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Old 25-08-2014, 18:17   #1
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Air vs water or both for cooling refrigerant

I have recently installed a Sea Frost system with a BD80 compressor, ducted fan output for air cooling, and water cooling.

I've had lots of issues with my water cooling, but that's environmental.

However, when it's been out of the system for a period, which seems to be lessening now that I'm putting chlorine tablets in the filter, my system will run continuously on high (~12A) with fan (closed cabinet, heat output ducted outside) only, and not reach our normal, very conservative (none of this way below zero stuff, even at the plate) freezer temperatures.

That's in contrast with our previous (other than it's eventual failure) very economical, quiet, Frigoboat keel-cooled system with its BD50 compressor. The thread of the failure can be found elsewhere in this forum, but it's not related to the point:

In Vero Beach, in the summer, there is no way for us to use air-only cooling.

I hear and appreciate - and heartily wish I could do without the water, as it's a problem in these waters, at least (another thread in this forum) - the air-only advocates.

But with a radiation, convection and conduction barrier of 6" extruded polystyrene, this new system can't approach the efficiency of my old one - or even get close to keeping it cold, by comparison, with air only. With water running freely, aside from it being very hungry (avg 5+A constant; ~120+ AH/day), it does.

Maybe the system is garbage. I suspect not; it's brand new and professionally installed and tweaked. But air alone doesn't make it here and now. In the winter, or in ME, maybe it would.

My two cents ☺

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Old 25-08-2014, 20:13   #2
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Re: Air vs water or both for cooling refrigerant

Skip, several people have been trying to tell you for a long time something is wrong. We have a standard air-cooled BD50 with evaporator plate freezing a larger box than yours and serving an even larger spillover reefer - it uses 50-60Ahr/day.

Your system is garbage. I don't know where or what, but it is. Simple math and performance tells you that. It doesn't appear that your box is the problem, so that leaves the system itself. Others have worse systems running better than yours.

You need to focus on why the system is not working and stop assuming that it is working well.

Mark
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Old 26-08-2014, 06:01   #3
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Re: Air vs water or both for cooling refrigerant

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Originally Posted by colemj View Post
Skip, several people have been trying to tell you for a long time something is wrong. We have a standard air-cooled BD50 with evaporator plate freezing a larger box than yours and serving an even larger spillover reefer - it uses 50-60Ahr/day.

Your system is garbage. I don't know where or what, but it is. Simple math and performance tells you that. It doesn't appear that your box is the problem, so that leaves the system itself. Others have worse systems running better than yours.

You need to focus on why the system is not working and stop assuming that it is working well.

Mark
Ah, now there's the rub.

Any professionals I've asked (granted, I've not spent yet another boatbuck to have people come out to try to analyze what's happening with hands on) say it's working properly. All visual cues (ice levels, temperatures at tender spots, etc.) agree. The installing company had a month to play with it (and replaced some defective-out-of-the-box stuff in the process) during the installation period. Failure to air-cool adequately, on the dock, in December in St. Augustine (not very hot) led to the addition of the water cooling.

The manufacturer insists it's working properly.

"You're ugly, I hate the way you look!" is different from "A nose job would make you beautiful."

So, do you have any suggestions, or directions on how to establish why it is that it's not working properly? Once the "why" is found, I expect it can be cured. But nothing I've done or checked or any other effort besides making sure the water can flow has made any power difference, let alone performance difference...

L8R

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Old 26-08-2014, 06:43   #4
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Re: Air vs water or both for cooling refrigerant

All I can tell you is the vast majority of all the coolilng systems in Vero Beach are air to air heat exchangers, look at how all the buildings, refrigerators and freezers, even the big ones in the supermarkets are cooled.
Sounds like somethings wrong with yours would be my guess.
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Old 26-08-2014, 08:04   #5
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Re: Air vs water or both for cooling refrigerant

I do not know what is wrong with your system. I was attempting to get you to think that something is wrong with it instead of thinking that all is correct and it is a function of your location. The vast majority of boat reefer systems are air-cooled with no problem. I have already stated that our air-cooled, similar-sized boxes use less than half the power than yours and we have a smaller compressor and are in the tropics near the equator.

