Calorifier cooling too quickly

[BlueChip]

My water in my hot tank cools very quickly. If the immersion has been on in the evening, by the next morning the water is only luke warm even though none has been run off.
The tank is well insulated and I have a NRV on the cold inlet so the heat is not escaping that way, so I can only think that that there is some thermal circulation of water from the heat exchanger back through the engine block.
Is this a reasonable assumption and if so how to stop it?

 

[LittleShip]

Is this a reasonable assumption and if so how to stop it?

Short answer Yes, especially if the cylinder is at the same height or lower than the engine. Fitting a one way valve would help the situation.

Tom.

 

[RAI]

You could test by heating by immersion and feeling the hoses from the calorifier to the engine, at the engine.

 

[vyv_cox]

Loop the hoses between the calorifier and engine downwards to below the engine. That will prevent convection.

Edit: my mistake, loop below the calorifier, not the engine.

 

[BlueChip]

The hoses come out of the engine and then run along at sump level to the calorifier which is mounted horizontally slightly lower than the engine. It's a Yanmar engine with freshwater cooling, so I assume the hot water to the calorifier is not pumped, in which case I cannot see that there would be any water pressure in order open a non return valve in the circuit.
Assuming the problem is hot water convection and the hoses are as low as they can be, what else can I do to stop the hot water circulating through the block and cooling down?

 

[vyv_cox]

In an indirectly cooled engine the water to the calorifier is pumped by the circulation pump, just as if it was the heater in your car. Should be plenty of flow to open a NRV. However, if the hoses to the heating coil loop below the calorifier it seems most unlikely that a thermosiphon can be set up.

 

[BlueChip]

In an indirectly cooled engine the water to the calorifier is pumped by the circulation pump, just as if it was the heater in your car. Should be plenty of flow to open a NRV. However, if the hoses to the heating coil loop below the calorifier it seems most unlikely that a thermosiphon can be set up.

My hoses do not coil below the calorifier, they have a straight run alongside the engine.
However, if the hot water is pumped a NRV would work. Where is the freshwater pump on a Yanmar engine, I wasn't aware it had one?

 

[vyv_cox]

Looping the hoses below the calorifier is far easier than doing anything else.

You have two belts on the front of your engine, GM and YM series. One goes around three pulleys, crankshaft, alternator and circulation pump. The other goes around two, crankshaft and seawater pump.

 

[BlueChip]

My Yanmar is a 3JH3E, I have only one belt, but a searching for the original brochure I now see that it has a centrifugal fresh water pump - which must be internal because I only have one belt.
There isn't any room below the calorifier, so I'll fit a NRV and see if that cures the problem.

 

[Bodach na mara]

I have a similar problem but ny calorifier is not connected to the engine, the heat comes from an Eberspaker boiler. (I have a "wet" heating system for that reason.) I have always assumed that the calorifier is not that well insulated and as it has a fairly low volume, any heat loss will result in a noticable drop in temperature. The situation is worse if the boat is subjected to any movement (pitching or rolling) after some water has been used as the replacement cold water is mixed with the remaining hot water.

 

[vyv_cox]

The belt drives the alternator and the (fresh) water circulation pump. The seawater pump is directly driven on your engine.

 

[Piddy]

The hoses come out of the engine and then run along at sump level to the calorifier which is mounted horizontally slightly lower than the engine. It's a Yanmar engine with freshwater cooling, so I assume the hot water to the calorifier is not pumped, in which case I cannot see that there would be any water pressure in order open a non return valve in the circuit.
Assuming the problem is hot water convection and the hoses are as low as they can be, what else can I do to stop the hot water circulating through the block and cooling down?

HI BC,

I cured this last year by doing two things. I extended the pipes so that they could be aimed downwards as far as possible at the exit and entry point into the calorifier as Viv says.

I also fitted a flap valve (something like this: http://uk.rs-online.com/web/p/check-valves/5103788/) into each pipe - checking for the correct flow direction - so that there could be no flow at rest.

I had noticed the engine was warm after an overnight stop - even though it hadn't run for 18 hours - this heat could only have come from the calorifier, which was being heated from the mains.

We can now shower the day after the engine was last run.

It worked for me!

 

[BlueChip]

I've just bought a couple of these - http://www.toolstation.com/shop/Plumbing/Valves/Single Check Non Return Valve/d20/sd2696/p77952 and plan to fit them at the weekend.

 

[Grumpybear]

I too have this problem, which has come on over time: it didn't happen for the first few years, so can anyone suggest what may have changed? The engine is a VP2030B, and the hoses run up and then down from the FW pump, along at sump level then up slightly to the calorifier which is sited in the lazarette.

The exploded diagram on the VP website, and the local VP agent, believe that the outlet (i.e. hot) from the FW pump is the left and slightly forward of the two connections on the top of the FW pump assembly, so I installed a NRV in that line about six inches from the engine. However, when the engine is running the other pipe (presumed to be the return from the calorifier) gets hot, while the one with the NRV in it gets hot only between the engine and the NRV. This suggests to me that the circulation is in the other direction; can anyone help by confirming or denying this? The next step would be to turn the NRV round, I guess.

Also, do I actually need a NRV in both lines, and do they need to be at the engine or calorifier ends of the lines?

Any helpful advice will be most gratefully received.

Giles

 

[Piddy]

I've just bought a couple of these - http://www.toolstation.com/shop/Plumbing/Valves/Single Check Non Return Valve/d20/sd2696/p77952 and plan to fit them at the weekend.

I chose the RS type as they have no spring to slow the flow of coolant. I was concerned to not overwork the internal water pump which is 25 years old....

Did they work OK?

Piddy

 

[Piddy]

I too have this problem, which has come on over time: it didn't happen for the first few years, so can anyone suggest what may have changed? The engine is a VP2030B, and the hoses run up and then down from the FW pump, along at sump level then up slightly to the calorifier which is sited in the lazarette.

The exploded diagram on the VP website, and the local VP agent, believe that the outlet (i.e. hot) from the FW pump is the left and slightly forward of the two connections on the top of the FW pump assembly, so I installed a NRV in that line about six inches from the engine. However, when the engine is running the other pipe (presumed to be the return from the calorifier) gets hot, while the one with the NRV in it gets hot only between the engine and the NRV. This suggests to me that the circulation is in the other direction; can anyone help by confirming or denying this? The next step would be to turn the NRV round, I guess.

Also, do I actually need a NRV in both lines, and do they need to be at the engine or calorifier ends of the lines?

Any helpful advice will be most gratefully received.

Giles

I fitted one in each of the pipes that happen to run across the easily accessible side of my engine. I added the valves and effectively extended the pipes by using a new section for each rather than cutting them - if that makes sense?

When heating water with electricity, there is no heat in the pipes so I conclude it works!

Piddy

 

[AndrewB]

Move to a warmer climate! Seriously, what you describe sounds normal enough for a small calorifier. I tried a non-return valve to limit thermal circulation, it cost a few quid, made f*** all difference to cooling rate, and introduced other problems.