Breaking a Thermosyphon

[Slowboat35]

My calorifier slowly circulates hot water around the engine circuit presumably by thermosyphon thus losing all the heat inside. Nice warm engine to start in the morning though!
I suppose a non-return valve would stop it but I seem to recall a method using a high loop in the plumbing. Does this work, and if so does it need to be on the hotter upgoing side or the cooler return side?
Calorifier is mounted below engine level.

 

[bikedaft]

Valve? Easy to fit/work, inline pipe etc

 

[Boater Sam]

I bet the hot flow from the engine goes to the top of the calorifier coil.
If it goes to the bottom connection it will not do it.

A high loop in either pipe may stop it but makes it more difficult to vent air.

 

[plumbob]

I found even turning the valves off to the calorifier coil didn't completely stop the heat losses. A fair amount of the problem is the very cold water that gets added every time you use hot. I have a non return valve on the cold feed too, so I have to live with it.

 

[Boater Sam]

I found even turning the valves off to the calorifier coil didn't completely stop the heat losses. A fair amount of the problem is the very cold water that gets added every time you use hot. I have a non return valve on the cold feed too, so I have to live with it.

So your valves don't close fully? Are they gate valves?
I fail to see the relevance to the primary circuit circulating of a non return valve in the cold feed to the calorifier.

 

[plumbob]

So your valves don't close fully? Are they gate valves?
I fail to see the relevance to the primary circuit circulating of a non return valve in the cold feed to the calorifier.

No. They are lever valves and close fully. Heat will be lost if the hot tap is operated as cold water from the storage tank replenishes the cylinder. Thus particularly last thing, adding cold water won't help particularly if you've been stationary for a few hours. Perennial problem. The non return just helps stop any hot water from the calorifier trying to get back to the tanks. Only careful management helps us. Life's too short.

 

[Boater Sam]

No. They are lever valves and close fully. Heat will be lost if the hot tap is operated as cold water from the storage tank replenishes the cylinder. Thus particularly last thing, adding cold water won't help particularly if you've been stationary for a few hours. Perennial problem. The non return just helps stop any hot water from the calorifier trying to get back to the tanks. Only careful management helps us. Life's too short.

Still makes no sense in relation to the primary heating circuit, engine to calorifier coils, having reverse circulation after the engine is shut down causing the engine to be heated and the calorifier to cool.

Of course drawing off hot water that will have to be replenished by cold causes the calorifier to cool but that is not what the OP is talking about.