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Old 02-07-2016, 09:16 AM   #1
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cold plate repair

Hello,
I have a cold plate refrigerator on an older Grand Banks. It works well but lately when it's running I'm getting sea water in the box though the drain. Any idea what would cause this.
Thanks
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Old 02-07-2016, 09:23 AM   #2
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Greetings,
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Old 02-07-2016, 09:30 AM   #3
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Thank you
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Old 02-07-2016, 09:38 AM   #4
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I've seen this on boats with drains close to the static waterline without loops in the drain hose. Was the boat rolling a bit under way?


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Old 02-07-2016, 09:58 AM   #5
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Hi cafesport,
The boat is in a slip. It has been rolling a bit but not much. The drain hose about 18" above where it connects to discharge hose. The water seems to be discharging from the boat properly.
This is a new problem.
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Old 02-07-2016, 10:09 AM   #6
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18" sounds ideal any thing else "t"Ed into it perhaps upstream?


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Old 02-07-2016, 10:25 AM   #7
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Cafesport,
No Ts in system. Water flows from the compressor stright out of the boat. Th drain connects into the discharge hose and 2" before it leaves the boat. When the compressor starts water flows up and into the box. When the compressor stops running the water drains out (sometimes)
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Old 02-08-2016, 07:41 AM   #8
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Very strange.

The usual setup only freon is pumped into the reefer box to the eutetic plate , never sea water,

What is the water supposed to do in a refrigerated space?

Most boxes only discharge condensate water after defrosting , so little its usually into the bilge, not overboard.
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Old 02-08-2016, 08:37 AM   #9
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Maybe it uses a seawater cooled compressor-heat exchanger. And somehow when the compressor runs, it has a cracked section and somehow it fills up the drain.

OR maybe the seawater cooled heat exchanger, the flow backs up and comes into the fridge cause the outflow is partially blocked. Perhaps the pump outflow shares the same drain as the fridge. And maybe it is designed to do that to show you there exists a problem with a partially blocked drain where the heat exchanger outflow is not draining properly. Tubes can fill up on the inside with stuff.
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Old 02-08-2016, 09:44 AM   #10
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Water cooled but no keel cooler right? Still sounds like the seawater cooling pump is back flowing into your box via the drain. A sag or belly in a hose or an obstruction of some sort would be the first thing I'd try to rule out.


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Old 02-08-2016, 04:17 PM   #11
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Quote:
Originally Posted by Paradise Cay View Post
The drain connects into the discharge hose and 2" before it leaves the boat.
Are you saying the drain line connects to a discharge line for something?

Or the drain line runs from the drain straight to a thruhull with no other hose of any kind connected to it?
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Old 02-08-2016, 04:35 PM   #12
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Quote:
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Cafesport,
No Ts in system. Water flows from the compressor stright out of the boat. Th drain connects into the discharge hose and 2" before it leaves the boat. When the compressor starts water flows up and into the box. When the compressor stops running the water drains out (sometimes)
If what you say regarding the way the two hoses run is true, what you are describing as happening is physically impossible.
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Old 02-08-2016, 09:47 PM   #13
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I had that old system on our GB when we first got it. My advice is to up grade to a plate eliminating the need for a drain. Another added benefit is that the new system will use much less electricity so you can stay on the hook longer.
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Old 02-09-2016, 08:51 AM   #14
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Perhaps I have figured it out.

I assume GB built the boats for block ICE and a drain is std on ICE boxes.

Way back boats were delivered almost as empty buckets ,

The owner selected the reefer, auto pilot , air cond , central heat, radio and nav gear and frequently the owners yard ,or the US boat dealer ,,, not the boat builder would do the installations.

If the Grunert was later installed I can see where the yard guy would think he needed to maintain an overboard drain that already exists.

In reality it is not needed.

Plug the spot where the sea water coolant exhaust gets fed from this drain hose.

Let the box hose drain into the bilge .

There should be an external (to the box) loop in the drain line to work as a trap, and not allow cold dense air escape the box.

When you periodically empty the box to scrub it out , the cleaning water will still drain as usual.

Does this solve the hassle?
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Old 02-09-2016, 10:40 AM   #15
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Quote:
Originally Posted by Paradise Cay View Post
Cafesport,
No Ts in system. Water flows from the compressor stright out of the boat. Th drain connects into the discharge hose and 2" before it leaves the boat. When the compressor starts water flows up and into the box. When the compressor stops running the water drains out (sometimes)
If what you say about the routing of the drain and pump discharge lines not mixing in anyway is correct, its physically impossible for what you're describing to be occurring.
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Old 02-09-2016, 09:27 PM   #16
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I have a 1990 Grand Banks with two refrigerator boxes and one freezer box, all three with cold plates, one raw water cooled compressor. The box drains for all three are not connected in any way to the raw water line which discharges just above the waterline. If your box drains are connected to a raw water line discharge somewhere, I would suggest re-piping to drain to the bilge. Not sure I understand how this can happen.
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Old 02-09-2016, 09:40 PM   #17
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FF resolved the confusion. My cold plate fridge has a drain in the bottom, a threaded hole with a set screw in it thus retaining cold air, I unscrew to drain water. Separate freezer has a drain too. Both drain to the bilge, works fine.Looks like someone came up with a complex design to overcome what is not really a problem.
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Old 02-10-2016, 08:35 AM   #18
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Rerouting the box drain-tube into the bilge avoids the problem, but doesn't explain why it happened. The OP states that the system used to work OK " . . but lately when it's running I'm getting sea water in the box". Something has changed which creates just enough back-pressure for the seawater to climb up the drain-tube and into the box. That suggests a partial obstruction before the thru-hull which allows just enough back-pressure to push seawater into the box. I suggest:

(i) Disconnect the discharge hose at the outlet end and see what you find (hose delamination, crustaceans, eel grass, North Korean satellite etc).

(ii) Maybe fit a "Y" rather than a "T" where the drain-tube joins seawater hose.


Edit: I know the OP says there is no "T", but there is a joint of some sort.
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