the range of 4 - 6 degrees should be the normal. And of course a lot depends on just where the temperature sensor is located. That, combined with the requirement to frequently defrost the food freezer compartment in the top looks like it is telling us that the fridge is running too long, but icing the top compartment instead of cooling the rest of the compartment and contents. This makes me wonder if you have stuff packed against the evaporator plates that is hindering air flow and heat flow from the rest of the compartment to the evaporator plate.
Of course, I am probably overthinking this. But there is always interesting detail concealed in those traces, waiting for us to find it.But I am just thinking about the way the heat load is “ balanced” between the freezer compartment and the main food compartment. As you have a separate freezer, if you put nothing that needs freezing in the fridge freezer compartment, and try jamming the little internal door open a little to help cool the main compartment, I wonder if that would give better temperature distribution? Perhaps fill the freezer compartment with those gell freezer packs to help keep the fridge cool for longer between run cycles. Just some thoughts for consideration and discussion rather than a proven solution at this stage.
rene460
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Post by Bora on Oct 4, 2020 12:39:20 GMT
As we don't use the small compartment I wonder if it's worth removing the wee door and perhaps even installing a fan in that space to circulate things a bit better.
We don't pack the fridge too tight, especially around the cooler area. The sensor is on the outboard bulkhead of the fridge to the right near the temperature control, probably about 75% of the way up.
The beers are kept in the bottom on the left so the front door is probably opened more than the top hatch.
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Post by rene460 on Oct 6, 2020 6:51:49 GMT
Hi Bora, my apologies, I have just realised that the original question was yours. I don’t know what set me off on the wrong track.
Not using the little compartment as a food freezer definitely gives scope for more experimentation, but I am not sure that I would take the door off as a first step. As far as I can understand the design intent, the outside of the plate is supposed to be enough to cool the larger fridge compartment. I think I would try the gel blocks or gel packs in the little compartment first. Once they have initially cooled down they provide a heat sink which will mean the compressor on/off cycle will be longer a bit like the eutectic fridges which have such a heat reservoir built in.
Certainly air flow over the outside of the plate is the most important for the fridge side of the plate, and so not packing closely around it is very important, as is providing adequate air circulation paths to the more distant parts of the compartment. Modern frost free fridges seem to use fan circulation to keep them frost free, so might be worth an experiment. But it will also cause more power consumption. At least with that temperature monitoring system, you have good information to help understand what is going on.
rene460
Apologies to Findhorn also - you must have wondered why I was addressing my comments to you. I am also wondering now.
rene460
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Post by Bora on Oct 6, 2020 7:01:21 GMT
rene - it's my fault! I changed my username from my old home port to the boat's name, Bora. Will certainly give the gel pack idea a go, we have a few lining the bottom of the freezer for now so will probaly just move them across.
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Post by rene460 on Oct 6, 2020 22:35:48 GMT
Hi Bora, thanks for the explanation, I was beginning to wonder about my sanity. I can relax now (and let it take its course!).
rene460
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Post by sailbleu on Oct 9, 2020 8:12:59 GMT
I just love the idea of the sensor push application Bora . Right in my alley Will look into it . First of all a remark on Rene’s suggestion to install a fan inside the fridge . Quite some years ago I started a frigoboat/ danfoss fridge- problem-topic on the board that eventually turned out to be a blocked evaporator . If interested you can find it the H&T section. Anyway , back then I , on one of the last pages , referred to an inside fan and I can now say this was not adding a lot to the performance . On the contrary , our fridges are not as powerful as the domestic ones . That’ s one thing , another thing is that circulating air inside our fridges disturbs the transition layer close or on the inner walls of the fridge . To explain this phenomenon the example of a standard heat exchanger comes in play . Inside industrial heat exchanger baffles are placed to redirect or chaotize the water flow ( or any other liquid ) so no ‘ doldrum ‘ areas exist inside the heat exchanger . These areas decrease the performance . Same thing here with a fan inside our fridge , the air circulation disturbs the inversion layer and reduces the cooling effect as more heat is absorbed through the walls of the fridge . Don’t forget , the back wall of a boatfridge is close to hull , sometimes facing the sun . Imagine a dark blue hull ?! . The thickness of the fridge insulation is a you know a compromise I do use my fan when de-icing the fridge though . I stop the compressor and have the fan blow directly to the evaporator. The time needed to melt the ice ( and at the same time warm up the fridge content ) is reduced with 50% .That much for inside fans. An extra fan to evacuate the hot air in and around the condensor and compressor however is a plus . Also running the airconditioning in combination with an extra fan blowing the cold air into the compressor compartment enhances the performance drastically . I know because I have this situation on my boat right now . Has to be said we’re in a marina so running the airco is easy . Drawing the ventilation from the bilge ( in case of no airco) might help also . The temperature there is close to the seawater temp. Definitely lower then the cabin temp. And kicking in an open door ,..make sure the condensor is dust free , they tend to clog up after a while . So the options numerous , all with limited improvement . But many smalls make a big . Regards
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Post by Bora on Oct 9, 2020 9:01:20 GMT
I’ll certainly look at increasing the airflow into the compressor compartment even if it means warming the cabin a bit....what’s more important? Cold beer or a cooler saloon?
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Post by sailbleu on Oct 9, 2020 9:58:20 GMT
I usually have my cold beer in the cooler cockpit surrounded by mesh ( wind permeable ) sun covers .
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Post by moonshadow on Oct 9, 2020 11:56:29 GMT
I noticed on my boat that some air return vent covers were never installed. I wonder if you have an air grate in the door of the compressor compartment. I am now thinking of mounting a small fan that runs when the compressor runs that will blow air out the the compartment into the cabin. It should be easy to mount behind the grate.
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Post by Bora on Oct 9, 2020 12:04:31 GMT
Not the best photos but looks like the fridge compressor on the left and freezer on the right. Seems to be a duct at the back of the compressor but no idea where it goes, not onboard. Can see the vent at the front of the door.
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Post by Zanshin on Oct 9, 2020 12:34:11 GMT
On my boat that duct is very short, it only goes to the bottom of the oven area.
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Post by sailbleu on Oct 9, 2020 13:09:42 GMT
@ Bora , off topic , do you connect your smartphone directly to the sensor-push sensors or by means of a gateway ?
Regards
Edit:
That duct goes behind the wooden back in the area between the hull and wooden back . Sometimes that coincides with a hull side exposure to the afternoon sun . Thus very warm. The hole in the bottom of the floor on the picture serves as a suction for air supply . A beter option is to place a ventilator on the hole so you definitely get air from the bilge compartment .
An extra fan unfortunately result in extra energy consumption. Choices , choices & choices .
Again , one golden rule , the cooler the condensor/ compressor area , the more efficiency .
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Post by Bora on Oct 9, 2020 14:01:56 GMT
I've wired the sensorpush gateway into a 12v-5v buck of the same breaker as the cabin lights (also does wifi and 4G). So i can access it when off the boat as well.
If you don't want to use the gateway you can pick up the sensors with bluetooth if you're close enough.
I'm certainly going to look at better ventilation options for this compressor area, may even be worth insulating the hull area above the water line to stop radiant heat coming through.
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