calorifier

[DavidGrieves]

Hi

Anybody ever fitted a calorifier to an engine (Volvo MD11C) that is direct seawater cooled?
I was thinking only a small one about 12 litre ish. Am I right in thinking it won't get very hot? Would also fit an immersion heater, so when power is available we can make use of it.
ASAP have a "hot pot" that would fit. Also thought about fitting zone valves so I could stop the hot water going to the calorifier and send straight to the exhaust...
Any suggestions???

Thanks in advance


Dave

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[cliff]

You Will need to fit a circulation pump for the calorifier feed. This needs to go in the outlet line from your engine (high spot on the head/manifold but below the level of the thermostat to prevent air locking the calorifier coil every time you stop the engine. The return line should go to the block.

As for pumps, something like teh Johnson CM30P7-1 should do nicely even though it is designed for fresh water it is magnetically coupled/driven (no seal to leak) and comes with a stainless steel impellor. I dare say if you look around you will find alternatives.

I am not sure what temperature the thermostat on your engine is set for but that will be near enough the temp you will in the calorifier. The motor should be wired through the ignition switch so it stops when the engine is switched off. An additional switch might be handy so you can stop the pump if you are only running the engine for a few minutes to get of your mooring/berth. Remember the coil will also draw heat from the tank if the tank is hotter than the coolant in the engine.

I find it handy to switch on the pump in winter to preheat my engine using the heat stored in the tank before starting as I do not have the luxury of glow-plugs.

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[dbentley]

Cliff,
I'm interested in doing this too on my boat, and your advice is most welcome. One question - is all the cooling water that has gone through the engine diverted via the new pump through the calorifier, or is the new route "in parallel" with the existing route for the water. If the former, then I assume it is vital to ensure that the calorifier does not have a thermostatic shut-off. If the latter, then how does one ensure that a sufficient flow of heat gets to the calorifier.
When I bought my boat, the surveyor found that the cylinder head was cracked, which he put down to an faulty attempt by the previous owner to create such a system, so I've had it disabled ever since (as cylinder head replacement was rather expensive...)
Thanks

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[Bodach na mara]

You are right. It won't get very hot, in fact probably won't get hot enough to be useful as the water from the engine block has to be at a flow rate high enough to ensure that it is still cool enough to absorb the exhaust heat.

<hr width=100% size=1>Ken Johnson<P ID="edit"><FONT SIZE=-1>Edited by Kenjohnson on 26/10/2004 12:43 (server time).</FONT></P>

 

[cliff]

Unless someone has buggered up the cooling system there should be two "loops". The first one should be raw water that is pumped into the block and up to the head as far as the thermostat. This "loop" does not circulate but rather lies static until the thermostat opens at which time the hot water flows through the open stat and more cold water enters the block. Eventually the temperature of the water in the block/head drops and the stat closes down. Under stable running conditions the stat will "balance" itself allowing a trickle of water to flow. Discharge from the stat joins second "loop" and is discharges into the exhaust.

The second "loop" is fed from the pump to the downstream side of the stat and on to the exhaust manifold to provide exhaust cooling and does nothing to cool the engine.There should be a swan-neck pipe from the thermostat housing to the exhaust manifold/water injection bend to prevent the head draining when the engine is shut down.

The "loop" you need to tap into is the block/head "loop". What happens (or should happen) is when you start the engine the cooling water pump pressurises the block/head "loop with the rest of the water bypassing the block head and flowing via the thermostat discharge housing to the exhaust manifold/water injection bend.

By tapping the block/head water off near the top of the head, passing through a circulation pump to the calorifier and back to the block you effectively are using the calorifier tank as a heat sink for water in the head/block. This could be described as a parallel "loop" so no additional stats are needed. Now as this water warms up it is continuously pumped through the calorifier and back to the block loosing heat to the calorifier. When fitting the coil in the calorifier you need to fit as large a coil as possible to optimise/maximise the heat transfer. When the circulating cooling water can no longer transfer heat to the calorifier tank contents (both coolant and fresh water are at the same temperature) the stat will open but now as the coolant is circulating the incoming cold water is quickly mixed with the coolant in the block and the stat will close down. The engine is now at temperature and the stat will hold the temperature at its preset temperature and hence the contents of the calorifier tank.

I have a raw water system on my boat and the calorifier heats the water to the point that SHMO burnt herself a few weeks ago - forgot to turn on the cold tap as well to cool the hot coming from the calorifier.

Anyone who cannot get hot water from their raw water driven calorifier needs to look at the cause - circulation pump not working, air lock, calorifier furred up, engine stat not closing / jammed open / missing!

There is no reason why you cannot get the hot water to the same temperature as the engine coolant so if you don't have hot water you could have a duff cooling system allowing the engine to run too cold.

If you pm me with your email address I can send you a schematic / flow diagram of the above which may make it clearer to you - a picture is worth a thousand words, or so it is said.

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[cliff]

"You are right. It won't get very hot, in fact probably won't get hot enough to be useful as the water from the engine block has to be at a flow rate high enough to ensure that it is still cool enough to absorb the exhaust heat."

See my post above then check out your engine - sounds like you have a problem.
Even raw water calorifiers will produce hot water as in hot enough to scald oneself - if one doesn't then one has a problem.

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