In other threads, you have described your boxes. They sound very well insulated and built, so I don't think this is a box issue. A BD80 running continuously at 4400rpm drawing 12+ amps and just keeping the ice levels, temps, etc up to spec is not normal, no matter what the manufacturer and other "professionals" tell you.

That compressor running full out should be able to remove ~800btu/hr. If your box really does have that heat load, then you do have a problem with the box. If your box is as you describe it, then it does not have that heat load, so there must be something wrong with the system itself. I can't imagine a case in-between those two determinants that would lead one to believe the system is working correctly.

Another thing to consider is that if your BD80 is running full time, then it is too small for your system. Do you really think that is true?

I think a BD80 should be overkill for your requirements. A BD50 should have been sufficient, and would have used half the amps in providing the same btu/watt efficiency.

Maybe it is just the compressor speed itself - lowering that may increase the btu/watt efficiency. Maybe there is something wrong with the installation or your cold plate plumbing. I can't tell, but I can tell you that your box/system performance is not normal compared to the vast majority of other boats. And your box is better insulated and built than most others (based on your description).

So if you want a suggestion, my suggestion is to do a heat-loss experiment with your box (I think I remember you having done this in a past thread). If your box needs >350btu/hr when cooled, then maybe there is something wrong with it. If not, then there is something wrong with the system.

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Old 26-08-2014, 08:27   #6
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Re: Air vs water or both for cooling refrigerant

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Originally Posted by a64pilot View Post
All I can tell you is the vast majority of all the coolilng systems in Vero Beach are air to air heat exchangers, look at how all the buildings, refrigerators and freezers, even the big ones in the supermarkets are cooled.
Sounds like somethings wrong with yours would be my guess.
Agrees with the above, but cites empirical evidence that water, somehow, is more effective/needed in a marine environment, else there wouldn't be such a proliferation of that modus on boats.

As to "something's wrong" with ours, there's no disagreement, despite the manufacturer's assertions of perfection - but what, and how to remedy, is the kicker...

L8R

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Old 26-08-2014, 08:44   #7
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Re: Air vs water or both for cooling refrigerant

Quote:
However, when it's been out of the system for a period, which seems to be lessening now that I'm putting chlorine tablets in the filter, my system will run continuously on high (~12A) with fan (closed cabinet, heat output ducted outside) only, and not reach our normal, very conservative (none of this way below zero stuff, even at the plate) freezer temperatures.
Does this mean, as it suggests, that you have no input grill in the cabinet? I would rig a fan blowing air into the cabinet, onto the compressor to see what happens.
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Old 26-08-2014, 08:46   #8
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Re: Air vs water or both for cooling refrigerant

Waters ability to absorb heat is magnitudes greater than air, combine that with usually the air temp will be higher than the water and you see why water is so tempting to use as a cooling medium. Water cooling is not new at all, 50 yrs ago as a kid I used to play with the hose that discharged warm water in our yard from our water cooled airconditioner, and of course every now and again ground source heats pumps become fashionable but have never made it to mainsteam.
From a reliability and simplicity standpoint, its just really difficult to beat at an air to air heat exchanger, and if they condenser is large enough and you move enough air over them they work really well.
Stupid question, but your condenser isn't in a confined space where it's not getting fresh air is it?
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Old 26-08-2014, 08:47   #9
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Re: Air vs water or both for cooling refrigerant

I have no idea what your cooling situation is but I once took a call on a computer system that had a fan reversed. Both fans were blowing out and the system was overheating. One fan blowing out with no input air will do the same things.
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Old 26-08-2014, 08:51   #10
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Re: Air vs water or both for cooling refrigerant

Quote:
Originally Posted by skipgundlach View Post
empirical evidence that water, somehow, is more effective/needed in a marine environment, else there wouldn't be such a proliferation of that modus on boats.
I don't think the proliferation bit is true. Keel coolers are not the same as water-cooled, and I don't think there are large number of boats with true water-cooled systems, and I certainly don't think that number is proliferating.

