Seafrost Fridge gets air in the water cooling line

[sailing_gal]

I have a Seafrost fridge/freezer. It has a rather large Danfoss compressor and is sea water cooled. The seawater intake is through a seacock and sea strainer that is solely for the fridge. It is located slightly starboard of the centerline, there is a scoop on the outside of the hull. The outlet for the water cooling is just above the waterline, on the starboard side of the hull. I have found that occasionally, when sailing hard on a starboard tack, air gets in the water hose and the centrifugal waterpump that feeds the cooling water to the system stops. I have had to go down into the lazarette, pull the hose off the compressor and blow back to clear the air so that the fridge will work. Not a good permanent solution. So, I am trying to figure out a better solution. I hate to replace the pump with a Jabsco, because that centrifugal pump will last forever, it just won't pump dry. I have thought about inserting a T just after the through-hull with an additional hose that feeds aft through the hull and then goes up and sits high in the lazarette to bleed out the air.

Seafrost told me that a scoop on the intake through-hull would fix the problem- but it doesn't. Any other ideas?

[Typhoon]

This is a Centri Puppy Jabsco like this ?

18510 Series DC Centri Puppy > Obsolete Products - Jabsco > Xylem Flow Control - Let's Solve Water.

Is the pump below the water line ?

Regards John.

[sailing_gal]

Water pump is below the waterline, right next to the strainer by the through-hull. It is not a Jabsco- it is a centrifugal pump- has the Seafrost label stuck over the manufacturer. Centrifugal pumps will not run with air in them.

[Typhoon]

Yes they don't like air and they will overheat and burn the seal if left running for to long without water . Only thing I could suggest would be to plumb it of a through hull that is more centreline and stays under water on both tacks . You also may find that in a rough sea the pump will get air locked as well. There are massive amounts of bubbles traveling along the bottom of a boat when bashing up wind .

Regards John

[sailing_gal]

Yes, it is in rough sailing that the problem typically occurs. Unfortunately, relocating that pump is not practical, as this through-hull is the only one that has a passage to the aft lazarette where the compressor, etc. is located. That is why I am thinking about a "T" and a "bleeding hose" before the pump to remove air.

[Typhoon]

You could rig it to bleed itself and never have to look at it again with some thing like this.

You should be able to get the air out before it goes to the pump

Regards John

Sorry for the rough sketch but you can get the idea I hope.

[sailing_gal]

Hi ColdEh,

Yes, your drawing is exactly what I am thinking about doing.

[Bleemus]

Or you could turn the fridge off when beating on starboard.

[Typhoon]

Just make sure you get the bubble tube/hose/pipe well above the water line .

Regards John

[sailing_gal]

Bleemus,

Turning off the fridge is not an option. Once air gets into the system, whether the fridge is on or off, it will stop the pump.

John, my only concern is that the hose will have a long horizontal run before it can be turned high up, but I suspect the air should go out in either case.

[Typhoon]

Just make sure the pump is as low as you can get it and tee off the hose up as high as you can while always having it below water line on either tack . Air bubbles will not go down the hose as long as the velocity inside the hose is not to great , then you may suck the bubbles down. So use a large diameter hose at the intake of the pump to slow down the velocity and allow the bubbles to rise up and out of the suction line.

Funny Seafrost never worked this problem out over the years .

Regards John.

[john61ct]

I am getting more and more certain I want to do everything possible to stick to air-cooled systems, KISS.

Even if it costs more up-front.

[svinvictus2]

I also have a water cooled Frigoboat system. We never have your issue. The seawater intake comes directly off my dripless stuffing box which is always below sea level. We teed the seawater fitting which is very simple and inexpensive. The run from the stuffing box is a bit longer than you mos likely have now but once done it makes no difference. You then have the entire weight of the boat forcing water up into your feed line.

[sailing_gal]

This is not a Frigoboat system, it is a Seafrost cold plate system.

[skipgundlach]

SeaFrost uses March pumps. I've burned one out and replaced one already. I have to bleed mine fairly often (it gets noisy if it's not got a full head of steam, the precursor to failure).

My pump is about 3' under water, and nowhere near able to come out under severe, even, heel. Yet, somehow, I manage to get air in it fairly frequently, even/particularly at anchor.

It's a major reason (the other being the massive amount of amps needed to achieve what I'd had with my Frigoboat keel cooled system, in the same box; somewhere between 1.5 and 2x the amp hours for the same results) that I'm unhappy with the system, as my condenser (air, nice box, as efficient as it's going to get) is in the engine room; that sometimes is notably hotter than ambient, which makes water cooling pretty much a necessity.

Mine are not cold plates, but look like it; they are actually evaporator tubes encased in a SS box, which makes for VERY simple defrosting (the single unreserved praise I have for the system), and no worries if you wanted to use a tool on it (I never have, other than a plastic spatula).

If your system doesn't run for hours at a time, and then not for many more hours, you have the same system; it will run until the plate at the end gets to the shutoff temp, and at a point (they come with a 6.5 ° hysteresis) turn on again; if you have the smart switch, you can make it constant low, medium or high power (when it's running) or on automatic, which uses an algorithm to control the compressor speed to match up to a set time of run/off.

Mine runs more or less constantly unless I marginalize the freezer, in which case it will cycle - but some of my stuff doesn't freeze hard.

To your problem, I have no solution, as I have the same issues. However, rather than doing what you do to cure it, if you will remove the hose at the pump output, it will (assuming your intake isn't clogged) blow out the air entrained and you're good to go again for a while. A nut driver kept in the same area will make a very short fix each time.