Water Heater

[George ( C&C 40 )]

Hi All,


I have a tough one here...

Since I've re-commissioned my C&C40 "Delphinus" this Spring the hot water heater has not worked properly. It's a dual 120 volt electric / engine coolant Raritan water heater. It works perfectly when used as an electric water heater but only gets the water a bit hot for 30 seconds when it is being heated by the engine's coolant. The water heater worked beautifully last year and had been properly drained in the Fall.

To fix the problem I have tried the following:

1. Replaced the engines thermostat with a new unit. No change.

2. Dissambled and cleaned both the freshwater coolant pump and the saltwater engine pump. No change.

3. Opened up and cleaned the heat exchanger. No change.

4. Completely flushed the entire cooling system with a pressurized water hose including the coolant circulation coils on the water heater itself. Re-filled with new coolant. Everything is flowing beautifully. Still no change.

5. Run the engine for a long time at pretty high revs to get the engine coolant really hot. Once again, no change in the water heater's performance.

6. Replaced all the engine's zincs. Reaching for ideas now and still no change in the hot water heater's performance.


What am I missing here?


George Jones

[Figment]

Was the engine running under a load during solution #5, or were you just racing-in-neutral at the dock?

An engine running (racing, even) with no load requires remarkably little coolant flow.

[George ( C&C 40 )]

Hi Figment,

I've tested it four times. Twice after motoring around for an hour or so and twice just tied at the dock in netural. Water heater performance was the same in both cases.

George

[Tim]

Have you checked to make sure the coolant bypass hoses are properly led to and from the tank, and are not kinked or blocked? This seems obvious, but you didn't mention it in your list.

[George ( C&C 40 )]

Hi Tim,

I'll check all the hoses again just to make sure. However, I did run pressurized water through the entire system when I first flushed the cooling system out and had good flow at the time. I also took the hoses off the water heater tank and ran pressurized water through the coolant coils just to make sure there wasn't any blockage in there. System appeared to have good flow everywhere.

George

[Figment]

I assume that the WH draws heat from the fresh water side of the heat exchanger.
Is the WH connected in a direct loop between the engine and the heat exchanger, or is there some sort of a bypass line that could be short-circuiting things? I've seen bypass systems set up on trawlers, so that the engine can continue to operate if the WH's coil should fail.
You bought this boat used, right? Is it possible that a PO hid a cutoff valve in some clever location which might have been bumped during the fall or spring evolution?

I suppose that a desperation move could be to disconnect the feed hose while things are running and see what sprays.

[George ( C&C 40 )]

Hi Guys,

I'll go back through and trace each and every line again. Maybe I missed a cutoff valve somewhere. I appreciate all the responses. I'll let you know what I find.

George