Calorifior not getting hot water

[ostra4]

We recently changed boats to Dufour 38 with Yanmar3JH sail drive engine .The boat has 40 litre calorifior fitted with immersion heater.The immersion heater works great but even after a two hour run under engine water is only very luke warm.I have removed calorifior thinking the coil was blocked and this was perfectly clear,the pipes leading to the calorifior were full of very rusty water so these were removed and everything flushed clean.The inlet pipe to the tank gets hot but the return stays cold even with the tank heated via immersion.I have left engine running with cap of heat exchanger after refilling system and topped up as needed when thermostat allowed water through,the inlet and outlet pipes to calorifior were slackened to allow any air to escape .Its like the water just isn't circulating at all through the system.Any suggestions as to what I could try next great fully received.
Andrew

 

[vyv_cox]

Almost certainly an air lock. Take the hoses off at the engine end and plug the nozzles with corks, ot put a jumper hose between the two. Now back-fill the calorifier loop by raising the hoses, filling one hose with water until it floods from the other. Replace the hoses on the engine without spilling any and all should be well.

It's worth checking that the calorifier is connected the right way around, hottest water in at the top, return from the bottom. This is not usually a problem with an engine driven circulation pump but with a small electric one the thermosiphon working against the pump can give poor or no flow.

 

[ostra4]

Thanks for that swift reply ,will give it a go ,I hope your right .At first I thought calorifior may be called up but heats up so quick on electric I think it must be as you say an air lock .Off for my tools !

 

[ostra4]

I forgot to ask but there is a cylindrical assembly which looks like a valve plumbed into pipes just before it goes back to engine,it says Wagner on it and 50 deg but no amount of googling has told me what this thing does ,it does look very corroded inside and I wondered if this had an bearing on problem ?

 

[macd]

I forgot to ask but there is a cylindrical assembly which looks like a valve plumbed into pipes just before it goes back to engine,it says Wagner on it and 50 deg but no amount of googling has told me what this thing does ,it does look very corroded inside and I wondered if this had an bearing on problem ?

Thermostat? Strange place for one, I know, but the "50 deg" suggests as much. Take it out and see if that solves your problem.

 

[ostra4]

Well I filled the pipes as directed,removed the strange thermostat thing and connected everything back up ,Im almost certain it's fixed! Ran engine and after ten or fifteen mins inlet and outlet pipes from calorifior both hot , success and thanks so much for your help .-