No hot water or bus heater?

[Durant F]

First shake down cruise on a new to me boat.
Runs extremely well.
Engine runs at perfect temperature of 180
But, neither the bus heater or hot water tank heat up from engine.
Hot water tank was “just” installed by PO before I took delivery.
Antifreeze is up.
Thoughts?

 

[Comodave]

Is there a shutoff valve on the engine? Our last boat had a valve on it.

 

[DennisB1]

I had a similar problem with the heating the hot water. The problem was the location of the supply and return line to the engine. The original install had both lines close to the engine water pump pressure source near equal pressure and would not circulate -- hoses would not get hot. I found another location on the engine (Cat 3208) that was more remote from the water pump now the hoses get to engine temp and hot water tank heats.

Take a careful look at supply and turn locations on the engine. One location needs to be near the pump (high pressure) and another needs to be more remote (lower pressure location) to create a circulation path.

 

[Durant F]

Thanks
Good replies!
Dave, I had zctulooked for one earlier, then with your response I went and looked again. None found.
Dennis, I will look at that tomorrow. Getting late. Thanks for the insight.
The hot water tank is where it was originally, I “assume” it worked as-is before. Assume us a big word… I will check and see. Thx

 

[O C Diver]

Mine utilizes a pump to increase flow. If it runs through a heat exchanger the pump would be a requirement for the second loop. I would expect to see a switch on the breaker panel for cabin heat or circulator pump.



Ted

 

[jgwinks]

Thanks
Good replies!
Dave, I had zctulooked for one earlier, then with your response I went and looked again. None found.
Dennis, I will look at that tomorrow. Getting late. Thanks for the insight.
The hot water tank is where it was originally, I “assume” it worked as-is before. Assume us a big word… I will check and see. Thx

The original might not even been hooked up to the engine. Mine isn't, it's just a small residential unit and runs on 120V only. I have to be on shore power or run the genset to get hot water. Replacing it with one with a coolant loop is on the upgrade list, I first have to figure out where to plumb it in on one of the Perkins engines.

 

[Durant F]

Diver… I looked, no switch
Winks… the original was connected to the engine, the boat came that way…

Not even 7am here on the west coast, I’ll get looking more later today.

Thanks for the replies.

 

[PhilPB]

Have you followed the water lines to see if there is a loop from the water tank to the engine?

 

[Durant F]

Phil, yes… lines are attached

 

[PhilPB]

When I followed my lines I discovered inline gate valves. I replaced my water heater when I put in complete new freshwater system and I went to electric only.

 

[CaptTom]

Air in the lines? If the water heater was recently replaced, the whole loop (water heater and bus heater) may have been drained. I don't think there's a lot of pressure there, just enough to circulate the water.

 

[jgwinks]

Air in the lines? If the water heater was recently replaced, the whole loop (water heater and bus heater) may have been drained. I don't think there's a lot of pressure there, just enough to circulate the water.

I found that true when I repowered the last sailboat. The circulating pump would not push the air out. Had to manually fill the lines and try to reconnect them without letting air in.

 

[Lepke]

For best heating the supply line should be just before the thermostat. Usually somewhere in the head. The return works best if attached just before the circulation pump so the pump suction helps pull the coolant thru the heater.

If you continue to have trouble, a small 12v circulation pump (like used in solar systems) in the heater supply line works wonders. About $15 to $25 on ebay.

 

[dvarholy]

Always be mindful of scalding hot 190F coolant. Wear thick gloves. Purging trapped air may be necessary, especially if the water heater is mounted higher than the engine. Make sure your hose routing does not create air pockets with unnecessary loops and bends. The centrifugal water pumps on most engines produce very little actual pressure, so the most level and direct path to the heater is best.

An air bleeder available from auto parts stores could be installed at the highest accessible point in the loop. Open the bleeder valve when the engine is running and hot. Any trapped air should quickly escape. The hoses should then begin to get hot.

As an alternative, a small centrifugal pump could be piped inline. The pump must be rated for HOT water and the type of coolant you are running. Centrifugal pumps are directional, so there will be an arrow showing which way it flows. It is a big help to already know the direction of flow within the cooling system, which would be indicated by arrows drawn on the pipes and hoses with paint marker.

The isolation valves serve more than one purpose. They allow the engine to be run if there are coolant leaks in the water heater or hoses. A less obvious purpose is to prevent backflow of heat from the water heater to the engine itself. If the boat is docked, the engine is off and cooled down, natural convection will cause heat to flow back to the engine. I discovered this when my starboard engine was "warm" despite not having been run for days. The 900 pound cast iron engine slowly wastes the heat. Thermodynamics works both ways, even without a pump.

Daniel

Tradewinds 43' MY

 

[CaptTom]

...A less obvious purpose is to prevent backflow of heat from the water heater to the engine itself. If the boat is docked, the engine is off and cooled down, natural convection will cause heat to flow back to the engine...

I found this, too. I put a solenoid valve in the line, powered through the engine "ignition" switch. The valve is only open when the switch is on. No more warming the engine block from the water heater.

 

[dvarholy]

Hadn't even thought of a solenoid. Would only need to install on one of the lines. Available from any HVAC supply.

Daniel

Tradewinds 43' MY

 

[sunchaser]

DF
What engine model? Likely there is a TF member that has an identical engine with a coolant loop to the water heater.

As well, what water heater brand and model? Does the tank heat up OK on electric?

 

[CaptTom]

Hadn't even thought of a solenoid. Would only need to install on one of the lines. Available from any HVAC supply.

Do you think an HVAC shop would have a 12VDC solenoid valve? I went straight to Amazon for mine:
https://www.amazon.com/gp/product/B018WRJYUE

Of course a valve on only one hose doesn't give you isolation if there's a leak, but a pair of vice-grips works pretty well on a heater hose in a pinch.

 

[Durant F]

Looked for switches and other suggestions.
Tried bleeding the lines
Added coolant
Did it again…
Still no heat.
Did a full throttle run (5.9 Cummins) and after about 30 seconds, bingo… heat!
Has worked fine since..
Thanks for the responses