If you count all air-cooled and keel-cooled as the same, I think water-cooling is a small minority. Even if you count the AB models with the ability to add supplemental water-cooling - although I don't know many with them who have actually hooked that circuit up.

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Old 26-08-2014, 08:58   #11
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Re: Air vs water or both for cooling refrigerant

Quote:
Originally Posted by skipgundlach View Post
Ah, now there's the rub.

Any professionals I've asked (granted, I've not spent yet another boatbuck to have people come out to try to analyze what's happening with hands on) say it's working properly. All visual cues (ice levels, temperatures at tender spots, etc.) agree. The installing company had a month to play with it (and replaced some defective-out-of-the-box stuff in the process) during the installation period. Failure to air-cool adequately, on the dock, in December in St. Augustine (not very hot) led to the addition of the water cooling.

The manufacturer insists it's working properly.

"You're ugly, I hate the way you look!" is different from "A nose job would make you beautiful."

So, do you have any suggestions, or directions on how to establish why it is that it's not working properly? Once the "why" is found, I expect it can be cured. But nothing I've done or checked or any other effort besides making sure the water can flow has made any power difference, let alone performance difference...

L8R

Skip
In fault finding refrigeration it can help to log temps across the whole system. This way it will be obvious which circuit or component is the issue. Use a infra head gun. They're cheap and easy to use.

If you still don't feel comfortable diagnosing then log temps on either a similar system or a system that is working well. Then revisit this forum. There are lots of good refrigeration experts here.

Knowing key specs like how much refrigerant was used is also helpful.

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Old 26-08-2014, 09:32   #12
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Re: Air vs water or both for cooling refrigerant

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Originally Posted by colemj View Post
Even if you count the AB models with the ability to add supplemental water-cooling - although I don't know many with them who have actually hooked that circuit up.

Mark
I've ordered a 12V CPU pump with a 1L per min. flow rate and I think 1 amp current draw and a MTBF of 3000 hours.
I'm going to hook it up to a 5 gl bucket just as an experiment to see if it improves cooling and how much it raises the temp of the water in the bucket.
It just may be that using my 157 gl water tank may be enough thermal mass so that it's water temp won't be raised much if any at all, and that would pretty much eliminate the concern of running salt water through the condenser.

Water cooling on top of the air cooling has to help some, doesn't it?
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Old 26-08-2014, 09:41   #13
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Re: Air vs water or both for cooling refrigerant

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Water cooling on top of the air cooling has to help some, doesn't it?
If your air cooling is insufficient, then connecting the water cooling will help. If air cooling is fine, then the water cooling will just use more amps with no performance difference. You will require a 20% increase in cooling need, or a 20% decrease in run time, to break even with the amp draw of the pump.

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Old 26-08-2014, 09:48   #14
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Re: Air vs water or both for cooling refrigerant

One boat I had a water/air cooled cold machine. The pump failed so I just went with the air as we were down Island. I found no difference in amps used really. But that's an aside to Skips problem. It sure sounds like something in your system does not work properly. You need to find the best boat fridge man around... not an installation guy who just puts things together. But a knowledgeable person. Good luck with that.!
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Old 26-08-2014, 09:56   #15
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Re: Air vs water or both for cooling refrigerant

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Originally Posted by colemj View Post
If your air cooling is insufficient, then connecting the water cooling will help. If air cooling is fine, then the water cooling will just use more amps with no performance difference. You will require a 20% increase in cooling need, or a 20% decrease in run time, to break even with the amp draw of the pump.

Mark
What I have is an OLD system that is operating marginally. One thing that does not help is the compressor / condensor is located in the Lazarette which has no air flow so I prop the lid open to allow some air flow at least.
Besides it airtight be an interesting experiment, I believe these things move more heat than most realize
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