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Old 26-05-2024, 03:58   #1
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Fresh water through the heat exchanger

As the title says.... I am concerned about fresh water through the heat exchanger on the D2-55.

When the refit is finished the boat will be taken to a large fresh water lake and will be there for many years.

The issue is that this fresh water in the lake is heavily mineralised (CaCO3 - calcium carbonate) and has very high PH (avg of 9.5). I am concerned about hard water scale build up in the raw water heat exchanger on the D2-55. The concern is that the hard high Ph water will gunk up the heat exchanger fairly fast.

Never having had a diesel motor with a raw water intake/heat exchanger system on the lake before I am not sure what to expect.

What I do know for sure is that ANYTHING with an element used for heating gets large deposits of scale on it. Electric kettles, hot water systems etc all get gunked up pretty badly here. (The fresh water from the lake is potable and we use it for all our water needs - in fact the water in the lake is 16% of all the fresh water on the planet! -its a massive lake).

So using this water for the raw water intake to the heat exchanger is the only way I can do it. I am VERY concerned about scale build up in the cores of the heat exchanger but I am not sure if this is going to be a problem or not.

Does anybody have any thoughts about this?
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Old 26-05-2024, 05:36   #2
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Re: Fresh water through the heat exchanger

You may eventually need to run a descaling solution through the heat exchanger. But I doubt you'll run into worse buildup issues than you would in salt water.
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Old 26-05-2024, 06:13   #3
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Re: Fresh water through the heat exchanger

Well that's the thing. We all know what sea water is and its properties, so if this boat was to stay on the sea it would be a known thing and I would know what to expect.

However on this lake with is very high Ph of 9.5 and its high rate of mineralization - seems to be a crap shoot as what the end result may be. I am quite concerned about this.

As an example, locally I replace the heater element on my domestic hot water system about every 3 months or so because the element breaks because of the thick layer of lime scale it gets on it - the temp of the hot water is approx 60c. Electric kettles get a thick build up of lime scale on the heating element.

The water in the electric kettle boils and gets a thick layer of lime scale, the hot water system heats to 60c - both get thick layers of lime scale that if not cleaned off in time break the elements on both devices. Point being that its not just boiling water that does this - hot water does it too.

I have an old kettle that does not have an element and that I put on top of a hot plate to boil water. It gets a thick crust of white lime scale on it (if i let it go for a few months without descaling it can get to 10mm + thick). So its not just elements that suffer from this problem.


Normally this would not be a problem because most boats use seawater as the raw water intake. However on this fresh water lake it is heavily mineralized. It is very HARD water.

What sort of temperature would the raw water in the heat exchanger get too when its in operation?

Looks like I had best learn how to open up the heat exchanger and take the core out before it goes back in the boat. Time will tell of course but I may be descaling the heat exchanger regularly.
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Old 26-05-2024, 06:25   #4
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Re: Fresh water through the heat exchanger

The hottest part of the heat exchanger should be no more than a few degrees hotter than the engine coolant temp. So probably not more than 190* or so.

To get an idea of when it might be time to look inside or so some cleaning keep an eye on water flow from the exhaust and engine temperature under load. If water flow starts to reduce or temp under load starts getting higher, you're probably getting buildup in the heat exchanger or exhaust elbow.
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Old 26-05-2024, 06:30   #5
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Re: Fresh water through the heat exchanger

I want to put in an EGT - that would show a spike in exhaust temps and would point to the engine getting hotter then usual (once a baseline is set when the boat is first put on this lake).

SO yes that is a way to know when the core of the heat exchanger is getting gunked up, but it would be better to avoid it as much as possible...however it is what it is. I am just trying to understand how big a problem this may be.
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Old 26-05-2024, 08:07   #6
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Re: Fresh water through the heat exchanger

Don't know that HX, but if it has an anode, you may need to change from zinc to magnesium or aluminum.
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Old 26-05-2024, 09:22   #7
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Re: Fresh water through the heat exchanger

Quote:
Originally Posted by Jim Jones View Post
I want to put in an EGT - that would show a spike in exhaust temps and would point to the engine getting hotter then usual (once a baseline is set when the boat is first put on this lake).

SO yes that is a way to know when the core of the heat exchanger is getting gunked up, but it would be better to avoid it as much as possible...however it is what it is. I am just trying to understand how big a problem this may be.
Coolant temp will tell more than EGT as far as whether the heat exchanger is transferring heat well enough or if it needs cleaning.
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Old 26-05-2024, 09:26   #8
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Re: Fresh water through the heat exchanger

Suggest you add 2-4 ltr. of white vinegar to your raw water system & let it sit overnight or longer.
Click image for larger version

Name:	VP D2-55 <a title=cooling.PNG Views: 17 Size: 105.4 KB ID: 290293" style="margin: 2px" />


This can be done easily by:
1. warm engine.

2. close cooling seacock
3.idle engine 15sec. to pump rw system dry.
4.remove strainer cap & pour white vinegar in strainer til it comes out exhaust.
5.stop engine & let it sit overnight or longer.
6. do this every 20-25 hrs.


This can be made easier by adding permanent tee,valve & hose at strainer intake,like you do for winterization/addition of RV antifreeze.
Then you can suck vinegar direct from vinegar jug.
Here is a workshop manual:
Cheers/Len
http://www.eddievan.com/documents/en...shopmanual.pdf
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Old 26-05-2024, 09:47   #9
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Re: Fresh water through the heat exchanger

Quote:
Originally Posted by deblen View Post
Suggest you add 2-4 ltr. of white vinegar to your raw water system & let it sit overnight or longer.
Attachment 290293


This can be done easily by:
1. warm engine.

2. close cooling seacock
3.idle engine 15sec. to pump rw system dry.
4.remove strainer cap & pour white vinegar in strainer til it comes out exhaust.
5.stop engine & let it sit overnight or longer.
6. do this every 20-25 hrs.


This can be made easier by adding permanent tee,valve & hose at strainer intake,like you do for winterization/addition of RV antifreeze.
Then you can suck vinegar direct from vinegar jug.
Here is a workshop manual:
Cheers/Len
http://www.eddievan.com/documents/en...shopmanual.pdf
WOW - thats a great idea ! Thanks for the heads up.

It may or may not turn out to be a problem - but since I am the worlds unluckiest guy and Murphy is my next door neighbor I am feel like its going to be an issue.
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Old 26-05-2024, 09:53   #10
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Re: Fresh water through the heat exchanger

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Old 26-05-2024, 10:05   #11
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Re: Fresh water through the heat exchanger

Quote:
Originally Posted by jamhass View Post
Don't know that HX, but if it has an anode, you may need to change from zinc to magnesium or aluminum.
I will be fitting Aluminum anodes for the fresh water.
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